Printed ORD Bot

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Re: Printed ORD Bot [X Stage]

Postby crispyfry » Sat Mar 31, 2012 6:13 pm

I got the X carriage printed and assembled over the past few nights. I decided to make this out of 2 parts and use ABS+acetone to glue them together. I have used this method in the past to join parts and it gives a very strong joint with none of the brittle-ness you see in superglue joints.

After posing the question to the ORDBot forum, I made the decision to remove one wheel from the carriage and use 3 wheels - 2 fixed (top) and 1 adjustable (bottom).

I also made some small changes to the hole pattern on the bottom face of the carriage, to give more adjustability to the extruder position, and to make sure a custom hotend mount plate I have will fit. I added the side triangular walls and the back face bevels for support and to give the acetone+ABS glue a larger surface area to bite on. I added 2 screw holes at the tops of the braces to help make sure the 2 parts go together flat.
2012-03-31_12-58-43_136.jpg
X Carriage Pieces in Print Orientation


These parts printed flat, but after I removed them they developed fairly serious warp issues. These are the first parts so far I've seen warp, and unlike the Z plates, for example, you can't "pull" them flat to the extrusion because the X carriage isn't bolted down firmly - it rides on wheels. I was able to remove most of the warp by heating the parts up to 110C on the bed and slowly cooling them down, combined with some "artful" bending. They are not perfectly flat but they are much better than they were.
2012-03-30_20-37-23_728.jpg
Warped Part

EDIT: I've been asked to include some post-warp-correction pictures. These are the best I could do:
2012-03-31_14-18-46_618.jpg
Back Piece Flatness Check

2012-03-31_14-19-07_195.jpg
Bottom Flatness Check


To glue the pieces together, I sanded the mating face of the bottom piece to flatten the surface out (the mating face of the back piece was against the glass - no sanding needed), then used a small paintbrush to apply a liberal coating of acetone+ABS glue to the mating face of the bottom piece. At nearly the same time I squash the pieces together as fast as possible, get the screws started, and get the carriage into a clamp before the acetone evaporates. After the initial set I went back and applied more glue to the joint to make sure it was filled and fully bonded.
2012-03-31_13-11-37_288.jpg
X Carriage Being Glued


After about an hour I took the parts out of the clamp and checked for flatness. Overall I think the part is usable, but I will very probably replace this with a metal part when they become available from Bart - what I have now is not an ideal solution.
2012-03-31_13-53-23_898.jpg
X Carriage Assembled


That about covers it. Still waiting on my shipment from Misumi to begin putting things together.
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Re: Printed ORD Bot

Postby JeremyBP » Sat Mar 31, 2012 7:37 pm

That's seriously impressive. Keep it up!
Are you printing on kapton? If so, try just slowly cooling the bed down before removing the prints until the parts lose adhesion and come off. That may help with warping. I've never printed anything with that large a base area in ABS though, so I'm not entirely sure.
I really can't wait to see how this comes out.
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Re: Printed ORD Bot

Postby crispyfry » Sat Mar 31, 2012 8:51 pm

JeremyBP wrote:That's seriously impressive. Keep it up!
Are you printing on kapton? If so, try just slowly cooling the bed down before removing the prints until the parts lose adhesion and come off. That may help with warping. I've never printed anything with that large a base area in ABS though, so I'm not entirely sure.
I really can't wait to see how this comes out.

Thanks for the compliment!

I'm printing on plain glass coated with a small amount of "ABS juice" - acetone with some scrap ABS parts dissolved in it. The holding power is unreal: I was breaking glass plates until I dropped the bed temp to 95C. Even then, sometimes I have to pop the whole plate in the freezer to get the parts to unstick.

When I printed the X carriage, I put them in the freezer a little sooner than I normally do. I think the higher and more unequal rate of cooling over the part may have contributed to the warp.
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Re: Printed ORD Bot

Postby Halfdead » Sun Apr 01, 2012 12:54 pm

I'd suggest borosilicate glass for the build surface. It's what I plan to be using.
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Re: Printed ORD Bot

Postby crispyfry » Sun Apr 01, 2012 4:08 pm

Halfdead wrote:I'd suggest borosilicate glass for the build surface. It's what I plan to be using.


