ORD Bot 3D Printer

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Re: ORD Bot 3D Printer

Postby mxk » Tue Jan 31, 2012 3:37 am

bdring wrote:Feedrate...I was talking about the step/mm.


Sorry, I misunderstood you. I believe that Makergear recommends starting at 1487 using a 16x micro stepping controller, which is usually how the RAMPS are set up. Since the plastruder has high reduction you may want to change that to 8x and adjust the settings in your firmware. It unfortunately depends a lot on your filament and the tension in the idler, so you will definitely have to adjust it to get it right.

I recommend the Ultimachine PLA; not brittle, good dimensional stability along the length (Chinese PLA often is put on the spool warm resulting in stretched or not round filament), prices are okay, and they always throw in samples of other colors.
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Re: ORD Bot 3D Printer

Postby bdring » Tue Jan 31, 2012 1:44 pm

Thanks. I found that same 1487 "feedrate" in the MakerGear forum.

The project is going together quite smoothly so far. 4 out of the 5 motors turned the right way on first try. I have never been that lucky :D
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Re: ORD Bot 3D Printer

Postby bwevans » Tue Jan 31, 2012 8:07 pm

The number Ive got for the makergear extruder is 1380 steps/mm although that seems fairly high to me. Im using a different geared stepper with a ridiculously small step angle and it only needs 242 steps/mm. If we assume the makergear has a 13.6:1 gear ratio - its hard to tell - and with the 10mm gear pitch diameter then you end up with 200*16*13.6/1/3.1459/10 = 1383.3879 steps/mm. So I guess 1380 is a good place to start.

The slide looks great! I would worry about making it any bigger... surely the wades could fit as is and worse case all you would need to do is make a mirroed version of one to get the gears facing out. <edit> Strike that... I dont really see why having the gears face inward would be a bad thing.
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Early Design Rejects

Postby bdring » Wed Feb 01, 2012 1:48 pm

Sharing the fails...

I was looking through my image folder for this project and found some early design rejects. At some point I thought these all were pretty awesome looking, but quickly realized their flaws. These are quite different, but the design cycle was pretty compressed and this only represents about 2 calendar days of work.


This was my first concept. My idea here was trying to use one common plate everywhere possible. While I am sure it would be rigid. The bottom cries out for a single plate across. That would have killed the scalability...FAIL
dsb_01.jpg


Here is a minor refinement. This cleaned things up a little, but again, the bottom still looks very clunky. the feet are OK, but I like the current ones better....FAIL
dsb_02.jpg


At ORD Camp I attended a few talks on visualization and graphical brainstorming. A great one by Graphic Facilitator Brandy Festo was awesome. One topic that was discussed was how some of our presentation tools can make anything look good and it is often best to present in more of a sketch mode in the early stages. It also implies that the design done when the presentation is too polished. When all the work is in CAD this can be difficult, but there are "sketchy" renders and you can remove all color. I think I get into the mode of trying to sell my ideas to myself and others too soon when I am really still in brainstorm mode. Unfortunately this talk happened after the design was done.

One day I want to work for a company (or own one) that hires graphic facilitators.
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Limit Switches

Postby bdring » Wed Feb 01, 2012 7:02 pm

Here is my design for the limit switches. It was tough to show well because they are designed not show much at all. The switches mount to the backs of the carriage plates. They are trigger by set screws that screw into t-nuts. The screw bottoms in the slot forcing the nut against the top. This allows full adjustment. The bed carriage uses the same idea.

The nice part is it does not add any new custom parts.
Attachments
limits.jpg
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Re: ORD Bot 3D Printer

Postby BenJackson » Wed Feb 01, 2012 9:12 pm

I'd restructure that to put your Z limit at the top. I've got two 3D printers (one each way) and it's much easier to deal with Z limit at the top rather than the bottom.

With the limit at the top you let it be at an arbitrary position and then jog Z into place and note the necessary G92 offset and put it in your preamble.

With Z at the bottom, if it is too high you can't jog down to reach the bed. If it's too low you risk running the printhead into the build surface. Even if you disable or remove the Z limit so you can jog to Z0 it's hard to put the limit switch in exactly the right position to repeat that zero.

With the limit at the top you just modify your preamble if you change your build surface (different kinds of tape, glass, etc). With the limit at the bottom you have to physically adjust it each time.
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Dual Limits

Postby bdring » Wed Feb 01, 2012 9:29 pm

Thanks,

That is good input. I will put the hole pattern on both sides of all axes. That way you can pick max, min or even both.
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Re: Z axis endstop at the top of the print space.

Postby LeonS » Wed Feb 01, 2012 10:02 pm

Ben, that is an awesome idea! I have never seen or heard of that approach.

Thanks for sharing!
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Re: Z axis endstop at the top of the print space.

Postby BenJackson » Thu Feb 02, 2012 12:06 am

LeonS wrote:Ben, that is an awesome idea! I have never seen or heard of that approach.

I can't take credit: That's how the MakerBot Thing-o-Matic works. I don't use that method on my Prusa because the Z travel is longer and its top speed is verrry slow.

The Prusa dual-motor Z is a clever idea but I dislike it in practice.
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Design Tweaks

Postby bdring » Thu Feb 02, 2012 2:18 pm

Here is a rendering of the latest design changes. All the parts are now compatible NEMA 14 (shown) and NEMA 17 motors. The Quantum size is running great with the NEMA 14 motors, but the larger sizes will need the 17 size. The larger size of the motors caused the feet go get a little taller. The Y motor also moved to the back. This allows the motor brackets for Y an Z to be the same. The front foot was previously pushing the Y motor forward and requiring its own bracket.

I am still waiting for my PLA to run the first parts. Other than than it is fully wired and running. I hope to bring a printing ORD Bot to PS1 DIY CNC night next Wednesday. If you are in the Chicago area stop by. It is free (donation suggested).

On another note, I added RepRap specific G-codes to myG-Code commenter page.

design_tweaks_02.jpg
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