PEEK parts processing ≠ ordinary plastic, these process misconceptions should be avoided

When PEEK parts are overturned during processing, the answer is often  "the machine tool is  good enough", but rather four things to consider first: whether the raw material has been dried, whether the stress has been removed cleanly, whether there are hard clamps during clamping,  whether the cooling has been oiled - all of which are processes before  after the machine is installed,  have little to do with the machine tool price. Engineers who specialize in robot dexterous hands  transmission components have been increasingly writing PEEK on their drawings in the past two years: lightweight, wear-resistant, self-lubricating, insulating,  its performance is truly impressive. But many teams turned over the car the first time they did it: when they got off the machine, they measured it to be qualified, but after two days, the distance between the holes floated; Thin walled components are properly clamped  will warp when released; Cutting quickly can cause the edges to turn white, stick to the blade,  become fuzzy  prickly. When we review CNC machining of engineering plastics, we usually ask each of these four things one by one,  after asking, we can basically determine how to connect this drawing.

1、 Four temperaments of choosing a factory based on materials first

The difficulty of PEEK lies in its material properties that are almost identical to precision machining. One is moisture absorption. The raw material will slowly absorb water,  after processing, the size will drift slowly with the water content - it is qualified after being taken off the machine but exceeds the tolerance the next day. Often, it is caused by moisture. Before being put on the machine, it needs to be dried in an oven,  the finished product should also be stored against moisture. The second is poor thermal conductivity. Cutting aluminum  steel, most of the cutting heat is carried away by chips  coolant; PEEK has slow thermal conductivity,  heat accumulates in the blade area. When the temperature is high, the material softens locally, resulting in white burrs on the surface  melting  sticking to the processed surface. The third is internal stress. The residual stress inside the extruded rod plate blank can be directly cut with a knife, releasing the stress imbalance  showing you the bending of the parts; Thin walled  large removal capacity parts are particularly obvious,  the blank needs to be stress relieved. After rough machining, there is still time to release it. The fourth is softness, elasticity,  flexibility. The elastic modulus is one order of magnitude lower than that of metal,  when the clamping force is slightly larger, it will deform under pressure. When cutting, the tool will rebound,  the size will be "clamped accurately  loosened".

By combining these four factors, PEEK precision components have become the type of activity that can most widen the gap between processing plants - the gap is  in the equipment price, but in the process details. Many suppliers are only good at metal cutting  do  establish separate drying, annealing,  air cooling processes for engineering plastics. They simply copy the logic of metal processing, which can easily lead to batch quality fluctuations.

2、 Rough processing: 90% rework, buried before startup

It is common for metal parts to be sawed off  directly fed onto the machine tool; PEEK works like this,  the rest is all about remediation.

The first step of drying: The raw material is fully dried in the oven according to the specifications,  the moisture content is reduced to eliminate this step. The evaporation of moisture will leave small pores near the grooves,  the size of the finished product will continue to change with moisture absorption. The second step is stress relief annealing: After forming  sawing, the internal stress of the bar plate is  small. Thin walled  thin plate parts should be treated once before rough machining. After removing the large excess during rough machining, a period of release time should be left before precision machining. When we review drawings, we often find that PEEK parts with tight cycles  the need for continuous rotation require the most rework - the stress release process, which cannot be waited for  urged. The third step is to identify the grade: the processing characteristics of pure PEEK, glass fiber reinforced (GF),  carbon fiber reinforced (CF-PEEK) differ greatly,  the rigidity  wear resistance of glass fiber  carbon fiber are added. However, the parameters  tool grade of the filler grinding tool need to be changed; Carbon fiber fillers also need to prevent delamination, improper feeding direction  clamping,  direct edge breakage. Cutting CF-PEEK with pure PEEK parameters is the most common mistake that new factories make.

Tip: When making outsourcing inquiries, you can confirm whether the supplier will include the drying  annealing processes in the formal process card, rather than randomly handling them based on the operator's experience.

3、 Clamping, cutting tools, cooling: none of them can simply copy metal experience

Clamp - keep the 'software'  deforming. Thin walled parts are clamped with pliers, which are circular when clamped  elliptical when loosened, which is the inevitable result of rebound. The mature approach is to increase the contact area  reduce the unit pressure: soft claws, contour supports,  vacuum suction cups are preferred over hard pressure plates,  the clamping force only needs to offset the cutting force, with any additional force being a source of deformation; The surface that can be clamped in one go will never be flipped over  aligned again.

Cutting tools - sharpness is the first principle. I would rather replace the knife than use a blunt knife to forcefully support it. A blunt knife is  used for cutting, but for squeezing  tearing, with high heat generation, whitening,  burrs; High speed, light  agile cutting, small cutting depth,  hot pressing the cutting below the softening temperature.

Cooling - mainly air cooling, do  apply oil. Directly pouring metal parts with emulsion is the most typical misconception: liquid infiltration  micropores causes moisture absorption, expansion,  residual pollution, debris mixed with oil stains sticks in the gaps,  the cleanliness for medical  semiconductor applications is directly inadequate. The standard practice is to use compressed air for chip blowing cooling, which  only removes chips but also controls temperature without leaving any pollution.

