A bottom stop-motion pulley or roller is a mechanical part in a yarn-break or motion-stop assembly. It should not be specified as if it were the electronic stop-motion sensor. The sensor may be healthy while a worn pulley, loose shaft or contaminated running surface causes intermittent movement and unreliable response.
This checklist is for buyers preparing a circular knitting machine bottom stop motion pulley replacement supplier quote. It covers the measurements that determine fit, the alignment checks that protect the stop-motion mechanism and the acceptance evidence worth requesting from a supplier.
Mechanical Part or Sensor?
Start by separating the failure into mechanical and electrical evidence. A stop-motion system may include a pulley or roller, shaft, bracket, yarn-contact element, switch or sensor and a control circuit. If the pulley has a flat spot or excessive side play, replacing the sensor will not restore smooth motion. If the sensor signal is absent with a freely rotating pulley, a mechanical replacement alone will not solve the stop.
Record the symptom before removing the part:
- intermittent stop during normal yarn delivery;
- pulley that does not rotate when the yarn-contact element moves;
- visible flat spot, crack, burr or contamination;
- side play on the shaft;
- rubbing against a bracket or guard;
- delayed stop or nuisance stop after cleaning;
- mismatch between mechanical movement and the switch or sensor signal.
For comparison, the site’s yarn stop-motion sensor replacement checklist addresses voltage and signal compatibility. This article addresses the mechanical pulley or roller that transfers motion in the lower stop-motion assembly.
Dimensions to Put on the RFQ
A supplier quote should not rely on the phrase “bottom stop motion pulley” alone. Include a marked photograph and a dimensioned sketch with:
| Field | Measurement or evidence |
|---|---|
| Outside diameter | Measured on a clean unworn section |
| Width | Overall roller width and usable contact width |
| Bore or shaft fit | Shaft diameter, bore, key, pin or shoulder |
| Running surface | Smooth, grooved, crowned or textured |
| Material | Plastic, metal, rubber-coated or composite |
| Axial location | Spacers, washers, retaining clips and bracket position |
| Rotation | Direction, free-running torque and speed relationship |
| Assembly | Machine model, stop-motion position and part number |
If the old pulley is badly worn, use the mating shaft and bracket to reconstruct the nominal dimension. Photograph any spacer stack before disassembly. A replacement with the correct outside diameter but the wrong width can shift the yarn-contact path or rub against the bracket.
Alignment and Contact Path
The pulley must sit square to its shaft and must remain in the intended contact path. Check the bracket for distortion, the shaft for bending and the retaining hardware for looseness. The yarn or motion element should contact the centre of the running surface without climbing an edge.
During the RFQ stage, ask the supplier to confirm:
- concentricity or runout tolerance;
- shaft and bore tolerance;
- surface finish and allowable contamination;
- whether the pulley is supplied with a shaft, bearing, washer or clip;
- the correct axial position in the original assembly;
- whether the material is compatible with oil, lint and cleaning practice;
- whether a sample can be approved before the production quantity.
Do not infer a pulley’s quality from its colour or apparent smoothness. The acceptance criterion is stable movement in the complete stop-motion assembly.
Supplier Quote Requirements
Ask for a line item that identifies the machine application, not just a generic roller. The quotation should include the supplier part number, compatible machine models, drawing revision, material, dimensions, MOQ, unit price, lead time, packaging and warranty or replacement terms.
For volume orders, request a first-article report or inspection record. The report should state what was measured and against which drawing revision. A supplier’s “100% pre-test” statement is useful only when the test is defined. Ask whether the test covers rotation, diameter, bore, runout, surface defects or only visual inspection.
The site’s circular knitting spare-parts RFQ template can be used to structure the request. Add a dedicated line for stop-motion pulley runout, rotation and yarn-contact position so that offers can be compared consistently.
Installation Procedure and Test Run
Before installation, isolate the machine according to the plant’s lockout procedure. Photograph the old assembly and mark the axial position of spacers. Clean the bracket and shaft, but do not polish away a reference shoulder that determines alignment.
A practical commissioning sequence is:
- confirm the received part against the approved drawing and part number;
- inspect the shaft, bracket, clip, washer and guard;
- install the pulley without side loading or forced interference;
- rotate it by hand and check for drag, wobble or contact with the bracket;
- verify the yarn-contact or motion-contact position;
- test the stop-motion response at low speed;
- run a representative yarn package at normal operating speed;
- record nuisance stops, delayed stops and pulley temperature or noise.
If the pulley is part of a bottom stop-motion system, test with the same yarn path and yarn type used in production. A system may behave correctly with a smooth test cord but fail with lint, hairiness or a different package tension.
Troubleshooting After Replacement
If the new pulley does not rotate, inspect shaft alignment and the retaining clip before blaming the part. If the machine stops repeatedly, check the yarn-contact path, switch or sensor gap and the control input. If the pulley rotates but the stop is delayed, record the mechanical movement and electrical signal separately.
A related feeder brake unit replacement may be relevant when yarn delivery is unstable, but it is not a substitute for verifying the stop-motion pulley. Likewise, a sliding block and rubber sleeve replacement addresses a different wear interface. Keeping these failure modes separate prevents unnecessary part changes.
Final RFQ Recommendation
A reliable circular knitting machine bottom stop motion pulley replacement request should specify diameter, width, bore or shaft fit, running surface, material, runout, axial position, compatible machine and acceptance test. Request the pulley as a controlled mechanical spare, not as an undefined part of a sensor system. The final approval should be based on movement, alignment and stop response in the complete assembly.
References
The supplier page identifies a circular-knitting stop-motion pulley/roller and provides application, construction, MOQ, delivery and quote details.
The listing provides a machine-specific bottom stop-motion purchasing signal and supplier contact route.
The market analysis gives current context for electronic control and Industry 4.0-ready circular-knitting platforms.
The supplier taxonomy illustrates the need to identify a circular-knitting component by application and assembly.
The catalogue provides broader spare-parts sourcing context for comparing a mechanical stop-motion item with adjacent components.