bumpy axis

I am using older printed parts, but I am just getting started with my machine.

I seem to be having a bumpy ride along my x axis, I believe this is causing the machine to loose steps on one side of the x axis.

To answer the begining questions.

I am using all parts purchased from the vicious store, with the exception of the printed parts and the pipe.

I am not using end stops

I believe that I am using the firmware that you provided Ryan, I cant say that will 100% certainty as a friend came over to help me assemble and he flashed the firmware / configured the board with repetier host.

I am using a pc to generate files, but I am running off of an SD card.

I will try to attached some pictures / videos to show my issue as well as a close up of the roller in question.

to add to my previous comments, the picture shows the result of me trying to mill a large pocket. Over the distance I am loosing steps so it isnt making it all the way to the end of the planned cut(starting x position)

If I run with the tool above the spoil board, the machine bounces and vibrates along the x axis. I start every operation by manually squaring the machine by using pre cut spacers between the rollers and the corner posts. After a long cut the rollers are no longer equal distant from the corner blocks.

One last thing, if I stay in the middle to bottom right corner of my machine (30"X50") I dont seem to have an issue and have successfully made cuts that travel over each other for multiple passes. I only seem to have an issue when I travel all the way to the left of the machine. This seems to happen when i am cutting as well as when I am simple moving the machine.

hopefully you can see in the top part of the picture where my lines have a sudden jog in them, I think that the machine is popping back into square.

Thanks for any help you guys are able to give!! It has been a fun machine!!

Can you post a video of the bumpy part?


  1. Take the belts off of all 4 steppers and move the gantry around to see if you can feel differences.
  2. Double and triple check that your machine is square and that the distances are the same for both X and Y frame rails. If not, the gantry is going to try and stretch or contract when it reaches either end of it’s travel.
  3. Once you’ve done the above, move the gantry all the way to one side (X or Y) loosen one end that holds the rod, make sure it is sitting nicely in it’s cradle, then retighten. Then do the other axis the same way. It’s a good idea to make some physical stops to run the gantry up against. You can find some on thingiverse. Or use anything physical to run the two ends of the gantry up against (tie wrap something to the frame rails as an example).
  4. Confirm, without belts that it is moving smoothly. (If not, you have something mechanical going on. Prints may be deformed and causing issues, etc.)
  5. Also confirm that it stays almost perfectly square at rest.
  6. Put the belts back on and test it out. Move the gantry all the way to one corner first to bottom out the X and Y using those physical stops you made. Then position it and run the job.

If it’s still having problems, time to look at the speeds things are running at, and you may want to change to series mode for your steppers (made a big difference for me).

I will try these options over the next couple of days! How do I post a video? I tried to post 2 of them last night and they both failed. Which made sense after I saw the 3000kb size limit, but most videos are at least that big.

You can upload them to YouTube.

Honestly it sounds like one of your steppers is not on or a loose pulley. Take the belts off and check.

Also your gcode could be off and expecting too much, maybe zip up the gcode from that pocket from the picture and let’s see what you were trying to do.

Also you have a really tall machine, shorter will really help.

Sorry for the delay on trying your suggestions. Wife seems to think finishing our living room is more important.

I will attach gcode tomorrow.

All steppers are confirmed moving. Working on checking for loose pulley.

Early on I was skipping steps like crazy and grinding the belt. Could I have Burt out my belt?

Ryan can I shorten the machine simply by cutting down the corner posts or do I have to cut the z rails as well?

Honestly I will likely print the new middle.

You can just cut down the corner rails. You’ll have more Z sticking up but that shouldn’t hurt anything. You can cut them down later if it starts to bother you.