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Progress on Richard

Posted by Anonymous User 
Anonymous User
Progress on Richard
April 21, 2007 09:09AM
Hello, I'm Erwin!

I assist Joost in building our own Cartesian prototyper called Richard (Dawkins).
Last week he posted a message with some pictures to show our progress.
Today we added the cross beams, an (alternative) idler/constraint bracket, the x carriage, and z studding ties. The components are made from aluminium and wood.

Find some new pictures attached!


Greetings,

Erwin
Attachments:
open | download - assemb.jpg (92.3 KB)
open | download - corner.jpg (51.1 KB)
open | download - idler_bracket.jpg (66.8 KB)
Re: Progress on Richard
April 21, 2007 10:34AM
LOL! I had a feeling that it would be easy to make the corner attachments for Darwin out of something besides ABS. :-)

That looks REALLY good Joost and Erwin!
Re: Progress on Richard
April 21, 2007 04:05PM
Well done! And if you don't mind - I'm going to copy it!

That said - you will likely have an issue with friction due to the metal on metal design of the idler bracket in contact with the rod. So grease will be needed.

Note also that the rod used could be replaced with tubes into which a hole could be drilled into which we could secure a screw-thus nullifying the need for trapped nuts. The tube would have to be sturdy tho so as not to flex.
Re: Progress on Richard
April 21, 2007 05:29PM
excellent! that is really cool. keep up the good work guys. man, at this rate you will be up and printing before me!!! =)
Re: Progress on Richard
April 22, 2007 12:23AM
Offcourse you can copy it - this is "open source engineering", so you should!

I have also looked at tubes (had som 12mm lying around, easier to saw than stainless steel, smaller sizes might be too bendy) but this would also mean deviation from the darwin design (different sizes) and thus recalculating a lot of the work that is done by Ed Sells, which could result in other issues. Bear in mind, we've never build one of these things before - or anything for that matter ;-)

Regarding the friction, I found that using a hollow aluminium tube (10mm outer diam, 8mm inner) and some vaseline works great as a "sliding bearing". It increases the surface and fits nicely around the 8mm bars.

edit: forget the part about the sliding bearing - it does not work very well. Tolerances make it stick to easy. Also, some oil works better then vaseline.

Also, in the moving wood parts (ie Z studding ties) it protects against wear. For the carriage, I used some old 8mm (bronze) bearings from a scanner and sanded the rods lightly to prevent sticking.

edit: this is still true... as long as there is no horizontal movement but only rotation

The only concern I have right now is the accuracy of the holes in the wood blocks, specifically regarding the Z studs moving the table. We will try to put that together today and see how/if it works.

Anyway, good luck - and if we can help, let us know.

Joost

Edited 1 time(s). Last edit at 04/22/2007 03:10AM by Joost.
Re: Progress on Richard
April 22, 2007 11:10PM
Hey Nathan,

You mentioned in a previous post the thing about the trapped nuts in the wooden corner brackets. As written, I had not done that - but will. Using the screws is not working very well; it is very difficult (i.e. impossible) to get the bottom frame aligned properly. When applying some force on the screws, they are basically pushed out of the wood or the wood splinters. It is too "brittle" (if that is the word) and also the wooden blocks are not accurate enough, so some force is required. So (next weekend) I will try to drill an additional center hole in the block (14 mm diam) and use M5 caps and nuts to fixate the bottom and top frame as per design. When the brackets are not fixated I can not get the whole thing together. Apart from that, it is all getting together pretty nicely.

Joost
Re: Progress on Richard
April 23, 2007 05:03AM
Hi Joost,
As an alternative to trapped nuts in wood you could try the method I used here: [hydraraptor.blogspot.com]. I just drill a hole at right angle to the path of the bolt and fill it with molten polymorph. When it sets I drill it and let the bolt tap a thread for itself. It spreads the load into the wood quite well. Similar to a system with captive metal cylinders used on Ikea furniture.

Chris
Re: Progress on Richard
April 23, 2007 06:12AM
Hi Chris,

Thanks for the tip! Will definitely try that - as soon as I get my hands on some polymorph.

Joost
Re: Progress on Richard
April 23, 2007 06:35AM
what I found

On my machine I am working on I am using MDF and had used 2 blocks stacked on top of each other I then had drilled one hole on the corner of all the blocks and inserted a nut and bolt to tighten the corners after they were allighned then made a block that had the 3 remaining holes alighned and drilled the remaining 3 holes on each corner so they were indexed on the 1st hole I found the mdf was able to be drilled and tapped for a 1/4 bolt. I used 3/4 inch but it was brittle I feel because I had assembled my machine like you seemed to have by assembling the top and bottom frame and the the z axis. I was going to try it using the instructions on the wiki and see if building the 2 frames on top of each other would give me better allighnment then adding the "z axis". I also found it was brittle because I had not yet cut my rods to size.

Bruce Wattendorf
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