Ok, so after all the trials and tribulations getting this printer going and learning I think there’s an upgrade I need to do. I’ll need to print 400mm or more conveniently 460mm on the Y-axis. The only limitation I see here is the length of the heater cable. I was thinking I could take the bed apart to add longer rails and slave another heater plate on there to double the length of the table, one long plate 2 heaters. the BL touch is working really well. any other problems I might run into? How are the heaters controlled for the beds on these anyway? The Y-axis motor seems to cope well with the weight of the OE bed might need a bigger motor for the added mass?
I’m actually working on exactly the same thing. In addition to expanding the frame, it may become necessary to add a second power supply, depending on what temperature you intend to run the bed at and whether the existing power supply can handle it.
The heaters are turned on and off by a MOSFET. The question is: what % of the MOSFETS rated current is it being driven at? I suspect they’d be cheap about it and use a MOSFET that’s rated only slightly higher than required so doubling the current draw is probably not a good idea. You’d have to crack it open, check the part number for the MOSFET, check the datasheet for the MOSFET and measure how much current the single bed consumes in comparison to know for sure.
On the subject of heating the bed, I foresee two potential problems.
Do I supply one thermistor value to the controller and assume the other one is “in sync”. If not, it will be necessary to figure out a way to prevent thermistor A from triggering more heat to bed B and vice-versa.
Will running two bed heaters overload the power supply? If so, external circuitry will be needed. The easiest method would be to use a pair of solid-state relays to switch the controller’s heater output back and forth between the bed heaters. This assumes a 50% duty cycle and that both heaters perform equally. If so, a single thermistor reading is needed. If not, it gets complicated. It’s possible that with only a 50% duty cycle, it may not be possible to reach the desired bed temperature. If not, then a second power supply is needed with external circuitry that powers the second bed when the first bed is being powered.
By the way, I already bought out 3DPC’s supply of solid-state relays for this. So; sorry.
Given that the bed on the BiquB1 runs on rollers, and the motor doesn’t actually carry any weight - just rolls it back and forth - I don’t think you need to worry about it.
Ideally, I’d like to do it all with one heater but I see the ones they make for this are all square and I’ll only need 200 x 400, so rectangular. They make em just not for 3d printers. I see the MOSFETs they use for the bed and nozzle aren’t plugged into the motherboard so I can add whatever I need, would the motherboard even have the capacity for an extra heater? I see there is a header marked heated enclosure on one of the drawings for it so maybe I can use that if it exists. Might just be simpler to make my own heater plate with everything built-in. I have lots of 24v power supplies and relays in stock, the bigger ones are ell enclosed for DIN rail or panel mounting though, and a lot more expensive than these little Chinese ones. I think I have a couple of Omron 280w ones I can call surplus.
My concern about the motor is more when it changes direction, the mass might be too much? You’re probably right though there’s not too much it has to do.