Tool Path Issue/Question

[mattgatten]

Hi Guys,

Long time no see! Been doing good. Having a good time with the HS-1.

Recently, I've been cutting a lot of parts for multi-copters. I'm doing pretty well with it and selling a bunch of them. I'm making them from 1/16 black G-10 Garolite sheets. I'm using a 1/16 carbide diamond cut bit from PreciseBits.com (highly recommend these for carbon or other composites) and they are working great.

However, I see something in the finished product that concerns me a bit. On some of the profiles, I'm getting what I call a lobe in the corners. Not all of them do it. As you can see, some of the other holes are perfect. In the top 'red circle' you can see it has one in the corner and the opposite hole has the same feature.

These holes were created using mirror and circular array functions to maintain symmetry, etc. So, initially, I thought it was something in my CAD. I have other parts with similar holes that do not exhibit this.

I thought my material might be lifting with the cutter but this isn't happening either.

Where should I look to determine the source of this issue and/or eliminate it? I'm using MOI for the CAD and ArtCam to generate my toolpaths. I haven't looked at the g-code yet so I suppose I could do that. I thought I would ask here first if it's an easy fix.

I like the accuracy my machine provides but this type of thing would keep me from calling any of it 'professional quality'. I am not blaming the machine AT ALL! I have done some amazingly accurate stuff with the HS-1 and believe this is something in a config, CAD, CAM, that I've done.

Ron, Nick, and the rest of you, have Merry Christmas!

Thanks in advance,
Matt

P.S. That part is 4.3 X4.3 inches and the sheet is 12X12.

[georgemyers]

No idea really since some are correct and some are not. Where it happens it that the entry point for the cut?

[mattgatten]

Yes, this is the plunge for each inner profile cut and it's there on each corner. I thought my material might be lifting but it's negligible. Plus, this 'feature' is very consistent. I can't figure it out.

I just opened the g-code and looked at it. There in the first 10 lines, you can see it make the plunge to .063 and make an arc. Then it immediatly makes a second arc. I do believe this is what is causing my trouble. I used a constant radius arc on this feature in CAD. Sooo, is this something that came from CAD or something ArtCam did in the postprocessor? If it's the way I exported the gCode, what is the standard Mach3 option I should choose. (If there is one). Hope I'm not being too much of an idiot here.

I'm putting a snippet of my gCode in the next post. At line 7 the first triangle starts. The error is the first thing that happens on the cut. I have witnessed this with my own eyes.

Ron, if you're listening, I could really use some help on this one. Folks aren't complaining about the quality because I'm not charging a lot and it's just hobby level multicopters. However, I know someone is going to say something or ask for more precision. This won't do. It's making me crazy. hahaha Still not blaming my machine at all because all of these errors are amazingly consistent and accurate! hahaha

Hope everyone had a great Christmas and has a Happy New Year.

Thanks in advance guys,
Matt

[mattgatten]

Here is the code. With comments by 'yours truly'.

1 G90
2 G20
3 G49
4 G0Z0.3937
5 M3 S15000
6 G0 X0.9231 Y0.3139 Z0.1969
7 G1 Z-0.0630 F10 // plunge
8 G3 X0.9652 Y0.3308 I0.0102 J0.0355 F20 // arc?
9 G3 X0.9589 Y0.3758 I-0.0319 J0.0185 // another arc?
10 G1 X0.3749 Y0.9589 // move to next corner
11 G3 X0.3180 Y0.9229 I-0.0206 J-0.0305 // arc (a single line of gCode)
12 G1 X0.3798 Y0.4084 // last corner
13 G3 X0.4130 Y0.3740 I0.0546 J0.0195 // last arch (another single line of gCode)
14 G1 X0.9207 Y0.3142 // moving back to the point where it plunged.
15 X0.9231 Y0.3139
16 G0 Z0.1969
17 G0 X1.0111 Y0.5918
18 G1 Z-0.0630 F10
19 G3 X1.0429 Y0.5600 I0.0318 J0.0000 F20 // these are perfect circles in CAD
20 G3 X1.0747 Y0.5918 I0.0000 J0.0318 // why are their 4 lines to make them?
21 G3 X1.0429 Y0.6236 I-0.0318 J-0.0000
22 G3 X1.0111 Y0.5918 I-0.0000 J-0.0318
23 G0 Z0.1969
24 G0 X0.9540 Y0.9833
25 G1 Z-0.0630 F10
26 G3 X0.9858 Y0.9515 I0.0318 J0.0000 F20 // hole
27 G3 X1.0176 Y0.9833 I0.0000 J0.0318
28 G3 X0.9858 Y1.0151 I-0.0318 J-0.0000
29 G3 X0.9540 Y0.9833 I0.0000 J-0.0318
30 G0 Z0.1969
G0 X0.5625 Y1.0404
G1 Z-0.0630 F10
G3 X0.5943 Y1.0086 I0.0318 J-0.0000 F20 // hole
G3 X0.6261 Y1.0404 I0.0000 J0.0318
G3 X0.5943 Y1.0722 I-0.0318 J0.0000
G3 X0.5625 Y1.0404 I-0.0000 J-0.0318
G0 Z0.1969

[mattgatten]

I'm also attaching the entire file if anyone wants to take a deeper look. Ugh. This is killing me.

Happy New Year again!
Matt

Attachments:

[georgemyers]

Matt

Don't quote me on this but I think I have read on the net that most people to not recommend entering a cut on a curve/arc. I have had the same problem to varying extents and some of it was due to loose v wheel(s) and another time a belt that had broken cords (NOT the same belt Ron provides on the machine).

Try doing a lead in/out of the cut, this cured all my problems.

[mattgatten]

Ramping moves? I think that might be what ArtCam calls them. I know there is something when I'm setting up the toolpath. I can easily move the start point for the paths too. I'll try that tonight on some other things I'm making.

Thanks George.

[mattgatten]

Well George,

Once again, it looks like you've saved the day. I added lead-in/lead-out moves and it appears to have had a dramatic effect on my results.

I'll post some pictures tomorrow. Posting from the shop PC. I love technology.

Thanks again,
Matt

[georgemyers]

Glad it helped.

Like the frames you are making, I spend a lot of time on the DIY Drones site reading what people are doing.