Having a hard time getting frame assembled.

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zenwebb
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Location: Minneapolis, MN, USA
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Having a hard time getting frame assembled.

Post by zenwebb » Mon Dec 24, 2012 9:26 pm

I've been trying to assemble my ShapeOko frame for about a month now (between school and work :P), but I just cannot get the Y axis motion to feel smooth! When none of the eccentric nuts are tightened, the motion is very smooth and slides with very little force. I've tried tensioning the wheels one by one as per the wiki instructions about 20 times or so, and every single time, the motion gets stiff, skips more and is harder to push by hand.

I just got done disassembling the Y axis and checked every V-wheel for the precision washer, and they all look fine. I've tried tensioning the V-wheels in an X configuration, meaning tightening one, then its opposite on the other side of the axis.

Maybe I'm not mechanically minded, but my motivation level has dropped significantly from when I originally ordered the kit. I had no idea it would be so difficult to set up properly, and I haven't even hooked up any belts, electronics or spindles yet :( Any ideas for what to do next? Is it OK for the Y axis motion to not be 100% "silky smooth"? Will the stepper motors overcome a lot of these problems?
Jason Webb
Grad studen, creative technologist, OSHW engineer
http://jason-webb.info

dointhangs
Posts: 179
Joined: Tue Jun 05, 2012 7:31 pm

Re: Having a hard time getting frame assembled.

Post by dointhangs » Tue Dec 25, 2012 3:37 am

zenwebb, they definitely dont each have to be fully tightened all the way (if thats what you are trying to do). my machine is not with me but i would guess mine are just half way tightened or so, so like a quarter turn on the eccentric nut. Its even possible that the machine will run pretty well just all the way loose too. I think in any case you should proceed to the next steps, and you can fiddle with this at anytime after its built! Yes it takes some energy to get this thing together but you will be glad you did... cheers
Shapeoko #298, dual drive upgrade, acme z axis, open bed endplates and a slightly larger ("expanded desktop") work area!

cvoinescu
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Re: Having a hard time getting frame assembled.

Post by cvoinescu » Tue Dec 25, 2012 10:20 pm

I'm sure there are varying opinions about how tight the V-wheels need to be. Here's my method: to test, grab a V-wheel with your fingers and try to forcefully rotate it against the stationary rail, holding the carriage in place. If you can barely rotate it, it's just right. Tighten all the wheels to this standard, except the idle Y side, which needs to be a little looser. All wheels and the rail must be clean; even a small speck may stick and increase resistance significantly. Wipe them vigorously with dry paper towels, even if they seem clean.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

levlandau2
Posts: 187
Joined: Tue Apr 17, 2012 1:52 am
Location: Minneapolis, MN, USA

Re: Having a hard time getting frame assembled.

Post by levlandau2 » Wed Dec 26, 2012 9:11 pm

Yes, they definitely have to be clean, although the parts should be clean if you are just assembling the kit. I have noticed that I tend to get more jerky motion when the rails or wheels become clogged with debree from milling (the wheels feel like they are going over a speed bump when the carriage is pushed).

I agree with what people above said, and don't think the eccentric nut tightening is critical. Best to leave it too loose rather than too tight (especially on the non-driven y-axis side). My method for tightening is to check whether there is play in the carriage by pulling it up and down and then gradually tighten the eccentric nut until the wheels are firmly against the rail and there is no play when the carriage is pushed or pulled up or down.

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