Quality management

  • For a company to operate successfully worldwide, only the highest quality standards are good enough. We continually invest in research and development to stay ahead of today’s latest demands with new high-tech materials and processing methods. Strict guidelines ensure that every individual process is subject to the most stringent quality controls, from the inspection of raw materials to the final product, and can be traced right back to the raw material, if necessary. Consequently, we are certified according to DIN EN ISO 9001 and DIN EN ISO 13485.
  • Our quality assurance system monitors our products continuously, from the time of arrival in the incoming goods department as raw materials, through to their delivery as semi-finished products. This allows us to guarantee the highest possible product quality standards and to fundamentally prevent defects and complaints. This process entails performing various tests at every stage of the work process, as the infographic shows.
  • The international standard DIN EN ISO 13485 refers to both the supply of medical devices and the associated services. The primary aim of this international standard is to harmonise the legal requirements for quality management systems of medical devices.

    The following Ensinger GmbH divisions are certified according to ISO 13485:

    • Stock shapes
    • Injection moulding
    • Industrial profiles
    • Compounding
    • Machining

    All of our MT materials are produced using a controlled formulation. This guarantees the consistency of the material you receive for your medical application. Our Quality Management System, which c

    omplies with ISO 13485, allows us to ensure that all requirements imposed on this type of material for medical applications are adhered to, monitored and documented. In addition, a change history is documented for each MT product. Adhering to this international standard also ensures that biocompatibility tests are performed on semi-finished products at regular intervals, as well as after every change in the formulation or any other significant changes to the production process.

    Packaging

    The packaging for medical products is an important aspect to protect the product from corrosion, contamination and damage. The product needs to be protected from high air humidity, dust and dirt, temperature extremes and direct sunlight during transportation and storage at Ensinger or on the customer's premises. Depending on the customer's requirements, this is achieved by using film or sleeve packaging, which can be adapted flexibly to the product, to some extent even shrunk or used in multiple layers. Furthermore, the product can be cleaned or washed and sterilized as required.

    Certification

    Experienced quality management is also reflected in a seamless traceability system. This principle is particularly important in the fields of medicine and pharmaceutical technology. By ensuring consistent documentation of individual process steps, full product traceability is assured at Ensinger. To secure this, Ensinger only issues certificates of conformity on an individual order-specific basis. This establishes a direct link between the certificate and the goods delivered. Consequently, this minimises the risk of non standard production materials, which are not compliant with biocompatibility requirements, accidentally being certified and entering the market.

  • Traceability is an important instrument for Ensinger, which makes it possible to determine and trace the complete process chain of a material at any time. The method known as upstream tracing is key to this. The aim of upstream tracing is to quickly and selectively determine the causes and party responsible for any problems with components or materials. The aim is to guarantee that sources of error are identified and resolved as quickly as possible. In addition, other customers who may be affected can be informed quickly in order to prevent further damage. For this reason, Ensinger only issues certifications on an order-specific basis.

QUALITY ASSURANCE

  • The Ensinger product portfolio contains materials with a variety of different declarations, including the following areas:

    • Direct food contact (in accordance with FDA, BfR, 1935/2004/EC, 10/2011/EC, 3A SSI, etc.)

    Biocompatibility (in accordance with ISO 10993, USP Class VI, etc.)
    Drinking water contact (including KTW, DVWG, WRAS, NSF61, etc.)
    Flammability (including UL94, etc.)
    as well as material qualification testing for the following industries:

    • Oil & Gas industry
    • Aerospace industry

    Depending on the material involved and in close cooperation with raw material suppliers and test institutes, we issue the listed confirmations relating to the materials by the customer’s request.  In the interests of ensuring full traceability, these confirmations are only issued by Ensinger in direct connection with an actual order and with the material supplied

  • Ensinger semi finished products for the food industry are manufactured in accordance with the requirements of the following legal European regulations on conformity for food contact:

    • Regulation (EC) No. 1935/2004
    • Regulation (EC) No. 2023/2006
    • Regulation (EU) No. 10/2011

    In addition to (EU) No. 10/2011, which is applicable across Europe, Ensinger products also comply with specific directives such as FDA approval for raw materials and recommendations on the suitability of plastics for contact with food issued by the Federal Institute for Risk Assessment of Germany (BfR). A suitability statement is provided by Ensinger's technical office with confirmation of the material listing. 

  • Ensinger products for the food industry are compliant to specific directives of FDA approval for raw material.

    • Read more about FDA conditions

    Certificates in accordance with FDA requirements are issued by Ensinger for stock shapes products intended for repeated contact with food. A suitability statement is provided by Ensinger's technical office with confirmation of the material listing.

    Specific products with raw material compliance to other international standards are also available on request, e.g.:

    • NSF/ANSI standard 51 "Food Equipment Materials"
    • 20-25 3-A Sanitary Standard
  • Drinking water does not fall within the scope of food manufacturing guidelines, but is monitored in accordance with special regulations which are not internationally standardised at present.

    Since drinking water is frequently used in the preparation of food, either as a manufacturing component or in cleaning processes, Ensinger semi finished products are available with raw material compliance to the following specific directives:

    • Germany - Plastics in contact with drinking water (KTW)
    • UK - WRAS (Water Regulations Advisory Scheme)
    • USA - NSF 61 (National Sanitation Foundation)

    The country specific test specifications are not transferrable and must be individually tested in each case. However, their statements are similar in respect to the suitability of specific application conditions for drinking water. These are comparable according to KTW, WRAS and NSF 61, and are classified into three categories: cold water (e.g. up to 23 °C), warm water (e.g. up to 60 °C) and hot water (e.g. up to 85 °C).

    Analogous to the issue of suitability for contact with food, raw materials intended for contact with drinking water have to pass suitable migration tests. As a rule, raw material manufacturers must carry out these migration tests for the qualification of suitable materials and decide for them­­selves according to which regional regulations they will carry out the tests.

