Pockets slightly undersized

LowRider CNC Troubleshooting
1

Not sure just what happened here.

I was cutting a little frame for my temporary ZenXY to help contain the “sand” and hold a piece of glass over it so it will be “complete” enough I can bring it into my office to share. The cut mostly went well - though I did accidentally do my first cuts in steel:

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Oops - I knew that was going to be close but didn’t mean for it to be THAT close :smiley:

Anyway - the cut seemed to go great. I dialed back my feeds and bit, turned up the router a notch, and used a finishing pass - which seems to have solved the issue I was having with cuts being slanted in Z when cutting towards Ymin. So…hooray!

But…when I went to drop the glass in I found that the pocket was slightly undersized:

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My first instinct was to suspect the glass - I didn’t bother measuring it and just went by the size on the package. Yeah…dumb…but…I was tired and in a bit of a rush so mistakes were all but expected. Except when I measured the glass…it was dead on.

So I measured my cuts…and they’re about 2mm undersized (or 1 mm on each side.) The outer cuts are spot on exactly the size I expected…so parting cuts worked but pocket cuts didn’t.

The one thing I did notice that was odd was that the two operations worked in opposite directions. I have the default in estlcam (12) set to climb milling as suggested in the docs - but cutting the pockets the machine did the cuts counterclockwise and cutting the parting cut on the outside it moved clockwise.

Double checked my CAD and the dimensions are right there…I wouldn’t expect it to be a CAM issue or a machine issue since the parting cuts were exactly on dimension. But…something has to be off somehwere as both the 3mm deep pocket for the glass and the full 19.5mm deep cut to remove the center were both off by the same amount.

Zip file attached with DXF, Estlcam project, and gcode

sand-frame.zip (21.6 KB)

Anyone have any thoughts on what went wrong here and how to correct it?

2

You really can’t change it, Estlcam cuts the pockets in the other direction and if you have flex you will have it somewhere then. :frowning:

3

Interesting…so estlcam always cuts pockets in the opposite direction of parting cuts? I haven’t done pockets since building the LR4 and can’t remember the last time I did any on the old MPCNC so I never really noticed the difference before.

Doesn’t that kind of defeat the point of chosing climb vs. convention milling if it’s going to choose to do the opposite on pockets?

Given that it’s a smaller build I’m a little surprised I have enough flex for that to come up. My X is only about 21" working area - quite a bit smaller than a lot of peoples builds.

4

I have never understood that to be honest. I just add a generous finishing pass in those cases. :smiley:

5

If it didn’t switch directions it wouldn’t be honouring your setting.

6

I would also look at the issue of “tabs too big, slots too small” which happens.

For me, I found that if I define the 1/8" endmill as 3.00mm, I get a good, tight fit between pieces. This has persisted from my Primo to my LR2, to my LR3, to my LR4. (Second LR4 under construction still) Various brands of 1/8" endmill, various DOC and feed rates. Defining the mill as 3.18mm makes parts that don’t fit together. Oh, and it shouldn’t be a runout issue, that covers 2 separate Makita routers and 2 Kobalt routers.

My first Zen table the glass didn’t fit, I had to re-do the glass opening cut. I adjusted the CAD, but the original CAD was correct. That was before I adjusted the tool size, I’d never cut tab/slot parts at that point.

That might not be you, but try some tab and slot cuts, and see what makes stuff work.