Gantry binding. I posted previously about a binding gantry in the Y axis

[Joseph Shawa]

At high speed the gantry was binding especially when it was cold in the garage. I found that lubing it helped but just yesterday it started binding even at warm temperatures. I had recently reverted to original settings when I re-installed LaserCut.

It seemed that the left side was the one hanging up and I noticed the belt on the right was considerably tighter.

Help: What is the method to properly tension the belts?

I loosened the belt and the problem seemed worse so I went back to tight.

I then loosened the left belt on the side that was sticking and completely removed it from the drive shaft in the back of the machine. I figured that it would bind even worse but surprisingly it did NOT bind at ALL!

So, I am stumped.

I put the belt back on in what seems to be only one position that it naturally goes to but I'm not sure that is correct. I cut a 5.2mmx5.2mm square and got a 4.8 by 5.0 rectangle out of it. It's not bad but I thought I'd calibrated to within .02 but that was just a light cut mark on plastic.

Help: Does belt tension affect parallel cutting? or anything?

The binding was the same so I changed my quickspeed setting in LaserCut and the binding stopped as I had done before. Note: In LaserCut I had a difficult time finding the setting that changed the test speed. Turns out that besides changing the Settings and then Download CFG to set the machine (goes BEEP) you ALSO have to Download Current to get the settings to take effect. Seems odd but true.

Anyway, any help on the belt and Gantry problem?

[Joseph Shawa]

I took the belts completely off and felt for any binding or excessive play in the Y axis. There was some resistance through full travel but not what I would call exessive. I re-greased any way. Same.

To re attach the belt I pulled the belt over the drive wheels such that as much slack was out on the lower half of the belt as possible without pulling the gantry. I cannot see any other way to do it. I then tightened both belts equally but I don't know how to test it except by feel and don't really know the outcome of an uneven tightening as once the belt is engaged with the drive and snugged a bit I cannot see how one side can move separately from the other.
I guess to make every thing as even as possible I could/should loosen the set screws one one of the drive pulleys or maybe both and then retention after snugging the two side up equally and then engaging the set screws.

Anyway I tightened it all back up an it seemed to run smoother. I even set my test speed to 500 where it had been having problems and all is well.....except.

My perfect squares are not so perfect. The X lengths are both very near to 99.97mm the Y lengths are 100.1 and this would be acceptable to me but the diagonals measure 142.24 from lower left to upper right and 140.12 from lower right to upper left. Not acceptable. I guess I'll tweak the belts and see what happens? Doesn't make sense to me.

Found a few threads on belt tension- didn't help much.

SOOO, I really looked into the gantry and rails to see what was going on and I just finished. It's 2:42 AM and I am going to share it with you.

First of all, F*** you NiceCut from China. Peter Peng I guess I thought you were too stooopid to build a laser machine when you told me you built it and I was right. I now believe that you built it AND you are stupid. Perhaps I am stupid for buying it but now I am smarter for having fixed your multitude of errors. I might even go into business. NiceCut USA. LOL

The gantry never did sit square to the table and the hole in the middle (Well? Frame? ). There was a slight trapezoid problem when I got the machine but I was able to nearly eliminate it by belt tension. Turns out that the occasional binding that happened did so because the tension was overcoming a misaligned gantry. When it would bind, if I forgot to re-zero it, Datum, then the head would occasionally bang the front of the case an ruing the alignment of the 2nd mirror. The Gantry was also rotated counterclockwise so the 2nd mirror would bump the case if I got within 11 mm of the lower left....Pain.

I figured if loosened all the bolts I could could swing the whole thing square. No, the holes were too small to allow free play. And they were off square by at least 15mm. Well, that's how much bigger I made the holes anyway.
I re bolted it to the table in upper right corner after I was able to verify that I could make square. I had clamped the rails down and measured around. Funny how the table itself is perfectly square and the damn holes weren't measured off of it! It looks like it was done freehand.
I use the gantry to guide the rail distance to the Upper Left hole which I had widened and tightened it down some.
I have to add, that each corner originally had TWO bolts which made rotating the assembly impossible so I am only using one bolt in each corner now. The only way that I could have drilled the proper 8 locations was if I had taken the top off completely. As it was, I drilled Upward from the cabinet below with a 1/2 in bit and worked the holes a bit to widen them.