  • Ensinger offers a variety of biocompatible materials (MT products) with different sterilisation capabilities for products ranging from medical devices to short-term implants.

    The biocompatibility of medical materials and products is certified in accordance with: 

    • ISO 10993 
    • USP class VI

    The biocompatibility which Ensinger confirms is only valid for semi-finished parts. Finished parts must be tested and approved after all processing steps by the manufacturer of the parts.

    FDA compliance is also frequently used in the field of medical technology to provide users with important information on risk assessment. As raw materials for use in the medical sector mostly comply with the requirements of the FDA, this can be certified accordingly on an order-by-order basis in order to guarantee seamless traceability.

    An additional advantage is that Ensinger has six certified cleanrooms in its production facilities. These areas are used to produce items such as special products for use in the semi-conductor industry and medical technology. Using a 3-zone cascade principle, the cleanroom suite is an ultra modern state-of-the-art facility and is qualified to DIN EN ISO 14644-1 Class 8 / EU GMP Class D. 

  • The Ensinger product portfolio contains materials with specific fire behaviour, assessed by relevant testing.

    Combustibility testing to UL94 is generally performed on raw material. Alongside testing in accordance with the specifications of UL or using a UL-accredited laboratory, listing and using so called yellow cards is also performed directly by UL itself. For this reason, a distinction must be made between materials with a UL listing and materials which only comply with the requirements of the respective UL classification (without listing). If listed materials are required for special applications, please consult our Sales Departments before ordering, as it is possible that specific raw materials may have to be used.

    Alongside flame retardant classification in accordance with UL94, there are other industry specific tests, which classify the combustion behaviour of plastics.

    • DIN 5510-2 is a typical fire test specification for German railway component applications and will be finally replaced at the end of 2016 by the European standard EN 45545 on requirements for fire behaviour of materials and components for railways components, which is already valid alongside.
    • FAR 25.853 is a typical fire test specification for aerospace applications.
      In addition to pure combustibility (using the vertical test), the standards also contain tests to determine smoke density and toxicity under the influence of radiant heat and flames.
  • Special Ensinger semi finished products are available, which are compliant for use in highly demanding oil and gas applications according to EN ISO 23936-1:2009 as well as NORSOK M-710, Edition 3. The tests were performed at the Element Materials Technology Laboratory, in the UK, choosing the test conditions so that both standards (EN ISO 23936-1 and NORSOK M-710, Ed. 3) were satisfied. A suitability statement is provided by Ensinger’s technical office with confirmation of the material listing.
    • EN ISO 23936 - 1
    • NORSOK standard M-710, Edition 3

    Both standards require quality control tests such as specific gravity, hardness, tensile property and elongation tests, as well as chemical resistance test procedures for the qualification of thermoplastic materials exposed to fluids at elevated pressures and temperatures over an extended period of time.

    There are no significant differences between EN ISO 23936-1 and NORSOK M-710 for the evaluation of thermoplastics regarding sour fluid resistance. The main practical difference is that the pressure, temperature and sour fluid concentration requirements for ISO are more stringent than for NORSOK M-710. So testing according to the conditions given in EN ISO 23936-1 is also relevant to compliance with NORSOK M-710. 

  • There are no aviation-specific statutory regulations for the field of semi-finished plastic parts which are directly applicable to subcontractors of corporations with aviation approval. Manufacturing corporations can draw on a series of national and international standards, which they can apply in cooperation with suppliers. If the specifications in the standards do not comply with the manufacturer's requirements, they are frequently supplemented by additional individual specifications.

    Ensinger, as a manufacturer of semi-finished products, is capable of complying with the required specifications and is familiar with the customary procedures and processes for product qualification and order processing in the aviation sector. An in-house sales team specialising in aviation and an efficient compliance management department ensures that in each individual case, according to customer requirements, Ensinger semi finished products can be supplied which are compliant with these main following European standards:

    • Material Data Sheets (for instance WL 5.2206.3)
    • Aviation Standards (for example LN 9388)

    In addition, Ensinger semi finished products can also comply with the most common international standards such as:

    • ASTM (USA)
    • Mil Spec (Military Specification/USA)
    • LP (USA – Federal Specification)
    • FAR 25.853
    • UL 94 -V0
    • ESA ECSS-Q-70-02
  • European standard EN 10204 defines different types of test certifications which can be made available to the buyer for each delivery in compliance with agreements concluded at the time of order placement. This standard supplements other standards which define the general technical terms and conditions of supply.

    We can supply you with the following types of test certifications in accordance with EN 10204.
  • In its own laboratories, Ensinger has a range of sources for determining material characteristics. 

    In addition, we work in close cooperation with various external test institutes, through which additional and more complex tests can be performed in a variety of areas.

     

  • Ensinger’s Stock Shapes division is classified as a downstream user as it does not manufacture or sell preparations (such as compounds) or substances (chemicals) which are subject to registration, but processes so called "products". Ensinger is therefore reliant upon information from its raw material suppliers. Downstream users such as Ensinger’s Stock Shapes division are not obliged to carry out tests or register their products in accordance with the REACH regulation.

PRODUCT HANDLING

  • The general rules for storing semi finished plastic products are:

    • They should always be stored flat or on a suitable support (in the case of rods and tubes) and with the greatest possible surface contact in order to avoid deformation through their own intrinsic weight or warmth.
    • If possible, the semi finished products should be stored in closed rooms under normal climatic conditions (23°C/50 % relative humidity).
    • Storage and handling should take place in such a way that the material designations and product numbers (batch number) are clearly recognisable on the semi-finished products and can be maintained. This allows clear identification and traceability of products.
  • There are several factors that should be avoided when storing and handling plastics:

