Machine losing position mid program

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steelcogs

steelcogs
So as the title says, my mill seems to be losing position in the middle of some programs. It doesn't always happen. This most recent example (in my attached picture) shows 4 holes (with 4 more on the right, not shown) that were firstly drilled. They are all spaced apart evenly and everything there went as planned (apart from my poor feeds and speeds). This was a predrill op to avoid any plunge/helix with my endmill since the corner is quite worn and atm I don't have the rpm to cleanly helix. The second op was to go down the center of the 3/8" predrill with a 1/4" endmill to widen out the holes to .800." The first two holes hit the first pass dead on by the looks of it. The next hole, you can see, is clearly off center. I could see the endmill not plunge directly in the center of the drill hole but I luckily stopped it before it could've ruined my part.

The other time this has happened (last night) while actually cutting was on this same part but on the first one I tried and it did end up screwing that one up. I ran part of that program before (I had it broken up in 3 DoC's) and needed to stop it before it did the 3rd depth pass. I reran the program from the start and it did the first two holes just fine (air cutting since I had already ran it) and I walked away for a minute since the program was basically proven to that point. I walked back and it had lost position and made 2 or 3 of the holes out of round when it shouldn't have cut anything at all. This was a completely different toolpath and gcode program from the one I ran tonight as it had no predrill (just a helix), was a different tool, and different feedrate.

I'll also attach the gcode for the one I ran tonight that lost it's position.

My only thought is that this is a bug for the pre release software I'm running (3.37.7pre), otherwise I have no clue why this would happen. Maybe some weird gcode thing I'm not sure.
 

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steelcogs

steelcogs
I'm using Clearpath Servos on all 3 axes. 23 size on X/Y and 34 on Z I believe. Masso settings attached.
 

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masso-support

masso-support

MASSO Support
Staff member
in one of the other forum topics was it you talking about gcode missing and you uploaded a photo of a nylon piece with some holes?, just trying to relate and see if it was the same machine and if we can get some idea on the issue.
 
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steelcogs

steelcogs
Yep, same machine. The part was completely remodeled (the first one was on HDPE and these newest ones were on aluminum)and re-cammed so I don't see how that could be it. At the time I was having the other issue with gcode lines skipping, it appeared that the skipped lines were causing the out of roundness. Since I'm no longer skipping lines, I suppose the issue very well may have existed before even updating to 3.37.7pre but I just couldn't tell beforehand.
 
masso-support

masso-support

MASSO Support
Staff member
so the HDPE is running fine now? whats the difference in the gcode between the two parts, things such as feedrates.
 
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steelcogs

steelcogs
I didn't bother re running the HDPE since that was all I had for stock. I did re run the original HDPE program as a dry run just to confirm that the lines weren't skipping - and they weren't, but I never verified the accuracy of the machine position.

The HDPE program had much faster feedrates since I needed to break the chip, around 50-60IPM. The aluminum program I posted the picture with in the original post on this thread was at most 20.25IPM.
 
masso-support

masso-support

MASSO Support
Staff member
Will you be able to run both files on something like a block of wood and we will also run your second file on our machine.
 
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steelcogs

steelcogs
Yeah it's pretty late now so I'll have to do it tomorrow, but I'll share my results. I suspect it'll be something I can't repeat though. I'm still annoyed I had my first aluminum program "proven" only to restart it to finish it and it cut material when it should've been cutting air lol.
 
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steelcogs

steelcogs
Alright, went to go do some test cuts yesterday and my very experienced self set Z zero with the wrong tool called up. Oops. Ended up popping spindle motor fuse and had to overnight some from Amazon (what would we do without Amazon these days).

Tried the most recent file (predrill, then bore to size) with a 2x4 with (essentially) the same results. Looking at the attached picture, you can see it lost its position in more than one spot. Again, the drilled holes (which are on a separate program, I suppose is worth noting. reason being I don't have enough TTS holders atm to hold all my main cutting tools and a 3/8" drill is like a one time use thing. So I just use a normal R8 collet and set my CAM to use a tool that I don't have set up in the Masso.) appear to be right on. The first hole it bores out is labeled 1 - and so on. So in the first .25" stepdown of that first bore, it already lost position from the center of the drill hole. It did NOT do this on my aluminum piece. The aluminum piece lost it at on hole 3. There are also a number of other areas where you can see the step down has lost its position and moved even further away from the center of the hole. It's sort of hard to see on the wood but look carefully.

I haven't re-run the file I used with the HDPE on wood since I'd have to go find another 2x4 but I don't suspect it'd be any different. I was wondering if it is perhaps my motor acceleration settings set incorrectly? Double check my masso settings file I added above but I believe it's set to 100 if I remember correctly. Admittedly I don't know the correct way to set this, but I set it so the jogging was snappy. I figured the clearpaths and ballscrews could handle it but I suppose I may be incorrect here.
 

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masso-support

masso-support

MASSO Support
Staff member
can you please run the same program at half the feed rates, basically in masso axis settings set all axis max feed rates to half the value and see if it makes any difference.
 
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steelcogs

steelcogs
Good news! I first tried running the program with like 20% of the motor acceleration I previously had set. So 20in/min^2. No luck. Halved the max feedrates and it seems to have fixed it! Currently set to just ran at 100IPM max speed and it worked.

So my motor setting is 6400 pulses/rev, which allowed me about 200IPM max rapids at the Masso's limitation. This took up something like 108hz or khz (can't remember) frequency. at 100IPM it only takes up to 54hz/khz. Is it just from running so close to the max frequency that was screwing it up do you think? I really was a fan of 200IPM rapids (and the faster jog rate lol) so if I set my motors and Masso board to only be 3200 pulses/rev, I should be ok to run 200IPM max since it only takes up the 54hz/khz frequency, right? Correct me if I am misunderstood.

Thanks for the help!
 
masso-support

masso-support

MASSO Support
Staff member
thanks for the tests @steelcogs and the test software that we sent you was to try to see if the USB was causing the data speed issues and was the core problem, now that we know that on slower speed it works fine we will have a further look.

Also 6400 pulses will give a very small resolution that is not possible to achieve on the machine mechanically and is just putting load on MASSO CPU, you can most likely make this as smaller as 1600 and then you might be able to still run the machine at 200IPM
 
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steelcogs

steelcogs
Yeah I did some original test cuts and dial indicator tests and I'm positive 6400 pulses won't do anything more than 3200 or likely 1600. I'm pretty sure my biggest limit right now is just physical backlash. I bought my machine already assembled and it likely only has a single ballnut per ballscrew.
 
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grindaur

Grindaur
I am having a similar issue to the author, I am running a Sherline/Masso setup using their standard Nema 23 motor (3.2V 2A, 1.8 /step 530 RMP max). The program is running a 3/16" end mill with spindle speed of 2000 RPM, cutting feed rate of 40"/minute, ramp feed rate of 40 "/minute). The issue is both the Z axis and today the x axis are loosing the zero point mid way in the program this has resulted in twice plunging toward the center of the earth and milling my tooling plate. Today the x axis reset to approximately 1" positive of the point it was supposed to be at . There was no readout change, the operation was a contour milling operation there was no tool retract/rapid movement involved. The program was run though simulation on both Fusion 360 and using GWizard, the issue is not with the Gcode. What do I do to address this. I cannot proceed when the past three attempts at milling a part have resulted in trashing the unit being machined?
 
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