Tuesday, January 11, 2011

New Z axis couplers and hot bed mount

So the PLA Z rod/motor couplers didn't work quite right.  The PLA is a bit brittle and as I tightened the screws, I heard a bunch of cracking.  It seemed to hold for a bit, but then later the couplers just slid off of the Z motor shafts.  You can see the cracking in the couplers in the following pics.

I milled out new couplers from some aluminium stock I had on hand.  I drilled through at 5mm and then drilled half way through at 8mm.  Then I cross drilled some 3mm holes for set screws and tapped them for m4 threads.  You can see the couplers on the machine in the following pics

And I've gotten a method for hot bed mount done.  I'm using plywood and have the heat bed attached to one sheet and have made it so I can detach the heat bed easily if I need to.  The attachment method allows for easy adjustment to level the bed to the nozzle.  You can see it in the following pics.

I still need to find connectors with sufficient ratings to connect the bed to the electronics.  Also need to decide on how to attach to the electronics.  And then I need to attach the endstops so it can auto home and stop the +Z motion before the belts hit the frame.  I hope to have things done and printing any day now.

Monday, January 3, 2011

New year, new machine

So last year I was working on my repstrap, and made good progress.  I built the machine based on the wolfstrap design.  It underwent some changes from my initial design.  I had originally built it with 1/4"-20 threaded rod as leadscrews, but I found it was a bit slow.  I then swapped out the x and y axis for belts.  This worked well, and I was able to get some calibration pieces printed, but I could not quite get the backlash out of the system.  I had my machine in my garage because of its size.  It was based on an Ikea Rast nightstand as the X gantry, so it was rather large.  With the weather turning cold in the winter, I was no longer able to get good extrusion because of the temps, and when it did work, the objects would not stick to the build platform.  I decided to fast track my mendel build so I would have something to work with over the winter.  I bought a set of PLA parts for a Prusa Mendel and completed the build right before the end of the year.  Here are some pics of the machine.

Here's an overview shot

I printed out a replacement Y motor holder out of abs to use instead of the larger design that I purchased.

You can see in the pic below that the placement of the fender washers block one of the 3 motor mount holes. I don't think this will be a problem, but we will see as I start to use the machine.

The belt clamps that came in the kit did not fit the spacing for the X carriage, so I cut some out of wood to use.

For the bed, I used springs from the hardware store.  They are a little long and take some force to mount them but it should work well to help level the bed.

I've got a RAMPS board soldered up that I need to connect up.  The wires from the steppers are short and terminated with JST connectors.  I'm planning on cutting those connectors off and soldering on new wires to connect to the RAMPS board.  I need to buy some cables to do the extension, and then I'll have the machine up and running.

One last issue I ran into was how to mount the extruder.  I have a stepper extruder with a 26:1 geared stepper that is about 4 inches long.  The problem is that the end of the motor hits the belt when I have it mounted front to back.  I will have to work out some method to mount it so that it does not hit the belts.  I may just build the wade's extruder that was included in the PLA kit I bought if I can't get the geared stepper to fit.  The gearhead weighs a good deal too, so the wade's design would be lighter as well so I may go that direction.