What components should be regularly inspected for damage to the coil of the stator shaping machine
A crushed end turn is easy to see and surprisingly easy to misdiagnose. The HMI may show the expected pressure. The tool may complete its stroke. The next part may even look acceptable after an adjustment. None of those observations proves that the winding was supported, located and contacted as intended.
The useful maintenance question is not “Which setting should we change?” It is “Where did abnormal contact begin, and which component allowed that contact?”
Set the safety boundary before opening the machine
There is a clear difference between an operator observation and a maintenance inspection.
An operator can normally preserve the failed stator, record the part and recipe, inspect the part from the normal safe position, note the angular location of a defect, and review available alarms or trends. Internal cleaning, reaching between platens, checking a cylinder or guide, loosening tooling, repositioning a sensor, or performing a guarded test/position cycle belongs to trained and authorized personnel under the machine and site procedure.
Hydraulic and pneumatic systems may retain energy after electrical power is removed. Regional requirements differ, so the applicable site procedure and machine manual control the work. If testing or positioning requires temporary energization, use the approved sequence rather than improvising around a guard or interlock.
Safety note: A stopped machine is not automatically an energy-isolated machine. Address electrical, hydraulic, pneumatic, gravity and spring energy under the approved procedure.
Why pressure alone is a weak diagnosis
Forming equipment may control inner diameter, outer diameter, axial height or a combination of these. Published equipment descriptions from SMT show that the result depends on coordinated tooling, support, guidance and controlled actuation—not pressure alone.
The same displayed pressure can produce a different local load when:
- a stator sits on debris or the wrong spacer;
- one protection finger is bent or an insert is missing;
- a segment sticks and then releases;
- a guide or platen has play or loses parallelism;
- a crossover or lead enters a contact zone;
- an end-position sensor has moved;
- the wrong part recipe is active; or
- the incoming winding is already outside its approved envelope.
Read the damage pattern before inspecting the machine
The defect signature ranks the inspection; it does not prove the cause.
On a narrow screen, swipe horizontally to view the full table.
| Damage signature | First inspection priority | Why it helps |
|---|---|---|
| Same angular position on repeated parts | Local forming surface, protection finger, fixture orientation, locator and the part feature at that angle | Repeatable position suggests repeatable contact or location |
| Damage on one axial end only | Upper/lower tooling, axial stop, stack-height setup, stator seating and platen relationship | The defect follows one side of the load path |
| Broad circumferential crushing | Recipe, stroke/pressure control, wrong tool set, incoming envelope and full tool closure | A global condition is more likely than one isolated burr |
| Scrape or enamel streak | Edge radius, burr, embedded debris, relative sliding and segment synchronization | A directional mark can point back to the first abrasive contact |
| Pinched crossover or lead | Lead presentation, protection feature, local keep-out zone and part orientation | A compliant feature may have moved into a hard closing path |
| Defect starts after changeover | Tool/insert identity, assembly, spacer, locator, recipe and first-piece approval | The change list sharply narrows the search |
| Defect appears after warm-up | Guide resistance, hydraulic behavior, lubrication state and fixture expansion | Time dependence should be preserved and compared |
Mark the stator orientation. Photograph both the damage and the tool-facing side. If permitted, keep the first failed part, the last accepted part and an unformed incoming sample. Without orientation and comparison, a valuable witness mark becomes only a picture of the result.
The seven inspection zones
1Forming surfaces and transition radii
These are the parts intended to touch or closely control the end winding: inner-expansion segments, outer wrapping blocks, upper and lower axial forms, cones, shoes and transition pieces. Inspect the actual contact path, not only the most visible face.
Look for burrs, dents, chips, raised edges, embedded copper or enamel debris, surface pickup, corrosion, cracked coatings, sharp transitions, loose inserts and uneven polished witness marks. A bright area can show repeated contact, but it does not tell you whether that contact is correct. Compare the location with an approved tool drawing, known-good tool, master sample or documented baseline.
Do not “improve” a radius by hand-grinding a mounted tool unless the authorized repair specification explicitly allows it. Removing material changes geometry and can leave abrasive contamination.
2Protection fingers, teeth and replaceable polymer parts
Protection fingers or teeth can help maintain clearance around slot insulation, wedges, leads or the winding. MPC describes cuff-support fingers, and SMT product examples describe individual slot-protection features. Architectures vary, but the inspection principle is consistent.
