The guards protect the end stop sensors and keep the wiring harness umbilical or the filament from getting squeezed between the top plate and one of the carriages.
These mount securely with 4 v-groove fasteners into the column's side grooves. Twisting the fastener 90 by degrees secures it or removes it.
I had two mishaps that these guards would have prevented:
The PTFE tube over the filament extruder was too long and it got caught between the top plate and one of the carriages as the printer was homing (at warp-9). This prevented the carriage from triggering the end stop sensor, causing the belts to grind as the control board was trying to bring the carriage home (from another galaxy, based on the amount of time it ran the motor.) Only powering down the printer stopped the insanity.
This caused the belt to detach from the carriage, needing to take off the top plate to reattach.
I made the mistake of homing the effector with the filament removed and the end of the filament just happened to get into one of the end stop sensors, triggering it. This made the controller think this axis was already home and tried to bring the other two into position.
This effort caused the effector to move to its maximum offset and lock up the two carriages. The printer kept trying while making a horrible belt griding sound, terminated by powering down.
I printed mine with ABS but see no reason why this would not work in PLA.
The plates are designed to print flat to make layer adhesion not a factor when clamping these with the fasteners.
The print settings are as follows for each model with required quantity shown in parentheses:
- Guard Plates (3x)
- 0.3 mm layer height
- 25% infill
- no support
- no raft
- V-Groove Fasteners (12x)
- 0.2 mm layer height
- 50% infill
- no support
- raft required
Note: These fasteners are generally useful for mounting to the TEVO Little Monster printer frame so I printed two sets of 12 and brake them off the raft when I need them.
Work-in the V-Groove Fasteners
Prepare the v-groove fasteners by removing them from the raft and attaching the mini holding plate to the column.
The fasteners are inserted with the top arms in the vertical position and fastened by turning them 90 degrees into a horizontal position.
You may need to use pliers to turn them for the first time. After that they can be fastened by hand.
Assembling the Guards
Important The side plates print opposite of how they assemble. The one on the left is the right plate and the one on the right is the left plate. In other words, the plate with the rectangular notch in the top edge goes on the side of the end stop sensor.
The horizontal bar is to be glued between the two side plates. I assembled these on the bottom plate upside down, clamped the horizontal bar between the two side plates and used a few tiny drops of MEK solvent to weld them in place. You can use any method to attach assemble the plates together.
Installing the Guards
Slide the guard over the column below the optical sensor and slide up to contact the top plate. Attach to the columns using 4 v-groove fasteners per column.
I am new to 3D printing and find Fusion 360 to be the easiest to use when taking an idea to a working model.
I use parameterized dimensions to allow easy tweaking and reducing the model size for faster test prints.