200mm*300mm Heated Bed


#1

I am working my way through what to buy for the Wilson ii (thinking of a 200300300mm build volume) and have read many reviews of pcb heated beds heating very slowly. I have also found that it would be cheaper to get a (https://www.aliexpress.com/item/silicone-heating-pad-heater-12V-200W-200mmx300mm-16-7A-for-3d-printer-heat-bed-12V-200W/32712689517.html?spm=2114.01010208.8.4.Jaq7aP) silicon heater and stick it to a sheet of 3mm aluminium (200*300mm) with the necessary holes drilled in it. However, the wires shown in the picture seem very thin for 16.7A (200W 12V heater). I assume this heater would require an additional mosfet/ relay so that the heater gets enough current (links please).
Final questions:
a) For this build volume will I need DRV8825 drivers (is it advisable to just start with these and never have problems) and high torque stepper motors.
b) How do you set up the DRV8825 drivers in Marlin?
c) What final height, width and length should I expect my setup to take up?

Many thanks in advance.


#2

For the DRV8825 drivers there is the Steps per mm to be set in Marlin. If you set the jumpers to use 1/32 step then you just double the steps per mm set in the default Wilson II firmware.

They will need the VREF to be set… all the ones I get all seem to be set to maximum voltage.

When you install the drivers make sure you put them the right way… typically for most setups it’s opposite to the A4988 but make sure before you put them in.

If you have done any research you will know the chatter about the drivers having the heat sinks on the chip is not the way to go. For larger printers I have started to add the heat sinks to the bottom of the driver on the gold pad apposite to the chip. then I use male to female pin extensions I got from a electronics store.

I just make sure a fan blows down through the middle of the drivers.


#3

Every so often you come across something and say "Now why the heck didn’t I think of that?"
Awesome idea, thanks!


#4

If you get the Chinese made DRV8825 drivers the current setting will be double the ref voltage, IE: 500mv == 1000ma. (genuine polulu’s are probably the same way). You can measure the ref voltage by clipping the positive lead of your meter to the screwdriver (if metallic) that you adjust the pot with as the pot screw is ‘hot’.


#5

Let me know if you find a way to power that off of a board! I was looking at getting a silicon heating pad but the only way I saw people doing it was with an external controller hooked up separately, and I didn’t want to deal with that. Unfortunately, that means waiting 10-15 minutes before printing to wait for the bed to heat up with a pcb heated bed.