What is it?
This grinder takes an inexpensive ceramic burr grinder and interfaces it with a powerful 12V worm-gear motor to make a user-serviceable, open-source platform for consistent grinding of coffee and herbs. You are free to make derivatives if you reference the original design and creator.
It is capable of producing coffee grounds fine enough for an espresso machine; the fine grounds pack well into a satisfying puck.
It is capable of producing coffee grounds for pour-over and French press coffee makers. Coarser grounds grind much faster.
It can be easily maintained and repaired, extended, and adapted to fit your needs.
What is it not?
- It is not free for you to sell prints. For that you need to be a member of my club
- It is not fast
- It is not going to beat the grind quality of an expensive grinder
- It is not risk-free - you accept any risks or consequences of choosing to implement this project which are not limited to:
- Possible overheating of an underpowered power supply
- Damage to the grinder
- Damage to the motor
- Associated risks, however minimal, of potential exposure to microplastics that, while unlikely to intrude in the grinds, can still be present in the operating area
- It will not bring world peace, but don't underestimate the power of sharing a good cup of coffee with someone
v1.1 improvements
The motor housing now has a place to put the barrel plug to remove strain from the motor wires.
BOM (links are not affiliate links):
- A 12V worm gear motor. I used a 200 RPM model for a decent balance of torque to speed. You may choose something else if you wish.
YWBL-WH DC 12V Gear Motor High Torsion Speed Reduce Electric Gearbox Motor Reversible Worm Gear Motor 8mm Shaft (12V 200RPM), Geared Motor - Amazon.com - An inexpensive burr grinder. There are several models that look nearly identical. I have bought both the model linked below as well as a $30 variant. The latter has better fit and finish, has a rubber ring to hold the handle (in the same shape as the “grip ring” STL) but they both produce similar quality grind.
Amazon.com: Coffee Grinder,Manual Conical Ceramic Burr Mill Best Coarse Grind for Office Home, Traveling Camping Consistent Grind Herb, : Home & Kitchen - A 12V laptop power supply - you likely have one lying around. Make sure it is 12V DC out!
- A barrel plug compatible with your power supply. I used this one for my laptop power supply:
https://www.amazon.com/Power-Connector-Female-Adapter-Camera/dp/B07C61434H/?th=1 - Two 608 skate bearings. Nearly any will do, as long as they are clean and spin freely with no grinding. It's OK if they are greased - that can help with their longevity.
SHKI ［10 Pack］ 608 2RS Ball Bearings – Bearing Steel and Double Rubber Sealed Miniature Deep Groove Ball Bearings for Skateboards, Inline Skates, Scooters (8mm x 22mm x 7mm): Amazon.com: Industrial & Scientific - 3D printing filament, of course. PLA is fine.
- A printer capable of printing accurate, decent parts, or a friend who has one and can be coaxed/bribed into helping.
- Print:
- 1 x 12V Motor Housing
- 1 x Split frame extended
- 1 x New gear 1
- 1 x Gear 2
- 2 x Spacer
- 2 x Wing nut or Wing nut 98 percent
- Recommended:
- 1 x Retaining Nut to help maintain your grind of choice (or purchase a metal nut that fits the thread for the grind selection knob). This will butt up against the grind selection knob to prevent it from loosening. This part will occasionally come in contact with the coffee or herbs you are grinding so you may want to evaluate the risk of using a printed part in this case.
- Optional:
- 1 x Grip ring or Tight grip ring if your grinder does not have a rubber ring for the handle
- 1 x Grinder lid to replace the lid of your grinder that would normally interfere with the grip ring
- 1 x Coffee Funnel to help prevent beans or herbs from going everywhere when filling the grinder
- For repairs:
- If the plastic interface that attaches the conical burr to the spindle breaks, the Coffee grinder part - GrinderInterface can be printed to replace it. However, while it does not come in contact with the coffee, some might be uncomfortable with having a printed part close to them. Use at your own discretion.
- Note that for some models I have included 3MF files that are pre-supported for PrusaSlicer.
- I would suggest 3-4 perimeters. 10-15% infill is more than sufficient.
- 0.3mm layer height is sufficient for the split frame and motor housing. I would suggest 0.15mm or 0.2mm layer height for the wingnuts. You can decide what layer heights to use for other parts.
Assembly instructions
- Gather your parts
- Insert the bearings in the bottom of the motor housing. The fit is tight: you will want to press the bearing in using a board or against a hard, mar-resistant floor.
- Insert the motor into the motor housing, making sure the motor shaft goes through the bearing exposed through the hole:
- Slip on one of the spacers on the motor shaft
- Press the smaller gear on to the notched shaft. The fit will be tight.
- Place the other spacer on the spindle of the larger gear
- Press the spindle of the larger gear on to the other bearing. The fit will be tight.
- Your motor housing is complete!
Before your first use:
- If you have opted to buy the grinder without the rubber ring, be sure to print one of the “grip ring” parts. I find that the “Tight grip ring” works best for me, as it really gets squeezed by the split frame, preventing the grinder from spinning. Simply slip the ring on to the grinder.
- Adjust the coarseness of the grind using the knob on the grinder (please read the instructions for the grinder on how to do this). You may need to experiment to get the size of grounds that you need.
- Optionally, I would recommend that you install either a metal nut (M6, I believe) or 3D print the retaining nut. This will prevent the grind setting knob from working itself loose.
- Connect the motor wires to the barrel connector.
- Connect your barrel connector to your power source and observe the rotation of the motor - when viewed from the side opposite of the motor, the large gear should rotate counter-clockwise. If it is spinning the wrong way, reverse the wires in the crimp connectors of the barrel connector.
Usage
- Gather your parts
- Fill your grinder with your choice of coffee beans or herbs
- Install the printed grinder lid to help prevent what you are trying to grind from coming out and to prevent the possible ingress of any particles from the gears, however unlikely it may be.
- Slot one side of the split frame on to the motor housing, ensuring the large gear is visible:
- Insert the top of the grinder's shaft into the large gear. The first few times you do this, the fit will be very tight. Rotate the grinder so that the bulge of the grip ring fits into the notch of the split frame:
- Slot the other side of the split frame so that the grip ring is sandwiched between the two sides
- Now, you are ready to install the two wingnuts. The wingnuts are installed on the two split “bolts” on the split frame. If they are too loose, you can print the “98 percent” size nuts, or even scale them smaller (in X and Y only), if needed. The first few times you install these, they will be difficult to line up and turn on the threads.
- You will need to squeeze the two halves of the split frame to get that second wingnut on!
- Hook your power supply up to the barrel jack and get grinding!
Dan the 3D Printing Dad
