wonky cuts - just on certain letters

[Rocco.G]

Hi all

I cut some 1" HDU letters on Saturday and they looked great. Well, that is until today when I took a closer look at them. There are several "u" and "n" in the copy. Since I had to drill 1/8" holes for mounting pins I added them then cloned the letter several times after adding the pin locations. it was this letter that came out strange plus a larger "r" on a different line of copy and larger size. i sent the file to support and they said that the file looks fine. i tried to attach the actual cut file but got an invalid file type message. if someone can remind me how to upload that file type I will.

i got the original file as an EPS from another sign maker, imported it into Aspire and made my tool paths. On the highest resolution the preview was great. The HDU was 15lb, 1" thick. The bit is an Amana 46292 and was never used before this job. I cut the letters at 5 ips and a pass depth of 1/8". My machine is a 6' x 10' prs-alpha (2020 vintage - with less than 100 hours on it - probably closer to 50*) with a vacuum hold down. Beause of issues with the ATC I ran the file as a manual system. it was only the u/n and that "r". Everything else was perfect.

*Yes I need to use it more but am always busy with the main portion of my sign business. Also, it seems that I'm always having some issue or other with this machine. And yes, i previously paid for a shopbot tech to come out and spend two days here to make sure it was all set up correctly, etc. But that's a rant for another time.

Support wanted me to see how much (if any) play I have on the x/y gantry but if the machine had slop then other letters would have been bad as well - correct?? All the copies of the u/n were exactly the same plus the r had the same kind of issue. Suggestions? Before letting loose on an expensive sheet of HDU i did a test cut with an "o" and a period. That I cut at 10 ips (not intentionally - I was playing with different speeds and never dialed it back to 5 ips) and they were perfect.

And yes I am being picky but this sort of thing shouldn't happen at all. I'll sand those letters slightly and my customer will never notice them.

Thanks for any input.

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[bill.young]

Is that at the start point of the cut for those letters? If you don't ramp into the cut you can sometimes get a divot and then bump when the bit plunges and then starts cutting, as the cutting force changes on the bit?

[Rocco.G]

it's not the start point. Since it was just a small bump on a few letters I hand sanded them to get the job out the door. After going back and forth with tech support, i did some more test cuts on a portion of the sheet, only cutting 3/8" deep. i cloned the letters in question and ran them at several speeds (3, 5,8,10 ips) plus a couple of the letters that caem otu perfectly. At 3ips the letters were Ok but at a higher speed they got worse (only the few troublesome letters). Tech support suggested changing the start point to be at the corner where the issues are happening. That's fine for a small job with a few letters, but not feasable for a larger job. On occasion I need to cut dozens to hundreds of letters so can't modify each and every path. Nor can I make test cuts to see how it will end up.

i think it's a combination of gong too fast (though the machine should be capable of this) and something strange with the source file (supplied by my customer). I've cut 3/4" acryic and 1/8" aluminum and never had this issue, though I'm cutting much slower and with a 3/16" or 1/4" bit. it was just a couple of letters out of the job but this machine is going to be the death of me. it's fine when I use it as a manual bit changer but using the ATC is always tricky. Rant ended.

Thanks

[Kyle Stapleton]

Check to see if all your motor gears are still tight.
With the bot powered on try to move it in the xy and z, if you can something is loose.

[Rocco.G]

Everything is tight. i really shook the gantry as hard as I could and nothing budged. I have a feeling it was just a bad file because it was just a couple of letters.