Heat Sink for Electric Furnace Controller

Discussion in 'Lost foam casting' started by Al2O3, Jun 18, 2018.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    My larger furnace build will need an electric controller to power the electric insert. I decided to build a new controller for my small furnace and use the old controller for the larger furnace. This heat sink is for cooling the solid-state relays and will mount on the side of the control box. Nothing too fancy and no tooling required. Just machined some fins in foam sheet, some piece work, and assembled with hot melt glue. It was a quicky pattern that only took about 30 minutes to make. More to come.

    1 Heat Sink Pattern.JPG 2 Heat Sink Pattern Bottom.JPG

    Best,
    Kelly
     
    Red97 and _Jason like this.
  2. Tobho Mott

    Tobho Mott Gold Banner Member

    Can't wait to see how it casts!

    Jeff
     
  3. Nice hot wax job!
     
  4. Jason

    Jason Gold

    Wouldn't it be faster to mill that thing out? Assuming you have a mill?
     
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    On a casting site no less Jason?.......Heresy! Blasphemy!

    I do have a mill but it wouldn't be faster for me......presuming it successfully casts the first time that is. Want to bet? I have about 30 minutes into the pattern. It'll probably take another 30 minutes to sprue it and coat it. How long it takes to cast will depend on what else I'm doing with it but I'm guessing another hour to vibrate it in a bucket, pour it, and degate it. So probably a couple hours all in plus a few pounds of cast aluminum scrap.

    I couldn't touch that invested time machining it. It's 14" x 7" x 1". You'd have to have some 1" plate (I don't) and then resize it. Cutting deep slots with a long small diameter cutter with 180 degrees of contact and on both sides contact skinny little fines would chatter like the dickens. If you had a high speed spindle and a coolant system (I don't) maybe, but then you'd have to figure programming time. I'd have to stand that part on edge in the vice and use a slitting saw stepping down the part so it remained 1" thick at the cutting point or it would flop all over the place without a more elaborate fixture.......then mill the perimeter.

    You can buy used extruded aluminum heat sinks on eBay for $20-$40 in that size range or use multiples smaller pieces, but it would still take some cutting and fitting.

    Best,
    Kelly
     
  6. I thought he meant mill the pattern out of solid foam instead of gluing all the fins on.

    looks like a great job getting them all on parallel.
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    The fins were cut with a stacked finger joint bit in three planks, 5 fins per plank, hot wired to reduce thickness, then glued together. If you look closely on the back side you can see the three planks. The perimeter flange and three SSR pads were hot wired piece parts glued on with hot melt glue. Ran a rabbit bit around the flange to finish it off. -Quick job.

    Best,
    Kelly
     
  8. Jason

    Jason Gold

    I was talking about milling it out of aluminum.

    Not blasphemy at all...
    Those fins can be cut on a table saw.
    I got a shop in mesa I visit and buy drops for 3bucks a pound. They have a mountain of plate from 1" to 6" blocks.
    Can't remember the name of it, it's close to a hotel I use at gateway.:( sucks to get old.
     
  9. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    That's a good resource to have. It'd be 10 lbs/$30 if they had a remnant the exact size. Think I'd just buy an extruded one for half that.

    https://www.ebay.com/itm/300x140x20mm-Aluminum-Heat-Sink-Cooling-For-LED-Power-IC-Transistor-Heatsink/132296152126?_trkparms=aid=222007&algo=SIM.MBE&ao=2&asc=44040&meid=ae572a8c04b14784a0287b30d6f88aed&pid=100005&rk=12&rkt=12&mehot=pp&sd=163051289846&itm=132296152126&_trksid=p2047675.c100005.m1851

    That's what I did on my first controller. Instead I spent that money on all the panel switches, meters, etc for the controller and bought them from Asia via eBay. Basically got me everything I needed except the circuit breaker, power contactor, PiD (which I had), and power cord.

    For this heat sink, it's free wheelium, free PoP (Been toting around the same 5 gal bucket for 15 years now), and 25 cents worth of foam.....and I get it made to fit and knowing I did so every time I use it in the future.......and I like that.

    Still better than some of the alternatives.

    Best,
    Kelly
     
    Hopefuldave likes this.
  10. PoP? Not using sheetrock mud? I'm learning.

    I'm dying to find out what's next...
     
  11. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Nah, it's non-setting mud.....Gypsum.

    K
     
  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Well, it was a good thing I didn’t have much time into the pattern because I screwed up the pour and suffered my second blow out of the day. Here was my first ala Jimmy Buffet……..blew out my flip flop.

