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.

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.

Façade Creations has introduced a quality management system in accordance with DIN EN ISO 13485:2016 in many areas for the development, production and distribution of thermoplastics at our facilities. With this certified quality management system for medical technology, Façade Creations offers its customers additional security.

Due to strict documentation during the individual process steps, consistent traceability with regard to the products and the raw materials used is standard at Façade Creations. For plastic materials within our medical-grade standard portfolio, a declaration of conformity is issued on an order-related basis. This enables our customers to have clear traceability.

For medical-grade products, the aim is to keep the materials and the manufacturing process as unchanged as possible. In case of changes, high evaluation standards apply within the scope of our medical-grade change management, and customers are informed of relevant changes as early as possible with a change notification. The aim is always to provide equivalent products despite necessary adjustments.

Plastic materials within our medical-grade standard portfolio are tested according to ISO 10993 pursuant to their intended use, preferably on the product. They fulfil the requirements specified in the respective test. However, the evaluation of biocompatibility can also be completely adapted to the customer’s individual needs.

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 Façade Creations 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 sterilised as required.

Traceability is an important instrument for Façade Creations, 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, so 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, Façade Creations only issues certifications on an order-specific basis.

Our 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, our products also comply with specific directives such as FDA approval for raw materials and recognised national recommendations on the suitability of plastics for contact with food. A suitability statement is provided by our technical office with confirmation of the material listing.

Our products for the food industry are compliant with specific directives of FDA approval for raw material. Certificates in accordance with FDA requirements are issued by Façade Creations for stock shapes products intended for repeated contact with food. A suitability statement is provided by our 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, our semi-finished products are available with raw material compliance to relevant national drinking-water contact standards, such as those applicable in Germany, the UK and the USA. 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 broadly comparable across the main regional standards, 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.

Façade Creations offers a variety of biocompatible materials with different sterilisation capabilities for products ranging from medical devices to short-term implants. The biocompatibility of our medical materials and products is certified in accordance with:

• ISO 10993
• USP Class VI

Our 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 team 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, which has been replaced by the European standard EN 45545 on requirements for fire behaviour of materials and components for railway components.
• 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 Façade Creations semi-finished products are available which are compliant for use in highly demanding oil and gas applications according to NORSOK M-710, Edition 3. Testing was carried out at an independent, accredited materials testing laboratory, with test conditions chosen to satisfy the standard (NORSOK M-710, Ed. 3). A suitability statement is provided by our technical office with confirmation of the material listing.

Both applicable 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 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.

Façade Creations, 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, together with an efficient compliance management department, ensures that in each individual case, according to customer requirements, our semi-finished products can be supplied which are compliant with recognised standards, including:

• Material data sheets
• Aviation standards

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

• ASTM
• Military specification standards
• Federal specification standards
• FAR 25.853
• UL 94-V0
• Space agency material outgassing standards (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 applicable types of test certifications in accordance with EN 10204.

In our own laboratories, Façade Creations has a range of resources for determining material characteristics, which can also be performed as part of a works test certificate 3.1 in accordance with DIN EN ISO 10204. 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.

Façade Creations’ 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”. Façade Creations is therefore reliant upon information from its raw material suppliers. Downstream users such as our Stock Shapes division are not obliged to carry out tests or register their products in accordance with the REACH regulation.

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.
• The effects of high-energy radiation, such as gamma or X-rays, should be avoided wherever possible, due to possible microstructural damage from 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.

All variations of the following material families should generally be protected against weather influence:

• PEEK
• PPS
• PPSU
• PSU
• PES
• ABS

Variants not dyed black should be additionally protected:

• Acetal (POM-C, POM-H)
• PET
• Polyamide (PA 6, 66, 11, 12, 46)
• Cast nylon (PA 6 C)
• 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

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 and define their own limits for admissible contamination. FDA and EU guidelines define directives and regulations on the migration of substances into products, but not on the degree of surface cleanliness.

At Façade Creations:

• Biocompatibility tests are performed on semi-finished products for the medical technology sector, providing 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.
• We work in compliance with GMP regulations for the food sector.
• Limiting values for admissible cleanliness are defined 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 shaped-part geometry, size and material. Common welding techniques used for processing plastics include:

• 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 include:

• 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

Our technical team can provide general adhesive recommendations tailored to your specific material and application on request.

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)

Façade Creations 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. Various factors can influence the dimensional stability of a component.