I aligned the 2nd hole, lower right so that the right rail was the same distance from the table Well (I don't know the name. It's the area around the table.) I tightened both the right side bolts firmly.

The lower left bolt was easy. I just brought the gantry down as a spacer making it the correct distance from the lower right side. I tightened all the bolts again very well.

There is some play in the gantry when only one side has the belt on. I tried to loosen the set screw on the belt gear to allow it to freewheel wheel while I did my last adjustment but couldn't get it loose and it was WAY too close to the Tube for comfort.

I got the belt on such that I was within less than a mm from parallel to the front of the machine. It could have been perfect if I was able to free the gear/pully. After tightening the belt to where it started pulling the gantry out of parallel I used the other tensioner on the right side to pull the gantry back to parallel. This type of correction was MUCH LESS than I had done before. The belt on the left responded by tightening a little bit also.
I cut a 100mm square an it was SPOT ON diagonally.


I hope someone finds this useful. If for nothing else but to AVOID NiceCut from Jinan China....."bolts came loose in transport" they used as one excuse when I complained originally, My Ass!


Good night. It's 3:12 AM

[Dave Sheldrake]

Steps per pulse and belt skip

[Joseph Shawa]

I don't think so. I haven't changed the steps/pulse in settings if that is what you are meaning.
The sides of my squares are the same length. It was the measurements from corner to corner that were different....a parallelogram.

Belt skip? Maybe but I couldn't get the gantry parallel to the front of the machine until I move the gantry mounting.

[Bert Kemp]

Check your language
i took the belts completely off and felt for any binding or excessive play in the y axis. There was some resistance through full travel but not what i would call exessive. I re-greased any way. Same.

To re attach the belt i pulled the belt over the drive wheels such that as much slack was out on the lower half of the belt as possible without pulling the gantry. I cannot see any other way to do it. I then tightened both belts equally but i don't know how to test it except by feel and don't really know the outcome of an uneven tightening as once the belt is engaged with the drive and snugged a bit i cannot see how one side can move separately from the other.
I guess to make every thing as even as possible i could/should loosen the set screws one one of the drive pulleys or maybe both and then retention after snugging the two side up equally and then engaging the set screws.

Anyway i tightened it all back up an it seemed to run smoother. I even set my test speed to 500 where it had been having problems and all is well.....except.

My perfect squares are not so perfect. The x lengths are both very near to 99.97mm the y lengths are 100.1 and this would be acceptable to me but the diagonals measure 142.24 from lower left to upper right and 140.12 from lower right to upper left. Not acceptable. I guess i'll tweak the belts and see what happens? Doesn't make sense to me.

Found a few threads on belt tension- didn't help much.

Sooo, i really looked into the gantry and rails to see what was going on and i just finished. It's 2:42 am and i am going to share it with you.

first of all,you nicecut from china. peter peng i guess i thought you were too stoopid to build a laser machine when you told me you built it and i was right. I believe that you built it and you are stupid.

The gantry never did sit square to the table and the hole in the middle (well? Frame? ). There was a slight trapezoid problem when i got the machine but i was able to nearly eliminate it by belt tension. Turns out that the occasional binding that happened did so because the tension was overcoming a misaligned gantry. When it would bind, if i forgot to re-zero it, datum, then the head would occasionally bang the front of the case an ruing the alignment of the 2nd mirror. The gantry was also rotated counterclockwise so the 2nd mirror would bump the case if i got within 11 mm of the lower left....pain.

