Dibloff's Build Log

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Re: Dibloff's Build Log

Postby dibloff » Wed Oct 24, 2012 3:24 pm

zkaplan wrote:Hi dibloff,

Zach from Inventables here. I am sorry that our pictures didn't clearly show the shaft on the other side of the motor. The shaft length was indicated in the technical specs but that is no excuse because after reading your story and looking at the pictures I think this is clearly an error on our part. I have asked our photographer to take another picture that clearly shows the shaft coming out of the back.

I'd like to offer you a $50 gift certificate to our store as a way of saying sorry for your hassle. To redeem it please send an email to help at inventables dot com and we'll hook you up.

Sorry about that.

Regards,
Zach


Dear Zach

Thanks for the explanation. I probably looked into the tech spec but I have not spotted the double shaft ending. I appreciate your offer, but I will kindly decline it.
I think you’re doing a great job with your web shop. I did not want to discredit your store in any ways, I’m sorry if it seemed so. I just wanted draw others attention to this issue.
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Re: Dibloff's Build Log

Postby Enraged » Wed Oct 24, 2012 4:05 pm

If you get the machine up and running, you can just print a modified, taller foot.

It's nice to see inventables stands behind their products and makes offers like that. Makes me more inclined to buy from them again in the future.
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Re: Dibloff's Build Log

Postby mikegrundvig » Thu Oct 25, 2012 2:09 am

Yeah, I'm pretty impressed with that offer as well. I already liked buying from Inventables but this just reinforced that further.

dzach wrote:The only difficulty I had with the OrdBot, which, I think, also exists with all of the RepRap designs using similar Z axis arrangement, is aligning the Z axes with the motor axes. Having the mounting plates thinner helps dissipate misalignments right at the motor by allowing the mounting plate to flex slightly. Thicker plates do not allow that and misalignments may show up in prints. This is a different issue than bent threaded rods, for which lead screws and nuts may be a solution.
The official OrdBot design uses a combination of 0.125" and 0.09375" aluminum plate in both 6061 and 5xxx series. I modified the design of the parts slightly to allow for using only a single thickness and grade of material across the board to reduce price and increase rigidity. Specifically 0.125" 6061-T6 aluminum was what we used for the group buy. The only visible difference was thicker parts in places and a wider radius bend in the extruder carriage. The extruder carriage was 5xxx to allow for a tighter bend without weakening - we had to go for a 0.25" inside radius rather than 0.125".

With that said, I flat out disagree with what you are saying. I just don't accept that the solution for misalignment is to let things wiggle and flex. The solution for misalignment is to fix the misalignment. Flexing might seem like a fix but it really isn't. It means something is moving in an unexpected direction. Motion that should have been traveling in one dimension is now split into several and stress is being placed on multiple parts in unexpected or at least unplanned ways. Flex in the Z motor mounts for instance would cause your layer heights to not match what's expected if I had to guess. Now in low quality 3d prints like pretty much all extrusion-based printers this might not be apparent as the layer height is pretty "loose" already. But that doesn't change the fact that it's not the right solution to the problem.

-Mike
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Re: Dibloff's Build Log

Postby dibloff » Thu Oct 25, 2012 2:58 am

I had some trouble with the thicker plates. I’m NOT COMPLANING. Again: I’M NOT COMPLAINING. I’m enjoying the build.
The thicker plates created less clearance for the belt to ride, so I replaced the plastic spacer under the idler with washers. I believe two 1mm thick washers. It looks on the pictures that the idler touches the plate, but it’s not.
2012_1024_Hadron 103.JPG

I also countersunk the holes in the plate with a 120 deg chamfer-bit. This way I could use a countersunk screw.
2012_1024_Hadron 102.JPG

Yeah. Having 1/8” plates is cool cause you’ll have more stiffness (and I vote for it), and you can cut the entire set from the same sheet, but the clearances are so tight on this machine that it’ll give a lot of headache. Again. I enjoy the build.
Actually tonite I had no desire to get out there and start tinkering with it. Miraculously my headache went away after tightening a single bolt on it :)
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Re: Dibloff's Build Log

Postby mikegrundvig » Thu Oct 25, 2012 3:01 am

Heh, I figured there would be a few clearance issues. Please do log them all as our club will need to buy appropriate parts instead.

