Home Position Shifts with Speed? Check the Referencing Edge
A home position that changes with approach speed may reflect input timing or the chosen reference edge. Compare the complete homing method before moving the switch.
Original delay example; reference behavior depends on hardware and homing mode.
What is happening?
A reference cam can initiate a search while a separate encoder mark establishes the final position. Other methods use the switch edge directly. Input filtering, capture hardware, direction, and mechanical hysteresis affect the result.
Check these five things
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Identify the configured homing method.
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Determine which event establishes the final reference.
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Record approach direction and referencing speed.
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Check input filtering and capture capability.
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Compare repeated results within the approved motion procedure.
Worked example
In a simplified switch-only example, a 10 ms observation delay at 100 mm/s corresponds to 1 mm of travel. At 20 mm/s it corresponds to 0.2 mm. This explains a possible speed effect but does not predict a hardware-latched system.
Quick diagnostic reference
| Item | Potential influence |
|---|---|
| Approach speed | Distance during delay |
| Switch hysteresis | Direction-dependent edge |
| Encoder latch | Reference capture behavior |
The mistake to avoid
Changing a home offset can hide variable referencing error. Diagnose repeatability before correcting a constant position offset.
How to verify the fix
Record repeated references at supported conditions and compare spread, not only average position. Validate travel limits after any approved change.
Field-work boundary: These are educational diagnostic guides. Use the exact equipment manuals and approved site procedures. Electrical testing and machinery changes belong to qualified, authorized personnel; control hazardous energy and validate affected functions before release.
Technical reference
Beckhoff: TwinCAT homing documentation. The examples and diagnostic tables above are original teaching material; they do not replace the product manual.