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Continuing issues

Posted by Marc 
Continuing issues
December 29, 2013 09:17PM
Travel, then Christmas kept me away since my last posts. I have a simple job requiring tiling so I went to go cutout the fences that were posted earlier this month. I wasted a lot of ply on this. I rediscovered that the settings for the tool paths aren't seemingly honored, and reset the default to match what I was trying to set from VCarve. Still, the errors were consistent. The tnut hole looks more like an oval than a circle and the puzzle joint is not symmetrical. This happens consistently so it doesn't seem to be a speed error. I'm using a straight 1/4 bit, router speed between 2-3, and 1 inch per second. Pictures here.

I have no idea what to try, this is extremely frustrating. I've got a very simple job to run, but I can't trust the machine to do anything dimensionally accurate. I can't trust the stop button anymore either, sometimes it works but more often it doesn't.

Is anyone getting anything good out of their machines? Please share your process.
Re: Continuing issues
December 30, 2013 03:08PM
Hi Marc,

For simplicity, we are contacting you to try and solve your issue offline. For transparency and documentation, we'll update here once we've found the solution.

Re: Continuing issues
December 30, 2013 04:37PM
Thanks, that will be more efficient. We'll report back here after we chat tomorrow.
Re: Continuing issues
December 30, 2013 04:38PM
I feel your pain. I was cutting some small pieces of three quarter bamboo ply (tough, tough material) and getting garbage.
What I ended up doing was:

1 clean HandiBot neoprene bottom of all dust. Maximizes friction between surfaces.
2 cutting depth of 1/4" max. One of the beauties of multiple passes is that if they align you know the strategy is good.
3 lubricate router bit religiously.
4 slow HandiBot down. There is a point at which it'll skip pulses. You don't want to get anywhere near that point. Too much resistance to cutter travel is all it takes.

HandiBot is a terrific little machine. When I got the bamboo ply pieces, which are slightly complex, they were better than they had any right to be. I'd post photos but that would be egotistical. Anyway, hang in there. Once you've got a cutting strategy that works you'll be in business.
Re: Continuing issues
December 31, 2013 12:53AM
I've been using a pass depth of .2". What speed are you running at? I'm set at 1" per second which seemed slow from what else I've read here, maybe it's still not slow enough. Ii'm working with average cabinet grade plywood right now.
Re: Continuing issues
December 31, 2013 01:56PM
Marc Goodner Wrote:
> I've been using a pass depth of .2". What speed
> are you running at? I'm set at 1" per second which
> seemed slow from what else I've read here, maybe
> it's still not slow enough. Ii'm working with
> average cabinet grade plywood right now.

May I suggest that rather than starting out fast you start slow? Then speed up if it works. I figure slow speeds are healthier for the machine anyway. And let's face it: With the Handibot job times are more dependent on set-up times than machine speed anyway.

I think i was at 10mm/sec and 5mm passes in the bamboo ply. All I know is that it worked.
Re: Continuing issues
January 02, 2014 01:15PM
I was under the impression 1" per second was slow. Completely agreed on setup, and after working through this I don't know that I'll ever try to go above 1" per sec again.

tl;dr this is all my fault from using an improper bit.

At David's advice I checked the machine over for loose bolts. I found some loose, particularly on the Z anti backlash nut. I had found a loose screw when unpacking the bot, never reported it as I couldn't see an empty hole. There was an empty hole on the backlash nut. This could explain some Z issues I'd had on an earlier project that a straight bit was recommended for.

I also talked with David about the straight bit I had and calculating ship speeds. First we both agreed I should move back to a proper end mill rather than the Freud router bit I'd grabbed at Rockler to get that unknown out of debugging. At the speeds we are running the bot at, and the speeds the router has available you cannot hit recommended chip loads. So the only thing to do is experiment. I'd say the advice on using the chip load calculator in the docs should be removed as such. It would be nice if we could documenting some starting feeds and speeds for the bot since the chip load calculator won't help you.

After applying some locktite and swapping back to the end mill I hit consistent Z issues where the cut would start in the material rather than on top. David said it sounded like missing Z steps and to slow down. No change. In reviewing everything one last time before calling David again I heard the Z motor grind when I parked the Z axis at 1" above the material in jog mode. I'd told it to go higher than it had room for. So, checked the vcarve files from the fence parts I was using and sure enough they had Z home position set at almost an inch above the table. So there was my consistent lost Z steps. It just so happened the previous bit I was using was much shorter than the end mill so this didn't happen.

So, this corrected reran the project and it's fine. I'm running at 1" per second with the router set at about 5. The material was some rather rough exterior grade ply scrap.

Now that bit. I swapped back to it and immediately hit the same issue that started this post. So maybe upping the router RPMs would do it, but it isn't worth it to try. I'll start a new thread on where to order proper end mills from.

Many thanks to David for working through this with me. I'm going back outside to work on some jigs for my project.
Re: Continuing issues
January 02, 2014 02:22PM
I had a similar issue with screws coming out, specifically the (2) M5 screws that hold the Z stepper mounting plate onto the X linear carriage. When I checked other screws most of the ones on the anti backlash nuts would take at least 1/4 turn to snug down.

Something to keep an eye on for sure.

Re: Continuing issues
January 02, 2014 03:02PM
Glad to hear we have you up and running. We are taking note of these reports of loose bolts. We currently are investigating whether bolts with Loctite preapplied is a better solution than applying liquid Loctite at the time of assembly.

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