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Working Notes. This is a stub!
Everything below this point is working notes.
Photos and Drawings
This repSTrap is based on the Darwin. Unlike the Darwin it uses bearings not sliders and there are no trapped nuts. Not even one.
I have developed/ stolen the following technologies / design principles while building the sgbot.
///Set and Forget. – No adjustment hell. Once something has been adjusted and set that is it. There is no readjustment. There is a clear line of dependencies. I.e. no circular dependencies where you adjust something which means something else is adjusted which requires you to adjust the original adjusted thing.
// No adjustment If something can be set in the build phased for the life of the machine it is. For example the threaded rods which drive the Z axis are fixed and cannot be adjusted. Either they work or they don’t and you get it right before building the XY mechanics.
//Small steps As each bits is made it is tested and tested and tested. Only when it passes all of it’s tests do we move on to the next thing and never test it again.
//Hard vs Soft Where there is a moving interfaces. One surface is hard and the other soft. This means you know where the wear is. For example the bearings are made of steel (hard) and run on aluminium slides (soft) so the bearings over time will wear a track into the aluminium and bed in.
//Kebab technology – i.e. No trapped nuts Basically there are no trapped nuts. Components are kept in place by a M8 nut on each side. I.e. like the bread in a kebab.
//Single use. Each component does one thing and one thing well. I have broken this rule a few times and each time I regret it.
//Simplicity For example the stepper motors directly drive their respective components without gearing. (which will wear and require maintenance)
//Bought accuracy. My wood sawing accuracy leaves a lot to be desired. It just ain’t pretty. Hence the MDF size determine the size of this reprap. E.g. the MDF comes in 450x900 size. And 800x600. as a result my reprap has a xy bed of 800x600 and sits exactly 450mm off the base plate. If the MDF came in 400x900 then my reprap would sit 400mm off the base plate.
//Solid as a rock. There is no give in this machine. I can stand on it and it will not move or lean. This is because it is braced in all directions.
//Screws not nuts and bolts. I use 50mm screws. Cheap and freely available and more importantly left over for another project.
//IF MDF can be used then use it. I.e. less plastic, less Steel. MDF is cheap and freely available. And in future will probably be CNC able. Therefore MDF could well become the REPRAP material of the future.
//2D shapes to make 3D shapes not 1D My main problem with the original Darwin was it used 1D objects i.e. steel rods to create a 3d object i.e. a perfect cube with 90 degree angles. I just was not accurate enough. So I moved to a 2D shape i.e. MDF sheet where when you drill a hole it stays there.
The result of all these rules of thumb are a reprap which is
1) Low cost. Uses screws instead of nuts and bolts and MDF not plastic and steel. 2) Bearing count 23. But I recon I can get it down to 12. 3) 8 threaded rods+2 unthreaded rods but it can be reduced to 5 + 2 unthreaded
4) 300 x 400 Z axis build area. With a Z axis of 250mm 5) Prints well at 25m/s with a Makerbot MK4 extruder. 6) Happily go to 50m/s but the extruder can't keep up
7) Darwin design but uses only three threaded rods on Z axis. 8) Z axis is rock solid.
9) Big red emergency stop button to be wired into Reset pin of Arduino 10) Nice area in the Z axis to dump spanners and often used tools. 11) It is so robust I can sit on it. (I am about 95kg)
There is no kit. This machine was built using two Saws, Pillar drill, a Screw driver, two 13mm spanners, a big metal ruler, glue and lots of G clamps.
Where accuracy is required I cheated by using pre cut MDF. For example the two uprights bits of MDF needed to suppot the x-y printing bed obviously need to be exactly the same size. (otherwise it would lean) I bought a 900mm x 450mm bit of 16mm thick MDF and cut it in two. This gave me two bits of MDF with a perfect 450 side and a rough 450 side. The perfect 450 was used to hold up the X-y printing bed with the roughly cut 450 points outwards to the back of the system. As a result I did not choose the size of the machine my MDF supplier did. My MDF was supplied in 900x450x16 and 800x600x16.
The machine has a base of 800x600 with a x-y printing bed of 800x600 which sits exactly 450mm high. If your MDF supplier has different sized MDF this should not be a problem. Just go with the flow.
Files and Parts
Generic/Daughter_part and CarrotStraightener. (As a gentle style recommendation, it's good to try to keep all your parts and files on the RepRap wiki rather than scattered around so that Mr. Bunny doesn't have to use a scripts and so on to get stuff back onto the wiki.) File:Uploaded files example.zip
Project Lead(s): Mr. Bunny Wiki-maintainers and helpers:
Description of tooling requirements.
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