    3 Blow Out Sandle.JPG

    Ok, it’s not a flip flop but definitely a blowout. Here was the second.

    4 Run Out Pour.JPG

    I should have known better. My flask really wasn’t big enough for the part because there were only a couple inches of sand above the part and my sprue extender didn’t cover enough of the top of the mold, so just a little bit of cup pressure was enough to float the sand.

    5 Mold 1.JPG 6 Mold 2.JPG

    It’s an interesting fail. Once it started running out I just kept pouring. After it started running out the cup never really filled and I thought all the molten metal was just escaping under the sprue extender. But when I demolded, the part had either already filled before the runout or kept filling. I never saw the sand puff or move.

    7 Casting with Run Out.JPG

    The lower half of the part was perfect but you can see how the sprue pressure moved the mold sand in the upper half. Sort of interesting too because the features of the upper half of the part remained intact but it swelled in the direction of the float caused by the sprue pressure working on surface area of the part.

    8 Swell.JPG

    Only one thing to do…….do it again. Zipped out another pattern.

    9 Remake Pattern.JPG

    This time I molded it vertically in a mold deep enough to accommodate. This time the pour was very uneventful. One thing is for certain, it does validate some of the measures I’ve taken on my next intake manifold lid casting project.

    10 Mold Pour.JPG 11 Cast Success.JPG

    Here’s the sheet metal work for the new furnace controller enclosure. I’ll eventually start a build thread update for my furnace but that may take a while…..too many projects!

    12 On Cabinet.JPG

    Best,

    Kelly
     
    Red97 and Mark's castings like this.
  13. Jason

    Jason Gold

    looks good. is that enclosure ss?
     
  14. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Negative....just carbon steel.

    Best,
    Kelly
     
  15. But did you step on a pop top?

    Looks like you might have had a good pour without the pour cup?

    And the real question, were you pouring in those shoes?:eek:
     
  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    No, but Parrot Heads rejoice!

    Hard to say.....doubtful, but ya never know. I've had a number of successful foam pours that I initially thought were going to be failures for one reason or another.

    Yard work yes, casting NO!

    Best,
    Kelly
     
  17. Jason

    Jason Gold

    Dude, thrown those stinky shoes away, I can smell your feet from tejas!
     
  18. PatJ

    PatJ Silver

    Looks like it turned out pretty well.
     
  19. Tobho Mott

    Tobho Mott Gold Banner Member

    That came out nice! Even the failed one looked like it came pretty close...

    My lost foam mold was the only one of 4 that actually turned out yesterday; also had 3 sand molds to pour and all 3 failed to fill on me (2 bronze, one aluminum). I think the bronze was not quite up to pouring temp. I saw the rainbow oil slick Jason talks about, but maybe it wasn't fully swirling properly, not sure. It seemed good to pour since it was all fully liquid, no thick lumps or anything left in the pot. Maybe it's time I finally built a decent pyrometer... I did at least find out my sand from Smelko doesn't burn onto the bronze like my new sand does. Got some tips from HT1 last week for fixing the new sand that I'll be implementing, but just haven't had time to secure all the ingredients yet.

    Back to being sort of on-topic, I might as well have been wearing Kelly's worn-out flip flops for all the good my steel toed leather safety shoes did me when I slopped a bit of bronze on the ground and molten drops flew everywhere: Foundry Burns

    Wasn't my weekend to be pouring castings I guess. After that spill I was able to pour all 3 bronze molds, then melt some aluminum, pour the last sand mold, and clean everything up, before heading inside to have a beer and a look at my burns... So, it could have been a lot worse.

    To top it off, my neighbour finally noticed I'm up to something strange, heard my furnace running and later in the day asked me about the whining shop vac blower noise he'd noticed. "Did it sound sort of like a shop vac had made a baby with a big bonfire? Yeah, that was my melting furnace, I was making some bronze castings. I really hope the noise didn't bother you too much..." Surprised he hadn't ever heard my furnace running before this. Normally, hoping to keep it low-key, I start melting in the evening once most people are inside their houses, which apparently had worked... but this was a rare mid-day melt. It was also one of the only times I did a second melt after pouring the first, so the furnace was running for longer. He didn't seem too freaked out upon learning there's a small foundry operating next door; he was curious but not bothered about the noise. I'm pretty sure he isn't gonna report me to the FD or anything, so I guess that is one worry to cross off the list. Maybe the day was not a total loss after all...

    Jeff
     
  20. I appreciate this thread. It reminds me I've been lucky, not good.
     

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