    • Weathering effects can have an impact on the properties of plastics. As a result, solar radiation (UV radiation), atmospheric oxygen and moisture (precipitation, humidity) can have a lasting negative impact on material characteristics
    • Semi finished products should not be exposed to direct sunlight or the effects of weather over prolonged periods
    • Plastics should not be exposed to low temperatures for prolonged periods. In particular, marked fluctuations in temperature should be avoided
    • Products stored in cold conditions should be allowed sufficient time to acclimatise to room temperature before processing
    • Hard knocks, throwing or dropping should be avoided, as cracks and fracture damage may occur
    • Avoid the effects of high-energy radiation such as gamma or X-rays wherever possible due to possible microstructural damage due to molecular breakdown
    • Plastic stock shapes should be kept away from all kinds of chemicals and water in order to prevent possible chemical attack or the absorption of moisture
    • Plastic should not be stored together with other combustible substances
  • The following materials, in particular, should be protected against the influence of the weather:

    All variations should be generally protected:

    • TECAPEEK (PEEK)
    • TECATRON (PPS)
    • TECASON P (PPSU)
    • TECASON S (PSU)
    • TECASON E (PES)
    • TECARAN ABS (ABS)

    Variants not dyed black should be protected:

    • TECAFORM AH, AD (POM-C, POM-H)
    • TECAPET (PET)
    • TECAMID 6, 66, 11, 12, 46 (PA 6, 66, 11, 12, 46)
    • TECAST (PA 6 C)
    • TECAFINE (PE, PP)
  • If correctly stored, plastics themselves do not pose a fire risk. However, they should not be stored together with other combustible substances.

    Plastics are organic materials and are consequently combustible. Their combustion or decomposition products may have a toxic or corrosive effect.

  • It is not possible to specify a maximum storage period, as this depends heavily on the materials, storage conditions and external influences.
  • Plastic waste and chips can be processed and recycled by professional recycling companies. In addition to this, it is possible to send the waste for thermal processing by a professional company  to generate energy in a combustion plant with suitable emission control in place. This applies, in particular, to applications where the plastic waste produced is contaminated, e.g. in the case of machining chips contaminated with oil.

  • The following cleaning methods are particularly suitable for cleaning plastics:

    • Wet chemical methods:
      • Also suitable for components with ultra-complex component geometries
      • Usable for most plastics
      • No abrasive influence on components
      • Caution in the case of materials which absorb moisture (PA), due to tolerances
      • Caution in the case of materials sensitive to stress cracking (amorphous) such as PC, PSU, PPSU etc.
    • Mechanical processes:
      • Primarily suitable for rough cleaning of plastics (brushing, wiping, etc.)
      • Caution with soft plastics due to possible surface damage (scratching)
    • CO2 snow - dry ice blasting:
      • Very suitable, as blasted material is subjected to practically no damage or influence.
      • The process is dry, non-abrasive and does not result in transfer of heat to the component
      • Ideal for soft materials and materials with high moisture absorption properties (PTFE, PA, etc.)
    • Plasma method:
      • Suitable for components with ultra-complex component geometries
      • Simultaneously exerts an activating effect on the plastic surface
      • No abrasive influence on the surface
      • No humidity in the system
  • The choice of cleaning process depends on:

    • Contamination (film, particulate, coating, germs)
    • Component geometry (bulk material, single part, scooping, functional surface)
    • Component material (plastic)
    • Requirements (rough cleaning, cleaning, precision cleaning, ultra precision cleaning)
  • There is no definition of the maximum residual contamination which may be present on a component for the food and medical technology sectors. Since no level of cleanliness is defined, individual producers have to set out/define their own limits for admissible contamination.
    The FDA and EU guidelines define directives and regulations on the migration of substances into products, but not on the degree of surface cleanliness

    The solution is:

    Semi finished products from Ensinger:

    • Biocompatibility tests are performed on semi-finished products for the medical technology sector. These provide a statement regarding suitability for bodily contact
    • Semi finished products for food contact are tested for the migration behaviour of certain materials
    • Cooling lubricants which comply with food regulations are used for grinding
    • Ensinger works in compliance with the GMP regulations for the food sector

    Definition of limiting values for admissible cleanliness in mutual agreement with the customer

  • A variety of different welding processes are available, which work either on a no contact basis (heating element, ultrasound, laser, infrared, gas convection welding) or by contact (friction, vibration welding). Depending on the process used, certain design guidelines must be observed during the design phase in order to guarantee optimum connection. In the case of high temperature plastics, it should be noted that an extremely high input of energy is required for plastification of materials. The welding method to be used depends on these factors; shaped part geometry, size and material. Common welding techniques used for processing plastics are:

    • Heating element and hot gas welding
    • Ultrasound welding
    • Vibration/friction welding
    • Laser welding
    • Infrared welding
    • Gas convection welding
    • Thermal contact welding
    • High frequency welding
    • Thermal conduction, radiation, convection, friction
  • Decisive factors for a good bonded joint:

    • Material characteristics
    • Adhesive
    • Adhesive layer
    • Surface (preliminary treatment)
    • Geometric design of the bonded joint
    • Application and load conditions

    To increase the strength of a bonded joint, it is advisable to pretreat the surfaces when bonding plastics in order to enhance surface activity. Typical methods include: 

    • Cleaning and degreasing the material surface
    • Increasing the size of the mechanical surface by grinding or sand blasting (particularly recommended)
    • Physical activation of the surface by flame, plasma or corona treatment
    • Chemical etching to form a defined boundary layer
    • Primer application

    When bonding plastics, stress peaks should be avoided and a compressive, tensile or shear load should preferably be applied to the adhesive bond joint. Avoid flexural, peeling or plain tensile stresses. Where applicable, the design should be adjusted so that the bonded joint can be configured for suitable levels of stress.

  • Chemical joining (bonding) of components offers a range of benefits compared to other joining methods:

    • Even distribution of stress
    • No damage to materials
    • No warping of joined parts
    • Different material combinations can be joined
    • The separating joint is sealed at the same time
    • A smaller number of components is required

MACHINING GUIDELINES FOR SEMI-FINISHED ENGINEERING PLASTICS

  • For the machine processing of plastics/semi-finished goods, normal commercially available machines from the wood and metal working industries can be used, with tools made of high speed steel (HSS).