Moisture uptake:

• Plastics with lower moisture uptake are generally much more dimensionally stable – for example, acetal (POM-C/POM-H), PET, PPS and PEEK grades.
• Plastics with high levels of moisture uptake exhibit a marked influence on dimensional stability – for example, polyamide and cast nylon grades. 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 include:

• 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 (simultaneous cooling and removal of chips from the working area), water-soluble coolants, or commercially available drilling emulsions and cutting oils. Spray mist and compressed air are very effective methods.

Machining amorphous plastics:

• Avoid using coolants for materials liable to develop stress cracking.
• If cooling is imperative, parts should be rinsed in pure water or isopropanol immediately after machining, and suitable coolants such as pure water, compressed air, or special lubricants should be used (your lubricant supplier can advise on suitable options).

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); the 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.

Façade Creations’ 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, but 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, followed by a holding period whose length depends on the material and its thickness, in order to thoroughly heat through the moulded part. The material then 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, which can act as 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. Care should be taken to ensure 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, whether during annealing, machining (frictional heat), or use (service temperature, hot steam sterilisation).

Semi-crystalline plastics:

• The annealing process leads to equalisation of material properties: increase in crystallinity, optimisation of mechanical properties, improved dimensional stability, and better chemical resistance.
• Machining can lead to localised overheating through frictional heat, resulting in microstructural changes and post-shrinkage. Acetal (POM) materials in particular are critical in this respect, as improper machining can lead to severe deformation and/or warping of the component.

Amorphous plastics are generally 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 and excessive thermal build-up, and 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 to achieve good chip deflection, avoid sticking of the saw blade, avoid overheating of the plastic in the saw cut, and produce a good cutting edge quality.

Recommendations:

• Use a corresponding tensioning device to avoid vibrations and unclean cutting edges, which can result in 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, giving an optimal, groove-less surface and reducing 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, to stabilise the component and avoid deformation – this gives good cooling of the material and overcomes flow chipping, preventing 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) to reduce friction and avoid a build-up of heat.

Recommendations: use a coolant; withdraw the drill frequently 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.

Drilling small diameter holes (< 25 mm):

• Use high speed steel (HSS) drills, with a spiral drill.
• Twist angle of 12–25° gives very smooth spiral grooves and favours chip deflection.
• Frequent removal of the drill (intermittent drilling) improves removal of chips and avoids thermal build-up.
• For thin-walled components, use high cutting rates and, if possible, a neutral (0°) chipping angle to avoid the drill catching in the component.

Drilling large diameter holes (> 25 mm):

• Carry out trial drilling with large drill holes.
• Select a pre-drilling diameter no larger than 25 mm.
• Carry out finishing subsequently with an inner cutting chisel.
• Introduce drilling into long rod sections only from one side, since drilling attempts which meet in the middle (bilateral drilling) can produce unfavourable stress characteristics, or even tearing.
• In extreme cases, or with reinforced materials, it may be advisable to carry out 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 offer optimised cutting performance and 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 workpieces 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, by contrast, involves the surface being processed using a milling head. Both processes are well-suited to producing even and/or equalised surfaces on semi-finished goods, though the resulting surface structure and gloss differ between the two.

Façade Creations’ cutting service can offer both planed and plane-milled semi-finished goods. Sheets over 600 mm can only be processed using the plane milling process; sheets under 600 mm can be processed using either process, with small cuts typically 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; dies 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.

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, and the roundness/straightness of the semi-finished goods. Particularly decisive working parameters are cutting speed, forward rate of advance, delivery, and 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.

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.

Tools: tools suitable for plastics must be used, always well-sharpened and smooth. 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 (our semi-finished goods 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 workpiece 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), and use suitable coolants.

Recommendations: minimise stress pressure, which can result in deformation and impression marks on the workpiece; select suitable parameters for the machining process; keep to a moderate feed rate; select a high cutting speed; ensure good removal of chips to prevent tool congestion; ensure chip removal is equal on all sides to prevent warping.

Typical de-burring methods for engineering plastics include:

• Manual de-burring – the most common method; flexible but the most work-intensive solution; allows simultaneous visual control of the component.
• Jet de-burring – a jet of abrasive material at high pressure is used on the surface of the component (common blasting methods: sand, glass beads, soda, dry-ice and nutshell blasting); 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 include liquid oxygen, liquid carbon dioxide and dry-ice; low temperatures lead to brittleness and hardness of the materials.
• Flame de-burring – de-burring using an open flame; caution is needed, as damage may be caused to the component due to excessive heat.
• Hot-air de-burring – the burr melts under the influence of heat; a very safe and well-controllable process that avoids damage or warping when process management suitable for the plastic material is used.
• 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.

