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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

• Preheating of semi-finished goods may be recommended for their further processing

PROCESSING

• Even fly cutting 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 a more homogenous distribution of stress in the semi-finished part
  • Leads to a higher quality of the component

Semi-cristalline, unreinforced materials – natural POM-C, PET white, and PEEK – are materials with consistent mechanical properties that are very dimensionally stable. These materials can be machined very easily and tend to produce short chips. They can be machined at very fast output speeds and high feed.

It is necessary to make sure as much as possible a low heat intake, however, because POM-C and PET – in particular – has a high propensity to experience post-shrinkage by up to approx. 2.5 Percent local overheating can cause Warping. With optimized machining parameters, very low surface roughness can be achieved for the above mentioned materials.

Polyamides such as natural PA6 and natural PA66 appear to have very delicate properties, obviously – this can also be alluded to in the sense of a "freshly molded" state. However, thanks to their chemical composition the polyamides appear to absorb moisture-this property gives the polyamides a very strong balance of strength and resilience.

The diffusion of moisture across the surface contributes to a nearly continuous spread of water content with limited semi-finished measurements and components over the entire cross-section.

For larger sized semi-finished goods (especially for round rods / sheets upwards of 100 mm diameter/wall thickness) the moisture content decreases from the outside inside.

The center is of a brittle and hard appearance in the most unfavorable case. In addition to internal tension generated by extrusion technology, machining can lead to an increased risk of tension cracking.

Furthermore, it should be noticed that the absorption of moisture can change the material dimensions as a consequence.

Throughout the manufacturing and construction of components made of polyamide, this "swelling" must be considered. In the case of machining, the moisture absorption (conditioning) of semi-finished products plays a large role. Particularly thin-wall components (up to ~10 mm) can absorb the moisture of up to 3 percent. The rule is:

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

Machining of PA6 natural and PA6 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.

General guidelines on the handling of semi-finished plastic items:

• In order to prevent deformation by their own intrinsic weight or warmth, they should always be stored flat or on appropriate support (in the case of rods and tubes) and with the greatest possible surface contact.
• In typical climatic conditions (23 ° C/50 percent relative humidity) the semi-finished goods should be processed in closed rooms where possible.
• Storage and processing can be performed in such a manner that the content designations and component numbers (batch number) on the semi-finished goods are easily visible and can be preserved. That enables items to be easily defined and traceable.

There are many factors to avoid when storing and handling plastics:

• The effects of weathering can affect the properties of plastics. As a result, solar radiation (UV radiation), atmospheric oxygen, and moisture (precipitation, moisture) can have a lasting negative impact on material properties
• Semi-finished goods should not be exposed to direct sunlight or the environmental consequences for sustained periods
• Plastics should not be subjected to extended periods of low temperatures. In fact, significant temperature variations should be avoided
• Items processed in cold temperatures should be given enough time before processing to acclimate to room temperature
• Sharp kicks, tossing or falling should be stopped, because there could be fractures and fracture damage
• Whenever practicable, limit the consequences of high-energy radiation such as gamma or X-rays owing to potential microstructural disruption related to the molecular breakdown
• Forms of plastic supplies should be kept separate from all kinds of chemicals and water to avoid potential chemical attacks or moisture absorption
• Plastic and other combustible items should not be placed together

There are various welding processes available that work either on noncontact basis (heating element, ultrasound, laser, infrared, 

gas convection welding) or through contact (friction, vibration welding). 

In order to ensure optimal relation, other design criteria have to be followed during the design phase, based on the procedure used. 

In the case of high-temperature plastics, it should be noted that the plastification of materials requires extremely high energy input. 

The welding method to be used depends on such factors; the geometry, size, and material of the shaped part. 

Common welding techniques employed in plastics processing 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)
• The 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 sandblasting (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.

There are many factors to avoid when storing and handling plastics:

• The effects of weathering can affect the properties of plastics. As a result, solar radiation (UV radiation), atmospheric oxygen, and moisture (precipitation, moisture) can have a lasting negative impact on material properties
• Semi-finished goods should not be exposed to direct sunlight or the environmental consequences for sustained periods
• Plastics should not be subjected to extended periods of low temperatures. In fact, significant temperature variations should be avoided
• Items processed in cold temperatures should be given enough time before processing to acclimate to room temperature
• Sharp kicks, tossing or falling should be stopped, because there could be fractures and fracture damage
• Whenever practicable, limit the consequences of high-energy radiation such as gamma or X-rays owing to potential microstructural disruption related to molecular breakdown
• Forms of plastic supplies should be kept separate from all kinds of chemicals and water to avoid potential chemical attacks or moisture absorption
• Plastic and other combustible items should not be placed together

Yes, you can check our Chemical Compatibility Chart for Plastics here. It shows the chemical resistance of the most common plastics against more than 1700 types of chemicals.

There are many factors to avoid when storing and handling plastics:

• The effects of weathering can affect the properties of plastics. As a result, solar radiation (UV radiation), atmospheric oxygen, and moisture (precipitation, moisture) can have a lasting negative impact on material properties
• Semi-finished goods should not be exposed to direct sunlight or the environmental consequences for sustained periods
• Plastics should not be subjected to extended periods of low temperatures. In fact, significant temperature variations should be avoided
• Items processed in cold temperatures should be given enough time before processing to acclimate to room temperature
• Sharp kicks, tossing or falling should be stopped, because there could be fractures and fracture damage
• Whenever practicable, limit the consequences of high-energy radiation such as gamma or X-rays owing to potential microstructural disruption related to the molecular breakdown
• Forms of plastic supplies should be kept separate from all kinds of chemicals and water to avoid potential chemical attacks or moisture absorption
• Plastic and other combustible items should not be placed together