Z drive isn't going up and down smoothly

I have ruined two projects because the Z drive has hesitation going up, then it goes way too deep. What the heck is wrong! I’ve done many projects without error. Any help would be greatly appreciated!

This sounds like a common problem called “missing steps”. Something is allowing the belt to slip when the z-axis is being raised. A frequent cause of this problem is loose grub screws in the z-axis pulleys. Worn or damaged belts can also be a culprit. Search the forum for “missed steps” if these suggestions are not the cause. Every x-carve owner has to deal with this issue eventually.

Before I started following a regular maintenance routine, one of those screws completely backed out and was lost on my x-carve.

If the problem is loose screws, use some blue locktite to keep them where they belong.

Thanks, screws are gone!! Do you know where I get get them?

Grub screws don’t have a head, so double check that they are not loose in the hole but below the surface.

The screws are M3 (aka 3mm) with a 0.5 thread pitch. They can be 3mm to 6mm long.

Inventables does not sell the screws alone - they come with their pully kits.

Online, you’ll pay about $5 for two screws or $7-9 for a larger 50 count or assorted lot. I purchased this assortment: https://www.amazon.com/Hilitchi-260pcs-Socket-Assortment-Plastic/dp/B014OMFU1I

If you cannot wait on shipping, you can use short M3 screws, or cut down a longer M3 screw. These can be found in the specialty fastener section of your local lowes/homedepot/etc. A bit of work with a file or sander does the job. For the z-axis pullys, having a screw head sticking out won’t harm anything as long as it is not rubbing the belt or the frame. These are what I cut down initially while waiting on the assortment package: https://www.lowes.com/pd/Hillman-3mm-to-0-5-Phillips-Drive-Zinc-Plated-Machine-Screws-12-Count/999994826

Here is what my pulley looked like for the last year with this modification. The irony is I never did actually use the grub screws from the assortment kit… I liked this configuration because it is easier to check visually.

These types of screws are also frequently used with radio control cars and drones, so if you have a shop nearby that caters to these hobbies, they may have some in stock.

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Thank you! I can’t see the grub screw, so I assume they are missing.