First cut

Talk about all things CNC
baudot
Posts: 7
Joined: Fri Jun 03, 2016 6:41 pm

First cut

Post by baudot » Fri Jun 24, 2016 4:13 am

I made this tiny test CAM program...
Image

Sent it to this newly built ShapeOko 3...
Image

And this was the results:
Image

Like the picture says, there are some problems with the cut: The circular parts aren't. And the facing pass left a ridge.

The one other symptom I see, and I don't know if it's something I should pay attention to: When I set the router to "Fast Jog" in the software, and hold down an arrow key, it still stutters a little as it jogs. Maybe this is a sign of the motor belts not being tensioned as well as they could be. Doing a one-man build, I couldn't get those belts as tight as I'd have liked.

Thoughts on what I should be testing to figure out these problems?

P.S. One trick I'm happy with in my setup: That tiny computer that's running the ShapeOko isn't nearly powerful enough to run Fusion 360. It's just a cheap little machine I got so I wouldn't be anchored to the ShapeOko while it worked. The folder where Fusion 360 drops CAM files is set to automatically sync between my main computer and this little laptop, using BitTorrent Sync. So I can work on my main machine, save the CAM program, walk over to the ShapeOko and fire up the CAM program I just finished there.

WillAdams
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Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: First cut

Post by WillAdams » Fri Jun 24, 2016 5:11 am

Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

RoguePirin
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Location: Illinois, USA

Re: First cut

Post by RoguePirin » Fri Jun 24, 2016 1:19 pm

It looks like you machine is not square, and you may have not accounted for belt stretch. Follow the links Will has provided and you will get much better results.

Also, when you jog, it should be very smooth; no stuttering. As you said, it could be belt tension. It could also be that you are jogging too fast.
Shapeoko 3 #677, Nyloc nuts, ¾" HDPE base with t-nuts, Dewalt 611 w/Super PIDv2

baudot
Posts: 7
Joined: Fri Jun 03, 2016 6:41 pm

Re: First cut

Post by baudot » Fri Jun 24, 2016 3:41 pm

Thanks for the links. That's.. a LOT of trials to try. I rather wish there was a flow-chart to narrow down which ones to do first, based on what was going wrong.

Not as if I had anything else planned for today, though. Tuning, here we go!

cvoinescu
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Re: First cut

Post by cvoinescu » Fri Jun 24, 2016 6:07 pm

Something is very loose. You can usually tell by turning the machine on so that the motors energize, and, with the spindle off, trying to move it by hand. You'll be able to wiggle it a little, and it shouldn't be too hard to tell which parts move with it and which don't. That should give you an idea of what needs tightening.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

baudot
Posts: 7
Joined: Fri Jun 03, 2016 6:41 pm

Re: First cut

Post by baudot » Sat Jun 25, 2016 1:14 am

I'm needing to do something more than just tightening the belts. I've tightened them as much as I feel safe doing, and while the cuts are visibly cleaner, both the problems are still present.

Image

I"ve also tried driving the router from my main computer, to make sure it wasn't a problem with the cheepie desktop I have driving it. No difference between the two computers.

Would someone recommend a known-good gCode file for me to test, for a quick, simple part using a 1/4" bit? I'd like to rule out that I'm generating bad code. In addition to the new ShapeOko, I'm also using the CAM features of Fusion 360 for the first time. Rather than trusting my work there, I'd love to have a known-good gcode file to test with. (I've already run the pen test. I'm looking for an actual carving test.)

DRobs86
Posts: 148
Joined: Fri Jun 05, 2015 4:19 am

Re: First cut

Post by DRobs86 » Sat Jun 25, 2016 1:46 am

If I were at home I would send you a test file. There are a couple out there though. Check the wiki.

I dont think this is your only problem, but what are your feed and depth settings.

Bonch
Posts: 25
Joined: Fri Apr 01, 2016 12:23 am

Re: First cut

Post by Bonch » Sat Jun 25, 2016 1:53 am

It looks to me that your Z-axis is very loose. Check your eccentric nuts and make sure the v-wheels are snug on the lower part of the Y-rail and that when you move them they are able to slightly move the Z-axis on the Y-rail. Also it looks like your router is not square to your spoil board which is causing the ridges. You may want to check all your bolts and make sure they are tight and adjust all the eccentric nuts.

Try that cut again and see if it cleans up after the above is adjusted.

baudot
Posts: 7
Joined: Fri Jun 03, 2016 6:41 pm

Re: First cut

Post by baudot » Sat Jun 25, 2016 2:06 am

DRobs86 wrote: I dont think this is your only problem, but what are your feed and depth settings.
For this file, I've slowed the feeds down to 1000 mm/min, and the cut depths are at most 1mm per pass.

I started off going faster than that, with deeper passes, but the cuts got thrown inches off, especially on the X axis, at high speeds.

DRobs86
Posts: 148
Joined: Fri Jun 05, 2015 4:19 am

Re: First cut

Post by DRobs86 » Sat Jun 25, 2016 3:23 am

It doesnt look like it to me, but are things too tight? If you push things around by hand does it all slide smoothly or does it cog along? If it cogs along then the eccentrics are too tight and the v wheels have deformed under the pressure.

You need to do some no load positioning and see if it moves as expected. I feel like it wont because you are making some pretty low force cuts and you are having this much trouble. How are your stepper drivers set? Are you confident your connections are good. I had a Z axis that wouldnt lift correctly and it turned out to be one of my solder joints (custom board) had broken.

Good luck.

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