alphaomega
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I just finished the third (and probably final) prototype of my miniature motorized roller mill.
I'm happy to say it now works 100% to my satisfaction. I changed to friction drive of the second roller, and it seems to work really well.
A close up video of it milling malt:
The 'tour' video:
If you really pay attention, you can see/hear it having trouble feeding (grabbing on to the grain). In the video I used 0.8mm pitch knurling rollers. After the video, I changed to 1.2mm pitch rollers and that seems to have solved that issue (the first video has 1.2mm pitch rollers).
This is the resulting crush (which I'm pretty happy with):
So far I've only test milled 500g of malt. It took 11 and a half minute. Extrapolating from that, milling a (for me) normal batch of about 5kg malt would take around two hours, which is well within what I was hoping for. The motor and gearbox did not heat up even the slightest.
As I'm pretty happy with the build now, if anyone is interested, here's how I built it (if not, at least I've written it all up for myself if/when I need it).
Tools required:
Drill press (a drill + stand will do)
Metric drill bits (4mm, 10mm + a drill bit slightly smaller than 10mm, like 9.5mm)
Hammer
Saw (to cut the acrylic sheet)
Torch
Plumbers solder
Stainless steel flux
Tape
Abrasive cleaning strips or fine grit sandpaper
Misc tools...
Materials required:
1x Drill template
2x Acrylic sheet 60x65x6mm
4x Bronze bushing 0806, (8mm ID, 10mm OD, 6mm)
4x Knurling roller, 28mm OD, 8mm ID, pitch 1.2mm
2x Dowel pin, 304 stainless, 8mm, 50mm
4x Threaded rod, M4, 100mm
4x Wing nut, M4
4x Spacer, 4mm ID, 50mm
4x Spacer, 4mm ID, 16.5mm
2x GT2 Timing Belt Pulleys 40 Teeth 8mm Bore For 6mm Belt
4x 28mm x 3.1mm Flexible Mechanical PU O Ring
1x Shaft coupling 8mm - 8mm
1x Gear motor, square, high torque, 54RPM
Making the rollers:
Clean out the center of the knurling rollers with fine grit sandpaper. Douse the pins with flux and place the 2 knurlers on top of each other and place that on spacers that give approx 6mm of rod sticking out of the other side of the rollers (M4 nuts standing up works). Make sure NOT to let more than 6mm stick out, as you'll need every bit of length of the shaft on the other side to mate with the shaft coupler.
Cut small pieces of solder and place where the roller and shaft meet. Heat. When the solder flows, add a bit more flux. Let cool and clean thoroughly all the flux. Do this for both the shafts.
Making the sides:
Cut out two pieces of 6mm acrylic approx 60x65mm. Secure them together using tape. Print out an accurate template of the motor screw holes and shafts (see example below). Tape it to the acrylic.
Drill the 4mm mounting holes. Drill the shaft holes, but using 9.5mm drill. Go very slowly and be really, really, *really* careful in starting the hole to get it centered in the template. Then change to 10mm drill and finish the the two holes off. I have found that drilling directly with the 10mm drill bit makes the holes slightly too large to ‘hold on’ to the bushings. Probably due to the drill bit heating up.
Remove the tape (and template). I have then found it useful to remove the two outer layers of protective film, before separating the two pieces of acrylic (they will stick together from the drilling), and marking the the two outmost sides. This way it is easy to tell the correct way to assemble, even after taking apart.
Gently tap in the the bushings in the shaft holes using a hammer.
Template:
Below is the template I used. Copy the text, paste it in a text editor, and save as 'template.svg'. Open the file with an image viewer that supports SVG and print it to scale (that is disable all scaling and stuff). Make sure the box is 65x60mm on the printout. Don't ask me HOW to make it the correct size on the printout. I only know how to do that for my printer and in Linux.
Assembly:
The parts:
Screw in the threaded rods in the mounting holes on the motor (just by hand). Place the 50mm spacers over the rods (I use the housings for discarded pens, cut to size). Place the shaft coupling on the motor axle.
Slip on two O-rings over each of the GT2 timing belt pulleys. Slide the longer parts of the shafts through the bushings of one of the acrylic sheets. Mount the timing belt pulleys. Leave just a little bit of slack, so the rollers can turn freely, then tighten down the allen set screws on the pulleys. (Note, in the picture, I used a drive shaft slightly longer than 50mm, I later changed to use a 50mm shaft for both rollers).
Slide the piece on to the threaded rods (the drive shaft going into the shaft coupling).
Add the 16.5mm spacers and the outer acrylic piece. Add the wing nuts and hand tighten. Tighten down the allen set screws on the shaft coupling.
Done
I'm happy to say it now works 100% to my satisfaction. I changed to friction drive of the second roller, and it seems to work really well.
A close up video of it milling malt:
The 'tour' video:
If you really pay attention, you can see/hear it having trouble feeding (grabbing on to the grain). In the video I used 0.8mm pitch knurling rollers. After the video, I changed to 1.2mm pitch rollers and that seems to have solved that issue (the first video has 1.2mm pitch rollers).
This is the resulting crush (which I'm pretty happy with):
So far I've only test milled 500g of malt. It took 11 and a half minute. Extrapolating from that, milling a (for me) normal batch of about 5kg malt would take around two hours, which is well within what I was hoping for. The motor and gearbox did not heat up even the slightest.
As I'm pretty happy with the build now, if anyone is interested, here's how I built it (if not, at least I've written it all up for myself if/when I need it).