I figured if loosened all the bolts i could could swing the whole thing square. No, the holes were too small to allow free play. And they were off square by at least 15mm. Well, that's how much bigger i made the holes anyway.
I re bolted it to the table in upper right corner after i was able to verify that i could make square. I had clamped the rails down and measured around. Funny how the table itself is perfectly square and the damn holes weren't measured off of it! It looks like it was done freehand.
I use the gantry to guide the rail distance to the upper left hole which i had widened and tightened it down some.
I have to add, that each corner originally had two bolts which made rotating the assembly impossible so i am only using one bolt in each corner now. The only way that i could have drilled the proper 8 locations was if i had taken the top off completely. As it was, i drilled upward from the cabinet below with a 1/2 in bit and worked the holes a bit to widen them.

I aligned the 2nd hole, lower right so that the right rail was the same distance from the table well (i don't know the name. It's the area around the table.) i tightened both the right side bolts firmly.

The lower left bolt was easy. I just brought the gantry down as a spacer making it the correct distance from the lower right side. I tightened all the bolts again very well.

There is some play in the gantry when only one side has the belt on. I tried to loosen the set screw on the belt gear to allow it to freewheel wheel while i did my last adjustment but couldn't get it loose and it was way too close to the tube for comfort.

I got the belt on such that i was within less than a mm from parallel to the front of the machine. It could have been perfect if i was able to free the gear/pully. After tightening the belt to where it started pulling the gantry out of parallel i used the other tensioner on the right side to pull the gantry back to parallel. This type of correction was much less than i had done before. The belt on the left responded by tightening a little bit also.
I cut a 100mm square an it was spot on diagonally.


I hope someone finds this useful. If for nothing else but to avoid nicecut from jinan china....."bolts came loose in transport" they used as one excuse when i complained originally, my ass!


Good night. It's 3:12 am

[Joseph Shawa]

I took care of mine. You can remove my quote now?

[Dave Sheldrake]

Maybe but I couldn't get the gantry parallel to the front of the machine until I move the gantry mounting.

Gantry isn't meant to be parallel to the front of the machine...that's arbitrary, it needs to be at 90 degrees to the side rails nothing more as the front of the machine is unlikely to be at 90 degrees to the side rails given it's made from cheap sheet metal

[Joseph Shawa]

Well in the case of my machine because the Gantry was not parallel to the front of the machine the cutter head would hit against the front cover and Hood when it was down in the left corner. Also, a horizontal cut would drift deeper in Y direction as it went from left to right. Irregardless of how it can be it is much more aesthetic now and my cuts are perfectly square without torquing on the belts.

[Joseph Shawa]

By the way. I can now use my full table starting at 1,1 where it used to be 3,11 or greater or it would bang the machine case and knock my mirror out of alignment.

I have perfect 100mm squares now. Not parallelograms. But I don't know if you saw the new if not previously recognized problem I am having. My 100mm square are perfect. It is only now, at least that I noticed that, that less that 100 mm squares are smaller than drawn and larger that 100mm squares are larger than drawn. Seems no one has any input on that one. You?

[Joseph Shawa]

<I wish people would come here and read before purchasing just any Chinese laser expecting performance like a $30,000 machine when they only paid $2,000.

Well, Bill, I guess I would rather buy the nightmare and learn a bunch before spending big bucks. Besides, what would we have to talk about and what problems would we be presented with to help others solve?

That said, I don't know how much one has to spend to get rid of the scaling problem that I have talked about in another post.
Does your machine cut 10mm squares AND 100mm squares without recalibrating it?
What will it cost to get THAT machine?

[Joseph Shawa]

And by what mechanism does your gantry get driven? Or are you galvo only?

[Joseph Shawa]

And Bill, can you think of any reason (settings) that the 100mm square comes out exact. No matter where on the table I cut it. But gets larger or smaller than designated at larger and smaller sizes?

Maybe I am not considering something that the software is. Perhaps if I calibrate to cut a 100mm HOLE rather than a 100mm Piece. I would then not be expanding my scale to adjust for kerf. I'll try that tonight. It might just be that I have to adjust my drawings after I get a consistent calibration. I'll bet a going with a big pattern for calibration would get me a lot closer. My digital caliper only goes to 150mm : (