Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: tbroland on November 22, 2013, 04:53:41 PM
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I am using mach3 control, probotix monster mill kit and vectric vcarve pro 7.0. My x and y axis use 1/2-10 precision acme lead screw with 280 oz-in stepper motors. My z has 3/8-12 two start acme precision lead screw with 400 oz-in stepper motor. Only when using the vcarve/engraving toolpath the z will gain height and cut above the wood. I have no other problems when using other toolpaths. I have already checked coupling slip and that is not happening. It seems to be losing its postion and I do not know why. Just wondering if anyone has seen this before and what to do to correct the situation. I know the electronics and kit that I have are capable of cutting 2.5d and 3d toolpaths but something gets out of sorts when using the vcarve/engrave toolpath.
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Could it be the V Carve toolpath is plunging the Z into the material faster than you normally do on other work and thus causing your stepper to be overloaded and its stalling a bit? Try reducing the feeds in the code to see if it helps.
Hood
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I will try that. I am about to do a test on cutting an arc with the x and z moving simultaneous just to verify correct movements then I will try the reduced feeds test on the vcarve toolpaths. I am like everyone else. My time is limited and I have to do testing spaced out over several days. Thanks for the advice though.
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Cut the Z axis acceleration in half. my machine acted similar when doing 3D carving, but ran fine doing 2D work. After reducing the Z accel, it's been perfect ever since.
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I reduced the z axis feed rate on the v-carve tool setup page and then ran a test. Now the z axis cuts deeper instead of gaining height. It progressively cuts deeper as the program continues to run. I checked the tool path in Mach 3 and the place it was cutting to deep definitely should not have been that deep. I was v-carving an image of the 40th anv. Mustang emblem and the program started with the a and was working around to the rest of the letters and I noticed it was cutting deeper with each letter. I let it go for a few minutes and finally had to stop it because it was too deep to continue. Any advice or suggestions?
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Have you tried reducing the Velocity and Accel in Motor Tuning? Sounds like you may be losing steps on rapid Z + moves.
Hood
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You need to reduce the acceleration in Motor tuning, not just the feedrate. Reduce the acceleration settings by 50%.
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Ok thanks.I will adjust the velocity and acceleration in Mach 3. I think I might have tried this with my x and y axes but I have not adjusted the z axis while testing a vcarve toolpath. Thanks for the information. I will post the results.
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I adjusted the accel. and velocity in the motor tuning and I still had the problem of the z cutting too deep. I then put all settings back to where they were originally and ran another test and then it goes back to cutting above the wood. I said ok I will meet in the middle on the settings(accelerate and velocity and the feed and plunge in the tool setup) to see if I can find a combonation that will work. So far nothing has worked. It either cuts deeper and deeper or it cuts above the wood. I am not sure what to do next. Everything works great except when the v-carve toolpath is used. I will not give up until I get the v-carve toolpaths working because that is why I bought it. When I get this solved I will share what the problem and solution is. Thank you very much for taking the time to offer you advice and suggestions.
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What are your Z axis acceleration and velocity settings?
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40 on velocity and 4 on acceleration. I dropped them down to 10 vel and .5 on accelerate and everything in between.
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Is your cutter moving in the collet?
Have you shut down Mach and then run the driver test? If so what does it look like?
What kernel are you running?
What is the frequency and Time in Int on Diagnostics page showing?
Attach your xml and I will look through that.
Hood
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I will check all of this and get this information. I am at work now so it may be tommorow before I can get this checked out. Thanks.
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The bit hasnt moved in the collet. Ran the driver test and it said system excellent. Pulse frequency read 24999. Time in Int=4.4 to 4.9, it fluctuates some. CPU speed= 2793.0000. PWM base = 5
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Was the line in driver test smooth or did it have spikes?
Your xml looks fine but your steps per unit seem small, what setup do you have, ie any microstepping, what pitch screws? any reduction between motor and screw?
You could try Sherline mode.
Hood
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Just a thought.
When you save the toolpath, what post processor do you use?
I was just thinking if your Mach 3 native units are set to metric, but you save the toolpath in inch, could that cause this issue?
Are your steps per calculated correctly for the Z ball screw, as you state that the Z has a different pitch/start to the other 2 screws.
I use Vcarve 6, Mach 3 and Probotix boards, drivers and motors and have done a huge amount of engraving without any problem.
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OK.I got off of work early and had some time to check some things out. I have been running all 3 axes at full step because I felt that I needed the full torque because my table has 69-1/2 inch long Y axis lead screw and the X has a 47 inch long screw. I have been running at full step since I first put this together and everything that I have ran has been fine except when I had time to try some v-carving projects, It always would cut above the wood after a small amount of time. So, I changed the driver board for Z to half step and ran a small v-carve toolpath and it did not miss a step. Worked great. So next I ran a larger v-carve toolpath(33 mins) and once again it worked great. I should have checked this a long time ago but 99 percent of the stuff I ran was just profile toolpaths and they were always perfect. I feel so stupid. Humility is a great way to learn things. Thanks to everyone who took the time to offer their expertise and advice.
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You really should be using 1/8 stepping, as it should give smoother motion.
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Ok I will certainly run them at 1/8. It doesnt take but a minute or so to change. Thanks again.
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Good you found the problem, I was certainly surprised to see such small pulses per unit for an Imperial setup :)
Hoood