Is this really backlash ?

Discussions and help on this commercial controller.

Moderator: twehr

Is this really backlash ?

Postby iGull » Mon Apr 16, 2012 2:21 pm

Hi
I recently installed the new 2012 controller, and am having great success with it.
However, I noticed something that on the face of it looks to me like classic Y backlash, but I'm fairly certain isn't - hence the reason for posting in this section.
The issue initially showed up when cutting some concentric circles (the inner was held with 'bridges' to the outer) - the inner was offset in Y. I tried various mechanical cures with absolutely no effect, so attempted something more scientific.

I made up a rectangular 60mm vertical 'snake' pattern which has has six 10mm segments. The left pattern starts at the top and cuts down. The right hand pattern starts at the bottom and cuts up. When cut, the starts and ends of both patterns are aligned - the segments in between are not !
The first section (bottom) of the right hand pattern is short by about 0.5mm, but both start and finish lines are aligned.
There's also something else that's strange - both axes use exactly the same mechanics (different steppers, but both 200 step) - over 60mm, the X is dead nuts on, the Y is 0.5mm short. Both axes have the same setup in software.
I know the mechanical setup is ok because I have been using it with my lasersaur controller and I have done many tests (I can't change the controllers right now for other reasons unfortunately). It's the same over the whole of the cutting area (1200*600mm).

Any thoughts or magic spelles ? - it smells like software to me :D

Main board 7.12.04.01
LCD 5.12.02.29
LaserCAD 5.93

I've attached the snake pattern that you can try. Make sure that you DON'T have 'auto order' set, otherwise it won't work - it should start top left, work down to the bottom, hop across to the right snake then work it's way to the top.

I'll posted this across on the lightobject forum in case anyone else there has seen it.

TIA

Neil
Attachments
backlash snake.zip
60*10mm backlash snake
(2.34 KiB) Downloaded 146 times
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

Re: Is this really backlash ?

Postby naPS » Mon Apr 16, 2012 3:04 pm

Can you post a couple of pictures showing what you're trying to explain? It would make it easier to diagnose.
naPS
 
Posts: 202
Joined: Sat Apr 09, 2011 1:53 am

Re: Is this really backlash ?

Postby iGull » Mon Apr 16, 2012 3:30 pm

naPS wrote:Can you post a couple of pictures showing what you're trying to explain? It would make it easier to diagnose.


Hi

I've attached a pdf with some graphical explanation that should make it easier to understand the problem.
Both 'snakes' are exact copies of each other - just offset in X and the cutting direction changed to check for any backlash.
The *.pwj5 file in the previous post is the cutting file that was used for the test - it would be good if someone else could give it a try on their LO 2012.

Cheers

Neil
Attachments
Backlash Snake.pdf
(230.36 KiB) Downloaded 192 times
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

Re: Is this really backlash ?

Postby whmeade10 » Mon Apr 16, 2012 3:40 pm

iGull wrote:
naPS wrote:Can you post a couple of pictures showing what you're trying to explain? It would make it easier to diagnose.


Hi

I've attached a pdf with some graphical explanation that should make it easier to understand the problem.
Both 'snakes' are exact copies of each other - just offset in X and the cutting direction changed to check for any backlash.
The *.pwj5 file in the previous post is the cutting file that was used for the test - it would be good if someone else could give it a try on their LO 2012.

Cheers

Neil


I will give it a go tonight when I get home from work and post the results.

-Bill
FSE 45w Deluxe CO2 Laser 5th Gen w/RetinaEngrave 3D | CorelDRAW X4
whmeade10
 
Posts: 215
Joined: Sat Dec 18, 2010 3:35 am
Location: Sedalia, KY

Re: Is this really backlash ?

Postby whmeade10 » Tue Apr 17, 2012 12:35 am

I just ran the test with the file you provided and it appears that I did not get the misalignmnet like you did. The left snakes were using your settings and then I changed them to cut through the 1/8" hobby ply on the right ones. Hope this helps you out.

EDIT: I have the smooth Y upgrade installed.

-Bill

Test.JPG
Alignment Test
Last edited by whmeade10 on Tue Apr 17, 2012 2:27 am, edited 1 time in total.
FSE 45w Deluxe CO2 Laser 5th Gen w/RetinaEngrave 3D | CorelDRAW X4
whmeade10
 
Posts: 215
Joined: Sat Dec 18, 2010 3:35 am
Location: Sedalia, KY

Re: Is this really backlash ?

