Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Mjolnir07 on June 20, 2008, 02:15:51 PM
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Hello all, thanks in advance for your help. I am a new CNC Hobbyist, I have built a 4 x 4 CNC from some plans I bought. It is a Joe 4x4 Hybrid CNC if anyone has built one. Now to my problem, I am running Mach 3 Version R2.63, I have everything calibrated fine, I jog the machine with MDI commands on X, Y, Z and if I ask it to move G00 Z 1.0 it moves a inch, all great. ???
Well when I output a file from VCarve Pro using the post processor of Mach 2/3 Arcs (inch) (*.txt) all is fine, EXCEPT on the first pass, it always cuts about 1/16th too deep. Always, I do not have any tool offsets loaded, I jog the bit to the top of the work surface, zero everything and run the file...1st pass is always too deep. If I make a file with say a 4" circle, pocketed 1/2" deep with a 2" circle pocketed 1/2" deep inside, the circles are spot on, 4" and 2" no prob, the depth of the 1st pocket is always 1/16th too deep, but the 2nd pocket, cut deeper as intended, is spot on depth wise.... ???
SO what would be causing the extra depth on my Z Axis? I hate to bother you all but am at my wits end. :-\
I will post whatever files or screenshots that would be helpful, I just really need to tackle this issue so I can make this thing work right. 8)
Thanks again for your time. 8)
Respectfully,
Michael Fuller
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Is the axis moving further than the code is telling it to go? Does the DRO show that it is moving further than the code is telling it to go?
Hood
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When I jog it on any axis it moves as intended, I can check any axis with a caliper that measures in thousandths and all seems fine, people have looked at the G Code and said it looks fine, but it cuts too deep on the Z axis 1st pass every time, if for instance the file has multiple depths to it, or layers, the 2nd, 3rd pass etc it does not add any " mystery " depth, but if I make a file where the Z depth is 0.00...it will still cut into the material almost a even 1/16th of an inch every time. I have no tool offsets set at all that I can see or find, a friend who works with CNC's came over and helped me check all 3 axis with his calipers, we jog it any direction with MDI commands it does fine, when I cut a file, ask it to cut say a word, .0100 deep into a piece of wood, it adds a 1/16 to it..I am stuck lol...
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Please attach your code, I am not the best with G-Code but I may see something there or hopefully Graham or others will if I dont. Also please attach your xml, you will need to rename it before you attach it or the forum wont accept it, copy it to your desktop then rename it to Mjolnir07.xml as that helps us keep track of whos xml it is.
Hood
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The Mach3mill.xml file?
Gcode for last project attempt.
Renamed Mach3mill.xml file
Much Thanks for your help.
Respectfully,
Michael
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Got to nip out for a while but from a quick look I see you have a tool height offset in the code, line N50 has a G43.
Hood
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Hi, Michael
Post your G-code file, If the second cir. Z depth is correct, Is the Z depth in the first one correct in your G-code.
Double check your VCarve drawing depth settings, If it was a Mach/Z axis error the second one should have the same error.
Thanks, Chip
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( V-Carve 1 )
( Mach2/3 Postprocessor )
N20G00G20G17G20G90G40G49G80
N30G70
N40T1M06
N50G00G43Z0.7874H1
N60S16000M03
N70G94
Thats the safe travel heighth I think isnt it...?
Respectfully,
Michael Fuller
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My apologies, when I read earlier and you said you have no offsets I thought you mean in your code but you are meaning in the tooltable.
Can you attach your tools3.dat please, you will find it in your Mach3Mill folder in the macros folder.
Hood
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Here ya go sir. And thanks again for the effort from all of you.
Respectfully,
Michael
P.S. Hey Hood, the web says the town you live in is a famous place for Golf....are there cries all day of " Four......." followed by a thwack and a wizz as the ball flies by? ;D
P.S.S. Wouldn't let me do a dat file so I zipped it....
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Well afraid I cant find any reason why your Z is cutting deeper than it should on the first pass, it seems to cut fine here (simulation) using your xml and tooltable, first cut in the DRO shows it going down to -0.1" and thats what the code is asking it to do. I checked the machine coords just to be sure and as I zeroed on -2" I expected to see the machine coords as -2.1" and thats what they were.
If I think of anything I will get back and maybe someone else will jump in with thoughts.
Hood
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Oh and no there are no cries of Four to be heard, cant hear that for the sound of mortars and machine guns :D There is an Arny training range right next to the Golf courses.
Oh and BTW Tiger Woods doesnt like Carnousties course, he got hammered at the Open here a few years back, suppose the Links courses are just not manicured enough for him :D
Hood
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Ok, thanks for checking, so maybe " noise " issue from some interferance on the cable traveling to the Z motor? Or checking my carriage again for any backlash or slop...? I was in the US Marines for 5 years so I would probably love the Army action ya have there. Been in a wheelchair for 20 years but I still love keeping up with the military stuff and going shooting at the range once in awhile.
As far as Tiger Woods goes, I'm glad he has got beat a few times, proves he is human and not a " Alien " from outer space here to take over the Golf world. His finish last week over 91 holes was a marathon I actually thought he would loose, think the play off thing of 3 or 4 holes would be better than making em do the extra 18 holes imo.
Well let me see what in hades can be causing my issue. Any list of ideas I should check you think? Where would you start? It runs great except for this issue LOL.
Respectfully,
Michael Fuller
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Could be noise but then I would have thought it would show up in all other Z moves as well.
Backlash, dont think its that, 1/16th seems quite a bit (had to convert to mm as my brain just dooesnt work in imperial unless I am thinking about my fishing days and then its just fathoms and nautical miles ;) ) Also if it was backlash then if you moved down on the work and zeroed it should have eliminated the backlash for further z minus moves, would just be positive moves that wouldnt go so far as they should. If you used a gauge block and were zero'ing out on an upward movement Backlash would mean your depths of cut wouldnt be as deep as the code was telling it to be. Think I have that right LOL
Suppose it could be a possibility of slop and when the cutter bites it drags the axis a bit lower taking the slop out but really that should show up as backlash unless it was something like the whole axis being pulled down but then it should really only happen the once as there wouldnt really be anything pushing it back up the way.
This is a strange one :(
Hood
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Hi,
I recently had a "similar" problem to this.
I have a Bridgeport mill with the knee driven for the Z. One day the Z axis began to stall, exactly in the same point in the program, (so i thought).
The machine worked fine in manual jog, I spent ages zipping the Z axis up and down and could not get it to fault.
Increased the accell and velocity to bring it near the edge and still would not stall, but run the prog and I got tha nasty stalling sound.
I was sure it was the code, so I changed the code, slowing the axis at the fault line in the code, no difference. ??? ???
The fault was so consistent "it had to be Mach" :-[
Boils down to a sticky z axis screw, a good clean and the addition of a grease nipple and its been faultless for weeks now.
So back to the problem Michael has, I would take as much weight off the z axis, use a pen or a pointer to view the z distances and give it a try.
I might be miles off but if this can be tested easily, it might be a way forward, even if it eliminates and unlikley possibility..
Cheers
Derek.