Losing steps?

[robtown (Unregistered Guest)]

I've encountered this twice now. First time I created a file with a lot of moves, 63 parts with a good sized pocket and clean-up pass around the perimeter, then two additional cuts on each part. I was cutting 1" sintra with a 3/8" spiral compression bit. It seems that as the cut progressed I was losing a little bit on the x axis, by the time it got to the last row of parts on the sheet it was a good 1/4" off (in x) than it should of been. Now, the router never bogged, and the table never "sounded" like it was straining at all, I had it set to a low number on the speed setting because I needed a good edge.

The second time was last night, I was running a v-groove test for a project on 1/8" acrylic. It was a 6" x 6" piece with a simple logo etched into it. about halfway through the cut my z axis lost it's zero by about 0.045000 so the v groove bit wasn't even touching the piece by the end of the cut. Again, no strain on the router or the table, a nice low feed speed.

Any ideas?

[artisan]

There are a few different possibilities for your problem. The first thing to do always, is to determine whether it's a software, or mechanical issue. If the steps are truly lost, then your router should NOT return to "zero". Can you repeat the problem? If you move to a different point, do you lose steps in the same way? In short, determine if the error is exactly repeatable....rerun your file and measure again. Use the FG command to jump ahead in the file and measure your points to see if the math changes. If this is the case, it's most likely not a mechanical issue. Once you've determined if the problem is software or hardware, you can head down the appropriate path. Good Luck. You can email me if you like...I'll be in all day....D

[robtown (Unregistered Guest)]

It doesn't return to the proper z-zero. It returns to +0.04 +/-

Using the v-groove bit it's hard to look at the code and correctly ascertain if the values are right, as it seems to generate a different z value for various letters and strokes.

The first example that I gave, the error was repeatable, and the only thing that made it go away was to setup and cut the parts one row at a time on the 4 x 8 sheet (on 8 sheets). Not too elegant, but it got me through the job.

This latest example was repeatable, as I did a number of tests on engraving stock, with different files, and on all it touched in some spots, but not in others. I thought I needed to surface the spoilboard at first, but the tolerances and the true amount that it was off on Z tell me it's more than a little MDF swelling, plus .045 over the total span of 3" seems a little extreme, I think I would be able to see it or feel it on the spoilboard.

[artisan]

What design software are you using?

[robtown (Unregistered Guest)]

AutoCad 2000 for the parts.

Illustrator for the v-groove stuff

[artisan]

This is interesting Rob. I've had little trouble with Autocad over the years, although the conversions can be tricky depending on the version. The fact that you are not returning to zero indicates a probable mechanical/electrical issue. On the other hand, the z problem sounds like a software issue....or as you seem to have eliminated....a spoilboard issue. Did you run the Bot over the area to check....ie, turn on the router and (M) in the x or y direction to see if you leave a mark in the spoilboard. Repeatable errors are usually software problems, as the Bot simply follows orders. If you want to email me the files, I'll take a look and troubleshoot them here and see if I can spot the problem. Email to ArtisanIAC at AOL.com....D

[Brady Watson]

Rob,
Check your timing when you start up Cut mode in DOS. It will give you a number and say Timing Check.

In my experience, my machine got twitchy when I had a lower than average number. I wound up hard coding the number to eliminate this after getting an average (running timing check 10 times, throwing out super high or low numbers and averaging) I hard coded the average number into the .ini file and I never had this problem again.

Still looking for my documentation on this...There is a command to run the timing check with a 2 letter command...except I'm in the office and the command is taped to the workstation in the shop


I'll try to get that for you when I go out there.

-Brady

[srwtlc]

Brady,

UP will reprocess timing. I have had problems from time to time where the timing was too low and my machine would be real sluggish, too high and it will be as you say "twitchy". I hit UP until I get something in the 50's and all's well. Although I'm not so sure if this will cause Rob's loss of position. I've had the Windows version skip on me though, and then I have to rezero.

Scott

[robtown]

Still using DOS version. Haven't had time to break open the case to make the necessary input switch changes.

Darrell, I'm sending my latest file to you. I'm pretty sure my solution will be a mechanical solution. When the router returns to zero, it's off in Z. Can't be 100% sure. I'll probably go up to the shop today, I want to run the file and pinpoint exactly where it seems to lose Z.

[ralph@moreheadkreations.com]

after cutting a partigular file, I noticed it was off, so I stopped it and retured to home (0,0) and noticed it looked off so I set up a reference point and run the program again just a little above the board to see if it would mess up again. I watched it and it messed up again but in a different spot then I stoped it and sent it to my reference point. I t was off aproximatly .125 inch in the x axis. I reran it several times with the same results. I have checked the file but don't thank thats the problem, since it messes up in different spots each time. Any sugestions?

[RTM (Unregistered Guest)]

I forgot to say that this is a PRT machine. cutting speed was 2"/second. there's a lot of tight curves in this file. So am wondering if that was to fast.going less then .125" deep

[Brady Watson]

RTM,
Chances are you are running much too fast for the file. Slow things down, adjust the router RPM for the speed you are running and try it again. I suggest that you start at .7 IPS and work your way up in speed where the cut quality looks the best.

-Brady

[RTM (Unregistered Guest)]

Thanks Brady, I finished cutting at 1 isp and it worked fine.