Problem with work zero

This forum is for general discussion regarding VCarve Pro

Problem with work zero

Postby Clockman » Sun May 13, 2018 1:31 pm

I had a mishap the other day when the cutter plunged down to the bottom of the 18mm MDF I was cutting and ran for a while before I could stop it, it would not cut true circles after that, so after calibrating and tightening the set screws, it cuts the circle perfect and the size is spot on, but it jumps to the left when going down to do the cut and after the cut it does not return to work zero, it is slightly off, and goes down deeper, I have added some photos so you can see before and after, in the photos I have dropped the Z down 1 inch from where I have the work zero set at so you can see it clearly, and when I home the machine again and press G28 it goes back to work zero perfectly, what is causing it to jump to the left
SAM_1214.JPG
SAM_1216.JPG
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby Adrian » Sun May 13, 2018 1:55 pm

Has to be something mechanical on the Z axis. Is it jumping at the same spot in the travel?
User avatar
Adrian
Vectric Archimage
 
Posts: 8264
Joined: Thu Nov 23, 2006 2:19 pm
Location: Surrey, UK
Model of CNC Machine: ShopBot PRS Alpha 96x48

Re: Problem with work zero

Postby Clockman » Sun May 13, 2018 2:00 pm

Thank's Adrian, yes it seems to be the same spot in the travel all the time , I can't seem to see what is causing it, when I had the mishap it must have been under a lot of stress before I stopped it
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby Adrian » Sun May 13, 2018 2:32 pm

How is the Z driven? Could be a damaged tooth if it's a pinion or toothed belt.
User avatar
Adrian
Vectric Archimage
 
Posts: 8264
Joined: Thu Nov 23, 2006 2:19 pm
Location: Surrey, UK
Model of CNC Machine: ShopBot PRS Alpha 96x48

Re: Problem with work zero

Postby potzmannwoodshop » Sun May 13, 2018 2:53 pm

Adrian wrote:How is the Z driven? Could be a damaged tooth if it's a pinion or toothed belt.


if this is the case you can just re position the belt.
potzmannwoodshop
Vectric Apprentice
 
Posts: 65
Joined: Wed Feb 15, 2017 2:03 pm
Model of CNC Machine: 2 SCM Routech Record 120s(1999, 2001)

Re: Problem with work zero

Postby Clockman » Sun May 13, 2018 4:01 pm

Thank you both for your help, I am not at the workshop now but the Z drive is linear similar to this one https://www.ebay.com/itm/Z-axis-X-CARVE ... 2712810756
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby garylmast » Mon May 14, 2018 12:17 pm

This happens every once in a while with me. The problem is the mill will bind for whatever reason and throw the G-Code out of sequence vs. the correct position of zero. The last time this happened was quite a disaster.
viewtopic.php?f=27&t=29131&hilit=something+went+wrong

Gary
garylmast
Vectric Wizard
 
Posts: 682
Joined: Fri Oct 23, 2009 4:03 pm
Location: Sandy, Utah

Re: Problem with work zero

Postby martin54 » Mon May 14, 2018 1:39 pm

What sort of motor have you fitted to it? if the motor shaft sticks out the top of the motor casing then it is easy enough to wind the axis up & down with no power on the machine. your z axis should move up & down with ease if the shaft is turned so finding any spots that are causing any kind of binding or any damage to the thread can easily be found.

If the end of the motor is closed then you would probably need to remove the motor to turn by hand as it is unlikely you will have sufficient access to turn the lead screw by hand.
User avatar
martin54
Vectric Wizard
 
Posts: 3810
Joined: Fri Nov 09, 2012 2:12 pm
Location: Crossgates, Scotland
Model of CNC Machine: Gerber System 48 (modified)

Re: Problem with work zero

Postby garylmast » Mon May 14, 2018 4:38 pm

I think the problem I have with the mill binding is I probably got too big of mill and/or traveling to fast. Whenever this has happens, I will trade off for a smaller mill which stops the problem.

