Mark Rehorst

I got the HDD bearings from a bunch of old HDDs. There's one bearing per HDD, so you need to take apart 12 HDDs.

In looking at the photos of the printer I noticed that the belt connections to the extruder carriage do not keep the belts parallel to the X axis guide rail. That is going to lead to variable belt tension depending on extruder carriage location and distorted prints. See: https://drmrehorst.blogspot.com/2018/08/corexy-mechanism-layout-and-belt.html

I made a test print with the new worm drive installed in UMMD and I have to declare it a failure. There is a lot of Z ribbing at 2mm intervals- so there is some quality problem, most likely with the worm gear because it spins one full rev for every 2mm of Z motion. Photo here: https://4.bp.blogspot.com/-_WnQ6nhaZ60/WsmkTYmsJ4I/AAAAAAAAVT4/lJ-1Y7xupYAy1mQkcWOniAC0kroV-nFkwCLcBGAs/s1600/04080001.jpg The problem was hinted at in the second video linked in my previous post. When I moved Z in 1 mm intervals, every other step was good and the steps inbetween were off a bit. I'll be putting the Rino back into the machine today.

I don't know where you'll find a 700x300 heater unless you pay to have one custom made. That's 2100 cm^2 and at 0.4W/cm^2 you're looking at almost 1 kW for the heater. You can use lower power, but it will take a while to heat up. The bed may sag a bit over a 700 mm span, so you might have to change the support and leveling structure or use a sensor and map the bed to compensate in the controller. It really depends on the print layer thickness you intend to use. If you want to print in 50 um layers over the entire bed surface you'll need to make changes. If you want to print in 0.5 mm layers you probably won't have to do anything. Otherwise, I don't see any issues. I've been working on a cheaper alternative to the Rino worm gear drive which cost about $140 via ebay, including shipping and the long, keyed 8mm shaft. The new design uses inexpensive worm gears from China and a NEMA-17 motor and costs about $40. I just installed it in UMMD and started testing two days ago. Video here: https://vimeo.com/263456441 and https://vimeo.com/263606489 I'll be publishing a blog post on the new design in a day or two. I switched to GT2 belt and pulleys which required a redesign of the belt clamps and the spacers that stand the pillow blocks off the plates at the bottom of the Z axis. I also redesigned the upper pulley plates with ridges that fits into the slots in the frame to prevent them from rotating. They now use a single bolt to hold them in position. The new worm drive uses 40:1 gears and 40 tooth drive pulleys which results in 1600 usteps/mm or 100 full steps/mm resolution, so full-step-multiple print layer thickness can be any multiple of 0.01 mm. The increased gear reduction will probably limit maximum speed to somewhere between 10 and 20 mm/sec, depending on the motor you use, but that's OK for the Z axis.

Perfect! I was just going to eat my breakfast and found this spam to go with my eggs.

DesignSpark doesn't export to any other format, unless you want STL, OBJ, or a 2D DXF file, none of which seem very useful. DesignSpark is free. All you have to do is install it.