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About those metal corners

Posted by jarjar 
About those metal corners
June 15, 2018 10:08AM
Hi there,

So I purchased some of these popular 2040 metal corners from RobotDigg to build my delta:
https://www.robotdigg.com/product/555/2040-or-3030-Alu-Vertex-for-Kossel-XXL-or-XXXL

And I was really surprised to see how terrible they are... Tolerances are all over the place.

- Top and bottom surfaces aren't even remotely parallel.
- Angles are not 120°.
- Bearing holes are oversized and the bearings wiggle.
- Provided idler pulleys are so badly machined that a 6mm belt don't even fit (slot for belt is about 5.6mm).

In conclusion I don't see myself building a precision delta with those pieces of crap.

Are there other experiences with these metal corners?

Edited 2 time(s). Last edit at 06/15/2018 10:15AM by jarjar.
Re: About those metal corners
June 15, 2018 11:31AM
Do you still have the cardbox, they came in? Send them back, but claim for an RMA ticket.
Re: About those metal corners
June 16, 2018 06:46AM
When I bought a set of Robotdigg 2020 corners, one of the top corners was terrible but the other 5 corners were good. They replaced that one after I sent them a photo. The 2040 corners that I subsequently bought from them were good, but I didn't use the idlers because I wanted to use toothed ones.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: About those metal corners
June 17, 2018 06:47AM
All the corners on my delta printer were terrible. I had to machine both sides to make them perpendicular to the vertical slot. When mounted on the milling machine one corner on all pieces was over 0.5mm off. This meant that all the vertical beams had a sort of spiral upwards from the print bed. The corners are not 60 degrees either, so that doesn't help. Unfortunately I got these with a used machine so there was no possibility of returning them. I have however corrected most of the misalignment by milling them. I also bolted down the corners on the milling machine while assembling the horizontal beams to them. This way I could control the distance between the corners and parallelism of the horizontal beams. I think the overall approach to this sort of structure is terrible, but at the moment I'm stuck with what I got. Good luck on your project!
Re: About those metal corners
June 18, 2018 09:00AM
That and the limitations of extrusion size is why I built my delta without metal cast vertices.

Edited 1 time(s). Last edit at 06/18/2018 09:01AM by cwaa.
Attachments:
open | download - 2018-06-15 002.jpg (472.9 KB)
Re: About those metal corners
June 19, 2018 12:22AM
@jarjar
@TheBlight
Where's the proof?

You both are fresh members and I'm suspecting conspiracy here.
Someone hired "influencers" to spread bad news about robotdigg?
Re: About those metal corners
June 19, 2018 02:43AM
Quote
o_lampe
@jarjar
@TheBlight
Where's the proof?

You both are fresh members and I'm suspecting conspiracy here.
Someone hired "influencers" to spread bad news about robotdigg?

I wonder how much they paid dc42?? drinking smiley
Re: About those metal corners
June 19, 2018 03:35AM
Thanks for all your feedbacks.

@o_lampe
Sending them back is not an option since this would cost at least as much as the corners...

There is a lot of Ultibot D300VS users which use the exact same corners but I didn't see a single complain about them.
That's why I wanted to ask here if I was the only one having a bad experience with them...

I still used these corners to build my delta since I had all of the parts and didn't see an easy alternative to them.
Assembly of the top and bottom triangles was a real PITA and the end result is certainly not a "precision" delta, but it works.

I filed the crappy idler pulleys to make the belts fit. I later noticed that even the tiniest amount of axial play between the idler and the bearings make them do a "clunk clunk" noise when moving. Very annoying.
So I purchased some extra idler pulleys from Ultibot (https://www.ultibots.com/2040-metal-frame-aluminium-idler/),
hoping they were better than the provided ones, but ended being just as bad.

Now I start wondering whether most delta builders have simply low expectations...

Edited 3 time(s). Last edit at 06/19/2018 03:37AM by jarjar.
Re: About those metal corners
June 19, 2018 10:02AM
Quote
o_lampe
@jarjar
@TheBlight
Where's the proof?

You both are fresh members and I'm suspecting conspiracy here.
Someone hired "influencers" to spread bad news about robotdigg?

I didn't say where these corners came from, and I have no idea where they originated from either. They came with a used machine and look like the ones in the link. To be perfectly honest I don't even know who robotdigg is.

Because the corners have been machined I don't have proof of how bad it was and I can't go back in time to prove so.

As for my credibility, check out this topic of a CNC lathe I made years ago. Should I make a post there to prove that it's me as well?
[www.cnczone.com]

I haven't needed any help from this forum before, but when I saw this discussion I figured I would register and share my experience. I won't make that mistake again.
Re: About those metal corners
June 19, 2018 11:06AM
I am not a new member and after a lot of research on delta printers, I decided against cast corners due to complaints. My entire build was planned so I did not have to use them. I think you are blowing hot air!
Re: About those metal corners
June 22, 2018 09:36AM
My corners from RobotDigg were as spot on as I could measure.

I rebuilt my mini delta with them, and it now doesn't need any form of mesh correction, it just prints flat all over the bed.


Even if they are a bit out, you can work it out as really every vertex should be treated like a pin joint.
Re: About those metal corners
June 22, 2018 11:38AM
How long have you worked for robotdigg?

Edited 1 time(s). Last edit at 06/22/2018 11:40AM by cwaa.
Re: About those metal corners
June 26, 2018 12:02AM
I've used their 2040 with no issues.

The complaints that you have are vague .

Top and bottom surfaces aren't even remotely parallel.
You only need one side to be parallel

Angles are not 120°
If they are not what are they ? 119.5?

Mind you that the corner angles are pretty standard.

If you truly want something "precision", go to some expensive CNC shop, give them a tolerance spec, ask them to fabricate it for you, and of course pay the money.
Re: About those metal corners
June 26, 2018 04:47AM
To be fair, my corners were for 2020, not 2040 so they're obviously a different product. However I'm very happy with them.

And no I don't work for RobotDigg, why on earth would I want to?
Re: About those metal corners
June 27, 2018 04:54PM
I've never gotten a delta corner that was a good tolerance and I can tell you it does not matter one bit. Get some brass shims and work with it. As long as they hold the extrusions tight you will be file.

Here are my builds and example prints. Both builds needed at least .5mm of shimming or more. I really liked the robodigg ones cause it seemed a lot stiffer than the plastic ones of my first kit.

[imgur.com] <-plastic parts with even worse tolerances

[imgur.com] <- delta with robodigg parts.
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