Since we have RepMan (kind of RepRap) 3D printer I was thinking about printing large objets. Of course you start with small things like minimug. But as you start learning how to get good small prints you’ll try something bigger and you will probably see large warping. It’s caused by different temperatures in the object. Professional machines uses heated print chamber to avoid this, but we can’t of course build heated champer since the printer is made from plastic or plexyglass. Great compromise is to build heated print bed. I was inspired by Zaggos work in Pleasant Hardware. But he has MakerBot which has only 10x10cm print bed. RepMan has 4times bigger. I wanted to build my print bed as quick as possible so I used ressistive wire which I have for a while, then some plexyglass and epoxy glue. It build like burger, in three layers 1)Plexyglass 2) ressistive wire + epoxy glue 3) plexyglass. After you do make this you should put it on the straight place, put something heavy and straight on it and leave it for few hours.
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Don’t ask me to exact ressistance of the wire etc. I dont know it You just should make sure that whole print bed rig consumes about 45-55 Watts (you can use more for quicker heating, but you can melt the plexy, so be carefull) for this size, for Makerbot should be enough 25-30 Watts.
I’ve added (dont forget to drill and sand the place for sensor and cable in bottom piece of plexy) temperature sensor which is done by my brother, so I know if it’s warm enough. BTW even plexyglass expands when it’s heated, I’ve had to place some spacers between print bed and lower support plexy contruction. You know, it’s a prototype, but it works
I’ve tried to print when the bed was about 70°C, its quite enough. But higher temperature could be better, I’ll test it later.
Here you can se the video from my first printing of „x-carriage-lower_1off“ Mendel part.