Sunday, September 22, 2013

3DR “Simple” Delta Printer, Part I

About 8 months ago I discovered personal 3D printers when I learned we had an Up! 3D printer at work specifically for employees to play with. This is a very nice little printer that prints in ABS plastic. I used it to create some parts for my injection molding machine, and I got hooked.

So about 6 months ago I got my first 3D printer, which is a Printrbot Simple:

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They had a special beta price for the first 200 printers of $250 for the kit. For that price, I figured I couldn’t go wrong. I ended up making a lot of modifications to the printer. All parts that are in blue are parts I designed and installed on this printer. I thought this printer was just wonderful, until I purchased a larger and more capable printer, a MendelMax 2.0. Once I got that printer running, I didn’t touch my Simple.

Then about a month ago, I saw an open-source design created by RichRap, one of the well-known early contributors to the personal 3D printer movement. I’d been wondering what to do with my Simple, and then I realized I could use all of the “vitamins” (things like the electronics, stepper motors, bearings, etc.) to build a new printer for not that more more in cost.

RichRap’s printer is called the 3DR RepRap Delta Printer. His printer uses 6mm diameter smooth rods, whereas my Printrbot Simple uses 8mm rods, and therefore has a bunch of 8mm bearings. In the spirit of using as many parts as I could from my Simple, I set out to modify his parts to use 8mm rods.

And there began an adventure. You see, his parts’ design files are published in Sketchup and STL files. I use Solidworks, so I couldn’t just open his files and change a few things. I figured it wouldn’t take much work to re-create his parts in Solidworks, and it didn’t. But I couldn’t leave well enough alone. I ended up adding curves where he had straight lines to make it look “nicer.” Here is the first version of my derivative design:

Progress 2

I use different colors to denote the different parts. The base of this printer is made from three identical parts that are bolted together, just like RichRap’s design. Once I had this design more or less worked, out, I printed a set of parts for the base. Here is the first one being “born” on my MendelMax 2.0:

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And here are the first three parts assembled:

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Not a bad start. Part II will continue the journey.

6 comments:

  1. Great work!
    I'm currently retrofitting my CNC machine with a print head with the intention of making a 3DR.
    I'm curious....How long does it take to print one of the base parts?

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  2. It takes about 5 hours to print one of these parts on my MendelMax 2.0, running at 40mm/s for the outer perimeter, and 80mm/s for inner perimeters and infill.

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  3. Two observations about using the Printrbot laser cut extruder body as a Bowden pusher.

    First, the rectangular gap between the bottom of the hobbed bolt and the top of the hotend is much too large, and without a hotend the cavity that it would normally mount in is positively gigantic. Both of those contribute to frequent filament bending and jamming. Our solution to that was a carefully cut wooden block that filled the big space, and a piece of Bowden PTFE tubing with the sides shaved down to fit in the gap. If we were doing it again, we'd make the Bowden adapter plate with a block to fit the gap and a socket for the PTFE to slip into for registration, with a pushfit on the outside.

    Second, the hobbed bolt that Printrbot uses, while quite serviceable for direct attached hotends, doesn't seem to have enough grip for a Bowden. After struggling with it for quite a while, we've switched to the Airwolf3D bolt and are very happy so far. We also bought some Hive76 bolts from Ultimachine, since we've heard good things about them.

    In the end we also switched to a modified version of the Greg's accessible extruder, which isn't quite as nice as the Printrbot in terms of filament loading but seems more reliable in the long run. It's entirely printable of course, and uses the three 608 bearings and some of the screws from the Printrbot, with just a couple of new M3 screws required.

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    Replies
    1. Thanks, Bill. That's really great information. I haven't looked at the extruder yet to see what would be involved in adapting it to this printer. I was assuming I could design a printable adapter that would take care of all these issues. Having your information when I get there will be really nice.

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  4. While you are at it, it would be great if you can make the base sections fit on a 120mmx120mm footprint. RichRap's are bigger by only a few mm, and cannot print on several mainstream machines (ours Up! mini). You can do this simply by chamfering one of the corners of the center intersection; it may be a bit unpleasing to look at but better for the people!

    Also, it would be great if you can share the SolidWorks files so that we can also work on this great design.

    Thanks, and keep up the great work!

    Ahmet Onat

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    1. See part II: http://trains.socha.com/2013/10/3dr-simple-delta-printer-part-ii.html. I've broken up the parts so they can be printed on a Printrbot Simple, which has a 100mm x 100mm bed.

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