Dryer vent heat shedder

I can’t call this a heat exchanger, as it doesn’t exchange any heat. It just sheds some of the heat from the dryer duct into the room. I am trying to keep some of the heat I paid to create, in the house, where I tend to hang out when it’s cold outside.

I know I’d get better return on the money I spent by feeding the dryer outside air, but I wanted to give this a try. A friend gave me the heat sinks, so I wanted to see if I could find a noble use for them. I love DIY projects anyhow. I kinda liken it to a homemade energy themed work of art.

A picture is worth a thousand words, so here’s a 25k word novelette. (Hey, technically these stereoscopic photos are 2 photos each, so they count double. Just cross your eyes to get your word-count’s worth.).

The parts needed for my dryer heat exchanger
The parts needed for my dryer heat exchanger. I spent $56 at the hardware store last night to get the bulk of it. The heat sinks a friend gave me, because they had my name on the boxes “FREE”.
A friend of mine gave me boxes of new, unused computer heat sinks.
A friend of mine gave me boxes of new, unused computer heat sinks.

I currently have 20 of these heat sinks. I fiddled around with them for a while to see how many I can fit on my duct, and I came up with 74. Two rows of 15 down the long, wide face with 14 spaced in between and a row of 15 down each side.

Laying out the heat sinks on my ductwork to see how many I would need total
Laying out the heat sinks on my ductwork to see how many I would need total.

I figured I’d start with the 20 I have, and see if it does anything for me at all before I mangle that many heat sinks.

The center row of heat sinks is spun 45 degrees so they fit better
The center row of heat sinks is spun 45 degrees so they fit better. I have them upside down to keep the goo from getting everywhere.

I rather like this dense arrangement. I’ve knocked all the cooling fans loose for now. I may re-install some of them. Possibly just down the center row maybe? A larger box fan running off the dryer’s timer may work better in the end.

2 hours measureing and marking to get the layout I wanted
2 hours measuring and marking to get the layout I wanted.
Took me a while to figure out the best way to drill the holes
Took me a while to figure out the best way to drill the holes.

I ended up drilling all the holes with a drill bit from the back side where I had my layout marks. I then de-burred the holes from the front, pushing hard, so I dimpled each hole. This flexed the metal so that the screws would tighten the sheet metal up to the heat sink.

positioning the heat sinks and holding them while screwing them on was tricky
Positioning the heat sinks and holding them while screwing them on was tricky. Duct tape for Duct work FTW!

The screws I used where some pan head self tapping sheet metal screws. Ended up not needing the self tapping feature as I had to pre-drill all the holes to keep the metal bits from preventing the heat sinks from coming up tight to the metal. Live and learn. I just ran them between the fins on the heat sink. They seem to hold tight. I hope that if I ever disassemble this thing, I can reuse the heat-sinks in the future. Maybe. Please?

The heatsinks came with some thermal paste, but I added extra for good measure
The heatsinks came with some thermal paste, but I added extra for good measure

It’s actually surprising how heavy the assembled unit is. A lot of light weight parts makes for a heavy finished product.

20 heat sinks screwed to some ducting. how silly is that?
20 heat sinks screwed to some ducting. how silly is that?

Carbon Monoxide poisoning is a risk when doing something like this, so the whole contraption is sealed up tight. I’d feel really bad if I killed myself trying to save a buck.

This fancy tape was the most expensive part to buy! What do you mean, I can't use duct tape on duct work?
This fancy tape was the most expensive part to buy! What do you mean, I can’t use duct tape on duct work?
The screws are all sealed with silicone sealer good for 400 degrees
The screws are all sealed with silicone sealer good for 400 degrees

I tried to keep the inside of the duct as smooth as possible to not collect any lint and cause a fire hazard. I am hoping the shallow screw heads will create just enough turbulence to keep mixing the hotter air with what’s already shed some heat to the walls.

Ready to wire up and mount on the wall!
Ready to wire up and mount on the wall!

