Garcad Hotend Ultimaker Original (UMO) Adapter

By calinb

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The .stp model and mesh for the adapter contains the 1/4-20 internal threads needed to mount the GHE. However, the threads must be "chased" with a tap first. Drill with a #7 drill bit (or perhaps a #8 followed by a #7) and then run a hand tap through the hole. The adapter shown was printed in MakerGeeks High Performance / Dishwasher safe PLA. Standard PLA is too brittle for tapped threads, in most cases--often it is even too brittle for cleaning-up printed threads by "chasing" them out with a tap! I recommend using a high performance PLA, ABS, PC, nylon, PET-G, etc. for this part. Given that the GHE/UMO adapter is a very small part, I printed it with a 0.25 mm nozzle. Nozzle temp was 230 C and speeds were solid infill @ 70 mm/sec, sparse (support) @ 46 mm/sec, and loops at 40 mm/sec, as sliced by Kisslicer. The infill is solid and print time was 18 minutes. Other relevant Kisslicer settings are included in a zip file archive here. (Be careful not to overwrite your current Kisslicer .ini files with them--better to append their contents to your current files with a text editor or make a new Kisslicer executable directory.) The best way to tap the part is to use a 3/8" socket that is deep enough to fit over the Bowden tube end of the adapter. Hold the part from turning with the socket and socket wrench and run the tap in and out (to clean the tap) until it is completely tapped. There are no threads in coupling section for the Bowden tube. Water is recommended as a lubricant for tapping "High Performance" (high temperature) PLA. Just about any filament, other than standard PLA perhaps, should work okay for this part, because the part runs cool. Even PLA would work, but it might be too brittle to tap or perhaps even install without inadvertently breaking it. Like the GARCAD slogan says, "NO PLAing AROUND!" (A GHE will print any FFF/FDM media that's available in the marketplace.) Enlarge the hole in the UMO lower wooden plate where the GHE is to be mounted to 1/2". Kisslicer likes to "print one at a time" from left to right and front to back, so I prefer to have my fan on the right side of the print head and hot end on the left side. Use a small sanding drum on a Dremel or other rotary tool or a rat tail rasp to bevel and round the edges in the relieved corner where the adapter will contact the corner. The adapter diameter is a bit too large to fit without a small amount of wood removal there. The Bowden tube should slide into the upper end of the adapter until it contacts the filament input port of the GHE. I routed my wires through the adjacent hole in the UMO wooden plate and the two small water lines barely fit through the diagonal hole from my GHE. My GHE is oriented with its inlet / outlet ports pointing toward the diagonal hole. Use nuts underneath the wooden plate to anchor the UMO "long screws." The UMO aluminum plate, and Garcad-supplied mounting hex nut and washer are not used with this adapter. The GHE heater resistance is lower than the standard UMO cartridge heater. Accordingly, you will need to change your Marlin Configuration.h file to a value less than the maximum, rebuild Marlin, and load the new code into your Ultimaker. A value of PID_MAX value of 100 worked for me and the GHE ran well--even before running autotune to obtain new PID values! If PID_MAX is set too high, your Ulticontroller will have a "brown out" and flicker and your UMO will reset. This is the line from Configuration.h when running my GHE (256 is the default UMO value): #define PID_MAX 100 // limits current to nozzle while PID is active (see PID_FUNCTIONAL_RANGE below); 256=full current Enjoy, and print something about 8 mm taller and 40-50C hotter than you've ever printed before!
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