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wfbrgb
05-08-2012, 02:01 PM
I am using a 3 month old Desktop 24x48 with a spindle. At the moment, we program everything in Partworks. We are using it in high school shop.

Initial cuts were fine, mainly imported jpg logos and simple Arial text. Previews in Partworks continue to look fine, but problems are appearing in the cuts.

I started to get some weird results when using "non-standard" fonts. I don't remember the fonts in question, but if I strayed away from Arial or Times the first pass would be fine but the second, deeper pass would shift to the positive Y axis about 1/4"

Then we tried another jpg and text combo. The text worked fine at 1/16" with a 30 degree bit (two passes for depth) but one letter from the first word jumped into the iddmle of the word and the logo which had been clearly off to the left of the text moved about 8 inches to the right and overlapped the text.

Lastly a jpg design was working fine. About half of the design was cut and then the other half of the design shifted about 1/2" to the left (single pass with a 90 degree bit).

The direction and errors are not constant.

I do get a grinding sound when the machine turns a curve so I was thinking maybe the feed rate was too fast and that throws the cuts off, but the text and logo combo cut everything fine, it just squished a 15 inch design into 8 inches with overlapping elements.

I can add whatever details might be useful. I am pretty new to Shopbot but not CNC.

adrianm
05-08-2012, 02:48 PM
Have you tried running the cuts at a slower speed to see if that works?

Non-standard fonts and converted JPG's can have lots of nodes which could casue problems if you're running at the edge of what the machine is capable of.

rcnewcomb
05-08-2012, 03:31 PM
If it looks ok in the preview then you are dealing with a machine issue.

If the preview is messed up then you may have some small loops in the drawing. "non-standard fonts" can have loops in them that cause problems.

Look at the fourth entry on ->this thread (http://www.vectric.com/forum/viewtopic.php?p=39654) to see an example

garyc
05-08-2012, 08:23 PM
Bob...
I believe you are pushing the bit too fast and deep. You will need to set the toolpath parameters to be appropriate for your machine, bit and material combination. If you post your material, bit, feeds and speeds we can help.

wfbrgb
05-24-2012, 06:41 PM
Thanks for your replies. I think that my feed rates were too high. I have since slowed them down and things are better.

Red oak, 30 degree engraving bit, .003 depth of cut, 1" per minute for a total depth of .06 worked just fine today.

dana_swift
05-24-2012, 07:39 PM
Bob: You say your machine is a "3 month old Desktop 24x48 with a spindle." Any possibility you really have a BT-48 standard? According to the SB website the desktop is only available as a "Desktop 24-18 ". Or did you mis-key the 1 as a 4?

Just curious.

D

ssflyer
05-25-2012, 01:10 AM
Thanks for your replies. I think that my feed rates were too high. I have since slowed them down and things are better.

Red oak, 30 degree engraving bit, .003 depth of cut, 1" per minute for a total depth of .06 worked just fine today.

Bob - I hope there are a couple of typos in that - 1"/min for 20 passes to reach 0.06"? That should't take more than a couple of hours to write your name! :D