Z-Axis migrating downwards

[WoodMarvels.com]

Hi there, have a odd problem, I set my z-axis depth to a specific figure and it has been cutting absolutely fine for years but now all of a sudden, it's migrating downwards while the shopbot shows the depth isn't changing.

For instance, I was cutting out a piece of wood that's 20 mm thick in two passes without issue, now, on the single pass about half way through it's already cutting into the sacrificial board (beyond 20 mm deep) while the shopbot software continues to show 10 mm depth.

Something is no longer maintaining height control on my ShopBot Desktop as it's cutting through material. I've re-zeroed the z-axis using the plate, that's always perfect, it's when cutting that it seems to go down.

[steve_g]

If it’s an Alpha, check to see if your resolution multiplier has chanced…
This number changes the resolution between moving and jogging. When wrong on the Z axis, retract moves are usually jog moves while plunging isn’t. consequently, the Z axis can work its way down, yet read correctly.
SG

[knight_toolworks]

fist thing to check always is the collet when bits slip the collet usually needs replaced. I usually can feel it takes turning to tighten the nut. you can also mark the bit shaft right at the collet and see if thats changing

[WoodMarvels.com]

BINGO, that was the problem! Thanks knight_toolworks!

fist thing to check always is the collet when bits slip the collet usually needs replaced. I usually can feel it takes turning to tighten the nut. you can also mark the bit shaft right at the collet and see if thats changing