Ah, *THAT* was what was coming

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Re: Ah, *THAT* was what was coming

Postby cdsteinkuehler » Thu Apr 17, 2014 3:00 pm

One more question: How many 608 bearings? They weren't on your list (unless they are random hardware?), but I think I've got enough already on-hand.
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Re: Ah, *THAT* was what was coming

Postby Nicholas Seward » Thu Apr 17, 2014 6:35 pm

My new design will probably need 21 608s. The proto used 17 608s. I will put the proto on GitHub in the next hour or two so you can take a look at the measurements. I want to drastically reduce the wood usage and the outer dimensions on the next version.
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Re: Ah, *THAT* was what was coming

Postby Nicholas Seward » Thu Apr 17, 2014 7:53 pm

GitHub

InventorView is free and will let you measure things.
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Re: Ah, *THAT* was what was coming

Postby cdsteinkuehler » Thu Apr 17, 2014 8:05 pm

Nicholas Seward wrote:InventorView is free and will let you measure things.


Thanks for the files! I tried InventorView, and it was totally crashy/buggy. I just signed up for the full version which is free if you mentor (I work with some kids at the local high school). Much better. :)

What material are you using for the flat stock? IIRC, it looked like acrylic? If so, I think I may be able to cut on the feeble laser-cutter we have at the office, assuming it's bed is big enough.
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Re: Ah, *THAT* was what was coming

Postby Nicholas Seward » Thu Apr 17, 2014 8:20 pm

I used one-side melamine coated MDF. I would have preferred two-sided melamine coated ply.

Any flatstock will do.
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Re: Ah, *THAT* was what was coming

Postby cdsteinkuehler » Thu May 01, 2014 1:56 am

I've been reviewing the design files and ordering parts. Now it's question and random thought time:

Bearing support:
* Do you think the design is OK as-is or do you think additional support for the bearing bolts is mandatory (ie: would you build another one just like what you've got)?

* If you feel more support is needed, what about just cutting another face plate and extending the sides to make more of a box frame? This seems pretty easy, although likely wastes material (and makes it harder to string). I'm not that worried about either of those issues right now, but they are important for a cheap printer for the masses.

Locking when powered off:
* It seems like what you want for locking is something like an elevator brake that fails safe (locked). You could put teeth (or rubber, or whatever) on the pulleys and have a magnet that pulled a locking wedge into place when no power was applied. If you wrap some wire around the ferrous material the magnet is pulling towards, you could pass some current through it to generate an opposite field and push the magnet away when power is applied. This should be cheap in bulk (or if you make your own windings), but could be expensive in low volume unless you find a good pre-wound coil.

* You could apply the same principle to clamping the string instead of the pulleys, but then you don't get a positive mechanical lock. I'm not sure if you really need that, but it seems better if it actually keys mechanically rather than just relying on pressure to keep things from moving.

Keep thinking outside the box!
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Re: Ah, *THAT* was what was coming

Postby Nicholas Seward » Thu May 01, 2014 11:30 pm

*The bearing bolts are fine. The y linear bearings are poorly supported. It will bug people more than it is a problem. (Interpretation, it is OK as-is.)

*I finally have a plan. I will basically be doing what you have said. Wood usage is a side concern. My main concern is rigidity followed by overall printer dimensions. The solution will use more wood but will address my main concerns. (Wood is cheap.)

*I am planning on moving my z rod mounts to the side boards with a slot around the rod. I will put a sawtooth pattern on that with a 5mm-ish pitch. I will print a springy piece of plastic that will save me from falls. I will make it so I can remove it or slide it over for 3D path printing.

*The Wally subforum has some tangentially relevant discussion about shorting the stepper coils when you loose power to at least make the falls be super slow and graceful.
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Re: Ah, *THAT* was what was coming

Postby Matt Michalka » Mon May 05, 2014 6:39 am

I finally have the frame cut out, painted, and put together. Now just to mount all the other parts and string it up. Hopefully I'll have it printing by the end of next weekend.
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Re: Ah, *THAT* was what was coming

Postby cdsteinkuehler » Mon May 05, 2014 10:02 am

Where did you get the coated flatstock you used for your CoreXZ?

I'm looking for something similar, but can't find anything locally. So far the best option seems to be some 1/4" maple plywood from one of the box stores. I'd like something I don't have to finish, but am not sure where to look for the melamine coated sheets.
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Re: Ah, *THAT* was what was coming

Postby Nicholas Seward » Mon May 05, 2014 3:08 pm

Looks good. I better hurry up with the redesign.

Check around at lumber supply companies. There is one local called Arcadian that I can get it from. I have to call ahead and give them time to pull a sheet or two but they don't mind working with me. I also use them to get interior grade plywood that can be cut on a laser. Lowes/Home Depot wood is no good for a laser.

Cabinet shops usually get the wood delivered so ask around and see who their suppliers are. To make life easier have them order a sheet and give them a little money for the trouble.
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