Musings on frame design

Looks like even the “online” notifications (when you are watching a thread on the web interface) don’t get notifications of edits either, so we may need to remember to “mention it” in another post so everybody get’s a notification.

@iRoc999 thanks for the files… very interesting, and now that I’ve seen all the parts, not at all what I was thinking. I wonder about the “side pieces” falling out - but I guess a little glue would fix that up.

Oh all intesecting parts would have a nice coat of glue for best results, but if the set up is doing it’s job the parts should hold pretty tight on their own.

Guess they didn’t think of that. Good thing I did.

One part-way fix is to take a 2x4 and mount it on edge on the back of the frame components. It will help, but not as much as a torsion box. It is also a technique to help keep a 2x4 relatively straight.

Another hint is to paint the lumber before assembly, at least on the non-bearing surfaces. It will help with stability due to humidity changes. … Just an observation I have made over time.

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if the motors are solid in relationship to each other, you don’t need a torsion
box on the rest of the machine, as nothing else in the frame is critical to
accuracy.

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On the topic of moisture and warping for the beam - what big box lumber would be best for avoiding moisture warp? Osb, pressure treated 2x6’s, something else? Maybe there’s a 10 ft steel fence pole that could be used?

how about backing the motor mounts with a crossbeam like this?

http://www.homedepot.com/p/ClarkDietrich-ProSTUD-1-1-4-in-x-6-in-x-12-ft-20-Gauge-Galvanized-Steel-Wall-Framing-Stud-120159/206843784

Or this, which is considerably stiffer (and spendier). It’s also usable for swamp rat fences so you might have some on hand already.

I used another 10’ 2x4 spanning between the arms and that seems to work for me.

One of those strapped to a 2x4 would do it, I would think…

Those steel studs are pretty flexible when not screwed to a sheet of drywall, although constraining the two ends might fix that.

I bought an extra 2x4 to go between the arms, but haven’t gotten far enough to cut the final frame parts and decide where to put it yet.

I think those have some flex to them though. Maybe Unistrut in the
electrical aisle would work better?

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I’ve dealt with some pretty large “things” built mostly with heavy Unistrut… that might be a good start.

I mean you could build the entire frame from 80/20 or Unistrut, but it would be pricey and not gain you anything over wood.

On the other hand, some Unistrut in the right places might add stiffness and be a good way to have a “versatile” mount (i.e. move the motors in/out, etc.).

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Unistrut between the motor mounts might not be a bad idea. Depending on how my frame comes out, I may add a 10 foot section. Ace hardware carries it for a reasonable price:
http://www.acehardware.com/product/index.jsp?productId=29078896&KPID=17479358&cid=CAPLA:G:Shopping_-Catch_All-_DT&pla=pla_17479358&k_clickid=0e9e55df-e34c-4aa0-a566-1a6cccdd03d6

So I am much less concerned about the design of the stock frame now that the PID values have been adjusted. I really only see jerky movement when the sled is nearly all the way at the top of the frame.

That said, I still love the idea of a simple panel saw using unistrut as the tracks.

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I plan to mount the Maslow frame to a wall. Thoughts on the best way to mount a 2x4 to the wall. (I would expect very little flex) but still being at an angle? I’m hearing 10* is a good angle. Thoughts from people already up and running?

Thx all!

In my case the wall is unfinished so I nailed a horizontal 2x4 to the studs just below the point where the frame meets the wall, and attached the frame to that.

What about creating a project for that?

Project: Torsion box-frame,
…made from parts that can be cut by Maslow

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Remember that the only thing that needs to be especially strong is the top beam.

the work area needs to be ‘flat enough’ so that the depth of cut isn’t messed up
’too badly’ (where too badly depends on what you are doing)

there are a number of torsion box frame ideas out there that can easily be cut
with a maslow.

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2080 aluminium 20c - 100c @2.4M length, expansion is 0.002856mm, according to NIST: http://nvlpubs.nist.gov/nistpubs/jres/048/jresv48n3p209_A1b.pdf

23.8 × 10^ - 6 × 120

I only used 2080 because I have 2x 2.4M lengths going spare… it also lends itself well to solidly mounting motors