Views: 0 Author: Site Editor Publish Time: 2026-10-19 Origin: Site
A part fits perfectly during assembly.
Why can its position drift after months in service?
Some issues do not show up during machining inspection. They emerge gradually after equipment has been running for a while. In precision equipment, meeting the drawing dimensions is only the starting point. Dimensional change in service matters just as much.
A semiconductor equipment project showed how this can happen. The part passed dimensional inspection, and assembly and initial testing went smoothly. After continuous operation, the wafer-handling mechanism began to show repeatability shifts, and the fit of some components changed.
The team checked machining accuracy, equipment structure and the control system, but found no obvious fault. Further analysis pointed to subtle dimensional changes in the part during use.
The components operated in a cleanroom and experienced temperature changes and frequent motion. Even small shifts could affect wafer positioning and assembly accuracy.
For precision equipment
Machining Accuracy + Dimensional Stability in Service
As equipment heats up and cools down, materials expand and contract. A higher coefficient of thermal expansion generally means a larger dimensional change under the same conditions. During thermal cycling, also check whether the part returns to its original dimensions at the reference temperature.
When plastic parts fit with metal shafts, ceramic components or other materials, their thermal expansion behavior can differ. Temperature changes may alter clearances and affect friction, positioning or sealing.
A part may meet its dimensions right after machining, then distort during storage or use as residual stress is released. Stock condition, machining parameters and any required post-treatment should all be considered.
Some engineering plastics absorb moisture and change dimensions. For humid or wet environments, water circulation or frequent cleaning, assess water absorption against actual service conditions.
For production runs, keep an eye on material condition and processing parameters across batches. Passing sample parts is only the start; shrinkage and process consistency need ongoing control.
Material selection is about more than heat resistance or strength. Thermal expansion, water absorption, residual stress, material structure and reinforcement can all affect dimensional performance.
CTE Coefficient of Thermal Expansion
How dimensions change with temperature
H2O Water Absorption
How moisture and media affect dimensions
σ Residual Stress
Effects of forming, machining and post-treatment
＋ Material Structure
Crystallinity and reinforcement type
When comparing values, match the specific grade and test conditions. Also consider mating parts, machining direction and critical tolerances.
PEEK / PEI / PSU / PI / PPS
Material Grade | Water Absorption (%) | Linear Thermal Expansion (×10⁻⁶/K) |
|---|---|---|
PEEK NA | 0.1 | 65 |
PEEK GF30 | 0.1 | 50 |
PEEK CF30 | 0.1 | 45 |
PEI NA | 0.4 | 65 |
PEI GF30 | 0.26 | 30 |
PSU NA | 0.3 | 60 |
PI NA | 0.3 | 42 |
PPS NA | 0.05 | 80 |
PPS GF40 | 0.05 | 45 |
Water absorption: 24-hour immersion in water at 23°C (ISO 62).
Linear thermal expansion unit: ×10⁻⁶/K (ISO 11359-2).
Source: Technical data supplied by the user.
✓ Temperature Minimum / maximum / cycling range
✓ Environment Humidity / contact media
✓ Precision Critical dimensions / fit tolerances
✓ Cycle Operating time / inspection conditions
Semiconductor equipment calls for cleanliness, low outgassing and dimensional stability. Precision machinery may prioritize wear, friction and fit. Sealing applications also need to account for temperature, media and long-term reliability.
JUTAI supports high-performance engineering plastics such as PEEK, PEI, PPS and PI, with material selection, stock shapes and precision machining.
For components with demanding dimensional requirements, we review temperature, media, precision and service life together, then assess the grade, stock condition and machining route. Samples can be validated against project requirements.
Define the Conditions
Temperature, media, precision and operating cycle
Match the Solution
Grade, stock condition and machining process
Validate a Sample
Check critical dimensions under intended conditions
If your component shows dimensional drift, a change in fit or positioning variation, share the service conditions and key tolerances. JUTAI can help assess both the material and the machining process.
