Heating plate for Mold Press Vulcanizer.

[Coper]

I need something like this or this.
I have a press, so I really only need heating plates.
Rubber vulcanization at 200 C.
Board size 200x200x20mm Aluminiu. Power 400W.
Voltage ideally directly at 230V.

My thoughts

Heating resistance R=U^2/P 230^2/400 = 132 Ohm
132 ohm is quite a lot for resistance wire-
I will try NiCr 0.3mm nikrothal 80 RESISTANCE AT 20°C 15,4 Ohm/m, Surface Area 9,42cm2/,m 132/15,4=8,57m
if I use a fiberglass tube as insulation, the power per area can be up to 5W/cm2
8,57*9,42=80,7 cm2 400/80,7= 4,96W/cm2 It suits.
the heating element must fit into the milled meander.
An 8m meander cannot be milled into an area of 200x200mm
i.e. I have to make a coil out of the wire.
I wind the coil around a wire with a diameter of 0.6 mm
thread length pi* (0,6+0,3)=2,82mm
number of threads 8570/2.82=3039 turn
coil length 0,3mm wire 0,4mm space 0,0,7 3039*0,7=2127 mm
2,1m it already fits on a 200x200 area
coil diameter 2*0,6+0,6=1,2m it should fit comfortably into a tube with an inner diameter of 1.5 mm

Coil production
A tensioned steel wire with a diameter of 0.6 m, which I turn with a cordless drill and wrap it with a 0.3 mm resistance wire.
The coil with the insulator is then inserted into a meander with a width of 2 mm and a depth of 2-3 mm and is sealed with a suitable adhesive with a temperature resistance of +600C

So much theory and my imagination.
Does anyone have real experience with this?



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[dick_freebird]

That size seems like it might allow you to either buy a
commercial hot plate or use an electric frypan as an
organ donor. Electric frypans are in the 100-1200W range
and have a crude thermostat for temp control. A used
lab hotplate will probably be lower power but have a
better controller.

Mate the flat hot surface to an aluminum spreader slab
and from there, to your press "floor plate". You can find
thermal pad material or just por the whole thing up with
JB-Weld (in my experience it has held up at 200C, you
can find higher-temp epoxies at higher cost). A high temp
silicone (automotive gasket maker) could be a good way
to accommodate TCE mismatches if your plates are not
all the same aluminum material.

A large electric stove "burner" (calrod coil) would give you
plenty of heater power, be made for 220V, you might find
an eBay temperature controller). Getting it attached and
keeping it attached to some sort of plate might be more
effort. Maybe sandwich the element between two plates,
with numerous studs for clamping force?

 

[KlausST]

Hi,

Similar applications: ironing plate, electric stove (oven and plates, even ceramic hob), enamel stove, clay oven..

Klaus

 

[FvM]

I'm mostly using cartridge heaters for similar applications. They come in a wide range of diameter, length and power. 230V is standard.

 

[Coper]

Thank you all for the responses, I will quickly respond to only the first post.

Use of pans, hotplates, irons, etc.
Not that I haven't thought of it, but
-Look at the links for the presses, they are not toys, but robust machines, because the pressing forces are from 130kg/cm2
-For an idea, something like this is inserted between the plates as a formatting frame
-temperature, for the production of precise dimensionally stable forms, it is necessary to precisely observe both the temperature profile and, above all, the significant increase in temperature over the entire area
That is why the heating plates are made of 20 mm thick aluminum, they have a heating element over the entire surface and a thermocouple and a good thermostat to measure the temperature.
Hotplates, etc. are not made for any of this, if you look them with a thermal camera you can see where they have a heating coil, etc. Their thermostats do not allow you to set the temperature with an accuracy of 1C, not to mention the controlled rise and temperature profile

Insulation of the heating element from the press
SiO2 Al2O3 fiber ceramic paper is used, thermal conductivity 0.08 W/m.K.