Check for a missing or incorrect part, bending, cracks, swelling, looseness, poor seating, sharp wear edges, embedded wire fragments and unequal height. On polymer or nylon components, look for compression set, glazing, splits and heat or chemical damage. Confirm that replacements match the approved material, revision and position; “looks similar” is not a release criterion.
3Stator nest, locator, clamp and stack-height setup
A forming tool cannot compensate for a stator that is not seated on its intended datum. Inspect nest faces, mandrels, locating pins, centering features, support rings, clamps, stops, washers or stack-height spacers used by the actual machine.
Look for contamination, loose fasteners, dents, fretting, play, damaged threads, incorrect spacer combinations and contact on a surface that should remain clear. Verify part orientation and confirm that leads, separators and lacing do not sit beneath a hard clamp or locator.
A simple but powerful check is to compare the stator’s seated height and stability with a documented good setup before examining more remote hydraulic components.
4Guide posts, bushings, linear guides, platen and fasteners
The tooling may be smooth yet close unevenly if the motion structure is no longer guiding it correctly. Depending on the machine, inspect guide posts and bushings, linear rails and blocks, tie members, platen faces, couplings, stops and securing bolts.
Inspect for contamination, unusual resistance, play, scoring, dry areas, lubricant leakage or mixing, loose bolts and unequal witness marks. Use the specified lubricant, point, quantity and interval; the final schedule belongs to the actual machine and service conditions.
Do not infer parallelism from a smooth unloaded stroke. Verify the approved machine/tooling relationship under the method specified by the builder.
5Cylinders, rods, seals, valves and the pressure source
Cylinder inspection mounting bolts, frame deflection, rod-end connections, rod dents or scratches, smooth operation, changed speed or cycle time, end-of-stroke shock or noise, leakage, stroke and auto-switch condition. It also links one-sided rod wear with eccentric or lateral load.
Inspect the installed system for loose mountings, rod marks, leakage, drift, hose or fitting damage, unstable pressure, abnormal noise, temperature change, filter condition and contamination indicators—as applicable to the machine. Compare an abnormal cycle with a known-good trend rather than relying on one instantaneous pressure value.
Never raise a relief setting, bypass a pressure limit or substitute fluid or seals without confirmed documentation and authorization.
6Position, pressure and part-present feedback
A displaced sensor can make mechanically healthy tooling stop at the wrong point or sequence at the wrong time.
Inspect home/end switches, proximity sensors, pressure switches or transducers, cables, brackets, flags and connectors used by the actual machine. Look for loose hardware, bent targets, cable strain, contamination, intermittent indication and disagreement between commanded and observed position.
Then verify the recipe: part number, tooling revision, stroke or position, pressure or force setting, speed, dwell, sequence and authorization level. Compare it with an approved master or change record—not memory.
7Guards, interlocks and service condition
Guards, light curtains, two-hand controls, interlocks, emergency stops and mechanical blocking are safety devices, not production nuisances. Inspect them under the site’s approved functional-check procedure. Do not bypass a protective device to gain a better view of the tool closing.
Also inspect the machine area for loose wire, insulation fragments, tooling fasteners, rags or measurement devices left in the danger zone. OSHA’s restoration requirements include checking that nonessential items are removed and components are operationally intact before energy is restored.
Do not ignore the incoming stator
Not every defect found after forming was created by the forming machine. Before the next trial, compare incoming parts for:
- end-winding inside diameter, outside diameter and axial height;
- one high loop, crossover or lead in a keep-out zone;
- rolled slot liner, displaced wedge or phase insulation;
- loose lacing or an unrestrained lead;
- prior enamel damage, contamination or foreign material;
- stator stack, orientation and part-family identity; and
- variation tied to a particular upstream machine, cavity, shift or lot.
If the incoming geometry has moved, a previously capable forming tool may now encounter an unplanned feature. Correcting only the forming station can move the problem downstream without restoring process control.
What to observe each shift—and what belongs in planned maintenance
Operator-facing observation
- Confirm product, recipe and tooling identification.
- Inspect the incoming stator and first formed piece.
- Record damage position, orientation and morphology.
- Watch the guarded cycle for unusual sound, hesitation or alarm.
- Check visible leaks, contamination and loose external items.
