Span2 gold hands cropped

Mark Rehorst


Former electrical engineer, I became a dentist in 2011.  I designed and built my printer, Son of MegaMax, using surplus machine parts at the Milwaukee Makerspace. My newest printer design, Ultra MegaMax Dominator, is a coreXY machine with a 300x300x695 mm build envelope. Details here:


3D printing, CAD, Design, Electronics Design, Prototyping, Soldering

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  • Ultimaker 2 Go
    Utm2 go small

    Ultimaker 2 Go

    Son of MegaMax

    I don't have an Ultimaker, but this silly thing won't let me enter a custom printer. I designed and built my printer I call Son of MegaMax (2nd generation of my previous design/build, MegaMax). You can see it here:


Commented on Ultra MegaMax Dominator (UMMD) CoreXY 3D Printer 12 days ago
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: 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.
Commented on Ultra MegaMax Dominator (UMMD) CoreXY 3D Printer 13 days ago
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: and 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.
Commented on Filament Spool Holder for 3D Printer 22 days ago
Perfect! I was just going to eat my breakfast and found this spam to go with my eggs.
Commented on Ultra MegaMax Dominator (UMMD) CoreXY 3D Printer 4 months ago
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.
Published Filament Spool Holder for 3D Printer 11 months ago
Updated Improved Filament Run Out Sensor 11 months ago