Tools required:
Drill press (a drill + stand will do)
Metric drill bits (4mm, 10mm + a drill bit slightly smaller than 10mm, like 9.5mm)
Hammer
Saw (to cut the acrylic sheet)
Torch
Plumbers solder
Stainless steel flux
Tape
Abrasive cleaning strips or fine grit sandpaper
Misc tools...
Materials required:
1x Drill template
2x Acrylic sheet 60x65x6mm
4x Bronze bushing 0806, (8mm ID, 10mm OD, 6mm)
4x Knurling roller, 28mm OD, 8mm ID, pitch 1.2mm
2x Dowel pin, 304 stainless, 8mm, 50mm
4x Threaded rod, M4, 100mm
4x Wing nut, M4
4x Spacer, 4mm ID, 50mm
4x Spacer, 4mm ID, 16.5mm
2x GT2 Timing Belt Pulleys 40 Teeth 8mm Bore For 6mm Belt
4x 28mm x 3.1mm Flexible Mechanical PU O Ring
1x Shaft coupling 8mm - 8mm
1x Gear motor, square, high torque, 54RPM
Making the rollers:
Clean out the center of the knurling rollers with fine grit sandpaper. Douse the pins with flux and place the 2 knurlers on top of each other and place that on spacers that give approx 6mm of rod sticking out of the other side of the rollers (M4 nuts standing up works). Make sure NOT to let more than 6mm stick out, as you'll need every bit of length of the shaft on the other side to mate with the shaft coupler.
Cut small pieces of solder and place where the roller and shaft meet. Heat. When the solder flows, add a bit more flux. Let cool and clean thoroughly all the flux. Do this for both the shafts.
Making the sides:
Cut out two pieces of 6mm acrylic approx 60x65mm. Secure them together using tape. Print out an accurate template of the motor screw holes and shafts (see example below). Tape it to the acrylic.
Drill the 4mm mounting holes. Drill the shaft holes, but using 9.5mm drill. Go very slowly and be really, really, *really* careful in starting the hole to get it centered in the template. Then change to 10mm drill and finish the the two holes off. I have found that drilling directly with the 10mm drill bit makes the holes slightly too large to ‘hold on’ to the bushings. Probably due to the drill bit heating up.
Remove the tape (and template). I have then found it useful to remove the two outer layers of protective film, before separating the two pieces of acrylic (they will stick together from the drilling), and marking the the two outmost sides. This way it is easy to tell the correct way to assemble, even after taking apart.
Gently tap in the the bushings in the shaft holes using a hammer.
Template:
Below is the template I used. Copy the text, paste it in a text editor, and save as 'template.svg'. Open the file with an image viewer that supports SVG and print it to scale (that is disable all scaling and stuff). Make sure the box is 65x60mm on the printout. Don't ask me HOW to make it the correct size on the printout. I only know how to do that for my printer and in Linux.
Code:
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"
width="65mm" height="60mm" viewBox="0 0 65 60">
<g transform="translate(30.0, 30.0)">
<!-- Box (outer dimensions) -->
<g transform="translate(0.0, 0.0)">
<rect x="-30.0" y="-30.0" width="65.0" height="60.0" style="stroke-width:0.1; stroke:#000000; fill: white"/>
</g>
<!-- Bushing Cog 2 -->
<!-- Uncomment ONE of the below to choose gap size-->
<!-- <g transform="translate(-9.0, 0.0)"> --> <!-- 1.0mm gap -->
<g transform="translate(-9.2, 0.0)"> <!-- 1.2mm gap -->
<!-- <g transform="translate(-9.5, 0.0)"> --> <!-- 1.5mm gap -->
<circle cx="0.0" cy="0.0" r="4.5" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<circle cx="0.0" cy="0.0" r="1.5" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
<!-- Mount holes -->
<g transform="translate(-20.0, -20.0)">
<circle cx="0.0" cy="0.0" r="2.0" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
<g transform="translate(-20.0, 20.0)">
<circle cx="0.0" cy="0.0" r="2.0" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
<g transform="translate(20.0, -20.0)">
<circle cx="0.0" cy="0.0" r="2.0" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
<g transform="translate(20.0, 20.0)">
<circle cx="0.0" cy="0.0" r="2.0" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
<!-- Bushing Cog 1 -->
<g transform="translate(20.0, 0.0)">
<circle cx="0.0" cy="0.0" r="4.5" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<circle cx="0.0" cy="0.0" r="1.5" style="stroke-width:0.1; stroke:#000000; fill:none;" />
<line x1="-1.0" y1="0.0" x2="1.0" y2="0.0" style="stroke-width:0.1; stroke:#000000;"/>
<line x1="0.0" y1="-1.0" x2="0.0" y2="1.0" style="stroke-width:0.1; stroke:#000000;"/>
</g>
</g>
</svg>
Assembly:
The parts:
Screw in the threaded rods in the mounting holes on the motor (just by hand). Place the 50mm spacers over the rods (I use the housings for discarded pens, cut to size). Place the shaft coupling on the motor axle.
Slip on two O-rings over each of the GT2 timing belt pulleys. Slide the longer parts of the shafts through the bushings of one of the acrylic sheets. Mount the timing belt pulleys. Leave just a little bit of slack, so the rollers can turn freely, then tighten down the allen set screws on the pulleys. (Note, in the picture, I used a drive shaft slightly longer than 50mm, I later changed to use a 50mm shaft for both rollers).
Slide the piece on to the threaded rods (the drive shaft going into the shaft coupling).
Add the 16.5mm spacers and the outer acrylic piece. Add the wing nuts and hand tighten. Tighten down the allen set screws on the shaft coupling.
Done
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