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1x2 Repstrap

Posted by Rezer 
1x2 Repstrap
June 08, 2011 03:39AM
I just noticed the repstrap wiki page now says the following:



WolfStrap and the newer 1X2 and 1X2 Tallcat machines seem to be the most popular.

Only problem is I can't find a single reference to the 1x2 anywhere other than the wiki, and the overall description of assembly is pretty light on details. Has anybody other than the creator actually made one of these, or is this a case of one person deciding their way is better and deeming it "popular" without any kind of actual popularity being required? I only ask cause I'm trying to settle on a design to start with and this thing looks at first glance to be much more difficult to assemble than other repstraps for no real benefit other than trying to look like a mendel...am I mistaken?
Re: 1x2 Repstrap
June 08, 2011 06:02AM
Yes, I've built one, and there are a couple of others who have built them. There is a Thingiverse page: [www.thingiverse.com] and the main source is [mrkimrobotics.com]

The original 'compact' version I built does have its problems, notably limited Z-axis height, which the 1X2 Shortcat overcomes, but has an advantage of using only one length of rod. The 'compact' is pretty well documented, but the other versions are a little sparse. The basic structure is relatively straightforward, and you become more confident to change things as you progress. I think each one made will tend to be unique, and up to the builder to resolve various problems along the way.

Is it awkward to put together? Yes and no. Not as many little bolts as Mendel, but quite a lot of parts on each threaded rod, so if you want to change a part or forget a nut/washer, it all has to come apart. Mine has been apart and reconfigured 5 or 6 times. I also didn't like the stacks of 608 bearings, and the side loading forces that were put on them; I ended up using linear bearings. I made a Y-axis table rather than conveyer belt, as the toothless belts are potentially less accurate and can suffer from belt crawl; I got mine printing, but had to home each layer. I printed Mendel motor pinion gears as the first thing, and quickly changed to T5 belt! A dot-matrix-printer-style toothed conveyer belt would give it the positional accuracy.

I always regarded the initial design as a stepping stone, either to improving the 1X2 by self-printed improvements, or for repstrapping a complete Mendel/Prusa/Next greatest reprap, and learning how everything works. I also set myself the target of building it from off-the-shelf, locally source parts (well, nearly, except for electronics and motors) and using no printed parts, as if this was the first ever reprap. The 1X2 suited these ideals well, and I was seduced by the way it looked more like a reprap than Wolfstrap-style repstraps. I'm slowly getting settings dialled in so it can 'reproduce'. Perhaps I should create a wiki entry for my version as a derivative... (please don't make a page for me just yet!)

If I was starting from scratch again, I'd probably go down the Wolfstrap route, probably using this as the basis: [www.thingiverse.com]

Edited 2 time(s). Last edit at 06/08/2011 06:10AM by droftarts.
Re: 1x2 Repstrap
June 10, 2011 12:30AM
Yeah, the toothless belt design is one of the things I was really raising an eyebrow over...I've been leaning towards a wolfstrap/eiffel myself since it may be possible to re-purpose either as a small cnc router if I ever progress to a mendel. Thanks a lot for the reply smileys with beer
Re: 1x2 Repstrap
June 10, 2011 03:15AM
Smooth belts worked well-enough to produce self-improving parts, though I have gone through 4 generations of motor pulley to get to something that is high quality - PVC tubing/smooth belt > low quality printed pulley > better quality pulley > high quality pulley with captive nut. Also, I didn't make the belts MrKim suggests, I used plastic/nylon packing straps that crawled a bit on the motor pinion. I think it's a worthwhile exercise, building a repstrap without using any printed parts and from basic materials, and I learned a lot doing it; I've had to make my own choices and experiment, so any Reprap I build I'm likely to change rather than following the instructions to the letter. Cost wise, I don't think it was much cheaper than starting with a set of parts, especially when I add in time, tools I bought and parts bought to experiment/in error/didn't work/replaced with something better, though I have yet to count up the final cost. The Wolfstrap route, like you say, would allow you to repurpose the machine, whereas it would be difficult to do that with the 1X2. But if you don't have the time, tools, space, aptitude, or just want to get printing, buy parts!
Re: 1x2 Repstrap
June 29, 2011 12:11AM
Congratulations, Droftarts.

Few people actually follow strictly scratch built Repstrap projects all the way to the bootstrap stage. It is a challenging project to undertake.

True Repstraps are as much about addressing issues of self-replication as about issues of cost. Your bootstrap, from flat "packing strap" belts with flat drive pulleys, to printed toothed drive pulleys is a notable achievement.

Especially if you would do it over differently, I hope you do write up your experiences of getting to your first print.

I still have my first wooden Mendel even though I had originally planned to replace it piece by piece with printed parts.
Re: 1x2 Repstrap
June 30, 2011 10:59AM
Hi MrKim! I've been a bit lazy about writing up my experiences for the wiki, as I have been moving house. I've now added longer 'dogbone' vertical arms and moved the X-axis motor and pulley to improve the Z-axis range of my 1X2, which has improved from 35mm to 95mm, allowing me to print the makerbot plates for Mendel Prusa, which I've just started. Generally it's holding up pretty well, and I'm glad I built it myself, despite it's limitations. I think I'm unlikely to pull it apart either; I might repurpose it as a PCB mill to produce RAMPS boards, which I think it would be capable of, or print PLA with it while the Prusa prints ABS. Or something else entirely!
Re: 1x2 Repstrap
January 09, 2013 02:07PM
Do you have any pictures of the frame. I started making one the got busy, so I could not finish it. Then the instructions on how to put it together are gone so help would be appreciated
Re: 1x2 Repstrap
November 13, 2013 11:24PM

First post. I joined because I would like to build a repstrap preferably the 1x2 (either shortcat, tallcat what ever) and the instructions for assembly are missing. Wondering if anyone has them could they post them or email them to me please.

Thank you
Re: 1x2 Repstrap
June 20, 2014 07:59AM
Hmm November 13 2013...

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