    In principle, tools with cutting edge angles like those used for aluminium are suitable, however, we recommend the use of special tools for plastic with a sharper wedge angle.

    Hardened steel tools should not be used to process reinforced plastics, due to the low holding times and long processing times. In this case, the use of tungsten carbide, ceramic or diamond tipped tools is advisable. Similarly, circular saws fitted with carbide tipped saw blades are ideal for cutting plastics.

    Therefore, only flawlessly sharpened tools should be used. Due to the poor thermal conductivity of plastics, steps must be taken to ensure good heat dissipation. The best form of cooling is heat dissipation through the chips produced.

    Recommendations:

    • Use tools which are specifically designed for plastics
    • Have a suitable cutting geometry
    • Very well sharpened tools
  • In the extrusion process, materials are melted and compressed in a cylinder via a screw conveyor and then homogenised. Using the pressure arising in the cylinder – and the appropriate tooling – semi-finished goods are delivered in the form of sheets, round rods and tubes and calibrated via a cooling system.

    Impact:

    • Internal tension develops
    • Fibres take up a specific orientation (if available)

    Ensinger offers a broad product portfolio of semi finished plastics, which may be processed optimally by machining.

    Internal tension:

    The resulting pressure in the extrusion process produces a shear movement and flow of the molten plastic mass. The semi finished goods discharged by the tool slowly cool from the marginal layer to the centre. The poor thermal conductivity of plastics results in different cooling rates. Whereas the margins have already solidified, the centre still contains plastic in the liquid state or fused plastic. Plastics are subject to a typical shrinkage pattern for that material. During the cooling phase, the plastic centre is hindered from contracting by the rigid boundary layer.

    Impact of the technological process:

    • Internal stresses (in the centre) are due to the technological process
    • Semi finished products are difficult to machine
      • High risk of cracking and fractures

     

    Possible solutions:

    • Material-specific annealing to minimise stresses
  • Dimensional stability is to be considered as a characteristic in every system, in each process step, from the production of semi finished plastics to the final end use. There are various factors which can influence the dimensional stability of a component.

    Moisture uptake:

    • Plastics with lower moisture uptake are generally much more dimensionally stable. For example: TECAFORM AH / AD, TECAPET, TECATRON, TECAPEEK
    • Plastics with high levels of moisture uptake exhibit a marked influence on dimensional stability. For example: TECAMID, TECAST. Moisture uptake/release leads to swelling or shrinkage of the material and conditioning may be recommended prior to processing.

    Stress relaxation:

    • Internal or "frozen in" stress acts only partly or has little effect on the dimensional stability of the finished part during processing at room temperature, resulting in a dimensionally stable finished part.
    • During storage or in use, this "frozen in" tension can break down, leading to dimensional changes.
    • Particularly critical: use of components at elevated temperatures, where stress can be reduced suddenly, leading to a change of shape, warping or – in the worst case – stress cracking while the component is in use.

    Heat input:

    • All processes which develop heat in the material are critical, for example: annealing, machining, use at high temperatures and sterilisation.
    • Temperatures above the glass transition temperature have an effect on microstructural changes and thus post shrinkage after renewed cooling.
      • Shrinkage and warping are particularly apparent in asymmetrical component geometries
      • Semi crystalline thermoplastics exhibit high post-shrinkage (up to approx. 1.0 – 2.5 %) and are critical with regard to warping
      • Amorphous thermoplastics show only slight post shrinkage characteristics (approx. 0.3 – 0.7 %) and are more dimensionally stable than partly crystalline thermoplastics
    • In many cases, higher thermal expansion (compared to metal) must be taken into consideration.

    Processing:

    • Ensure good heat dissipation in order to avoid local increase in temperature
    • In the case of higher machining volumes, it may be advisable to introduce an intermediate annealing step in order to reduce the development of tension
    • Plastics require greater production tolerances than metals
    • Avoid higher tensional forces to avoid distortion
    • In the case of fibre reinforced materials, in particular, attention should be paid to the position of the component in the semi-finished goods (observe extrusion direction)
    • When machining, a component_optimised procedure should be chosen
  • There is currently a trend towards using dry machining with engineering plastics. As there is now sufficient experience available in this area, it is frequently possible to machine plastics without the use of cooling lubricants. Exceptions for thermoplastic machining processes are:

    • Deep drill holes
    • Thread cutting
    • Sawing reinforced materials

    However, it is possible to use a cooled cutting surface to improve both the surface quality and tolerances of the machined plastic parts. Furthermore, this allows faster feed rates and consequently reduced running times.

    Machining with coolants

    If cooling is required, it is recommended to cool

    • Via the chippings
    • Using compressed air
      • Advantage: simultaneous cooling and removal of the chips from the working area
    • Use of water soluble coolants
    • Commercially available drilling emulsions and cutting oils can also be used
      • Spray mist and compressed air are very effective methods

    Machining amorphous plastics

    • Avoid using coolants:
      • Materials liable to develop stress cracking
    • If cooling is imperative:
      • Parts should be rinsed in pure water or isopropanol immediately after machining
      • Use suitable coolants
    • Pure water
    • Compressed air
    • Special lubricants: information about suitable lubricants is available from your lubricant supplier

    Advantages of dry machining

    • No media residues on the components
      • Advantageous for components used in medical device technology or in the food industry (no migration)
      • Influence of cooling lubricants on the material (swelling, change of dimensions, stress cracking, etc.) can be ruled out
    • No interaction with the material
    • False assessment/treatment by the machinist is excluded

    Note

    • Especially with dry machining, cooling is essential to achieve good heat dissipation!
  • Dimensionally precise parts can only be made from stress annealed semi-finished products. Otherwise, the heat generated by machining will inevitably lead to the release of processing stress and component warping.

    Ensinger semi-finished products are always, in principle, subjected to a special annealing process after production in order to reduce the internal stress created during the manufacturing process. Annealing is carried out in a special recirculating air oven, however, it can also be performed in an oven with circulating nitrogen or in an oil bath.