Postby naPS » Tue Apr 17, 2012 2:22 am

I had the same type of issue you're experiencing here.

Do you have the smooth Y-axis setup? Or the original 2.0 version with the threaded rod?

I had a pulley mysteriously go out of round, and this happened as well.

I switched to the smooth Y set-up, changed out my X-axis pulley, and tightened the shit out of the belts and the bearing mounts. Worked great after that.
naPS
 
Posts: 202
Joined: Sat Apr 09, 2011 1:53 am

Re: Is this really backlash ?

Postby twehr » Tue Apr 17, 2012 1:00 pm

When engraving, there is an issue for some setups that has shown up in the x axis related to the firing of the laser on the leading vs trailing edge of the signal. Since we have not seen this in vectors (or maybe nobody noticed) in the y axis, I have not given it any thought. I would be curious to know if changing from trailing to leading (or leading to trailing - whatever your set up) would affect the output.
tim
--
"The answer is usually easy and obvious once you know what it is." tw

DIYLaser Blog
SemiHomemadeTools.com
twehr
 
Posts: 439
Joined: Mon May 24, 2010 4:49 pm

Re: Is this really backlash ?

Postby iGull » Tue Apr 17, 2012 1:12 pm

Bill, many thanks for trying that for me - it is really a great help !

If I can believe your software (and I've no reason to disbelieve it :D ), then it would indeed indicate that it is definitely backlash I have.

To that end, I stripped out the complete Y axis assemblage this morning. My front pulley mounts are dual bearings in each doubled up 6mm acetal mount plate. The shafts for the pulleys (regular toothed pulleys BTW - not smooth) are 'shoulder screws' - accurately ground 6mm M6 screws - pretty much industry standard for this type of job. They feel as bullet proof as when I put them in. However, the long shaft at the back with the axial stepper is a slightly different matter. My shaft (all 1500mm of it :D ) is 12mm alloy tube with turned aluminium ferrules on each end. The ferrules fit into either a standard shaft coupler (grubscrew type rather than clamp type as that was all I had) or they fit through a single version of the same front mount plate. This single version may be an issue as it is not quite so rigid as the front units (even though held at both ends).
I've CNC cut another pair of plates and will double up the bearings to suit along with replacing the alloy shafting with some 10mm steel shaft which I'll turn down to suit the pulleys. If that doesn't cure it, I have some petrol in the garage that I'll put in a bowl and let the laser fire down on it :D :D :D

@naPs, thanks for the info, I tried the belts as a matter of course - no change - still not sure what advantage the smooth pulleys offer - perhaps you or someone can explain - I'll turn some up and swap them in if warranted.

@Tim, strangely, when trying to get to the bottom of the problem, I swapped leading to trailing edge of the pulse to see if it made a difference - it didn't.
I even swapped steps, changing from 1/16 to 1/10 (remember my system isn't a 2.x) - again, no change.
As you accurately say in your sig Tim - "The answer is usually easy and obvious once you know what it is." :D :D If only we could find out the answer prior to the problem, we'd be on a winner :lol:

I'll find out if any of the changes have fixed the issue and report back - if nothing else, the Y axis rear should be as bullet proof as the front.

Cheers

Neil
EMOs are a sign of weakness ...
iGull
 
Posts: 171
Joined: Mon Dec 06, 2010 2:59 pm
Location: Edinburgh, Scotland

Re: Is this really backlash ?

Postby naPS » Tue Apr 17, 2012 4:11 pm

Hey there Neil -

I'm not using the smooth pullies, but the smooth rods that link the pullies to the stepper on the rear of the machine. It made a world of a difference for me. That, and tightening the shizz out of the belts.
naPS
 
Posts: 202
Joined: Sat Apr 09, 2011 1:53 am

Re: Is this really backlash ?

Postby gavztheouch » Tue Apr 17, 2012 4:30 pm

This might have been mentioned or tried already but its worth saying as it has been a problem for me in the past. :oops: Have you checked the grub screw on the pulley on the motor is tight, or if you have a centrally mounted motor the pulleys on the shaft.
Timothy hay for rabbits delivered over the UK http://www.timothyhay.co.uk
gavztheouch
 
Posts: 144
Joined: Sun Dec 12, 2010 11:08 am
Location: (Stirling) UK

Next

Return to Commercial DSP CO2 Laser Engraving/ Cutter Controller

Who is online

Users browsing this forum: No registered users and 1 guest