question about offset

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21 Apr 2019 22:41 #131429 by sm
Replied by sm on topic question about offset
here is the part

part.JPG[attachment=18797]part.JPG
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21 Apr 2019 22:44 #131430 by sm
Replied by sm on topic question about offset
doesn't appear to me it worked. let me try it again
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22 Apr 2019 00:44 #131436 by tommylight
Replied by tommylight on topic question about offset
That looks like offset not set correctly, but i never used offsets so i can not help much.
I am sure someone else with more experience will chime in soon.

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22 Apr 2019 02:13 #131450 by sm
Replied by sm on topic question about offset
offsets? did I set any offsets in my gcode?

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22 Apr 2019 12:20 #131492 by tommylight
Replied by tommylight on topic question about offset
Sorry, i did see G40 in your gcode so i just assumed it had used G41 or G42 somewhere, it did not.
Back in a while

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22 Apr 2019 14:20 #131509 by tommylight
Replied by tommylight on topic question about offset
Just checked the gcode you posted earlier, it works as it should. The part in the picture is not the same as in that gcode. Or is it ?
Did you also check for backlash ?
Also how are the accelerations set in the INI file?

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22 Apr 2019 16:22 #131522 by sm
Replied by sm on topic question about offset
Hi tommylight,
you checked my gcode? did you mean you ran it on your machine? and you received a square as it should be?
you are right, what I have received is approximately half of this square.
I am using ball drives, and the fact that three other sides were cut exactly they should tells me that drives are moving as they should.
As I understand also the acceleration probably is not what caused that shortage, as, again, three other sides were cut as they should.
my machine is not traditional one - it uses diamond wire as a cutter. so, if feed is faster than cutting speed - the wire will be banded and that will certainly affect everything (precision and final shape of the part). I spend lots of time trying to find out what the appropriate feed and that low number in my gcode is what I came up with. the part shown on the picture is good - all sides are in parallel, long side length pretty much as I expected to be. and while this gcode was running I constantly watching the wire to make sure it is straight. the only mystery to me is this side #3, which somehow was cut shorter than others. that is why I posted my gcode thinking that I perhaps put in it some incorrect codes or perhaps some codes I've been using are not modals and should be repeated on lines?

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22 Apr 2019 16:42 #131524 by Todd Zuercher
Replied by Todd Zuercher on topic question about offset
The problem looks pretty obvious to me from the photos, after you mention that the machine is actually a cable saw.

The cable needs a minimum pressure to cut, and the pressure of the material against the cable deflects the cable, So while the machine's XY movement may have achieved it's commanded position the cut position of the cable has not yet and may never fully get there. That is why you see the slight curve after turning a corner where the cable continues to cut and is pulled in line with the new direction. The solution is to either program a pause at corners to allow the cable cutting to "catch up" under light to no load, or program an over-cut in the 1st direction before backing up and starting the new direction.

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22 Apr 2019 16:42 #131525 by tommylight
Replied by tommylight on topic question about offset
That would mean that one of the axis is set to half travel, so encoder scale or step scale should be adjusted in the INI file. That is also confirmed by the corners on our part, they are not at 45 degrees as they should be.
Screen shot:

45 degree corners!
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22 Apr 2019 16:51 #131528 by sm
Replied by sm on topic question about offset
Hi Todd,
Thank you. If you had a chance to read one of my replies - this is what I was struggling with and that is why feed is set to such a low number.
while part was under cut, I constantly was watching it and and at the end of each line, I've been pausing it to make sure it can "catch up".
and this part confirms that wire was straight, because all four sides came out in parallel and length of two sides as expected. in the material the very first side (the bottom one) was cut also about 10mm.
but on the side #3 somehow it decided to make it half of it. :(

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