    The annealing process involves thermal treatment of semi-finished goods, moulded or finished parts. The products are slowly and evenly warmed to a material-specific defined temperature. This is then followed by a holding period, the length of which depends on the material and its thickness, in order to thoroughly heat through the moulded part. Subsequently, the material has to be slowly and evenly cooled back down to room temperature.

    • Residual stresses, which have arisen during production or processing, can be extensively and almost completely reduced by annealing
    • Increase in the crystallinity of materials
    • Optimisation of mechanical material values
    • Formation of an even crystalline structure in materials
    • Partial improvement in chemical resistance
    • Reduction of warping tendency and dimensional changes (during or after processing)
    • Sustainable improvement in dimensional stability
  • An intermediate annealing stage can be beneficial when machining critical components. This applies, in particular:

    • If narrow tolerances are required
    • If components with a strong tendency to warp, due to the required shape, need to be produced (asymmetric, narrowed cross sections, pockets and grooves)
    • In the case of fibre reinforced/filled materials (fibre orientation can enhance warping)
      • Processing can lead to additional enhanced stresses being introduced into the component.
    • Use of blunt or unsuitable tools:
      • Initiators of stress
    • Excessive heat input into the component – produced by inappropriate speeds and feed rates
    • High stock removal volumes – primarily as a result of one-sided machining

    An intermediate annealing step can help to reduce these stresses and alleviate the risk of warping. In this respect, care should be taken with regards to ensuring that the required dimensions and tolerances are observed:

    • Prior to intermediate annealing, components should first be dimensionally pre-worked with an approximate safety margin (roughening) as annealing can lead to shrinkage of the components
    • Subsequently, the final dimensioning of the parts should be performed
    • Support the component well during the intermediate annealing step to avoid warping
  • Heat treatment always has direct effects on plastics and their processing:

    • Annealing
    • Machining (frictional heat)
    • Use (service temperature, hot steam sterilisation)

    Semi crystalline plastics

    • Annealing process leads to equalisation of material properties: Increase in crystallinity, optimisation of mechanical properties, improved dimensional stability, better chemical resistance
    • Machining can lead to localised overheating through frictional heat, resulting in microstructural changes and post shrinkage
    • TECAFORM is particularly critical in this respect, as improper machining can lead to severe deformation and/or warping of the component

    Amorphous plastics

    • Are less critical with regard to post-shrinkage and warping
  • Plastics can be cut using a band saw or a circular saw. The choice depends on the shape of the stock shape. Generally speaking, heat is generated by the tooling when processing plastics and, as a result, damage to the material is the greatest danger. For this reason, the right saw blade needs to be used for every shape and material.

    Band saws:

    • Most suitable for cutting round rods and tubes to size
    • It is recommended that support wedges should be used
    • Sharp and sufficiently set saw blades should be used for:
      • Good chip removal
      • Avoidance of high friction between the saw blade and material, as well as excessive thermal build up
      • Avoidance of saw blade blocking

    Advantages:

    • Heat generated by sawing is well dissipated thanks to the long saw blade
    • Band saws allow versatile application for straight, continuous or irregular cuts
    • Produces a good cutting edge quality

    Circular saws:

    • Primarily suited for cutting plates with straight cutting edges to size
    • Table circular saws with the right power drive can be used for straight cutting of plates with thicknesses of up to 100 mm
    • Saw blades should be made of hardened metal
    • Use a sufficiently high feed rate and adequate offset:
      • Results in good chip deflection
      • Avoids sticking of the saw blade
      • Avoids overheating of the plastic in the saw cut
      • Produces a good cutting edge quality

    Recommendations:

    • Use a corresponding tensioning device:
      • Avoidance of vibrations and unclean cutting edges, which can result from this, or even lead to breakage
    • Prefer warm cutting of very hard and fibre-reinforced materials (pre heat to 80 – 120 °C)
    • Tungsten carbide saw blades wear well and provide an optimum surface finish
  • Plastics can be processed on commercially available lathes. For optimal results, specific plastic cutters should be used.

    Cutting tools:          

    • Use tools with small cutting radii
    • Broad nosed finishing cutting edge for high quality finish requirements
    • Knife like cutting geometries for machining flexible workpieces
    • Use favourable geometries for fixing
    • Special chisel geometry for parting off
    • Cut circumferences and polished surfaces

    Advantages:

    • Optimal, groove less surface
    • Reduces the build up of material on the application

    Recommendations:

    • Select a high cutting speed
    • Use a cutting depth of at least 0.5 mm
    • Compressed air is very suitable for cooling
    • Use of a lunette due to reduced rigidity of plastics
      • Stabilise the component
      • Avoid of deformation

    Advantages:

    • Good cooling of the material
    • Overcomes flow chipping, which can arise with some plastics. Prevents jamming and rotating with the lathe part of the blade
  • When drilling, particular attention must be paid to the insulating characteristics of plastic. These can cause heat to build up quickly in plastics (especially semi crystalline plastics) during the drilling process, especially if the drilling depth is more than twice the diameter. This can lead to "smearing" of the drill and internal expansion arising in the component, which can lead to compressive stress in the part (especially when drilling into the centre of round rod sections). The stress levels can be high enough to cause a high level of warping, dimensional inaccuracy, fractures and bursting open of the finished component or blank. Appropriate processing for the material will prevent this.

