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Mk3 Heated Bed

Posted by scubi 
Mk3 Heated Bed
April 21, 2015 02:36AM
Hi Guys
I am building the Mendel90 and was thinking of buying the Mk3 Heated bed. It comes fully assembled with the thermistor.
Whats your opinion on the PCB bed,

Re: Mk3 Heated Bed
April 21, 2015 09:22AM
It's an option. Some people swear by using an aluminum plate as a heat spreader, some people swear just a pc board + glass is fine. Neither are right or wrong, it's just...an available option. Same thing goes for what hot end to use, mechanical vs opto vs hall effect end stop, etc...
Re: Mk3 Heated Bed
April 21, 2015 02:45PM
I use one of those on my Prusa i3 - works very well with just kapton tape on it, as I use an inductive sensor for auto-levelling and therefore can't use a sheet of glass.

Initially I had a problem as I couldn't find a suitable thermistor table to match the one that came with my heatbed - in the end I chose type 7 as that seemed to match the thermistor that the seller provided. Your mileage may vary...
... here's the line from my configuration.h file (my comments added):

#define TEMP_SENSOR_BED 7 // best fit for thermocouple on RepRap-me aluminium heatbed
Re: Mk3 Heated Bed
April 22, 2015 05:36AM
Thank you for that. Appreciate it.
Re: Mk3 Heated Bed
April 23, 2015 01:11AM
Hi Scubi,

I've had an MK3 running for some time now and I would recommend it. A couple of things I learned along the way:
- buy the 12$ IR thermometer so you know what temp your actually seeing. Similar to David's comment above I had trouble getting the desired temps right and my stock thermistor was about 10d off. Going to try David's idea and see if accuracy improves.
- I have never put tape of any kind on my bed... however you might want to as mine is pretty scratched up from my early days
- you'll want to get some cork or cardboard to insulate the underside of the bed. Unless you configure a seperate power supply for the heated bed this will help stabalize temperatures and take pressure off your single ps.. also helped mine heat up a bit faster
- I spray windex on the bed every 10 prints or so... not sure I need to but figure it can't hurt.

Hopefully there are a few helpful items in that list!
Re: Mk3 Heated Bed
April 23, 2015 06:34AM
I made a cork sandwich for my Prusa's bed - the bed itself, then 2 layers of 2mm cork underneath (with cut-outs on the top piece for the wiring) and a sheet of 1.5mm ali at the bottom. It still gets warm underneath! But at least it now takes half the time to get up to ABS temperatures, especially when I put a sheet of corrugated cardboard on top during the warm-up.

This is all hard-mounted to the Y carriage, as I use auto-levelling.

Edited 1 time(s). Last edit at 04/23/2015 06:36AM by David J.
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