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Author Topic: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!  (Read 13189 times)

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Hi,

Want to introduce myself my name is Roberto Soriano I have a fully licensed MACH 3 software which was bought with my CNC machines from 3DROUTERS.COM long gone I think... Well I have been cutting several small parts very basic shapes in 5mm Acrylic...

I was cutting today and everything was running normally... When I took the finished piece out of the table and measured it was 1/16th of an inch shorter in width... I double checked my drawing ins Autocad Saved in DFX re-measured and everything was fine... Well after trying to figure out what was happening I simply re-draw the parts again from scratch... And convert it via LAZYCAM from DXF to GCODE and we carved the pieces into a piece of wood to measure if they where correct... And of course it was this time no mistake and carved into the wood...

So we started cutting again in the Acrylic and once the piece was finished we took it out and Guess what this time it was 1/16th of an Inch  Bigger in width... I mean it had already been setup and carved into wood once the only thing I did was Edit the GCODE for Feedrate speed but no mods to anything... This happened to me in MACH 2 couple of times any ideas?? I will appreciate any help!

Regards,

Roberto Soriano

Offline Chaoticone

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Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #1 on: March 24, 2009, 11:24:26 PM »
Robert, it sounds like you may have been skipping steps to start with, compensated for it in the drawing and now it is too big. That or possibly you have a mechanical slip somewhere. Were both parts in the same place on the table when you tested them?

Brett
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Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #2 on: March 24, 2009, 11:28:59 PM »
Hi,

Yes actually the Wooden part where we carved the first run was where we placed the plastic to cut it out we didn't even move the ZERO it was just right after we cut the first run we started the second one in the Acrilic that is why is so weird...

Offline Tweakie.CNC

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Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #3 on: March 25, 2009, 03:09:18 AM »
Hi Roberto,

As Brett has already said it sounds like missing steps to me. Remember that lost steps in one direction will become gained steps in the opposite direction. I suggest that you check for any binding on the axis travel as well as the leadscrews.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #4 on: March 25, 2009, 10:11:58 AM »
Hi,

Yeah we have checked the machine and the screws are fine for all Axis... I still don't understand what you mean by Missing steps?

Thanks.

Roberto
Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #5 on: March 25, 2009, 11:51:19 AM »
Hello,
By missing steps they mean that your step motors cant keep up with the load, and they loose steps.

Were your cuts in acrylic more aggressive than in wood? (higher feed, bigger depth of cut?)

Fernando
Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #6 on: March 25, 2009, 12:16:19 PM »
Now that you mention it I think that I cut with faster speed rates and feeds and also the depth of cut... Yeah that might be the problem. So you suggest cutting with lowe depths and Feedrates? Should that solve the problem?

Regards,

Roberto

Offline Hood

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Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #7 on: March 25, 2009, 12:22:25 PM »
probably best dropping the accel and velocity a bit in motor tuning if your motors are missing steps.
Hood
Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #8 on: March 25, 2009, 12:25:55 PM »
You can try what hood suggested, since that is what you should really aim for, to limit accel and velocity rates in tuning so that your motors never miss steps.

But yes, that is what i suggested lower feedrates and depths of cut. Stepper motors lose their torque when increasing their speed. so if you are making a faster cut, you would have less available force to make that cut, and if on top of that the depth of cut is bigger, you need even more force for that.

Fernando
Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
« Reply #9 on: March 25, 2009, 01:30:42 PM »
Hi,

Ok I did the following:

- Checked measurements in AUTOCAD
- Erased the previous G-CODE files
- converted once more the DXF files to G-CODE
- Reduced the Feed rate and the depth of the cut...
- Cut the part again and I got 1/16 error again?

Could it be a software issue? Maybe Autocad?? Th thing is my Height is perfect but the lenght is what is giving me all the trouble... And a part previously cut is perfect and did it with the faster feed rates and depths??

Ideas? Thanks guys by the way!

Regards,

Roberto