    Tools:

    • Well sharpened commercially available HSS drills are normally sufficient
    • Use drills with a narrow bridge (synchronised drilling):
      • Reduced friction and avoidance of a build up of heat

    Recommendations:

    • Use a coolant
    • Frequent withdrawal of the drill for chip removal and additional cooling
    • Avoid the use of a manual feed to ensure that the drill does not become caught and to prevent cracking

    Recommendations for drilling small diameter holes (< 25 mm)

    • Use of high speed steel drills (HSS drills)
    • Use a spiral drill
    • Twist angle of 12 – 25°:
      • Very smooth spiral grooves
      • Favours chip deflection
    • Frequent removal of the drill (intermittent drilling)
      • Better removal of the chips and avoidance of thermal build up
    • In the case of thin walled components, we recommend:
      • High cutting rates
      • If possible, select a neutral (0°) chipping angle in order to avoid the drill catching in the component and thus tearing of the drill and/or lifting of the workpiece by the drill

    Recommendations for drilling large diameter holes (> 25 mm)

    • Carry out trial drilling with large drill holes
    • Select a pre drilling diameter which is no larger than 25 mm
    • Carry out finishing subsequently with an inner cutting chisel
    • Introduce drilling into long rod sections only from one side
      • In the case of drilling attempts which meet in the middle (bilateral drilling), unfavourable stress characteristics, or even tearing, may arise
    • In extreme cases/in the case of reinforced materials, it may be advisable to carry out the drilling on a pre warmed component at approx. 120 °C (heating time approx. 1 hour per 10 mm cross-section)
      • To ensure dimensional accuracy, finish machining should take place after the blank has cooled down completely
  • Plastics can be milled using customary machining centres. This should be done using tools with adequate chip space in order to guarantee reliable discharge of chips and to prevent overheating.

    Tools:

    • Suitable for thermoplastics
      • Slot milling cutter
      • Face milling cutter
      • Cylindrical milling cutter
      • Single cutter tools
      • Fly cutter
    • Single cutter tools
      • Advantages:
      • Optimised cutting performance
      • High surface quality with good chip removal at the same time

    Recommendations:

    • High cutting speeds and medium feed rates
    • Ensure good attachment:
      • Rapid surface machining and high spindle speed coupled with correct fixture alignment result in a higher quality machined finish
    • Thin work-pieces can be secured to the router table using a suction fixture or double-sided adhesive tape
    • End milling is more economical than peripheral milling for flat surfaces
    • During peripheral milling, tools should have no more than two cutting edges in order to minimise vibrations caused by a high number of cutting edges and chip spaces should be adequately dimensioned
  • Planing and plane milling are chip production methods with geometrically determined cutting, used to produce certain cuts, equal surfaces, grooves or profiles (using shaping milling).
    Planing involves a straight line of material being removed across the surface using a planing machine cutting tool. Plane milling, on the other hand, involves the surface being processed using a milling head. Both processes are well-suited to produce even and/or equalised surfaces on semi-finished goods. The main difference is that the appearance of the surfaces is different (surface structure, gloss).

     

    Planing and plane milling at Ensinger

    • Ensinger's cutting service can offer both planed as well as plane milled semi-finished goods
    • Sheets > 600 mm can only be processed using the plane milling process
    • Sheets < 600 mm can be processed using both processes
    • Small cuts are processed by planing
  • Threads are best introduced into engineering plastics using chasing tools for male threads or milling for female threads.

    Tools

    • Chasing tools are recommended
    • Two-dentate chasers avoid burring
    • gDies are not recommended. In the case of a return, re-cutting is possible

    Recommendations

    • Taps often have to be provided with an allowance (depending on material and diameter, approx. value: 0.1 mm)
    • To avoid squashing of the thread, do not select a pre-setting which is too high
  • The grinding quality is influenced by:

    • The grinding machine
    • The tool being used
    • The grinding medium
    • The working parameters of the grinding process
    • The material being processed
    • The roundness/straightness of the semi-finished goods

    Particularly decisive working parameters are:

    • Cutting speed
    • Forward rate of advance
    • Delivery
    • Cross-sectional advance rate

    Optimally adjusted machinery and the right choice of parameters for the corresponding material ensure that very good surface quality with slight roughness, diameter tolerances up to h9, roundness and straightness can be achieved.

    Grinding at Ensinger

    Our cutting service is able to provide ground round rods. Thanks to high surface quality and narrow tolerances, ground round rods are easy to process and are suitable for continuous production processes.

  • To ensure good surface quality, the following machining guidelines should be adhered to:

    Tools

    • Tools suitable for plastics must be used
    • Tools must always be well sharpened and smooth (sharpened cutting edge). Blunt cutting edges can lead to increased heat generation, resulting in distortion and thermal expansion
    • Tools should be adequately spaced to ensure that only the cutting edge comes into contact with the plastic

    Processing machine

    • Flawless, high-quality finished surfaces can only be achieved with low-vibration machining

    Material

    • Use low-stress annealed material (semi-finished goods from Ensinger are generally low-stress annealed)
    • Note the properties of the plastic (thermal expansion, low strength, poor heat conduction, etc.)
    • Due to the minimal rigidity of the material, the work-piece must be adequately supported and lie as flat as possible on the supporting surface in order to avoid deflection and out-of-tolerance results

    Cooling

    • Use coolants for processes involving high levels of heat generation (such as drilling)
    • Use suitable coolants

    Recommendations

    • Stress pressure be minimised, as this can result in deformation and impression marks on the work-piece
    • Select suitable parameters for the machining process
    • Keep to a moderate feed rate
    • Select a high cutting speed
    • Good removal of chips is crucial to prevent tool congestion
    • Ensure that chip removal is equal on all sides to prevent warping
  • The typical de-burring methods for engineering plastics are:

    Manual de-burring

    • Most common method of de-burring
    • Flexible, but most work-intensive solution
    • Visual control of the component can be performed simultaneously

    Jet de-burring

    • A jet of abrasive material at high pressure is used on the surface of the component. Common blasting methods: sand, glass balls, soda, dry-ice and nutshell blasting
    • Is also used as a surface treatment method

    Cryogenic de-burring

    • Removal of burrs at temperatures around –195 °C using a jet or by drum tumbling of the components
    • Commonly used coolants: liquid oxygen, liquid carbon dioxide, dry-ice
    • Low temperatures lead to brittleness and hardness of the materials (polymers)

    Flame de-burring

    • De-burring using an open flameˌ
    • Danger: damage may be caused to the component due to excessive heat