Gary
garylmast
Vectric Wizard
 
Posts: 682
Joined: Fri Oct 23, 2009 4:03 pm
Location: Sandy, Utah

Re: Problem with work zero

Postby Clockman » Wed May 16, 2018 10:31 am

martin54 wrote:What sort of motor have you fitted to it? if the motor shaft sticks out the top of the motor casing then it is easy enough to wind the axis up & down with no power on the machine. your z axis should move up & down with ease if the shaft is turned so finding any spots that are causing any kind of binding or any damage to the thread can easily be found.

If the end of the motor is closed then you would probably need to remove the motor to turn by hand as it is unlikely you will have sufficient access to turn the lead screw by hand.


Martin, I have access to the motor shaft and I have tried turning the axis up and down with the power off and I can't find any binding, everything moves very smoothly, I can't find anything mechanical wrong, when it returns to work zero it is bout 0.2 inch too low and about the same sideways, if I run it again from that position it does not jerk on the way down to do the cut and goes back in the same circle that I cut before perfectly, I have tried Picsender and UGCS to send the G- code,
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby martin54 » Wed May 16, 2018 10:05 pm

I would still think this is a mechanical problem, have you checked for backlash & that the shaft coupling is tight, anti backlash nuts on these linear slides are often delrin so you will get wear over time & a shock like your machine had could easily have knocked it out a bit :lol: Same goes for the couplings if they were put under a lot of force.
Is the lateral movement always in the same direction ?
User avatar
martin54
Vectric Wizard
 
Posts: 3810
Joined: Fri Nov 09, 2012 2:12 pm
Location: Crossgates, Scotland
Model of CNC Machine: Gerber System 48 (modified)

Re: Problem with work zero

Postby Clockman » Thu May 17, 2018 11:57 am

Thank's Martin, yes I agree it must be a mechanical problem, I have double checked all connections and the coupling and all are tight, I would have to take it all apart to replace the anti backlash nut if I can get one, and the acme threaded rod, but I can't see any damage to the rod, yes it is delrin, and the lateral movement is always the same, I will have to live with it for the moment as it it is working okay, the cutter goes back into the circle that I cut from the work zero position even when its 0.2 inch off, Thank's for your help
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby martin54 » Thu May 17, 2018 5:02 pm

Wasn't meaning you replaced the nut just that it may need a bit of adjustment, have you checked for backlash ? Don't forget you are only looking for a very small amount of movement :lol: :lol:

Not that I think you need one but a new anti backlash nut shouldn't be to hard to find, guessing it's a standard size lead screw so should be an off the shelf item but that would be easy enough to check anyway :lol: :lol:
User avatar
martin54
Vectric Wizard
 
Posts: 3810
Joined: Fri Nov 09, 2012 2:12 pm
Location: Crossgates, Scotland
Model of CNC Machine: Gerber System 48 (modified)

Re: Problem with work zero

Postby Clockman » Fri May 18, 2018 6:59 am

I am not sure how to check for backlash, I will read up on it and then check to see if that could be the problem
Clockman
 
Posts: 48
Joined: Thu Jun 02, 2016 2:45 pm
Model of CNC Machine: Xcarve

Re: Problem with work zero

Postby garylmast » Fri May 25, 2018 7:13 pm

This happens every once in a while with me. The problem is the mill will bind for whatever reason and throw the G-Code out of sequence vs. the correct position of zero.


My recent double sided project, the material was 3-5/8" thick. On the rough cut I used 1/2" mill going a total depth of 60 mm. I forgot to edit the tool information because I was going so deep with the material I was using, which turned out to be too fast. Half way through the cutting sequence, I stopped and checked the Z-height. Turned out it dropped 14 mm. On the backside, at a slower speed, I did not have any problems.

However, on the finish past, things didn't look right, so I stopped it again and check the Z-height. Again the mill dropped about 5 mm. It turned out it slipped in the collet. That collet now is on the way to the city dump.

Two more ideas to check of you're having Z-height problems.

Gary
Attachments
IMG_0838.jpg
garylmast
Vectric Wizard
 
Posts: 682
Joined: Fri Oct 23, 2009 4:03 pm
Location: Sandy, Utah


Return to VCarve - General

Who is online

Users browsing this forum: No registered users and 18 guests