Cutting depth issue


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  1. #1
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    Default Cutting depth issue

    Hi,
    I work for a company that has a Cammaster Cobra ATC, CR510, and we use Vcarve Pro and the software that came with the machine, it's been running fine and I got past the learning curve on this enough to do my own setups and drawings.
    Recently though I've run into an issue I cant figure out, neither can our "guru" I have some photos but it's late, so for now briefly the issue is I set up a profile tool path outside cut on 3/4" MDF, and then an identical profile path, same tool etc to cut out two roughly 8" square holes in the middle of the 2 foot by 4 foot piece, I set the depth cut to "z" on both. It cuts the outside perimeter perfectly, right to the very top of the spoil board, however, on that inside cut the cutter is leaving almost 1/8" of material at the bottom.

    I've tried zeroing the machine with the tool we use for doing that in T5, and measuring the 3/8" rough compression cutter I used in T2, no difference, the only think I can think of is maybe a bug/corruption in the software and it needs to be reinstalled. We've had the machine about 2 years but it doesnt get a lot of use and can sit for a few weeks at a time not used, so wear etc is not likely an issue here.

    If I open up the TAP file showing all of the cut information, it shows the Z cut in both paths is where I had it set to; 00000000, so that information is correctly being saved to the TAP file, yet the inside cut is like z -1/8"

    If someone has some ideas on this that would be helpful, I'll post some photos to-morrow of the piece, for now here's our machine;

    Cutting depth issue-screen-shot-33-jpg

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    Member ger21's Avatar
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    Default Re: Cutting depth issue

    I'm not familiar with WinCNC, but my guess is the issue is with your tool lengths, or the Z zero position of the different tools.

    Gerry

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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting depth issue

    Is your spoil board bowed up a bit on the edges? Maybe try setting Z zero in the area where the square is being cut?

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    Quote Originally Posted by Jim Dawson View Post
    Is your spoil board bowed up a bit on the edges? Maybe try setting Z zero in the area where the square is being cut?
    Hi guys, thanks for the responses, we keep pretty good on resurfacing the spoilboard to maintain flatness, it was done about 10 days to 2 weeks ago, it's one more of the things we'll probably do shortly again just to rule out, out of flatness as a possible cause, but I actually measured the table in about six different places with the bit we use in T5 and monitored the WinCNC window where it shows the Z of the bit, it was zero at x1y1 and it didn't vary more than from that to -0.023" at the far right corner- a very small amount- nothing like the 1/8" we are seeing on these cutouts!
    Here are two photos which will make it a lot clearer, while table warp is always a possibility, it would have to be warped by 1/8" across 2" to do this!

    The first photo is one of the panels with two cutouts, it's about 48" by about 24", keep in mind the perimeter using T2 with a 3/8" rough compression cutter was set to cut to "z" for the depth, it cut right thru the MDF and it's bottom veneer and the part was easily removed from the waste edge frame left over. Using the exact same toolin T2 it cut those two squares out, same tool, same profile path, same spindle speed, same cut thru to "z" in the tool path, the only difference is it was cutting inside the lines instead of outside the lines, yet instead of cutting to "z" as it did all the way around the perimeter, it left almost 1/8" at the bottom (second photo of one of the cutout scraps.
    I've cut all the pieces in the other two photos and didn't have this problem, it seems to be confined as best as I can tell right now- to just inside cutting such as the first photo.

    It's totally baffling, I've gone over everything multiple times and I don't see a reason for this.

    One other thing I noticed to is, I usually like to cut the 3/4" stuff in two passes, so I usually set up two passes, and click "OK" and the machine makes two passes, but this time I noticed when I went back to that in the tool path that it was displaying ONE pass full depth, so I set it again, saved, and went back to look and it was again back at one pass full depth. So I said "screw it" and ran the part and the machine ran TWO passes as I wanted despite the toolpath apparently reverting back to one pass.

    The two issues have been happening on several pieces of late, I've gone over everything in the vcarve and WinCNC and it's baffling.

    Also typically I like to run rough climb cut in two passes and keep the depth of those two cuts to 0.70" and the offset to 0.01" and then follow up with a finish 3/8" bit in T3 conventional cut to cut the remaining material to "z" and to offset to 0.0", but with this almost 1/8" material being left I thought I'd troubleshoot and leave off doing that finial finish pass with T3 because it was like it was being skipped over somehow, and I set the rough cut to do the whole cutting down to "z" to eliminate that step of changing tools and so on, keeping it all on one tool, but like I indicated- the same tool and everything was still causing this.