    Hot-air de-burring

    • The burr melts under the influence of heat
    • Very safe and well-controllable process
    • Avoidance of damage or warping of the component using process management suitable for the plastic material

    Infrared de-burring

    • Comparable to hot-air de-burring, but an infrared heat source is used for heating instead of hot air

    Rumbling

    • Treating the parts together with abrasives in rotating/vibrating machines

Most common errors

  • Surface has started to melt

    • Blunt tool
    • Insufficient lateral play/clearance
    • Insufficient coolant feed

    Rough surface

    • Feed rate too high
    • Tool unprofessionally sharpened
    • Cutting edge not honed

    Spiral marks

    • Tool friction during withdrawal
    • Burr on the tool

    Concave and convex surfaces

    • Point angle too great
    • Tool not vertical relative to the spindle
    • Tool is deflected
    • Feed rate too high
    • Too mounted above or below the centre

    "Stumps" or burr at the end of the cutting surface

    • Point angle not large enough
    • Blunt tool
    • Feed rate too high

    Burr on the outside diameter

    • Blunt tool
    • No space in front of the cutting diameter
  • Surface has started to melt 

    • Blunt tool or shoulder friction
    • Insufficient lateral play/clearance
    • Feed rate too low
    • Spindle speed too high

    Rough surface

    • Feed rate too high
    • Incorrect clearance
    • Sharp point at the tool (slight radius on point of milling cutter required)
    • Tool not centrally mounted

    Burr on corners of cutting edge 

    • No space in front of the cutting diameter
    • Blunt tool
    • Insufficient lateral play/clearance
    • No lead angle at the tool

    Cracks or flaking at the corners

    • Excessively positive inclination at the tool
    • Tools not sufficiently run-in (action of tool is too hard on the material)
    • Blunt tool
    • Tool mounted below the centre
    • Sharp point at the tool (slight radius on point of milling cutter required)

    Chatter marks 

    • Excessive radius on point of milling cutter at the tool
    • Tool not mounted firmly enough
    • Insufficient material guidance
    • Cutting edge width too large (use 2 cuts)
  • Tapered drill holes

    Possible causes:

    • Incorrectly sharpened drill bits
    • Insufficient play/clearance
    • Feed rate too high

    Burnt or melted surface

    Possible causes:

    • Use of unsuitable drill bits
    • Incorrectly sharpened drill bits
    • Feed rate too low
    • Blunt drill bit
    • Land too thick

    Surface splitting

    Possible causes:

    • Feed rate to high
    • Excessive play/clearance
    • Excessive incline (thin land as described)

    Chatter marks

    Possible causes:

    • Excessive play/clearance
    • Feed rate too low
    • Drill overhang too great
    • Excessive incline (thin land as described)

    Feed marks or spiral lines at the inside diameter

    Possible causes:

    • Feed rate too high
    • Drill not centred
    • Drill tip not in centre

    Over-dimensioned drill holes

    Possible causes:

    • Drill tip not in centre
    • Land too thick
    • Insufficient play/clearance
    • Feed rate too high
    • Drill point angle too great

    Under-dimensioned drill holes

    Possible causes:

    • Blunt drill bit
    • Excessive play/clearance
    • Drill point angle too small

    Nonconcentric drill holes

    Possible causes:

    • Feed rate too high
    • Spindle speed too low
    • Drill penetrates too far into next part
    • Parting off tool leaves "stump" which deflects the drill bit
    • Land too thick
    • Drilling speed initially too high
    • Drill not clamped centrally
    • Drill not correctly sharpened

    Burr left after parting off

    Possible causes:

    • Blunt cutting tools
    • Drill does not travel completely through the part

    Drill quickly becomes blunt

    Possible causes:

    • Feed rate too low
    • Spindle speed too low
    • Insufficient lubrication due to cooling

Processing

  • When machining carbon-fibre and glass fibre reinforced plastics the following factors should be observed:

    Tooling

    • Use hardened steel tools (carbide steel K20), or ideally polycrystalline diamond tooling (PCD)
    • Use very well sharpened tools
    • Regular control checks of tools, due to the abrasive effects of the materials

    Clamping semi-finished goods

    • Clamp in the extrusion direction (highest compression strength)
    • Use the lowest possible pressure

    Pre-heating

    • Pre heating of semi finished goods may be recommended for their further processing

    Processing

    • Even fly ccutting of the bilateral edge zones of the semi finished part:
      • Ideally, each fly-cutting process should have a max. cutting depth of 0.5 mm
      • Results in more homogenous distribution of stress in the semi-finished part
      • Leads to a higher quality of the component
  • Semi-crystalline, unreinforced materials TECAFORM AH / AD natural, TECAPET white and TECAPEEK natural  are very dimensionally stable materials with balanced mechanical properties. These materials are very easy to machine and tend to produce short chips. They can be machined with very high delivery and high feed rates.

    However, it is important to ensure a low heat input as far as possible, as TECAFORM and TECAPET in particular have a high tendency to undergo post-shrinkage by up to approx. 2.5 %. Warping can occur due to local overheating. In the case of the materials mentioned above, very low surface roughness can be achieved with optimised machining parameters.

  • Polyamides such as TECAST T natural, TECAMID 6 natural and TECAMID 66 natural, tend to have have naturally very brittle characteristics – this may also be referred to in the context of a "freshly moulded" condition. Due to their chemical structure, the polyamides tend, however, to absorb moisture - this property gives the polyamides their very good balance between toughness and strength.

    The moisture uptake via the surface, leads to a virtually constant distribution of water content over the entire cross section with small semi-finished dimensions and components. In the case of larger dimensioned semi finished goods, (in particular for round rods / sheets of 100 mm diameter / wall thickness upwards) the moisture content decreases from the outside inwards.

    In the most unfavourable case, the centre is of a brittle and hard character. Added to the internal tension produced by extrusion technology, machining can carry a certain risk of producing tension cracking.

