Sunday, January 14, 2007

 

Lego Bricks!

The Lego Bricks have arrived! (apparently they're not Legos... they're Lego Bricks!)


I was hoping for a compartmentalized box, with the pieces randomly segregated into their own little packages; I didn't even get any Lego bags!


Still, it was just that much quicker before they pile had formed!


And the XY axis was quick to follow! I did most of this by memory/picture, and had it together in 10 minutes. I'd already prepped the motors while waiting for the shipment to arrive so they just popped right on.


I've already found a weakness in this design; the black 1x2 that the axle goes through, along with the two 1x2 red flats below it, can work loose and derail the pinion gear. I've tried to push it down as hard as I can, and it seems to hold, but I suspect it needs to be glued or something to ensure it doesn't pop off during use.


A little electrical tape securely holds it on for the time being. I'll replace it with hot glue once I'm ready to secure it all down. I used hot glue on my prototype and it worked perfectly; it also comes off cleanly with a fair amount of prying.


Aside from the guide brick coming loose, the XY axis moves back and forth nice and smooth. Once I decide how I'm attaching the limiter switches (and decide which of the two I've got to use), and glue stuff down, these axis should be done!

While the XY axis went together easily, the Z axis was a bit more of a problem. I decided it was too tall, with too much wobble potential, so I moved it below the XY axis, instead of on top.


The general setup and idea still seems sound, but there was a flaw in the design, well two. They all center around the rack gearing that runs down the inside of the inner piece. The motor mounts on the outside frame, through a guide, and meshes with the rack on the inner frame, pushing it up and down. I made some miscalculations on how the transition pieces (black pieces on the inside, with the nubs sticking towards the center) line up with the bottom of the white piece (the one with the rack attached to it). I did a little rearranging and was able to get the pieces to line up, but I only used two of the four transition pieces. In addition to that, the white piece is too thick and sticks the rack out beyond where the pinion gear sits. I'll need to use some flat pieces to line them up if I want more than two.


I've hooked up the motor to the frame (without a gear, and ran it on 'calibrate' for a few hours, to dry some epoxy I used to attach the axle to the motor), but I still need to replace the white piece to get the pinion gear to line up with the rack. The design still looks fine, but it needs some correction.

I'll be posting both the html directions (though they need work, and I'll hopefuly get a second or third version updated over the next couple weeks) and the Lego designer file, once I've corrected the issues with the Z axis, in the next couple of days. From what I've discerned from Lego, I can share this stuff freely, so long as I don't make any money off it, and I call everything Lego Bricks.

I reinstalled my computer around new years, and I don't have my video software up and running yet, so it'll be a couple days before I get video up. I should also have the Z axis sorted out by then, so I should have all three running!

I've still not gotten the IO working on the host software in the svn, so I'm do all this with the 'windows release' version from last year. I've been a little distracted making room for two new recliners that are arriving Saturday, but I hope to get back to that next week some time.

Comments:
This is extremely cool.
 
Wouldn't it be neat if you could just buy a bootstrap pack from Lego to get into 3D printing. -
 
Z axis didn't work out as I'd hoped... so that's back to the drawing board...

The XY are working great, and I've got the limiter switches working on it... but the guide brick for the axle keeps popping off... (one of my axles doesn't appear to be on perfectly straight/centered, so there is slight wobble... now that I've secured the motor down, it's transferring the wobble to the guide brick... I've glued that brick, and will test it out later today (after it's dry...) The other axis seems true enough that I won't need to glue that guide brick down until I'm serious about long term running...

So long as everything holds together, I should have some video of it in action tonight!
 
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