Common defect comparison  investigation:

4、 Tolerance marking: It is customary to require plastic parts when using steel parts, which is another form of waste

The size of PEEK is significantly affected by temperature  humidity,  the tolerance must follow the material. It is  advisable to directly move the steel part drawings. Key matching positions - bearing holes, locating pin holes, gear installation surfaces - tolerance tightening, key inspection; It is neither economical nor necessary to reasonably relax the non matching surface, with a full icon ± 0.01mm. Testing also needs to consider the status: it is best to place the parts in a constant temperature environment before placing them on the three coordinate system. When they are just taken off the machine, the cutting heat data may  match the assembly site; Batch inspection focuses on batch consistency, with full inspection of the first piece  random sampling of key dimensions during the process, which is more reliable than only conducting final inspection  selecting scrap products. The size of moving parts such as gears  sliders is  enough,  whether the movement is smooth  whether there is any abnormal noise  jamming after assembly needs to be verified by trial assembly. For projects with component level assembly requirements, priority should be given to confirming whether the outsourced factory has the conditions for simple trial assembly verification after the completion of the parts. Do  take all of them back to your own laboratory  discover assembly interference again.

5、 5 things to confirm before quoting

1. Material grade  filler. Pure PEEK, GF  CF-PEEK, different grades have completely different tool parameters,  the three words "PEEK" are  written clearly.

Who is responsible for the pre-processing of raw materials. Drying  stress relief annealing should be done by the processing plant  the material supplier,  the process record should be kept  . It should be agreed upon before starting work.

3. Cooling method. Whether to use air cooling  micro lubrication, it is strictly prohibited to pour emulsion for medical, semiconductor,  optical purposes,  it should be included in the process documents.

4. Tolerance  inspection status. What are the key fitting positions, how much tolerance is tightened, whether constant temperature placement is required for measurement,  whether the report is included with the goods.

5. Should we try to install  verify. Is there a component trial assembly process for gear  slider moving parts,  can the problem be reported  adjusted on the spot.

Common Misconceptions

The first misconception is to treat PEEK as a "harder plastic"  dry it according to metal habits. Emulsified liquid pouring, vise hard clamping, blunt knife slow walking - familiar actions on metal parts, each one is a defect source on PEEK,  a new set of processes must be started according to the rules of plastic.

The second misconception is to avoid drying  stress relief,  to urge continuous rotation. These two processes do  produce visible progress to the naked eye, but they are a prerequisite for dimensional stability; Nine out of ten percent of the parts that pass the shutdown but exceed the tolerance the next day are lost before the startup.

The third misconception is that the tolerance is as strict as the entire drawing,  the inspection only focuses on the final inspection. Full icon ± 0.01mm is neither economical nor necessary, tightening key positions  relaxing non matching surfaces are the right path; Without checking the constant temperature state  recording the batch trend, the "qualified" measured cannot be matched at the assembly site.

Frequently Asked Questions

Q: Can cutting fluid be used for PEEK parts processing?

A: It is  recommended to pour with oil  emulsion. PEEK can absorb moisture,  liquid cooling can cause size drift  residual pollution. It is particularly taboo for medical, semiconductor,  optical applications; The standard practice is to use compressed air to blow chips, combined with sharp cutting tools  lightweight temperature control parameters. Micro lubrication is a specific operating condition choice, but it is recommended to specify the cooling method in the process documents before placing bulk orders, so as  to allow the workshop to freely operate according to metal habits.

Q: Should we choose PEEK  metal for robot gears?

A: Observe the load conditions. Light load, medium low speed, self-lubricating, low-noise, weight reducing  insulated transmission - internal gears of dexterous hands, end transmission of collaborative robots, PEEK/CF-PEEK is more suitable than metal,  its weight is 40% to 70% lighter than aluminum parts; Steel  stainless steel gears are still used for heavy load, high torque,  high temperature conditions, relying on slow threading  gear grinding to ensure tooth profile. The selection of materials follows the force analysis  does  focus on a single material.

Q: What should I do if there is still a deviation when installing it after passing the inspection?

A: First check the detection status  timeliness: Did the parts cool down  remain at a constant temperature during coordinate measurement? Has the rough material been dried to relieve stress? These two items were  controlled,  what was measured was' false qualification '. Recheck the assembly fit: PEEK  metal mixed materials have a large difference in thermal expansion coefficient,  the gap will change after temperature changes. Compensation should be left in the design stage. The sequence is to first solidify the process (drying, stress relief, air cooling, light clamping),  then discuss tightening the tolerance.

Q: What are the differences to pay attention to when processing CF-PEEK  pure PEEK?

A: After filling with carbon fiber, the rigidity  wear resistance improve, but when the filler grinds the cutting tool, the service life is significantly shortened,  the parameters need to be replaced as a whole; The greater risk is delamination,  the feeding direction  clamping are  correct  the edges collapse directly. When quoting, the brand name should be written in full,  the cutting tools  cutting strategies for carbon fiber parts should be separately listed in the process documents. Pure PEEK parameters cannot be used universally.

Q: What kind of supplier is suitable for undertaking PEEK projects?

A: Robot dexterous hands, transmission gears, insulation parts, PEEK parts in medical  semiconductor equipment can be connected  single piece sampling to small batch production. Pure PEEK, GF, CF-PEEK all need corresponding processes; It is best for outsourcing factories to provide hardware component services that integrate design, intelligent manufacturing,  assembly,  can do component trial assembly  component level delivery. Software, algorithms,  controls are led by the customer, while outsourcing service providers only provide hardware collaboration  do  manufacture complete machines.

Summary

The difference in PEEK parts processing is  in the machine tool price, but in the four processes before  after the machine: blank drying to relieve stress, clamping with light pressure  soft support, sharp tool air cooling, tolerance detection  material processing. Writing these four things  the process card can basically eliminate most of them, with the phrase 'qualified after shutdown  out of tolerance the next day'. It is recommended to clarify the brand, key matching positions, cleanliness,  trial assembly requirements during the drawing stage of the R&D end. When conducting project reviews, align the pre-processing plan with the testing requirements before production - the cost of plastic parts is saved in the process,  in the materials. Welcome to provide drawing consultation. We can provide 2D drawings, 3D models,  technical requirements to obtain DFM process evaluation  itemized quotations.