Aluminum Sheet Between Heater and Glass

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deckingman
Do you have heat insulation under your bed? Any idea what 8mm or 10 would do to the warm up time? If it's say 25% thicker would the warm up time be 25% longer or is that too simple? Price wise, 6 mm would cost me £31.57, 8 mm £36.03, 10 mm £37.96 so there is hardly any difference and on that basis I'd be tempted to go for 10 mm. Just a bit concerned about warm up time though.

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deckingman
Also, I haven't bought the heater yet but I've seen a 400 x 400mm 1.5kW which seems insanely high unless it was a miss print. Assuming it isn't a miss print, should I be tempted? As control is going to be "bang bang" via a SSR, would a heater that powerful lead to overshoot probs? I'm guessing not if the warm up time is in the order of 5 minutes but correct me if I'm wrong.

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dc42
I hope you don't mind me interrupting.

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dc42
It is worth insulating under the bed to avoid wasting energy and to prevent things under the bed getting too hot, but it won't cut the heating time by very much. The warm up time is dominated by the heating power and the thermal capacity of the bed plate.

That insulation sounds expensive to me - what material is it?

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dc42
could pose a fire risk of the SSR fails short circuit or the electronics leaves the heater fully on.

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the_digital_dentist
I don't get it. Everyone knows you need a flat surface to print reliably, yet so many keep buying thin, flexible aluminum and then put glass on top of it. Why do people keep buying the thin, flexible aluminum? It makes no sense. Why not just get a flat aluminum plate such as cast tooling plate in the first place and be done with it? Unlike galss, aluminum is thermally conductive so the temperature will be even across the surface and you won't have print adhesion problems. Surely the cost of a thin flexible aluminum plate, plus glass to fit, and the goop you're going to have to slather on to get prints to stick can't be much less than the cost of a piece of cast tooling plate. We're talking about a few dollars/euros here, not hundreds. Are the few dollars/euros you save worth all the screwing around to find a magic formula to try to get your prints to stick?

Since you're developing the printer yourself, I advise you to try out a 3 point leveling system. When you level the print bed you're adjusting it so that it lies in the XY plane defined by the printer's guide rails. It takes only three points to define a plane. The typical 4 corner "leveling" system bends the bed plate and the undercarriage. You can't level a bent plate, neither can autoleveling. With enough screwing around you may get the center of the bed flat/level enough to print on but you aren't likely to be able to use the entire bed. The further you get from the center the worse it will get. Auto leveling assumes that the bed is a plane so its not necessarily going to help.

Here's a 250 mm diameter ABS print on my 317 x 305 x 6.35 mm cast tooling plate bed supported by a three point leveling system:

IMG_1051.JPG

I have never seen anything of similar size done on a thin piece of aluminum with a glass plate and a 4 point leveling system.

What's the point of building a machine with a 200 x 400 mm bed if you can't print on the entire surface? The thin aluminum/glass/4 corner leveling is done in cheapo (and some not so cheap) printers because it is a couple dollars/euros cheaper than doing it the right way, or the "designers" don't know any better. The whole point of developing your own printer is to do something better than you can get elsewhere. If you're just going to copy their mistakes, just get one of those cheapo kits and save yourself a lot of trouble sourcing the parts.