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A couple of questions.
Are the marks at 12,3,6 and 9 O'clock ?
Are your circular moves G2 & G3 or a bunch of little G1's ?
Scott
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Recently I have been making a bunch of circular parts, and noticed this odd pattern on the side walls.
I'm pretty sure it is related to the steps from the motors. How can I reduce these marks?
A couple of questions.
Are the marks at 12,3,6 and 9 O'clock ?
Are your circular moves G2 & G3 or a bunch of little G1's ?
Scott
www.sdmfabricating.com
That's my first thought, too, if it's outputting many small G1's you'll be seeing a complex polygon, not a true arc. What CAM software are you using, with what Post-processor?
I'm pretty sure the move is a G3, as it has a distinct sound over a bunch of little G1's.
Hm. I get perfect circles and arcs on my 1100. What size bit are you using and what feed rate?
The circle is fine - these are just surface finish marks, probably less than .001 roughness.
The bit was a 3/8 HSS 90 degree drill point end mill (45 degree side angle) running at 4k rpm and maybe 7ipm or so feed.
I'll ask again. Is this the only mark ? Or are there 4 of them 90 degrees apart , or 2 of them 180 degrees apart ? If so it could be a mechanical issue like backlash.
If it only appears in one place it is almost certainly in your code.
Please let us know.
Scott
www.sdmfabricating.com
It's not my code. The code has one big G3 that goes all around the circle. It's not the entry point either. This particular feature is near, but not necessarily at, 45 degrees. I don't recall if there are other marks at 90 or 180 degrees to this as the piece has been sandblasted since.
On other pieces with arcs in them, I see a similar appearance where a linear move in one axis only has a relatively nice surface finish, but once the contour starts arcing, the surface finish gets worse.
I think this mill has about .001 of backlash.
Here's another picture with a circular move.
There are a few of these patterns around the circumference, but not necessarily evenly spaced.
Last edited by beanbag; 02-11-2012 at 07:03 PM.
That looks like chatter. Does the cut make noise there ?
If you have 2 marks at 3 and 9 o'clock it would indicate that there is backlash in X if you have 2 marks at 12 and 6 o'clock it would indicate backlash in Y. If you only have 1 mark at some other place I doubt that it is a mechanical issue.
Scott
www.sdmfabricating.com
No chatter at all.
When I get chatter, I get a series of very finely spaced diagonal lines.
The pattern in this picture appears at something like 5 oclock, and maybe another one at 4 oclock, another at 6:30, but nothing from then till 9.
Last edited by beanbag; 02-12-2012 at 05:32 AM.
Are you doing the full DOC in increments? I get marks like that when the tool comes around and does a plunge to the next depth at the same place on the tool path/ part location.
This pocket was cut with a roughing end mill.
Gerry
Red hair and black leather, my favorite color scheme...
from Vincent Black Lightning 1952 by Richard Thompson
Sorry to hijack this thread, but Gerry's picture illustrates the same problem I'm having on a multi-pass pocket cut. That bump evident in his picture is there on a 1/8" EM pocket I'm doing, and it's at least 5mil off location from the rest of the pass. Which is more than the tolerance off my axis + the deflection of my carbide tool. Where does this bump come from?
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