-Mike
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Re: Dibloff's Build Log

Postby dibloff » Thu Oct 25, 2012 3:05 am

Here is a view of the belt bracket with the belt installed into it
2012_1024_Hadron 002.JPG

I installed the end switches tonight. I used small custom made clamps to lock the cable to the plate. I drilled and tapped M3 threads directly into the plate and used some loctite on all screws. This is the carriage plate assembly
2012_1024_Hadron 004.JPG

Here is the Z axis plate
2012_1024_Hadron 007.JPG

And the tray viewed from below
2012_1024_Hadron 008.JPG
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Re: Dibloff's Build Log

Postby dzach » Thu Oct 25, 2012 5:53 pm

With that said, I flat out disagree with what you are saying. I just don't accept that the solution for misalignment is to let things wiggle and flex.

The problem seems to be axial collinearity. In practice, making the motor axis and the threaded rod / lead screw collinear proves to be a difficult exercise, given the budget and the simplicity of the rest of the design. Small angular misalignments at the motor / threaded rod coupler get amplified by the -usually low Z- position of the Z-axis nut and, together with any wobbling due to a bended threaded rod, appear on the X-axis and in the print. So, easing unnecessary constrains (e.g. having an open ended Z-axis at the top or allowing subtle 2 DoF flexing of the mounting plate) proves to be a practical and extremely affordable solution that vastly improves quality of the printed parts.

In any case, I enjoy reading your build blog. In the end we can all gather useful information about what modifications are feasible and practical within the budget of an OrdBot.
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Re: Dibloff's Build Log

Postby dibloff » Thu Nov 01, 2012 3:33 am

It’s a new week, the same old challenge. The thicker idler plate and motor mount made the belt setup miserable. I first used a stack of washers (about 4 of them) above each v-bearing but then the set screws were not long enough to reach the end stop switches.
2012_1024_Hadron 105.JPG

Here is the idler end:
2012_1024_Hadron 104.JPG

So I decided to countersink the mounting holes so I can bring the tray back down. This will give more rigidity to the tray against transverse wobble. As you can see it worked out nice. Here is the idler end again. There is 1-1.5 mm gap between the belt and the plate.
2012_1031_Hadron 010.JPG

I omitted the plastic ¼” spacer and used two 1mm thick washers
2012_1031_Hadron 004.JPG

Here is the motor end, you can see there is an ample amount of gap between the belt and set screw.
2012_1031_Hadron 012.JPG

I ended up offsetting the idler wheel to the left as shown. This was necessary because I’m using M5 screws for the end stops and the belt kept rubbing against them. This is caused by the fact that the idler has a larger diameter than the driving pulley. In general it’s a sourcing issue. If there would be an idler pulley with a 11 mm belt track diameter it would have been ideal. This one I believe is 17 mm dia.
So here is the idler plate. With the oval hole and wide open eyes it looks like a face asking me “now what?”
2012_1031_Hadron 001.JPG

Since the tray is back to it's original height the end switches will be able to hit the set screws.
2012_1031_Hadron 011.JPG
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Re: Dibloff's Build Log

Postby dibloff » Thu Nov 01, 2012 3:39 am

Have not received the extruder yet, although I've gotten an email about being next in line, and a notification about the shipping too. Keep waiting. Now comes the wiring. I've got a crimping tool @ Fry's (http://www.frys.com/product/1922790?sit ... IN_RSLT_PG) but it did not work on the terminals supplied by Panucatt. Plan B.
All the mechanical setup is complete now. I managed to set up the X frame rail perpendicular to the main rail. It was a 30 min job.
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Re: Dibloff's Build Log

Postby mikegrundvig » Thu Nov 01, 2012 6:32 pm

I'm not using the same belt clamps or larger diameter pulley as you but I do have the thicker plates and I'm just not running into the same problems you are. Sorry for the issues!

-Mike
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