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Reflow Fred Style! :-) 
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That's the thing, there is a heating element just below the plate, so the plate is going to distribute that heat much more evenly than if there was nothing there, refer bottom side of slice of toast on previous page :-) I'd blow cold air in from the bottom on the ramp down, if I used a fan. I think with insulation and maybe 1 or two more elements it should heat up fast enough and stay steady in a controllable way without frying my entire work area. Keep in mind, no garage, small apartment, in a building, in the most populous city in Europe...

Fred.

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Sat Mar 10, 2012 1:39 am
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I DO like the idea of a small home project resulting in Megadeaths... But I still think the insulation won';t make it warm significantly more, not on a level you can't overcome with more elements. It's easy to time, even now - rise and fall times.


Sun Mar 11, 2012 12:53 am
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Insulation on the back panel is going to have a marked effect, I promise. It's single skin, just thin zinc coated steel, and it is at the same temperature as the inside and pretty much tracks the temperature inside in real time, you can feel it radiating at your hand a foot away, from the back side. On the front, you can put your hand on the glass and it's still cold, even when inside is 230C. The sides are only warm, and the top is moderately hot. Insulating the top and back will make a big difference, the sides less, the bottom not much at all. You're right that pumping more power into it will have more effect, and I'll do that if I have to, but that requires mechanical mods, which I'm not well setup for.here. So it's a last resort.

I went out tonight to get insulation and steel for this and came home with some Chinese drill bits and a Chinese drill and an old VCR that someone was throwing away :-) Sadly missed the insulation section by 5 minutes, so will have to go elsewhere or back there on Wednesday night or so to get that. It stays in pieces on the coffee table until then.

Fred.

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Sun Mar 11, 2012 1:56 am
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I picked up the remaining parts for the first stage of mods today. I am still waiting on the PCB to measure the temperature. Will install the insulation and put it back together for a zero to tstat timer test. Once the relay and the PCBs arrive I'll pull it down again to setup the electronic control. Hopefully some pics and so on tomorrow.

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Tue Mar 20, 2012 3:11 am
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Fred wrote:
Will install the insulation and put it back together for a zero to tstat timer test. Follwed by a tstat to zero test.

Hopefully some pics of the hilarity and housefires and so on tomorrow.


Don't feel bad, I'm sure lots of people had their first reflow ovens over insulated. You'll probably be in good company!


Tue Mar 20, 2012 11:08 am
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LOL :-p

The existing setup, with the single skin back, is a fire risk, for sure. Refer exhibit A the melted eee pc. I need to be able to exist with things on and around this thing without fear of a core melt down :-p cool down will be similar to before - with the door open :-p

I don't think there were enough pokey tongue out faces, so here is another :-p

:-p

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Tue Mar 20, 2012 12:13 pm
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Yesterday was a smokey fail, but today, after more research, I had success! You can no longer roast marshmellows behind the unit. Only inside now. The corners still get pretty hot, and you can't hold your hand on the back for long, but you can touch it. Before it was near glowing with closer than 150mm being too close to hold your hand at for long. The top is a similar success story just getting hot, and not obscene. I'll pull it apart again tomorrow to add a couple of screws to the back panel to stop it buckling with the heat and put more insulation in it on the sides. Then it'll just be a matter of waiting for the PCB and SS Relay that I need to control it. LOL pics of fire and smoke and so forth coming soon.

0 - tstat test was EXACTLY 7 minutes again. Upon reflection I realised that the sensor is in the knob, outside the chamber, and possibly driven by current duty through itself as much as the chamber side radiation. IE, it was an invalid test. I'll have to repeat once I have a probe inside and go from there.

Fred.

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Thu Mar 22, 2012 2:41 am
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In response to Abe's earlier criticism about thermal capacitors and aluminum plate:

0.91 kj/kg K for Aluminium
0.49 kj/kg K for Mild Steel

Mass of my ally plate vs mass of the steel grill it replaced: I have no scales, so I made a rough balance and it's only slightly heavier. So you could say it's twice as bad as it was, however the benefit of more even heat distribution and being able to put PCBs in without them falling through the cracks outweighs that considerably. Also, the overall thermal mass of the internal steel environment means that this is really quite insignificant.

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Fri Mar 23, 2012 1:58 pm
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Toaster Oven: 40 Euro
Materials, tools, and sensors: 30 Euro
Performance gains from insulating, and double skinning the back: Minimal
Saving your marriage by not burning the house down with a toaster oven on steroids: Priceless

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Fri Mar 23, 2012 6:10 pm
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The rommelsbacher speedy bg950 lost her PCB-virginity tonight! I put a FET driver onto a proto board and a CPU onto my priceless one-of-a-kind Jaguar A3S5 board. The CPU wasn't too bad, but I had a few bridges. I'll improve my syringe orifice and application area and try again at some point in the future. Still no thermocouple board, hopefully that comes next week some time so I can get the show on the road properly.

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n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Fri Apr 13, 2012 9:33 pm
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