I just got my new Longmill MK2.5 built from the beginners kit. I had the X-axis traveling too far into the +X direction. I thought I solved it by reading other posts because I think I had the screws on the anti backlash too tight on the X -axis which resulted in a few perfect carves. This morning I went to run a cut and the X-axis traveled too far again. The carve will be going perfectly and when the router is traveling above the surface the X-axis will overshoot its intended position and continue carving with an offset.
I have checked and made sure the coupler is tight.
I don’t want to loosen the anti-backlash screws too much. I’m not sure if this is my issue since I read about people not having enough X-axis movement.
I have checked the V-wheels and the bottom wheels can spin in place with the eccentric nuts closed all the way I don’t have any movement from the router gantry though so I don’t think that is an issue.
I did x-axis tuning with a very slight adjustment.
I have jogged the axis back and forth 48" to see it is comes back each time but I can’t get it to recreate the problem.
I can manually move the axis by hand without much friction
What else am I missing on this to ensure I don’t ruin more material for my carves?
The run time on this machine is less than 5 hours.
Though this is my first Longmill I have a Bob’s CNC Evolution 4 for 4 years so I am somewhat familiar with hobby CNCs. Despite this random issue the Longmill cuts so much faster and cleaner so I am very excited to get it working flawlessly.
Welcome to the dungeon. Nice point to point post. You have ticked off a lot of checks to do. There are however a few more to find on the Issues and fixes page you might want to check.
Thanks for the link I will try some of these solutions this afternoon. I may reflash the firmware as well. Because this is a random error it may take a few carve to determine if these have solved the problem.
I was thinking the same with that as well but I have the eccentric nuts turned all the way closed as far as they go and these are nearly brand new V wheels. If I open up the eccentric nuts and loosen the top V wheels and hold the XZ gantry up while re-tightening the top V wheels will I give the eccentric nuts less room to move and get the XZ gantry tight to the rail?
@kpeoples86 If the nuts are as closed as they will go and things are still loose, something is not right. FWIW, I’ve found the best way to adjust them is to put a wedge under the bottom of the gantry plate and push it until the bottom wheels are finger tight. Then adjust the top ones to the same degree. Now, that said, I have a Mk1 with the adjustable wheels on the top. I know that Sienci changed the placement at some point so my process may well be irrelevant and I have wasted your reading time.
Alright so I don’t know why but re-flashing the firmware failed I am not sure why that occurred I am guessing maybe it’s because the firmware might be at the latest version. I am not sure how to check the version that it is currently on.
I tried adjusting the XZ gantry V wheels to grip onto the rail a little tighter but I couldn’t get it any tighter than what I already had it. I went to do a test cut on the piece I had already carved earlier and the whole cut started in the negative X direction which thankfully didn’t run into the metal parts of the hold down.
I went back and did a bunch of straight and diagonal jogging and noticed that I had my front Y-axis bearings were spinning and so I went back to the assembly instructions and adjusted the coupler and ACME nut on both Y-axis screws. I also noticed the coupler on the X-axis we not up against the bearing and so I also adjusted that. I was happy that something was wrong in hopes that it would fix the issue.
Instead of doing an actual test cut I decided to just let it run an outline above the board to make sure it would cover the correct areas and move back to the home position. The outline runs and the gantry gets to certain areas and I can hear a weird noise from the stepper motors and when it goes back to its home position it is off in +X and -Y direction. I have run the outline multiple times and the return positions can vary each time. I’m not sure what I should focus on now.
Does loosening the v-wheels a bit help? As what I understand of it, they should be snug enough to have some friction but you should also still be able to turn them on the spot a bit by hand.
Does the weird noise happens more or less on the same spot? Does your Y still holds its zero?
@Spamming_Eddie I did loosen the V wheels to the point of just being able to move them by hand and then gave it the slightest twist to tighten again. The outline noise did seem consistent so I did start looking at the speed of the outline and found it was based on maximum travel speed in the firmware. I started messing with the overall max speed and changed it from 5500 to 4000 and I got better results but it was still off occasionally.
At this point the X and Y were not coming back to home every time. Sometimes X would come to the right spot but only about a third of the time.
@Mickus I am using the SLB. I just got this machine 2 weeks ago.
I changed the X and Y acceleration from 1000 to 750 on top of slowing down the speeds mentions above and I still had a little bit of stepper motor noise during the outline. I slowed it further to 500 and the noise went away during the outline run and the gantry came back perfectly. I set the speed back to 5500 and the noise was still gone and the gantry came back perfectly. This is just a single design I have been trying out but at least the results are more consistent. I will probably leave the acceleration at 500 even though the max could be a little higher. I think this matter is resolved by fixing the mechanical issues with the axis bearing and changing the X and Y axis acceleration.
