The Hell Ya Beller Fun with hot, pointy, sharp, and caustic stuff.

7May/114

Mendel Heated Bed

I've been struggling for months to get my "Sells" Mendel working reliably.  The mechanicals have been solid for a long time, but I've had flaky problems with the electronics and extruder all along.

I finally broke down and replaced the Gen3 electronics with a RAMPS board and after working through some issues, it finally seems to be working.

I usually print in ABS so I also invested in a Prusa PCB heat bed from Ultimachine.  There isn't much information out there on mounting the thing and most of the pictures I saw had people mounting them on a piece of plywood.  This is probably perfectly safe but there's something that bothers me about mounting something designed to get hot on top of something flammable.

I had a piece of 12" smooth Hardiboard.  This is siding material made from cement infused fiber.  It's very flat, very hard and heat resistant.   As a test, I held the torch on a scrap for a while to see what the result would be.  It scorched the topside but barely penetrated at all.

It's a little heavier than I'd like, but the combination of the hardiboard and PCB is actually lighter than the old acrylic and removable MDF that I was using before.

The downside is this stuff is damn hard to cut and throws off a lot of dust.  I milled a couple pockets for the thermistor and the wires so the bed would lay flat.   I also cut a few notches to remove material and lighten it further.  It seems to be working well.

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  1. How big of a benefit do you find the heated bed when extruding ABS? Without the heated bed, what’s the result? Do the printed items just pop off the substrate before the print is done?

  2. Seems like we have similar Problems (well you had apparently). I’m still on gen3 and thinking about moving to RAMPS, would you say it’s worth the cost?

    I also recently bought a ultimachine heatbed and am wondering which Thermistor you are using and how you plan to attach it to the PCB.

    Thanks for sharing.

  3. Definitely worth the cost. I have the 100k thermistors from Makergear. It’s justed taped to the center of the bottom of the heatbed with kapton tape. I had to create a hollow in the material it’s mounted to but it works fine.

  4. The benefit for small objects isn’t too noticeable but it’s huge for larger objects. Almost no warping. Objects pop off pretty easy. Sometimes the self-detach as the bed cools.


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