Why is automatic test equipment useful for connector force testing in a cleanroom?
Motionwell Automation delivered a series of cleanroom-grade Automatic Test Equipment (ATE) machines for electronics manufacturers in Singapore. The ATE series performs mechanical and electrical testing of electronic components, connectors, and sensors within ISO Class 7/8 cleanroom conditions.
Manual insertion-force testing produces a spread that comes from the operator, not the part. Two technicians seating the same connector by hand will apply different approach angles and different rates, and the resulting force curves cannot be pooled into one capability study. Automating the handling removes that variable, and doing it inside the enclosure means the specimen never leaves the clean envelope between test steps. The same reasoning drives most cleanroom automation projects: the machine is built around the contamination boundary first and the test second.
Automated test equipment sits alongside the rest of Motionwell’s laboratory and test automation work, which covers sample handling, instrument integration and result capture for regulated environments.
How is the ATE built for ISO Class 7/8?
Cleanroom Integration
Each ATE machine is fully enclosed with 4-6 FFU (Fan Filter Unit) modules that maintain ISO Class 7/8 cleanroom conditions:
- HEPA-filtered air circulation within the test enclosure
- Positive pressure maintenance to prevent particle ingress
- Material selection compatible with cleanroom protocols
- Easy-clean surfaces for routine maintenance
Multi-Station Test Architecture
The ATE uses a circular transfer system with multiple test stations:
- Automated component loading via collaborative robot
- Sequential test execution across stations
- Real-time pressure and displacement monitoring
- Automated pass/fail sorting based on test limits
- Data logging in SPC-ready format
Cobot Loading System
A collaborative robot handles automatic loading and unloading of test specimens:
- Tray-based batch loading for high throughput
- Vision-guided pick-and-place for precise positioning
- Dual tray system for continuous operation (load while testing)
- Automatic sorting of tested parts by result
Because the cobot shares floor space with operators loading trays, the cell was assessed against the same collaborative-operation rules covered in our note on cobot safety standards rather than treated as a fenced industrial cell.
What are the headline machine specifications?
| Parameter | Specification |
|---|---|
| Cleanroom | ISO Class 7/8 (4-6 FFU units) |
| Transfer | Multi-station circular |
| Loading | Collaborative robot |
| Control | PLC + Siemens HMI |
| Data | SPC-ready logging |
| Tests | Force, fatigue, pressure, electrical |
How does the machine hold measurement repeatability over a long run?
Positioning and Repeatability
The cobot loading system achieves positioning repeatability of +/-0.05mm at the test fixture interface. This level of precision is necessary for connector insertion force testing, where even minor misalignment between the test probe and the connector housing introduces measurement error. The cobot’s tool center point is calibrated against a precision reference pin at the start of each production batch, with the calibration offset stored in the PLC for real-time compensation.
Jig and Fixture Materials
Test fixtures and specimen nests are machined from nylon (PA66) and POM (polyoxymethylene/acetal) engineering plastics. These materials serve dual purposes:
- Electrical insulation: Nylon and POM provide surface resistivity exceeding 10^12 ohm, preventing electrical interference with the device under test. This is essential for accurate resistance and continuity measurements on electronic connectors and sensors.
- Wear resistance: POM’s low friction coefficient (0.2-0.35) and dimensional stability ensure consistent specimen positioning over extended production runs. Unlike metallic fixtures, POM nests do not generate conductive particles that could contaminate the cleanroom environment or short-circuit test specimens.
Fixture changeover for different connector types uses a quick-change mounting system with dowel-pin alignment, enabling tool-free swaps in under 2 minutes.
Pneumatic System Architecture
The ATE machines use SMC and Festo pneumatic valve banks for actuator control throughout the test stations. Valve islands are centrally mounted within the machine enclosure, with individual solenoid valves controlling each pneumatic cylinder.
All pneumatic cylinders are equipped with magnetic reed switches for closed-loop position detection. The switches detect the piston’s extended and retracted positions, confirming that each actuation cycle completes fully before the PLC advances to the next test step. This prevents test sequence errors caused by incomplete cylinder strokes – for example, ensuring a connector is fully seated in the test socket before electrical measurements begin.
