Y-Axis Motor Relocation Bracket & Tensioner for large NEMA-17 motors on Ender 3 Printers

Y-Axis Motor Relocation Bracket & Tensioner for large NEMA-17 motors on Ender 3 Printers

Modeled to accommodate the vertically oriented 2040 extrusion and v-roller movement of a stock, original Ender 3.

This part is designed to accomplish the following on an original Ender 3:

• Provide clearance between the Y-Axis stepper motor and bed-adjustment knobs.
• Integrate a belt tensioner into the motor mount
• Create a level, parallel belt path from the printer bed.
• Maintain (approximately) the same Y-endstop position

In addition, the design is optimized to:

• Interface snugly with the Ender 3's v-slot extrusions (you might need a hammer)
• Be printable with minimal supports (see slicer recommendations)
• Use Ruthex threaded inserts instead of direct-threading into plastic, wherever possible.

Parts Needed:

A note on machine screws: All countersunk machine screws can be subbed out for button head machine screws, but you will need to use nominally longer screws.

Tools and Installation:

In addition to the obvious hex keys, you will need a soldering iron with a conical tip to gently push each insert into place at 240-300°c (into PETG.) Any plastic squeeze-out can be trimmed flush with a razor blade. 

You will need to tap the holes at the end of the 2040 extrusion with an M5 tap before installation.

Start by installing the threaded inserts. All of the threaded inserts should be set either flush or slightly depressed.

Next, install the mounting sleeve. You may find that you need a hammer in order to do this. If you do, use a block to more evenly distribute the force and avoid denting the part. Mine was difficult to mount, but I've since increased tolerances between the sleeve and extrusion. I've tested some cross-sections of these modified sleeves, but because my original prototype fit so tight, I haven't test-fit an entire sleeve. Once more, your feedback would be helpful.

Next, the stepper motor should be mounted to Bracket A via a countersunk M3 x 8 machine screw through the one hole which will accommodate it. 

Mount Bracket A to the Mounting Sleeve. Insert both M5 x 30 screws (axles) through Bracket A, and install both idler pulleys. If using both smooth and toothed idlers, the upper pulley should be toothed, and the lower pulley smooth.

Insert the hex-head M5x35 (or button-head M5x40 with jamb nut) bolt through the front of the tensioner shuttle

Loosely thread both M5x30 axles through their respective holes and into their corresponding nuts on Bracket B and the Tensioner Shuttle; just enough to keep the pulleys from falling off. Mount Bracket B to the Mounting Sleeve.

Install the Tension Block between Bracket A and B, such that the slotted dimples point back and away from the Mounting Sleeve. Fasten it into place with the two M3 x 30 screws and their corresponding nuts.

Install the remaining 3 motor mount screws through their holes in Bracket B, through Bracket A, and into the stepper motor.

The M5 axles should be tightened just enough to eliminate axial play in the idler pulleys, without imparting drag.

With the pulley installed on the Tensioner Shuttle, the head of the hex bolt will have enough play to allow for the Shuttle to be placed atop the motor mount assembly with the bolt protruding through the Tension Block.

Mount the Y-endstop. The mounting screws for the Y-endstop will thread directly into the plastic of Bracket B and the Mounting Sleeve. Though printing with polyholes should result in fairly accurate dimensions, you may find you need to ream the holes with a 2mm or 5/64" drill bit. If you find that the pins on your endstop switch protrude further than the endstop cutout can accommodate, consider trimming them with flush-cutters.

The driven GT2 pulley can be loosely mounted to the motor shaft until the belt is mounted.

As for the belt, I recommend fishing it through the rear (motor-mount side) of the extrusion out to the front. Terminate that front end, and mount it to the bed. From there, the other end can be routed through the motor mount and tensioner pulleys and pulled taught against the rear mount of the print bed. Trim to length, terminate, and mount.

With the belt fully installed, it should practically be pinning the Tensioner Thuttle against its foremost endstop. From there, the Tensioner Knob can be threaded on to draw the shuttle rearwards until your desired belt tension is achieved.

Printing:

Filament:

This part should be printed with a material that is reasonably tough, flexible and somewhat heat tolerant. I would highly recommend PETG, and discourage the use of PLA. Though I didn't use it on this prototype, I would still recommend PETG-CF for extra stiffness.

Orientation:

All of the 3mf files should contain parts properly oriented for printing, but in the event they don't, use auto-orientation.

Suggested Slicer settings:

(These are not rules; just suggestions. Nomenclature per OrcaSlicer)

Quality:

• Nozzle = 0.6mm (to accommodate carbon-fiber filament)
• Layer height = 0.2mm (A lower setting makes for better v-rail fitment) 

Precision:

• Precise wall = Enabled
• Polyholes = Enabled
• Polyhole twist = Enabled
• Precise Z height = Enabled

Strength:

• Wall loops ≥ 2
• Sparse infill density ≥ 75%
• Top shell layers ≥ 7 (default)
• Bottom shell layers ≥ 5 (default)

Support:

Both mating surfaces for the motor and the Y-endstop will require “normal” supports. The Tensioner Shuttle is best printed with “Tree" supports. Make sure your clearances are dialed in to avoid excessive adhesion.

Remember to account for shrinkage if you want an accurate part! I had to scale the print to 100.6% on the X and Y axis in order to achieve accurate dimensions with my given printer and filament. In OrcaSlicer, shrinkage compensation can be saved in any given filament profile. 

This is a variant of my own original model. The only significant difference between this and Rev. 1.20 of my original Y-Axis Motor Relocation Bracket is the addition of a belt tensioner.