 

Now I just need to add 2 stainless steel housed thermistors so I can monitor the air intake and exit temperatures. If I see a temperature difference, that means it’s working. I can use a 55 gallon plastic bag to figure out the air flow of the dryer. Some magical maths will tell me how much heat I am dumping into the house vs throwing out with the wash-water (clever, eh?). If I get any good results at all, I will try to collect enough heat sinks over time to finish this project.

54 more heatsinks needed. New price for these appear to range between $10 and $100 (Seriously?!?). Glad I am not damaging the heat sinks too bad, but the dollar value of this project kinda makes me a little sad.

 

 

I have some laser scans off of a ROMER arm of my cell phone and 2 tablets  (including…

I have some laser scans off of a ROMER arm of my cell phone and 2 tablets  (including a Nexus 7). They are saved in .IGS, .XYZ and .PSL formats.

How can I convert these into a .stl I can use for my RepRap?

I'd rather keep my few favors for the scanning and not the conversions in Polyworks or Reshaper.

I couldn't figure out how to get more than all the points in a line in Meshlab.

Suggestions?

Rebuilt build platform for my MakerGear Prusa Mendel RepRap with mirror

I rebuilt the heated build platform on my MakerGear Prusa Mendel. I’ve been having problems with it ‘eating’ glass. I didn’t recess the thermistor enough, so the glass would try to ‘bend’ over it, and break.

These are 3D stereoscopic images. You can look at them crossed eyed and get the full effect. You can click for a larger view as well.

image of Original print bed with broken glass.
Original print bed with broken glass. I used the printer like this for months. Really limits what you can print. I’ve actually not used the printer in 2 months because of it being broken like this.

 

image original build platform
This is how I’d configured the board to accept the heater. The notches are for the thermistor and wire runs.
image of Lining up the dremel to route out the board
Here I am lining up the dremel to route out the board. I wanted to recess the heater flush with the face of the board. So I used the router fence I had printed on my printer.
image of routed lines and chiseling out the excess
Here you can see my routed lines and chiseling out the excess. Running the dremel-router was a l of fun.
image of recessed area for the heater PCB
I’ve finished the recessed area for the heater PCB. It was fairly easy to use the chisel to chunk out the bits between my routed grooves. I used the grooves as a depth gage and tried to go that deep.
image looking at the bottom of the board
Here we are looking at the bottom of the board. I cut in 2 notches for the belt clamps as well as 4 holes for the bolt heads. This allows the board to set much lower than it could previously and still offer ‘springyness’.
image of installed print platform
I’ve installed the print platform. Notice that the bolts are recessed in so they sit flush to the board as well as the heater PCB. This will allow a full sized piece of glass.
image of installed heater PCB
The installed heater PCB looks pretty good I think.
image of heater PCB sits flush to the print bed platform
You can see the heater PCB sits flush to the print bed platform now. Hopefully I’ve got everything right now, and I will no longer break the glass print surface.
image of print platform height
You you can see how low the print platform is now. I’ve barely enough clearance over the Y carriage pulley. I’ve still got over an eighth inch of give too!
image of a cut mirror for a build platform
I am not very good as cutting glass. I broke my first piece. This is a mirror panel I rescued from the trash. Originally from Ikea. It’s very thin glass. I’ve heard good things about printing on mirror. Going to give it a try.
image of mirrored print bed
You can see my shiny new mirrored print bed. You can see that the mirror edges extend all the way to the edge of the build platform. I think this looks cooler. It also gives me more room to clamp the print surface down and avoid nozzle contact with the binder clips.
image of MakerGear Prusa Mendel RepRap with mirrored print bed
Now to level the print bed. This is going to be tedious as I have to remove the print surface to make any adjustments. I may try to cut my broken mirror piece down to use for leveling. It would expose the bolt heads.

All in all, I am pretty happy with these modifications. I should get a bit more print height. It looks cooler, and maybe I will turn the printer on again soon and start printing again!

The next serious modification will be a water cooling block for the nozzle. I’ve an idea for that…