Bearing based spirographic WDT tool

Manual gear-box style automatic WDT tool.
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updated August 4, 2023

Description

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This is a crank driven manual (non electric) WDT tool. It helps get rid of clumps in your coffee basket and evenly distribute coffee before pulling a shot.

3D printing settings:
My tool was printed with ABS+ @ 0.4 nozzle, .2 layer height.
Walls: 5
Top & bottom layers: 4
Infill: 60% (it can be 40% as well)
No supports
Brims needed only for adjustable needle holder and nut

Please be aware of the ABS thermal shrinkage, I used 100.5% scale but it's still on the smaller side (probably 100.6% is more appropriate).

BoM:
5x M3x12 screws with as small of a head as possible. I used the cheapest ones with Chinese writings on a box :D
1x M3x20 barrel head screw (for adjustable pin)
1x M3 spacer (mine is .6 thick and 7 mm OD)
1x M3 nut (just to press fit the bearings)
10x MR63ZZ ball bearings (those are 6 mm in OD, 3 mm ID and 2.5 mm height)
2x 6813 type ball bearings (those are 85 mm OD, 65 mm ID and 10 mm height)
10x acupuncture needles (I use .35 x 60 mm with 1.4x30 mm handle)

Tools:
- 1.3 drill bit - needle sockets are 1.6 mm in the STL but after printing you still need to correct the diameter of the socket with a drill bit. The needle handle is 1.4 mm but when you use the same diameter drill bit the needle will not be well fitted. Use 1.3 and then use force (Luke ;)) to press it into the socket
- something to cut the needles (I used a bicycle shifter/brake cord cutter)

Assembly remarks:

0. IMPORTANT: do not use too much force! All screws are threaded into plastic, be gentle :D
1. Use a longer M3 screw to press bearings into gears & handle (like on the photo).
2. Put one 6813 bearing on the lower body, the second one press into the upper body, then apply spacers. Press both together.
3. Prime all screw holes wit a screw before trying to mount gears/handle/needle holder to the body.
4. If necessary use 3 mm drill bit to correct the hole in needle holder_nut.
5. The whole design is based on my naked Profitec portafilter and Weber UniBasket. Please adjust lower body and needle length for your basket.
 

6. My assembly order:

  1. Put 6813 bearing on the lower body + spacer
  2. Put second 6813 bearing in the upper body + spacer
  3. Join upper and lower body, check if it moves nicely (it will, but it's nice to know how smooth it goes).
  4. Cut all needles to 64 mm (all needles comes with a plastic protective sleeve, I just cut the sleeve to 64 mm, then used it as a jig to cut all needles, just insert the needle back into the sleeve cut in line with your jig and you're done). [UPDATE: Please make three of the needles - marked with blue circle on the last photo - shorter by 12-13 mm to improve coffee distribution]
  5. Correct all needle sockets with 1.3 drill bit. I used Dremmel tool but it's much better and easier to use manual drill bit holder available for around USD 5-10 everywhere (see photo).
  6. Press all the bearings into place (gears & handle - see photo).
  7. Press all needles into sockets using pliers. Be careful not to bend the needle handle.
  8. Mount gears into upper body using M3 screws. Start with the one without the needles, then go from the smallest to the biggest. Please do not tighten the screws! They should just touch the bearings, not squish them.
  9. Mount adjustment needle holder (with needle already in) with needle holder nut and long M3 screw + washer. Mind the orientation of a needle: the needle should go outward (see photos).
  10. Mount the handle the same way as gears. Mind the spacer ;).
  11. Adjust the adjustable needle so it will not be bent when placing the device on the portafilter.

Check if everything is moving smoothly. You will hear a rattling sound coming from the gears (normal for a small backlash and small number of teeth) but not rubbing or hopping. Loosen the gear mounting screws if necessary.

P.S. If you need to disassembly the device use bearing removal tool to press big bearings out of the upper body (remove all gears, handle and needle holder before).
 

P.S. 2. One of the photos shows the older version of the device with fixed needle holder (not adjustable). Used because it's the only one I got with 6813 bearings visible before assembly.

 

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