Manual Coffee Grinder Conversion (J-Max)

Here is a j-max manual to electric coffee grinder conversion build.

Happy printing and thank you for the support!

Notes

This build requires soldering and de-soldering of a component from the power supply. Soldering mains and dc side will be necessary.

I have included a step file to make alterations to the design if you need. The step assembly also includes basic models of the motor, power supply, receptacle, and grinder.

The main body print is about 285mm tall so make sure your printer can print items at least that tall.

You will need the following supplies:

Coffee Grinder

Motor

Power Supply

Receptacle Module

3/8" Square Steel Stock

3/8" Drive to ¼", 6 Point Socket

Hardware Links:

¼-20 Threaded Rod

¼-20 Nuts

¼" Washers

M3 Hardware

Set Screws

Hardware List:

SHCS M6 x 20mm lg. (QTY.3)

¼-20 Threaded Rod cut to 95mm long (QTY.2)

¼-20 Nuts (QTY.6)

¼" Washer (QTY.2)

SHCS M3 x 50mm lg. (QTY.3)

SHCS M3 x 25mm lg. (QTY.7)

SHCS M3 x 20mm lg. (QTY.2)

SHCS M3 x 8mm lg. (QTY.2)

Set Screw M3 x 6mm lg. (QTY.4)

Print Settings

I printed all the parts out of PETG at 0.3 layer heights with a 7 walls for extra strength.

None of the parts need supports!

Note when using this setup

Using this specific grinder and stand, when making large adjustments to grind settings I would recommend unclamping and reseating the grinder drive into the socket and than re-clamping, though for small alterations with grind settings it should be okay.

Build Instructions

Power Supply Alterations

Step 1: Disassemble the power supply by taking off the four foam pads to reveal the screws and unscrew. Take off the one side of the plastic shell. 

Step 2: Trim the cable coming out of the supply leaving about 6 inches and pull the outer sleeving from the cables.

Step 3: De-solder the power cable receptacle on the other end of the power supply, you'll need a solder-sucker or some solder wick.

Step 4: Trim the wires on the receptacle module so there is about 6" of wire lead and solder in the receptacle module making sure you have the hot, neutral and ground wired correctly. 

Step 5: Close the power supply back up and secure the case half with the 4 screws.

Soldering Motor to Power Supply

Step 1: Once the power supply has been altered and all the parts are printed route the motor cable through the “Top Bracket”. Fit the motor with a couple screws and trim the motor leads on the inside of the “Top Bracket” leaving about an inch. After trimmed remove the screws from the motor and pull the leads all the way through to get more space to work with the leads.

Step 2: Trim the leads coming out of the power supply so you have about an inch or two of wire. 

Step 3: Solder the leads such that the motor spins clockwise, I had to solder the motor leads inverted with the power supply leads(black to red and red to black). Make sure you do this soldering with the leads going through the top bracket. 

Step 4: Wrap electrical tape or using heat shrink to insulate the solder joints.

Pre-assembly

Step 1: Cut the two 95mm lg. ¼-20 threaded rods to length and file/sand ends smooth.

Step 2: Cut the 3/8" steel square stock to 60mm long 

Assembling

Step 1: Push the ¼-20 threaded rods through the two holes in the main body. Thread the nuts on the inside of the main body to the threaded rods. Place a washer and nut on the outside portion of the threaded rod sticking outward and tighten the nuts to secure the rods into place.

Step 2: Slide the power supply into the main body print. 

Step 3: Use three of the M3 x 25mm lg. SHCS to secure the top bracket to the main body. (The motor should be dangling at this point so these holes should be easily reachable). Use the two M3 x 20mm lg. SHCS on the outer top side holes, these are probably redundant but I put them in mine without issue.

Step 4: Secure the motor into place with the three M6 x 20mm lg. screws.

Step 5: Bundle up the wire leads coming from the receptacle module and slide the back cover print into place. Secure the back cover using the remaining four M3 x 25mm lg. SHCS on the side of the main body. 

Step 6: Push the receptacle module into place and secure it using the two M3 x 8mm lg. SHCS.

Step 7: Screw in the three M3 x 50mm lg. SHCS into the motor shaft to 3/8" rod adapter. These screws simply add strength to the adapter so it doesn't easily shear. (You might be able to get away with slightly shorter screws but I would go anywhere under 35mm lg.). Thread in the two set screws into the side holes of the adapter.

Step 8: Push the adapter onto the motor shaft and secure the set screw. Insert the 3/8" square rod into the adapter all the way and secure with the other set screw.

Step 9: Screw the remaining two set screws into the side of the socket adapter cover. Push the socket onto the 3/8" square rod and push the socket adapter cover onto the assembly and secure with the two set screws.

Step 10: Put the remaining ¼-20 nuts into the knobs.

Step 11: Set the grinder to the setting you want and place it into place making sure the hex drive is fully seated in the socket. Secure the grinder in place with the clamp and knobs.

Step 12: You're done!