• 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 (a slight radius on the point of the milling cutter is 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, blunt tool, tool mounted below the centre, sharp point at the tool.
• Chatter marks: excessive radius on the point of the milling cutter, tool not mounted firmly enough, insufficient material guidance, cutting edge width too large (use two cuts).

• Tapered drill holes: incorrectly sharpened drill bits, insufficient play/clearance, feed rate too high.
• Burnt or melted surface: use of unsuitable drill bits, incorrectly sharpened drill bits, feed rate too low, blunt drill bit, land too thick.
• Surface splitting: feed rate too high, excessive play/clearance, excessive incline.
• Chatter marks: excessive play/clearance, feed rate too low, drill overhang too great, excessive incline.
• Feed marks or spiral lines at the inside diameter: feed rate too high, drill not centred, drill tip not in centre.
• Over-dimensioned drill holes: drill tip not in centre, land too thick, insufficient play/clearance, feed rate too high, drill point angle too great.
• Under-dimensioned drill holes: blunt drill bit, excessive play/clearance, drill point angle too small.
• Nonconcentric drill holes: feed rate too high, spindle speed too low, drill penetrates too far into next part, parting-off tool leaves a “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: blunt cutting tools, drill does not travel completely through the part.
• Drill quickly becomes blunt: feed rate too low, spindle speed too low, insufficient lubrication due to cooling.

Semi-crystalline, unreinforced materials such as natural-coloured acetal (POM-C/POM-H), natural-coloured PET and natural-coloured PEEK 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 low heat input as far as possible, as acetal and PET materials, in particular, have a high tendency to undergo post-shrinkage of up to approximately 2.5%. Warping can occur due to local overheating. With these materials, very low surface roughness can be achieved with optimised machining parameters.

Unreinforced polyamides – including natural-coloured cast nylon and natural-coloured PA6/PA66 grades – tend to have naturally very brittle characteristics, particularly in a “freshly moulded” condition. Due to their chemical structure, polyamides tend to absorb moisture; this property gives them their very good balance between toughness and strength.

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. With larger-dimensioned semi-finished goods (particularly 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, and added to the internal tension produced by extrusion technology, machining can carry a certain risk of producing tension cracking.

Moisture uptake can also change the dimensions of the material – this “swelling” has to be allowed for in the processing and design of polyamide components. 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%.

Cast nylon grades tend to produce short chips and are therefore good to machine. PA6 and PA66 grades form a flow of chips, and more frequent removal of chips from the tool/workpiece may be necessary, along with ideal machining parameters and the choice of suitable tools, in order to generate chips which break off when very short and to avoid breakdowns in the process. We generally recommend pre-heating to 80–120°C with larger-dimensioned workpieces (e.g. round rods over 100 mm and sheets with a wall thickness over 80 mm), and machining close to the centre, in order to avoid tension cracking during processing.

Amorphous materials such as polycarbonate, PSU/PPSU and PEI are very prone to develop stress cracking due to contact with aggressive media, such as oils and fats. Cooling lubricants often contain media which can trigger tension in the material, so the use of cooling lubricants should be avoided when machining these materials as far as possible, or a water-based medium should be used instead.

Material-specific machining parameters should be used wherever 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.

Construction design considerations: 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). These 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 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, leading to a distinct increase in surface roughness (hair formation, spikes, rough surface).
• Avoid re-cutting with the milling machine, as this 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.

Our sintered polyimide product groups 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 grades containing 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 and ensure very high quality; the film should be opened just before use.

Our carbon-fibre-reinforced polyaryletherketone composite materials, filled with 50% or 60% carbon fibre fabric, are considerably more complex to machine than short-fibre-reinforced products. Due to the layer structure of the material, incorrect machining can have different effects, including edge chipping, delamination, fringing, and breaking through of fibres. For this reason, specific processing is required for such material, established on a case-by-case basis depending on the component in question.

Design of semi-finished goods: the suitability of the material for a certain application, and the quality of the finished part, depend primarily on the position of the component in the semi-finished part. During the development phase, it is important to consider the directionality of the fibre fabric, 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 compared with HSS or carbide steel tools, we recommend the use of PCD tools (polycrystalline diamond), ceramic tools, titanium-coated tools, or 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 carbon fibres, regular changing of tools is necessary, avoiding 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 workpiece can be expected, so we recommend dry machining.

Machining and tooling parameters: avoid using high feed forces; use very high point angles (150–180°); use very low feed rates (approx. < 0.05 mm/min); use high cutting rates (approx. 300–400 mm/min).

This information provides initial guidance only; detailed parameters vary depending on the individual case, and our technical team is happy to advise.