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 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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