Linear Slider sticking at seams

We have a robot which uses liner sliders to lift our tubes. The linear sliders have rack gears attached to them that are moved by the smallest gear (pinion I think) up and down. When the sliders are moved to the point where the pinion gear goes over the the crack where two rack gears connect, it sticks. If you put two rack gears together (teeth side to teeth side) they fit perfectly. But if you put a rack gear over the crack where two rack gears sit next to each other on the slider, you can wiggle it side to side. What can we do to fix this problem? We already tried a larger gear. Would lubing the sliders help?

Perhaps a picture? I’m really having a hard time seeing this in my head…


There shouldn’t be any seams.

We combined these four items to make our sliders, Linear Slide, Rack Gearbox Bracket, Rack Gears and a 3-Wire Motor. Here is a picture of the seam and a picture of the the gear sticking.
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Hmm, interesting. Our team never really had those problems from what I remember of using the linear slides two years ago for the entire year and last year very early. Is there only one place where it continues to happen? Or is it happening over every spot where two rack-gears meet? If so have you tried swapping one or both of the problem racks out for a different one?


No, we have a double slider set up to lift twice as high. Only one set of sliders gets stuck. They get stuck on the 1st crack which we have partially fixed by pressing the metal pieces which the screws go into further into the rack gears.

We have tried swapping out different rack gears with no success.

Are you sure that it is a problem with the racks themselves? My team has never had a problem with the seam between two rack gears causing problems.

We do tend to get spots on our sliders where there seems to be a steep increase in friction due to tiny variances in the width of the sliders. We often can’t see these spots because the variance is so small be we can figure out where it is by sliding a slider up and down it. It sometimes helps to put lubricant on the sliders or to attempt to find the trouble spot and carefully bend it back into place with a pair of pliers.

Check to see if there is anything else catching/sticking… I’ve had a similar problem, but it turned out to be the object the slides were lifting was catching on the bottom of the slide.


We experienced this as well, especially when we ended up “making” longer pieces of slide rail. In the end, we were able to remedy it by slightly morphing the slide rail in the spot of most resistance.

You have a double slider, but only one gets stuck at the first joint. Is it the lower one?

If it isn’t the rack gear that is different, then it could be something about the location of the first rack-joint, such as the tension or side torque in the rack system when the pinion is near that location in the system.

If move all the racks down 1 or 2 holes, all the cracks will move as well, which might move the crack out of the danger zone. When the rack gets stuck in the same place, but now there is no crack there, you’ll have to find another hypothesis for your problem.

Thanks everyone! We put some grease on the sliders and stabilized the racks with supports and it works much better.