3D printing: Here come the hot steppers

Shortly after becoming completely fascinated with 3D printing last year, I decided to get a printer to use at home. After a bit of research, I settled on the RepRapPro Tricolour Mendel kit. The features and machine specifications were on par with other machines available at the time, but the Tricolour Mendel featured the ability to have three extruders and hotends installed. This would allow multi-color or multi-material prints without pausing mid-print to swap out materials.

Reprappro tricolor Mendel buildParts awaiting assembly

The first thing I learned when assembling the frame was that I had not paid close enough attention to the part of the instructions that mentioned components may need fettling before assembly. In particular, many of the parts with holes required cleaning with a drill bit to allow the threaded rods to pass through them. After the parts were cleaned up, the frame went together fairly easily.

Reprappro tricolor Mendel buildAssembling the RepRapPro Mendel frame

Next up the motors and y-axis carriage were installed. Note that the y-axis clamps which hold the belt to the frog came were printed out of PLA. Over the course of a year, the heat from the print bed along with the strain of the belt warped these clamps and caused the belt to loosen. If you’re building a new unit, make a note to print these out of ABS and replace the PLA clamps so you don’t have the same issue.

Reprappro tricolor Mendel buildX, Y and Z axis hardware assembled
1 year later: warped y-axis belt clamps

The last bits of the build included assembling and installing an extruder, hotend, electronics and wiring it all up. Surprisingly, it all worked on the first try even if there were plenty of adjustments to be made.

Reprappro tricolor Mendel buildController installed, wiring complete for single extruder configuration
Reprappro tricolor Mendel buildThe very first test print, a frame part to build another Mendel. The print quickly failed, but it was fantastic to see the printer melting plastic and nearly working as expected.
Reprappro tricolor Mendel buildThe second part ever printed. This time the print finished, but the quality was very poor. The root cause was an extruder tensioning screw that wasn’t tight enough.
UntitledThird part printed: extrusion issue corrected, starting to look like it should

One thing that wasn’t documented in the RepRapPro build guide was the need for cooling. Without any cooling, PLA has a tendency to curl up while being printed. For a newbie, this can easily give the impression that there is a problem elsewhere (x/y/z axis calibration, hotend/extruder calibration, etc). I found the easiest solution was to place a desk fan directly in front of the printer and to let the desk fan run on the lowest setting. The without fan/with fan differences were fairly astonishing as seen in the first batch of prints seen below.

Reprappro tricolor Mendel buildMake robot and Ultimachine robot printed without cooling
No cooling (left) vs. active cooling (right)50mm tower without cooling (left) vs. with cooling (right)
Maker Faire RobotMake robot with no cooling (left) vs. no cooling & slowed print speeds via slicing software (center) vs. original faster print speed with cooling (right)
Octopus printOctopus happy to have sufficient cooling during print

Finally, the build was considered a success once I was able to print the well known Yoda bust.

Untitled3D print you must. Fail you might, but succeed you will eventually.
Timelapse video of Yoda bust printing.

Pierre Baillargeon

Pierre Baillargeon is an engineer from South Florida who holds a Master of Science degree in Computer Engineering, having graduated from Florida Atlantic University in August of 2005. Pierre currently works as a Robotics Engineer at a non-profit biomedical research organization and is known to enjoy photography, gadgets and skillfully constructed pizza.

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