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3d Printed Fluid Bed Roaster
Hi All,

I recently submitted a 3d printed roaster here:

Now I am attempting a fluid bed design.

Core Components:

1) 18V, 120W portable vacuum motor + PWM controller + 2.5" cold air intake filter
2) 1800W ceramic heat gun element - nichrome with narrow ceramic channels. Should conduct more heat to the air at the expense of added static pressure.
3) Fuji PXR4 PID + 4" probe + SSR
4) Bake-a-roun Pyrex Tube!!! It is a DIY fluid bed after all

The rest will be made with a refractory concrete made by Rutland. I have used this mix in a few other projects and am very happy with it. To prevent dusting from bean impacts I'll be sealing the lower roast chamber with a ceramic adhesive stable up to 1200C. Should bind any small particles to the surface and prevent contamination.
Early pic of the mold being printed. It is inverted here (and in the following three photos) so you are looking at the roast chamber upside down.
Finished mold for lower roast chamber. This is a not-insignificant print. Total height is 180mm (the exact limit of my printer). Print time was 36 hours and in total 280 grams of filament was used ($4).
Filled with concrete mix, bit of rain.
A temporary guide in place used to mount 4" bolts into the base. These will be used to mount the lower roast chamber to the control box that will sit below.
Printing a compression chamber for the vacuum housing. This is a bit of a lossy / non-ideal design. It will guide the air from the vacuum outlet (which right now is tangential to the rotation of the radial compressor and route it to a 30mm opening that will mate with the lower roast chamber intake.


This was made for an earlier iteration where I was trying out an axial compressor. This is the final stage which includes stators and a turbulence reduction cavity. It worked and boosted the dynamic pressure, but the total length of the axial compressor was close to 100mm and required at least 40-50mm gap beneath (not accounting for a filter). The entire design was too tall. The radial compressor overcomes this by taking air in at a right angle.

Will post more pics as it comes together ;)
Edited by Linnaeus on 11-20-2017 05:35
This looks great! I don't think anyone else is building something like this.

Please keep us updated. Looking forward to seeing it roast!

KKTO Roaster.
Interesting. I have an airflow prototype 3-d printed. Never thought about printing molds.
Quick update.

So, I made an error with this mold and printed an infill for any support pieces touching the build plate (you can see it in the first image of the mold print in progress). The result is that the "bowl" for the roast chamber was one giant chunk of plastic that was not easy to remove. I have tried one round of baking it out, which worked rather well - but has left a bit of a residue. I'll have to fire the rest of the plastic off (either in the oven or a fire pit).

Additionally, in trying to burn the plastic out I heated up the block a bit too much (430F) before all of the moisture had been baked out. This has resulted in some small cracks. I've sealed the cracks with rocksett, they are barely visible and should not impact the strutctural integrity of the finished part, but the OCD person in me wants to start from scratch.
upside down
Right side up
The bowl showing some of the PLA residue
The ABS vacuum guide
Next to the 18V 120W vacuum
Wired up to the PWM - works a treat.
Some of the other parts lined up and ready to go

Next step is to print the lower housing which will encase all of the electronics and support the roasting chamber above the vacuum housing.

I will embed the heatsink for the SSR in the intake path for the vacuum housing. In this way, I'll have active cooling for the SSR and will (VERY SLIGHTLY) increase the intake air temp.
Edited by Linnaeus on 11-21-2017 05:30
Baked out the remainder of the plastic residue and was able to fit the glass top and heating element.

Fit is very good with no wiggle room on either. The heating element has a mica sheath to prevent conduction within the refractory.
Below is an assembly of all the pieces designed thus far:
JackH wrote:

This looks great! I don't think anyone else is building something like this.

Please keep us updated. Looking forward to seeing it roast!

I agree with Jack, I've never seen anyone doing 3D printing for molds and making operational fluidbed roasters from them. This looks like it would be a whole lot less hassle without having to fabricate sheet metal parts. But, one would have to have the expertise in programming the printer.

Very nice indeed!

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
If you can do the cad drawings, there is software that slices it up for printing.
I don't really have any metalworking skills, and have always been jealous of the cancellation/sheet creations that people are building. But I do love 3d printers. There is no other tool that makes engineering prototypes so accessible to a hobbyist.
More assemblies - working on the base now and fit for the PID/PWM... not too happy with what I've come up with as it will be a bit bulky, but want to pull the trigger soon so that I can get this operational.

