On a recent CNC machining project, a customer’s drawing specified ESD PEEK. During our material review, we overlooked the ESD designation and ordered standard PEEK instead. The machining itself was not the problem. Even a dimensionally correct part would still be nonconforming because ordinary PEEK does not provide the required static-dissipative performance. Once we caught the mistake, we had to purchase the correct stock and machine the parts again.
The material quote made the cost impact clear. The specified grade was approximately RMB 1,500 per kilogram, or about $230/kg. Standard unfilled material was approximately RMB 500 per kilogram, or about $80/kg. The correct stock cost roughly three times as much, even before accounting for the first batch of material, machine time, and schedule delay.
ESD PEEK Is a Material Grade, Not a Note
Unfilled PEEK is a high-performance thermoplastic with excellent heat resistance, chemical resistance, and mechanical strength. It is also an electrical insulator.
Static-dissipative PEEK is electrically modified so accumulated charge can bleed away at a controlled rate. This function matters in semiconductor equipment, wafer-handling components, electronic test fixtures, and other static-sensitive applications.
| Item | Standard PEEK | ESD Grade |
|---|---|---|
| Electrical behavior | High resistance; typically used as an insulator | Controlled resistance for gradual charge dissipation |
| Material formulation | Unfilled PEEK resin | Electrically modified PEEK compound |
| Common applications | Structural, insulating, and high-temperature parts | Semiconductor fixtures, wafer-handling parts, and test equipment |
| Price in this project | About $80/kg | About $230/kg |
| Key acceptance criteria | Grade, dimensions, and mechanical properties | Grade, dimensions, and specified electrical performance |
Once the ESD designation appears on a drawing, it is part of the material requirement. The customer does not need to repeat it in an email or flag it separately. Leaving it out changes the material specification, even if every machined dimension is correct.
Cleaning or annealing a finished unfilled part will not turn it into a static-dissipative grade. An antistatic coating may change the surface behavior, but it does not replace the base material specified on the drawing.
The Material Price Was Only Part of the Loss
CNC material cost is based on the purchased blank, not the finished part weight. A blank includes saw allowance, workholding stock, and material that will eventually become chips. The price difference must therefore be calculated from the amount purchased.
In this project, the two materials differed by approximately $150 per kilogram. Using the wrong stock added several costs:
- The ordinary material already consumed;
- Programming, setup, and machine time from the first run;
- Purchasing the correct specialty grade;
- A second round of machining and inspection;
- Schedule delays caused by reordering and rescheduling.
A material check before cutting takes only a few minutes. Finding the error after machining can cost almost as much as producing the parts again.
The Drawing Still Needs a Specific Grade
Although ESD PEEK identifies the required function, it does not define one universal compound. Commercial grades can differ in surface resistance, volume resistivity, filler system, stiffness, thermal expansion, stock form, and available sizes.
Before purchasing material, the customer and manufacturer should confirm:
- The material manufacturer and full grade designation;
- Whether an equivalent grade is acceptable;
- The required surface or volume resistance range;
- The test method and test conditions;
- The required plate, rod, or tube size;
- Material certification and lot traceability requirements.
For PEEK machining, the callout must lead to an actual stock-shape grade available in the required size. When a drawing lists only a general ESD designation, the machine shop should confirm the missing details before ordering or cutting material. It should never substitute an unfilled grade without approval.
Dimensional Inspection Cannot Verify Electrical Performance
Calipers, micrometers, and a coordinate measuring machine can verify part geometry. They cannot determine whether a plastic part provides the required static-dissipative behavior.
Incoming inspection should compare the supplier’s label, lot number, material certificate, purchase order, and work order before the stock reaches a machine. Color may provide a visual clue, but it is not proof of the material grade.
When electrical performance is an acceptance requirement, the drawing or purchase order should state whether surface resistance, surface resistivity, or volume resistivity will be measured. It should also identify the test method and conditions. The finished part can then be tested against a defined requirement instead of relying only on the raw material label.
Material Prefixes and Suffixes Must Follow the Job
Designations such as ESD, GF30, and CF30 are not extra letters. They identify different PEEK grades, including static-dissipative, glass-filled, and carbon-fiber-filled formulations.
The complete material designation must move unchanged from the customer drawing to the quotation, material purchase order, work order, and inspection documents. Keeping only the base resin name removes information that may determine the part’s function.
The same rule applies to other specialty polymers, including bronze-filled PTFE. A change in filler or grade can affect price, physical properties, machining behavior, and inspection requirements.
A Simple Material Check Before Machining
A short verification process can prevent expensive rework:
- Copy the complete material designation from the drawing into the quotation.
- Confirm the exact grade and performance requirements when details are missing.
- Include the manufacturer, grade, stock size, and documentation on the purchase order.
- Match the received label and lot number to the order and material certificate.
- Complete a final material check before cutting the stock.
- Add an electrical test when the drawing specifies ESD performance.
This process is especially important for specialty engineering plastics, where a short grade code can change both the function and price of the material.
Conclusion
With ESD PEEK, three letters changed both the required function and the project cost. Overlooking them resulted in a roughly threefold raw material price difference and made the first machined parts unsuitable under the original drawing.
The practical rule is simple: treat every material prefix, suffix, and grade code as part of the engineering requirement. Confirm the full grade and electrical acceptance criteria before purchasing stock or starting the machine.
For prototype or low-volume plastic parts, send the complete drawing, material designation, quantity, and required test documentation with your RFQ. A material review before production is far less expensive than remaking finished parts.