Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: dodiano on March 24, 2009, 11:09:27 PM

Title: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 24, 2009, 11:09:27 PM
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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Chaoticone 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano 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...

Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Tweakie.CNC 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.
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Hood 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano 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
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl on March 25, 2009, 01:35:24 PM
might be a stupid question, but i might as well ask it. Are you compensating for tool diameter?

Post your gcode so we can check it.
Fernando
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 25, 2009, 01:41:01 PM
Yes I am compensating,  Actually I draw the offset within AUTOCAD so it is compensated for the tool it is weird casue one side is larger... We have 2 programs one that cuts holes for the parts and the other that cuts the actual part itself... Still don't know what is worng it does the same thing for the holes? it throws me a hole with the same 1/16th error? Weird thing is that with other files there is no problem only this specific one??

Regards,

Roberto
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl on March 25, 2009, 01:48:23 PM
Might be the loosing steps thing.
Post your gcode
Fernando
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Tweakie.CNC on March 25, 2009, 01:54:34 PM
Just another thought - when you are converting your DXF files and using tool offset, if the AutoCad lines are not all joined and a small gap is encountered the offset can revert to the other side of the line. (I know what I mean here but I am not sure I have explained this very well). I think it is called joining polylines.

Tweakie.
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl on March 25, 2009, 01:57:12 PM
Good observation tweakie, I did understand you ;)

But i think by offsets he meant just drawing the offset in autocad, not using tool offsets within mach.

Fernando
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 25, 2009, 02:02:24 PM
Yeah I'm doing the offset within autocad... Basically if I draw a square I draw another one that is 0.15 bigger for tool compensation... Sorry I stayed Jurassic this way but on MACH 2 i did it that way... How you set the offset of 0.15 in MACH 3?? I did check the file and the lines are  joined...

 
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Hood on March 25, 2009, 02:53:09 PM
Are the DROs in Mach showing the true sizes?
Hood
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 25, 2009, 02:57:30 PM
DROS??
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl on March 25, 2009, 03:00:51 PM
Digital read outs... its the place where the axes positions are displayed. X, Y, Z, A, etc...
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Hood on March 25, 2009, 03:01:30 PM
These
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 25, 2009, 03:57:53 PM
Well they are showing the true Sizes... the 3 Inches in lenght of the bigger part being cut is done perfectly is the width the one that is giving me all the trouble, the part measures 7 15/16 inches x 3 inches ... Will post the Code in a sec not in the machine right now but they are going to send it to me.

Regards,

Roberto
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 25, 2009, 04:20:56 PM
Ok here is the code:

N1 (File CAJAVER2PERFIL )
N2 (Default Mill Post)
N3 (File Posted in Mill Mode)
N4 (Wednesday, March 25, 2009)
N5 G90 G80 G40 G91.1
N6 G0  Z1.0000
N7  X3.9762  Y-0.0985
N8 M3
N9 G1  Z-0.0600  F8.00
N10  X-0.1425   F8.00
N11  Y3.2015   
N12  X8.0950   
N13  Y-0.0985   
N14  X3.9762   
N15 G0  Z1.0000
N16  X8.0950  Y3.9948
N17 G1  Z-0.0600  F8.00
N18  Y5.0135   F8.00
N19  X-0.1425   
N20  Y3.9948   
N21  X8.0950  Y3.9948   
N22 G0  Z1.0000
N23 M5 M9
N24 X0.0 Y0.0
N25 G40 G80

M30

Regards,

Roberto
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: vmax549 on March 25, 2009, 04:28:08 PM
ON the axis giving the error Double check the coupler where the motor Mounts to the Ball screw shaft. MAKE sure they are TIGHT.

(;-) TP
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: fer_mayrl on March 25, 2009, 04:35:33 PM
What diameter cutter are you using?
Fernando
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Hood on March 25, 2009, 05:14:34 PM
Your code is giving you these dimensions. The Y axis is moving a total of 3.3inch so if you have a 0.3 dia cutter(I use metric but still seems a strange size even for imperial ? ) it will be exactly 3 inch however the X is moving a total of 8.2375 so with a 0.3 dia cutter  you will end up with 7.9375.

Hood
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: RICH on March 25, 2009, 07:08:28 PM
Roberto,
How overeall width of the piece that you are cutting.
Can you post the gcode of the piece? In fact, one each with the different feed rates.
Don't think Autocad is your problem.
What program are you usiing to generate the gcode?
RICH
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: RICH on March 25, 2009, 07:43:13 PM
Robereto,
I assume this is the piece.

Looks like it's cut just the way you coded it. The width is 7 15/16" (7.9375").
Red is cut piece, yellow are z moves ( circle is 0.300 cutter), dimensions in white

RICH

Hey Hood,
All my re-sharpened mills are weird sizes post resharpening them.  ;)
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 26, 2009, 12:35:58 AM
Hi Guys,

Yes the 0.3 difference is the tool offset so as Rich says those are my measurements so they are good... But I am getting 1/16th inches added there somehow... Gcode is generated by LAZYCAM.

Any ideas? Will try checking the machine but all looks perfect!!

Thanks
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Hood on March 26, 2009, 03:12:26 AM
Sorry I need to read properly, I was thinking the part was meant to be 8 inch and it was cutting 7 15/16 . I gotta learn to read :(

Hood
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Tweakie.CNC on March 26, 2009, 03:45:48 AM
Following up on TP's posting you could also check for backlash in the leadscrew, leadscrew moving in the thrust bearing, leadscrew nutplate loose in it's mounting or anything else that has worked loose on the axis drive chain.

Tweakie.
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 26, 2009, 07:03:58 AM
Will check the machine and let you know... It is properlly coded so I guess it is the machine!!

Will let you know.

Regards,

Roberto
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: RICH on March 26, 2009, 07:05:56 PM
Mount a ball point pen on the gantry, remove any z moves from the code. run the program a few times
onto a piece of paper. No mess this way and you'll have a visual on repeatability. Then address what seems bad.
Just a economical thought.
RICH
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: dodiano on March 27, 2009, 03:48:06 PM
Hey Guys! It is working!! I dissarmed the axis and set it up again and it is working we cut the parts today!!

Thanks for the help!!
Title: Re: Newbie here... Have a huge issue wih MACH 3 AND I REALLY NEED HELP!!!
Post by: Tweakie.CNC on March 28, 2009, 02:46:39 AM


 ;D


Tweakie.