- Stop and escalate repeat damage instead of tuning through it.
Authorized planned maintenance
- Clean and inspect tooling and protection components.
- Verify nest, locator, tool identity and fasteners.
- Inspect guides, platen relationships and actuation.
- Verify sensors, targets, cables and feedback.
- Lubricate only at specified points with traceable material.
- Review defect and alarm trends by cycles and part family.
The interval should be set from the machine manual, component instructions, cycle count, material, environment, changeover frequency and history. A universal weekly or monthly table would be false precision.
Change one cause at a time
When several corrections are made together, an accepted part does not prove which one mattered.
- Preserve the failed part, orientation, original recipe and trend data.
- Classify the damage and identify the earliest witness mark.
- Isolate energy and inspect the shortest physical path to that mark.
- Select one verified repair or authorized adjustment.
- Record replaced parts or old/new values.
- Restore tooling, guards and the machine state.
- Use the approved test/position procedure if motion observation is required.
- Run a first piece and defined short repeatability run.
- Compare mechanical, dimensional and electrical evidence with the acceptance plan.
If the defect recurs, do not add another undocumented tweak. Reopen the evidence trail and check whether recurrence follows angle, tool cavity, stator lot, cold/warm state, shift or changeover.
Post-maintenance release gate
One cosmetically acceptable stator is not enough. A defensible release covers five layers.
| Release layer | Minimum evidence |
|---|---|
| Safety restoration | Tools and loose items removed; components intact; energy-control process completed; guards/interlocks restored; affected personnel clear |
| Configuration | Correct product, tool/insert/spacer set, locator, recipe and approved settings |
| Motion/load path | Approved test shows smooth, synchronized motion with no abnormal contact, drift, noise, leakage or alarm |
| Product acceptance | Defined end-winding dimensions and keep-out zones pass; no new enamel, insulation, wedge, lead or stator damage |
| Electrical/repeatability | Product-specific electrical tests and a defined short run pass; intervention and release authority are recorded |
The minimum useful inspection record
Capture enough information for another shift to reconstruct the event
- machine, date, shift and authorized person;
- stator part/lot, recipe and tooling revision;
- last good and first bad cycle when known;
- damage type, angular position, axial side and photographs;
- incoming-versus-formed comparison;
- original position, pressure, speed, dwell and available alarm/trend data;
- tooling, protection, locator, guide, actuator and sensor findings;
- one correction made, including old/new part or setting;
- first-piece dimensions, visual result, electrical result and short-run quantity; and
- release authority and recurrence-monitoring window.
Bottom line
When a stator forming machine crushes a coil, inspect outward from the first witness mark. Start with the contact tooling and protection parts, then verify the stator support and location, guide/load path, actuators and pressure system, feedback and recipe, and safeguards. Include the incoming stator in the investigation.
The most reliable sequence is: preserve evidence, make the machine safe, inspect the shortest physical path, change one verified cause, restore safety, and prove recovery with mechanical, dimensional, electrical and repeatability evidence.
FAQ
Which parts should be inspected first after coil crushing?
Begin with the forming surface at the damage location, nearby protection fingers or inserts, and the stator nest or locator. Then move outward to guides and platen, cylinders and pressure circuit, sensors and recipe, and safeguards.
Should forming pressure be reduced when a coil is crushed?
Not as the first action. Preserve the original pressure and position data, then check location, interference, tool condition, segment motion and incoming geometry. Pressure may be part of the cause, but a lower number can mask a mechanical problem.
What tooling wear can damage enamelled wire?
Burrs, chips, raised edges, embedded debris, cracked coatings, sharp transitions, loose inserts and uneven wear can create abnormal contact. Confirm the finding against the approved tool condition and repair specification.
How often should a stator forming machine be inspected?
Use the machine manual and component instructions, then refine the schedule using cycle count, part family, environment, changeover frequency and defect history. There is no defensible universal interval.
Can an insulation-resistance test prove that the coil was not damaged?
No single test proves the absence of every defect. Use the product’s approved electrical test sequence together with visual, dimensional and repeatability checks.
What must pass after replacing a forming insert or adjusting a sensor?
Verify correct part and position, tool and fixture relationship, recipe, safeguards and motion. Then approve a first piece and defined short run using the required dimensional, visual and electrical checks, with traceable release records.