I had one, I broke it. I'm now using cheap glass from my local Lowe's and it works just as well - 2 bucks per sheet and I can run out and buy more when I break them.
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Re: Printed ORD Bot

Postby Enraged » Sun Apr 01, 2012 5:49 pm

where do you buy borosilicate glass? or just cut up a Pyrex dish?
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Re: Printed ORD Bot

Postby alwayswill » Sun Apr 01, 2012 6:24 pm

I just found out the other day...

Looks like McMaster-Carr sells "Heat-Resistant Borosilicate Glass"

http://www.mcmaster.com/#catalog/118/3622/=gx3dqx

-Will

Enraged wrote:where do you buy borosilicate glass? or just cut up a Pyrex dish?
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Re: Printed ORD Bot

Postby Enraged » Sun Apr 01, 2012 6:43 pm

Mcmaster won't ship to Canada, so I guess I'll keep looking for a source. Thanks!
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Re: Printed ORD Bot [Y Plate]

Postby crispyfry » Mon Apr 02, 2012 12:07 am

I designed and printed the Y plate today. I had been holding off on this for a couple days because I wasn't quite sure the best way to do it. Hadron uses a massive piece of plate aluminum, which I can't (aka haven't bothered to) source locally and couldn't machine with the necessary tolerances even if I could get my hands on it. I looked at Quantum's build plate, which is of a printable size, but it's still bigger than it needs to be. Then we have to address the fact that you can't put a heatbed on top of the something made out of the material you're printing because it gets very soft!

So I ended up designing a small plate roughly the dimensions of the back of the X carriage - just big enough to carry 3 wheels spaced apart appropriately. On spacers will sit an intermediate plate that interfaces with the bed. This intermediate plate could be wood or metal. The spacers give space for the bolt heads for the wheels, belt clamp, endstop trigger, etc.

Here's what I ended up with. Just a simple, minimalistic plate and 3 0.25" spacers. It's hard to tell in the picture but I'm getting some weird resonance issues during fill when both motors are moving. I haven't been able to track down a cause yet, but I'm tentatively thinking the linear bearings are slightly out of alignment.
2012-04-01_18-32-52_351.jpg
Y Plate and Spacers


And here's a tolerance check when the print was finished. Nothing to complain about! (Nominal is 0.25", indicated is a hair heavy.)
2012-04-01_18-34-14_912.jpg
Spacer Height Check


Warp on this part is minimal. I'm going to chalk that up to not using the freezer to break the part loose.

Misumi shipment should arrive Tuesday, and then I can start throwing hardware together. I'm holding off on ordering the eccentric spacers until the V-wheels are in stock, which is supposed to be April 16 according to the makerslide store. So, those components will be critical path for the build.
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Re: Printed ORD Bot [Misumi Parts & First Assembly Steps]

Postby crispyfry » Wed Apr 04, 2012 2:43 am

My shipment from Misumi finally arrived today. This means I've got 85%-90% of the hardware I need to build this bot. Still to buy or make are:
    - Z rod couplers
    - Makerslide eccentric spacers and V-wheels (including bearings)
    - Intermediate HPB holder

I broke down and ordered some additional motors today as well, for 2 reasons: 1) it allows me to delay cannibalizing my current printer for parts which allows me to print last-minute changes later without moving a bunch of parts back and forth, and 2) they are higher torque and lower current than my current motors, so I can push the bot faster without the drivers overheating. I only ordered 3, for X, Y, and E. Z motors don't see much strain.

The extrusion I ordered from Misumi is 550mm long, so I will have to trim it down to the right length.

Here's a shot of the extrusions and printed parts. This is not the complete set of parts.
2012-04-03_18-27-33_256.jpg
Extrusions and Printed Parts


And here's the first steps in the assembly: bolting the Z plates onto the ends of the X axis piece of Makerslide. I'm pleased to report everything went together smoothly.
2012-04-03_18-35-32_152.jpg
X Axis with Endplates
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