The rear intake will have a cold air filter mounted ontop - it's serious overkill, but will go towards preventing any buildup / fires without adding restriction.

Probably would have been better to just 3d print a mesh cylinder and put a nylon over it.
Some screen grabs of the first half of the enclosure.
And with a mock up of the 2nd half of the housing:

And with the rear intake filter + PID/PWM:
Edited by Linnaeus on 11-25-2017 07:28
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."
Wanted to show off a little design element that makes me happy. The SSR heatsink is ducted into the vacuum intake path. I hope that this will prolong the life of the relay by keeping it super-chill, and also give the tiniest little boost to my ambient air temps :)

It's starting to come together - here's where the vacuum housing connects to the roast chamber. This part is printed in ABS with a flange also printed in ABS. Unlike the PLA, which has a glass transition temp of 60C, ABS has a tglass of 85-90C and won't really deform until 105C or so.

Finished printing the base out as well. The PWM fit is a little loose - so I'll be printing a little frame to keep it secured. I'm applying an epoxy + copper powder (real metal powder) to this piece. When cured it can be buffed up and aged. Will post those pics tomorrow.
Too much care for the SSR, for my 1400W element it runs cool enough without any heatsink, about 40C degrees.

I would be rather worried about the real specs, when such 40A unit stopped working in my roaster, opened it and was surprised to find inside a 16A triac, which make a cinic joke the 40A engraved on the case...
Be also aware that when these SSR die, they don't break the circuit, conversely, they short, so you will have full power without any control, other than mains switch or unplug from the wall faster than a fire break out.
DIY: TO based IR to bean 800g
Moded commercial: Dieckmann RoestMeister, Nesco, popcorn.
PID/ramp/soak controllers, MS6514 USB/Artisan/App
Grinder: mod'ed Porlex to 47 conical burrs
Thanks renatoa, In testing, this ssr ran between 45-55c. Every little bit helps ;) and with enough cooling a 16A triac could probably handle 18+ amps. Heat is the enemy of all electronics.
Edited by Linnaeus on 11-27-2017 01:04
Testing the fit of some of the parts. Was able to loft about 200g of test beans. Will need to seal the joint between the vacuum and roast chamber with silicone though - the ceramic element did cause a lot of back pressure.
Not totally happy with the finish, but here's a little background on the process.

The finish is created using a 2 part resin and a powdered copper that looks like this:

The resin is mixed, and then the copper is added.

Once dried the finish looks like this:

The piece is then buffed using a piece of 000 steel wool. After buffing the part it looks like this:

I may add one more coat with a black dye in the resin, or I may just drop some black shoe polish on top. One of the challenges is that when buffed with steel wool, the copper shines up, but the resin dulls a bit. Giving it a bit of a haze. This can be corrected by adding more copper to the resin, but it gets very thick and difficult to paint.
Did some more testing, and to get the highest pressure rating possible I will have to seal with silicone. Unfortunately, this means that the connection between the vacuum housing and the roast chamber will be semi permanent. If I approached this project again I would make a larger flange inset in the refractory RC and coat it with high temp silicone. That way the two parts could be easily separated for maintenance.

Here's a little pro/con. Most vacuum motors have way too much airflow, when you dial them back, they lose the majority of their pressure rating. The ceramic heating element used here adds a significant amount of static pressure (con). The pro is that the radial compressor can be run in it's optimal power band. I would guess that I get about 50 cfm through the heating element - but also get 8-10 inches of pressure. The other pro here is that the high air pressure within the heating element means that there is a higher air density. Higher density means more air molecules in contact with heated surfaces and a higher heat transfer rate.

In many fluid beds the limiting factor is getting enough heat transferred to the air before it comes in contact with the beans. The limiting factor in this design is the airflow through the element. Once it's all sealed up I will do a test of the maximum green coffee volume that will fluidized. Keep your fingers crossed for 500g.
Very frustrated today. I went to test my heating element, and found that it is only drawing 400 watts, despite being specced as a 1600W - 120V element.

Lesson learned, I should have tested this before assembling / siliconing parts in place. Now it's going to be a major PITA to remove the element / clean up silicone / remove the gasket between the RC and the vacuum housing.

On another note - here is an image of the final air intake assembly

And the probe mounted (lower left) + heating element mounted / wired up (center)

I also printed a little flange so that the PWM would sit flush
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