    In addition, it should be remembered that as a consequence moisture uptake can change the dimensions of the material. This "swelling" has to be allowed for in the processing and design of components made of polyamide. The moisture uptake (conditioning) of semi-finished goods plays an important part in the case of machining. Especially thin walled components (up to ~10 mm) can absorb up to 3% moisture. As a rule of thumb:

    A moisture uptake of 3% causes a dimensional change of about 0.5%!

    Machining of TECAST T natural:

    • Tends to produce short chips
    • Is therefore good to machine

    Machining of TECAMID 6 natural and TECAMID 66 natural:

    • Form a flow of chips
    • More frequent removal of chips from the tool/work-piece can be necessary
    • Important in order to generate chips which break off when they are very short and to avoid breakdowns in the process:
      • Ideal machining parameters
      • Choice of suitable tools

    Generally speaking, we recommend pre-heating to 80 – 120°C with larger dimensioned work pieces (e.g. round rods > 100 mm and sheets with a wall thickness > 80 mm) and machining close to the centre, in order to avoid tension cracking during processing.

  • TECANAT, TECASON, TECAPEI are amorphous materials, which are very prone to develop stress cracking due to contact with aggressive media, such as oils and fats. Also, cooling lubricants often contain media which can trigger tension in the material. The use of cooling lubricants should therefore be avoided when machining these materials as far as possible or a water based medium should be used, for example.

    Similarly, material specific machining parameters should be used as much as possible

    • Do not use feed rates which are too high
    • Avoid the use of high pressures
    • Avoid excessively high tension
    • Preferably select a higher rotational speed
    • Use sufficiently sharp tools

     

    Points to be observed with construction designs

    • Construction designs should be adapted to match amorphous materials
    • Avoid shear forces (constructive and in processing)
    • Design edges/geometries according to the type of material (preferably choose inner edges which are slightly rounded)

    The materials can be used to manufacture very dimensionally stable prefabricated parts with very narrow tolerances, taking suitable machining parameters into account.

  • Materials containing a PTFE component (e.g. TECAFLON PTFE, TECAPEEK TF, TECAPEEK PVX, TECATRON PVX, TECAPET TF, TECAFORM AD AF) frequently exhibit slightly lower mechanical strength.

    Due to this PTFE content, several aspects should be taken into consideration when processing:

    • Materials tend to lag behind the milling tool
      • There is a distinct increase in surface roughness (hair formation, spikes, rough surface)
    • Avoid re-cutting with the milling machine
      • Also leads to rougher surfaces
    • A further "re-cutting process" may be necessary in order to smooth spikes to the desired surface quality
    • De-burring is also often necessary
  • The TECASINT product groups 1000, 2000, 3000, 4000 and 5000 can be processed dry or wet with standard metal working machinery.

    Tools

    • Use fully hardened metal tools
    • Tools with a cutting angle as used for aluminium processing are very suitable
    • For highly filled TECASINT products with glass fibres and glass beads, use tools fitted with diamond or ceramic tips

     Processing

    • High cutting speeds and low feed rates coupled with dry machining improve results
    • Wet processing increases the cutting pressure and promotes the formation of burrs, but is recommended to extend tool life
    • Synchronous milling prevents chipping and cavities
    • Intermediate tempering is normally not necessary

    Due to the increased tendency of polyimides to absorb moisture, it is advisable to seal these parts with a vacuum barrier film to avoid dimensional changes to ensure very high quality and should be opened just before use.

  • TECATEC is a composite based on a polyaryletherketone filled with 50 and/or 60 % carbon fibre fabric. Machining TECATEC is considerably more complex than machining short fibre reinforced products. Due to the layer structure of the material, incorrect machining can have different effects:

    • Edge chipping
    • Delamination
    • Fringing
    • Breaking through of fibres

    For this reason, specific processing is required for such material. This has to be established on a case-by-case basis, depending on the component in question.

    Design of semi-finished goods

    The suitability of TECATEC for a certain application and the quality of the finished part depend primarily on the position of the component in the semi finished part. In the development phase, it is important that the directionality of the fibre fabric is considered, especially with regard to the type of load (pulling, compression, bending) on the application and subsequent machine processing.

    Machining tools and tooling materials

    For higher standing times in comparison to HSS or carbide steel tools, we recommend the use of

    • PCD tools (polycrystalline diamond)
    • Ceramic tools
    • Titanium coated tools
    • Tools with functional coatings (plasma technology)

    In addition to higher standing times, these tools help to minimise the feed forces when the specific material is also considered in the design.

    • Select a moderate cutting sharpness
    • Establish a good balance between surface quality (with very sharp blades) and tooling standing times (blunter cutting blades)
    • Design milling geometries so that the fibres are cut, otherwise there is a danger of fibre fringing
    • Due to the higher abrasiveness of the carbon fibres, regular changing of the TECATEC tools is necessary
      • Avoid too much heat input and warping due to blunt tools

    Machining

    • There is a greater risk of chipping and burr formation during the machining process if the fibres run parallel to the woven fabric than if processing is transverse to the woven fabric
    • For narrower tolerances, components can also be tempered several times during the manufacturing process
    • Due to the higher fibre content, good heat distribution in the work piece can be expected. For this reason, we recommend that the material should be dry machined

    Machining and tooling parameters

    We recommend paying attention to the following parameters:

    • Avoid using high feed forces
    • Very high point angles (150 – 180°)
    • Very low feed rates (approx. < 0.05 mm/min>
    • High cutting rates (approx. 300 – 400 mm/min)

    This information is intended to provide initial assistance in the machining of TECATEC. Detailed information varies, depending on the individual case.

Purchase and delivery

  • Our company gives great importance to the careful handling of customer complaints. In any case of a complaint, we thus endeavour to learn from our mistakes. We subject our products and processes to a critical review and carry out exhaustive testing. However, to ensure that we are able to draw the right conclusions from customer complaints, we rely on the support of the customer. It is important that we have all the relevant information at our disposal. In the case of complaints that are difficult to describe, a picture or sample part should ideally be provided for assessment. Please talk to us about the settlement of customer complaints.