    I set the T5 tool to x1y1 and into a piece of paper just dragging the paper and set that to z=0 and measured T5, T2 and T3 which is what I was usung, I did that at least twice or three times, it didn't make any difference. I even tried setting that inside cut to z=+010 and it of course put up a warning about cutting into the spoil board, so I left it at "z"

    Our guru said to try the pocket tool path, that's good for cutting out small pieces, but that path wants to grind up the entire piece of scrap being cut out, that's a lot of sawdust and wear to cut large pieces like these two cutouts, which is why we've always used the profile cut and very often a few small tabs, and it's always worked great.

    As this is, I had to take a jigsaw and cut the rest of the material out around both of those cutouts, and the hand route the openings to clean them up.


    Cutting depth issue-screen-shot-34-jpgCutting depth issue-screen-shot-35-jpgCutting depth issue-screen-shot-36-jpgCutting depth issue-screen-shot-37-jpg

    Attached Thumbnails Attached Thumbnails Cutting depth issue-screen-shot-35-jpg   Cutting depth issue-screen-shot-37-jpg   Cutting depth issue-screen-shot-36-jpg   Cutting depth issue-screen-shot-34-jpg  

    Last edited by wolff2018; 04-01-2018 at 12:19 PM.


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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting depth issue

    Interesting. Have you noticed what the DRO is reading when it is cutting out the squares? Does the machine ''think'' it's at the proper depth?

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    I have not specifically looked at that Jim, I might run a test piece and take note of that. I know I looked in the TAP file for the part and it showed the z cut was at 0.0000000 as programmed and expected, so it appears to be properly saved into that TAP file from the drawing and toolpath portion, but it's like the machine is not interpreting that right and stays up.
    If I saw the z cut was at 0.0000000 for the perimeter cut, and the z cut was at 0.2000000 or something for the inside cut, then I would have figured that the z depth for that tool path was not being saved into that TAP file correctly, but that wasn't the case.

    Since so far no one has been able to post soemthing like "oh, we had that problem, this is what it was..." I think maybe my next step is to have our guru resurface the spoilboard and then set the z and measure all the tools, then we'll know for sure that was done and correct and can rule that out if the problem persists.
    I've never run the resurfacing bit, our guru has always done it, I'm still learning from him and I've gotten to the point where I am good to go with doing drawings in Vcarve or working with the dwg files from the drawing room, and setting up tool paths and running the jobs, but there's a lot I still don't know how to do yet.
    I'll have him specifically show me how to resurface the spoilboard so I'll know how to do it, it's one of those things I didn't need to do and he was always around to do it himself, but he's very often on the road, sometimes for a week, so if it needs to be done he's not here to do it.

    He is as baffled as I am on this issue.

    I need to run more MDF this week, so I need to come up with a fix for this, I think resurfacing and measuring the tools is the first thing we need to do Mon or Tues, even though resurfacing was done about 10 days ago and I measured the tools I was using 2-3 times, I'll just do it again and rule that out for sure.



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    Default Re: Cutting depth issue

    This is specifically where the machine is set to x1xy which we have as x0y0, giving us a 1" gutter allong both sides of the table, so the lower right hand corner out of view is where we have the zero point set on the workpiece, as you can see it's just inches away from the first cutout, the perimeter cut was perfect.

    Cutting depth issue-screen-shot-34-jpg

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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting depth issue

    I actually have had this problem before, but before I try to take you deep into the technical weeds I want to try to eliminate the simple stuff first. In my case, the vacuum was not pulling down the spoil board and I had to cover it with stretch wrap to get a seal. It was a new spoilboard and I didn't check the bow in it before I surfaced it. So the edges would pull up off of the table slightly, the spoilboard should have been placed so the center was high and the edges contacted the table. It should have been flipped over. I also had a known problem with the Z positioning, but I was able to compensate for that.

    If you have a vacuum table, are you setting Z zero with the vacuum turned on? And if so, is the spoil board being pulled down solid to the table?

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    Quote Originally Posted by Jim Dawson View Post
    I actually have had this problem before, but before I try to take you deep into the technical weeds I want to try to eliminate the simple stuff first.
    You bet!

    Quote Originally Posted by Jim Dawson View Post
    In my case, the vacuum was not pulling down the spoil board and I had to cover it with stretch wrap to get a seal. It was a new spoilboard and I didn't check the bow in it before I surfaced it. So the edges would pull up off of the table slightly, the spoilboard should have been placed so the center was high and the edges contacted the table. It should have been flipped over. I also had a known problem with the Z positioning, but I was able to compensate for that.

    If you have a vacuum table, are you setting Z zero with the vacuum turned on? And if so, is the spoil board being pulled down solid to the table?
    I know I've not set the Z zero with the vac on, maybe that's a procedure I've been missing and forgot about, we always set that Z zero point at the machines' x1y1 corner, which is directly over the steel I suppose, so I wouldnt think it would change- unlike setting it in the middle of the table where the spoilboard and it's underlayment are not supported by steel underneath- in which case the vac on would pull down that area a little I'm sure.
    You might be on the right path, so I will check that with the vac on and off, and I think we'll resurface the board, zero and measure the tools with the vac on of course and see if it solves this.

