MH20 and MH20i fault finding

Poor measuring performance:

Possible cause	Remedy
Loose mounting.	Ensure shank mounting screws are tight and mounting to CMM is secure.
Problem with TP20 probe module (see 'TP20 installation').	Diagnosis of the probe unit should be carried out with axes correctly locked and without head adjustment between probe points.
Problem with swivelling / indexing unit.	Diagnosis of indexing unit should only be carried out following confirmation of satisfactory probe performance.

No probe signal and / or no probe status LED:

Possible cause	Remedy
Cable faulty / not connected.	Check continuity of cabling from head to interface / machine control.
Probe interface faulty / not connected.	Ensure correct connection of interface/machine control.

Poor repeatability (MH20i only):

Possible cause	Remedy
Axes lock procedure incorrect.	Ensure lock lever is fully rotated to lock position.
Axes unlock procedure incorrect.	Ensure lock lever is fully rotated to unlock position during indexing.
Forces imparted onto head during lock-up.	Unlock and re-lock holding lock lever only.
Attempted lock-up in incorrect un-qualified position.	Unlock, reposition correctly and re-lock.

Axes ‘rattling' during indexing (MH20i only):

Possible cause	Remedy
Incorrect unlock procedure.	Ensure lock lever is fully rotated to unlock position.
Incorrect indexing procedure.	Index each axis separately.

NOTE: The MH20 and MH20i are not user serviceable and should be returned to Renishaw if suspected faulty.

Poor measuring performance:

Possible cause	Remedy
Stylus configuration too long or not rigid.	Use shorter stiffer stylus configuration.
Poor stylus assembly.	Ensure stylus joints are kept to a minimum and that all joints are clean and secure.
Contamination / damage of stylus ball.	Inspect for damage, clean thoroughly with solvent.
Trigger force too high.	Use lower force module.

Unwanted triggering during probe or CMM movement:

Possible cause	Remedy
Trigger force too low / stylus configuration too heavy.	Use higher force module / reduce mass of stylus configuration.

Probe fails to rearm after trigger:

Possible cause	Remedy
Trigger force too low / stylus configuration too heavy.	Use higher force module / reduce mass of stylus configuration.
Probe reseat failure.	Re-trigger probe. If problem persists please return to Renishaw for service.

Loss of measuring accuracy:

Possible cause	Remedy
Mounting not secure.	Check that the MH20i is correctly mounted on the shank and that the screws are secure. Check clamping mechanism in CMM quill is secure for MH20 and MH20i.
MH20 / MH20i not fully locked.	Ensure that the thumbwheel / lock lever is turned fully clockwise.
Force imparted to probe module after locking.	Re-qualify the probe.
MH20 / MH20i worn or damaged.	Use only with the specified probe and extension combinations.
Faulty probe module.	Check by substitution or return to Renishaw or your supplier.

CMM support