Air preparation units with filter-regulator-lubricator (FRL) assemblies maintain clean, dry air supply at each valve bank. Operating pressure is regulated to 0.4-0.6 MPa depending on the test force requirements.
SPC Data Export
The PLC logs all test measurements (force, displacement, resistance, continuity) in real-time and exports the data in SPC-ready format. Data can be filtered and exported by:
- Batch number: All test results from a single production batch grouped for statistical analysis
- Serial number: Individual device test history for traceability and warranty tracking
- Test parameter: Specific measurement types isolated for process capability studies (Cp/Cpk calculations)
Export formats include CSV for offline analysis and direct OPC-UA connectivity for real-time SPC charting on Siemens WinCC or equivalent SCADA platforms. Control limits and alarm thresholds are configurable per test parameter through the Siemens HMI interface. Where the customer wants the same data feeding a plant-level availability and quality metric, the logged pass/fail and cycle records map onto the calculation described in our explainer on what OEE actually measures.
Circular Belt Transfer with Pallet System
The multi-station test architecture uses a circular belt transfer system with a pallet-based workpiece carrier. Pallets circulate continuously around the loop, stopping at each test station via pneumatic stopper pins. Each pallet carries a single test specimen in a precision nest, maintaining the specimen’s orientation through all test stations.
The circular layout provides several advantages over linear transfer: pallets automatically return to the loading station after completing all tests, the cobot loads and unloads at a single station, and the system can buffer multiple pallets simultaneously to decouple station cycle times. Pallet identification uses RFID tags embedded in the pallet body, enabling the PLC to track each specimen’s position and test status throughout the loop.
The equipment class this build belongs to is set out on our automated test equipment and cleanroom automation equipment pages.
Constraints and trade-offs
Four decisions on this machine closed off other options, and each one cost something.
Circular pallet transfer instead of a linear line. A linear transfer would have let stations be added or removed without re-timing the loop. The circular layout was chosen because it returns every pallet to a single load/unload station, which means one cobot serves the whole machine and only one opening has to be made in the cleanroom enclosure. The price is that the station count is fixed by the loop geometry, so adding a test later means re-timing the whole ring rather than bolting a station onto the end.
A cobot rather than a hard-automation gantry. A dedicated gantry would be faster per cycle. With mixed connector types and modest volume per variant, the changeover cost dominates the cycle time, so the loading device had to be reprogrammable rather than quick. The cobot also fits the footprint an enclosed cleanroom cell can afford. What is given up is peak throughput on any single high-volume part number.
POM and nylon nests rather than machined aluminium. Metallic nests would be stiffer and cheaper to machine to tolerance. They were rejected on two counts that matter more here: metal fixtures shed conductive particles into a Class 7/8 envelope, and a conductive nest can short or load the device under test during continuity measurement. The trade-off is that engineering plastics creep under sustained clamping load and the nests are treated as consumables with a defined replacement interval.
Reed-switch position confirmation instead of timed sequencing. Advancing the sequence on a timer is simpler to program and slightly faster. Every cylinder here carries a magnetic reed switch so the PLC advances only on confirmed end-of-stroke, because a connector that is not fully seated still produces a plausible-looking force reading. The cost is more I/O, more wiring, and a machine that stops rather than guesses when a switch fails.
The one thing this platform does not do is functional electrical burn-in over long dwell times. The circular transfer decouples station cycle times only within a few seconds of each other; a test that needs minutes belongs on an offline rack, not in the ring.
Related work
This project showcases Motionwell’s robotics integration and custom machine design expertise for the electronics and semiconductor industry. The vision-guided handling and inspection logic is described in more depth on our machine vision inspection capability page, and a related high-mix build is documented in the SCARA vision-guided panel assembly case study.
If you are scoping a test cell and want to talk through station count, changeover time and data capture before drawings exist, send us the part and the test spec.