    The workpiece seems to be pulled down nice and snug to the table with the vac, I don't move the machine unless that's the case, at best if an edge is up and won't pull down on a full sheet I'll lay some flat bars of steel along there out of any toolpath so it's secured down.

    Still, I can help but think how the two cutouts are less than 2" away from the edge of the workpiece and that edge perimeter was cut perfectly to Z, I could see the issue you speak of if these were cut out in the center of a 4x8 sheet, but that's not the case here.



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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting depth issue

    It will be interesting to see the results when you are able to get back to the machine. I do agree that is a bit odd that you would see this problem over a 2'' span.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    Quote Originally Posted by Jim Dawson View Post
    It will be interesting to see the results when you are able to get back to the machine. I do agree that is a bit odd that you would see this problem over a 2'' span.
    Someone suggested I do this;

    1) Make sure that any erroneous user offsets on the Z are removed by typing in "G92.1 Z0" and press enter

    2) Calibrate switch to spoilboard using any tool

    3) Press "Measure all tools"

    4) Set the Z datum in VCarve Pro at the bottom of material, toolpath and cut.
    I'm going to check that to-morrow, I have not calibrated the switch before buf if our "guru" is in to-morrow I'll talk to him, he's done that and resurfacing the board before I haven't



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    Default Re: Cutting depth issue

    Quote Originally Posted by wolff2018 View Post
    Someone suggested I do this;



    I'm going to check that to-morrow, I have not calibrated the switch before buf if our "guru" is in to-morrow I'll talk to him, he's done that and resurfacing the board before I haven't

    That is certainly possible. But if you are using the same tool then the offset should remain constant, don't know why it would change.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    Quote Originally Posted by Jim Dawson View Post
    That is certainly possible. But if you are using the same tool then the offset should remain constant, don't know why it would change.
    That's the big mystery! I can see if maybe I used T2 for the rough cut and then used T3 for a finish cut, that making the two tool paths maybe I slipped a digit or something by accident on one of them, that could explain it happening maybe once, but not on every piece over a few days adding up to maybe a dozen pieces!
    Every piece I make is almost always a one-off item, we don't make a dozen of each, so that means every piece that gets cut, or at least every sheet that's cut if a few parts will all fit on one sheet- gets it's own individual drawing and tool paths set up and saved as it's own individual file, both as the vcarve and the TAP.

    That's why I seriously doubt its something in my drawings or tool path setups, I do each of them one by one and carefully check each entry I put in, and then review it. it's going to be something with the calibration, the software or the machine, figuring that out is going to be the challenge.

    I did this engraving on an oak board a few months ago for myself, in part to learn how to set up and do something like this, first time I used the engraving path and brought in my own font to do it, it turned out perfect the first time and it used small script for a signature at the far end, so while I'm still new at this I'm not totally green with setting up tool paths and jobs.

    Cutting depth issue-img_3491-jpgCutting depth issue-img_3489-jpg

    Attached Thumbnails Attached Thumbnails Cutting depth issue-img_3491-jpg   Cutting depth issue-img_3489-jpg  


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    Default Re: Cutting depth issue

    We FOUND the problem after running more test drawings and scraps, drawings by both of us...
    We still found about 0.053" of material being left on the bottoms of SOME of the inside cuts as before, and after calibrating, measuring tools and all the rest.

    It turns out there is play in the head that appears to be about that amount, we can lift the head up and it will stay there, and push on it and it drops about 1/16" or so.
    Here's a video showing the play in the head, that's pretty much the amount of material left over, so it fits perfectly in retrospect with the inside cuts and climb cut v/s conventional, it's pretty obvious now that the apparent randomness was due to the vertical lift forces from the bit depending on which bit was used (compression cut, finish cut) and in which direction it was cutting, so depending on those the head was being pushed up, and at other times it was pulled down.
    The fix was as simple as tightening that nut, we'll see to-morrow when I finish the work on it and test.

    https://www.youtube.com/watch?v=XrtT9lofDNg

    Cutting depth issue-screen-shot-jpg


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    Community Moderator Jim Dawson's Avatar
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    Default Re: Cutting depth issue

    Yeah, that's pretty loose. Happy you found the problem.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Cutting depth issue

    Quote Originally Posted by Jim Dawson View Post
    Yeah, that's pretty loose. Happy you found the problem.
    Isn't that just crazy though! after all the measuring tools, checking and rechecking drawings, and going in circles, we discover what the cause was- a loose nut! LOL!



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