PEEKprocessing technology

1. Shrink molding

In compression molding, plastic material is heated and placed into a mold core. The mold is closed under pressure and heated. After the part is cold, it is removed from the mold and deburred. This process is very suitable for high polymer, and it is necessary to use PEEK to produce standard manufacturing methods for parts. Parts manufactured by reduction molding have better surface smoothness. The setting time is very fast and the setting cost is low.

2. Injection molding

Injection molding is one of the more common processing methods for plastic parts, including PEEK. In injection molding, molten plastic is introduced (forced) into the mold under high pressure. After cooling and setting, the part (or parts) are removed from the mold. Minimal post-processing is required, generally by pruning burrs and unnecessary plastics. Injection molding can be used for thin-walled parts and can produce intricate parts with fine details. Injection molding parts have good surface smoothness and excellent processing accuracy. From a production standpoint, the benefits include high productivity and high labor costs.

3. Extrusion

Extrusion is used to make polymer components with stable cross-sections, including tubes. This is another common machining process for PEEK parts. The heated plastic passes through an open mold under high pressure. Product cost is usually low, setup time is quick, and initial cost is low.

4. Centrifugal molding

In squeeze casting (sometimes called rotomolding, centrifugal molding, or rotomolding), molten composite material, such as PEEK, is placed into a mold and sealed. The mold and polymer are heated to the point where the polymer is liquid. The mold then rotates on each axis. The centripetal force co-distributes the polymer on the inner surface of the mold. This manufacturing method can be used to create intricate hollow parts with thick walls and very low residual stress. It applies reinforcing fibers. Centrifugal molding gives excellent surface smoothness at limited resource tooling costs. It is especially suitable for short-term or long-term production operations.

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What are the factors affecting PEEK processing?

1. Machinery and equipment: standardize plastic machines

Machines for PEEK injection molding: PEEK can be molded on the required plastic machines provided by most famous equipment suppliers. Depending on the type of PEEK you are molding, the processing temperature for the plastic machine barrel will be somewhere between 350-400?C. Most standard injection molding machines can reach the above temperature without retrofitting. If it is necessary to carry out the renovation of the heating device, it is often necessary to improve the injection molding process of the comprehensive electric heating coil or thermal resistance / control board. It is recommended to use a ceramic heating ring because of its higher heating consistency. In addition, you can also try to use heat-resistant insulation materials to insulate the barrel, thereby saving energy costs. The universal screw is suitable for PEEK injection molding. Copper and alloy raw materials should be used as much as possible (in contact with the melt). All metal components should be smooth and relatively highly polished to avoid material dissolution due to long-term retention of the equipment in the barrel.

2. The necessity of drying PEEK raw materials

Related Dry PEEK Raw Materials: PEEK powder should generally be dry but absorbs moisture from the air. It is recommended to place the powder in the tray in a basic drying box and dry it at 150-160¡ãC for 2-3 hours, and continuous drying can be considered. The aim should be to reduce the residual moisture content to <0.02%. Dehumidification or hot air dryers can also be used, and must be able to maintain a leak point or saturation temperature of -40¡ãC.

3. Cleanliness is the key

When dealing with PEEK injection molding products, it is necessary to prevent environmental pollution. Most other polymers can dissolve under the processing temperature of PEEK, so a clean drying oven and feeding system must be used. Before processing PEEK for injection molding, the screw and barrel should be cleaned properly and efficiently to ensure that the system environment is clean and free of other material residues. Recycled materials may be the main source of environmental pollution, ensuring that PEEK raw materials will not be polluted by other materials during operation. It is important to remember that any contaminants that are inadvertently drawn in during the entire injection molding process will cause small black spots to appear in the final PEEK injection molded part.

4. Gate design scheme

The large gate design is suitable for PEEK injection molding. The gate specification lies in the maximum thickness of the part, the number of dies and the geometry of the part. PEEK is a semi-crystalline polymer with better shrinkage than amorphous thermosetting plastics. In addition, the direction of the cooling gradient at higher processing temperatures tends to cause more shrinkage compared to polymers processed at lower temperatures. Try to use a larger gate design to achieve a better feeding effect. At Victrex, there is a universal standard that the gate is 2/3 thinner than the larger cross-sectional thickness of the injection molded part. According to the type of PEEK you want to mold, the minimum gate value of unfilled PEEK is 1mm, and the minimum gate value of filled PEEK is 2mm. The gate design types of general injection molding products are generally applicable to PEEK injection molding parts. You can choose to use the submerged gate for the appearance design of thick-walled or small component products, but this type of gate is not suitable for injection molding of components with relatively large thickness, because this type of gate is easy to produce gates in advance Freezing and cleaning will affect the subsequent feeding effect of thick-walled pipe products.

5. Temperature control

Carry out better temperature control on the mold. Mold temperature is very important to obtain semi-crystalline product workpieces that take advantage of the unique properties of PEEK.

Problems needing attention in PEEK processing

1. Choose the CNC blade that suits you

PEEK raw materials have the advantages of continuous high temperature, high toughness, and high toughness, so you should choose a suitable CNC blade that is wear-resistant and heat-resistant during processing. At the same time, pay attention to the cutting edge geometry and drilling angle of the CNC blade to ensure the processing efficiency and the quality of the finished product.

2. Control processing parameters

When processing PEEK, it is necessary to control the main processing parameters, including feed rate, speed ratio, tool feed rate, etc. Too many or too small processing parameters may affect the processing efficiency and finished product quality. At the same time, attention should be paid to cleaning the drilling area immediately to avoid defects such as thermal cracks in the PEEK equipment during processing.

3. Scientific design of fixtures

Scientific and reasonable fixture design can ensure the reliability of machining accuracy of tooth-shaped parts. In PEEK processing, attention should be paid to the fixing and clamping method of the parts by the fixture to prevent many problems such as movement during the deformation process of the parts.

4. Maintain a stable processing environment

PEEK raw materials have high requirements on the environment, and the temperature and humidity in the processing environment must be kept stable. At the same time, it prevents many problems such as electrostatic induction during processing, and ensures the reliability and safety of processing quality.

5 Quenching

Annealing is a kind of processing technology to be carried out in PEEK processing, which is used to release the stress and reduce the probability of dry cracking of the stress surface of PEEK raw materials in the processing process. Quenched PEEK is nearly impossible to deform. Depending on the time required for curing, several quenching steps may be required.

6. Cutting machine

In many cases, silicon nitride CNC inserts are suitable for machining PEEK. If PEEK is added to carbon fiber material for enhancement, or if you want to be particularly strict with dimensional tolerances, you should use diamond tools. It also prevents pollution if the cutting machine used does not use metal materials.

7. Refrigeration

PEEK does not have an exothermic reaction, and it must be refrigerated during processing to avoid deformation and cracking. Except medical components, standard liquid coolant can be used. For medical components, PEEK raw materials must be refrigerated with compressed gas, because the liquid coolant will affect the compatibility of PEEK.

8. Punch

The tensile properties of PEEK are smaller than other plastics, so deep drilling will also cause gaps.