Bonded Heat bed for 12"

[tsteever]

Thanks Printbus, that makes a bit more sense.

Chad, do you have a Rumba? I will be waiting in line for a SSR once you get it working! I think I will explore this, and upgrading to Lead screws before changing out the heat bed.

[printbus]

A few closing comments before I try and stay out of this (really, I promise).

An SSR is an electronic device, not mechanical. I've already mentioned there is a functional difference between an SSR for switching an AC load vs DC load. Note that the outputs on an SSR for DC control have a polarity to them. This needs to be considered when you're wiring them up. I don't know from first hand experience if wiring them backwards will damage them, but they certainly won't work that way. Unlike (most) mechanical relays, the control input to a SSR are also polarized.

Being an electronic device, "on" resistance is going to be more of a concern that it was with the mechanical relay. I've read comments of some SSRs people bought for 3D printer heat bed use where they complain the on resistance was unacceptably high, even though their heater drew less than the SSR rated current. The more on resistance the SSR has, the more power you'll lose as heat in the SSR. Some SSRs state they need to be installed on a heatsink to operate at the rated load current, and that internal power dissipation explains why. If the SSRs you are looking at don't specify the on resistance, consider purchasing one for a higher current than you need. A 40 amp SSR will likely have less on resistance than one rated for 25 amps. Yeah, the heftier ones or ones that specify a lower on resistance will cost more.

In retrospect, beefing the hell out of heat bed wiring in order to reduce warm up time may have aggravated the problem. It could be that Marlin was inadvertently sort of optimized around a slower responding heat bed. All it would have taken is for the person developing the control loop to have an inefficiently wired heater.

For those comparing quality between printing PLA on a heated bed and printing on a cold bed, consider that there may be another factor involved in any difference that you see. I know that on some small prints of mine, heating the bed has seemed to add just enough residual heat that the PLA part never properly cooled until the print completed. This meant that the entire print involved layers extruding onto material that was softer than if I printed on a cold bed. Extruding onto soft material is another easy way to end up z artifacts. For example, I know I've seen this happen on 20mm calibration cubes if the infill is high enough. This may not be as much of an issue for ABS, but I've been surprised at what it can take for PLA to cool. Adding more heat from the print surface just makes this worse.

[pichuete]

Thanks printbus for all the info. I'm happy to inform that I finally manage to solve my banding issue. . I bought a 3/16 aluminum 6061 plate(a little overkill) And replaced my glass. Also I drilled holes in each corner to fix it with the y plate using spacers with the pcb in between of curse. Since I have abl running already this doest affect my first layer consistency .

This constricted the pcb so it can only flex down on heat cycles without affecting the z height.

My print quality now is great. So definitely the heated bed was causing my banding .

[BLKKROW]

Thanks printbus for all the info. I'm happy to inform that I finally manage to solve my banding issue. . I bought a 3/16 aluminum 6061 plate(a little overkill) And replaced my glass. Also I drilled holes in each corner to fix it with the y plate using spacers with the pcb in between of curse. Since I have abl running already this doest affect my first layer consistency .

This constricted the pcb so it can only flex down on heat cycles without affecting the z height.

My print quality now is great. So definitely the heated bed was causing my banding .

Can I ask how much space do you have between your Glass and PCB?

[Chadd]

I figured as much, I may go ahead and order one of the MK3 bonded heat beds and being done with it. So basically to fix the issues with the 12" printer you have to rework the Y bed assembly. The majority of the problems I have had with mine are related to the Y bed. Everything from inconsistent Z axis homing, first layer issues, banding, to Y axis crashing.

I would be hesitant to tell anyone to buy one of the 12" printers without getting the aluminum bed and also doing something with the heat bed itself.

Thanks printbus for all the info. I'm happy to inform that I finally manage to solve my banding issue. . I bought a 3/16 aluminum 6061 plate(a little overkill) And replaced my glass. Also I drilled holes in each corner to fix it with the y plate using spacers with the pcb in between of curse. Since I have abl running already this doest affect my first layer consistency .

This constricted the pcb so it can only flex down on heat cycles without affecting the z height.

My print quality now is great. So definitely the heated bed was causing my banding .

[pichuete]

20150829_231654.jpg here is a picture that better illustrate what i did . the only problem of this method is that you need to have a reliable ABL because im not longer able to level my bed .

Also im planning to put the thermistor inside the aluminum bed similar to the ED3d in some place near the edge of the plate so i can actually read the bed temp not the PCB.

[tsteever]

Wow, that is a lot of aluminum. Did you have to adjust your acceleration settings or jerk settings at all? I'm thinking if I went that route I would want to take my aluminum bed to a shop and have them mill some holes in it to reduce the weight.

[pichuete]

Wow, that is a lot of aluminum. Did you have to adjust your acceleration settings or jerk settings at all? I'm thinking if I went that route I would want to take my aluminum bed to a shop and have them mill some holes in it to reduce the weight.

Yeah. I'll probably should bought a 1/8 instead. I haven't had issues but my acceleration and jerk setting where low already.. 1000 for acceleration and 15 xy jerk

I regularly print slow 30m/s for outter perimeters.. And no more than 60 for infil

[tsteever]

I wonder if there would be a way to mount the aluminum so you could still level the bed. Would clipping it to the glass just defeat the purpose? I like the idea of a PID loop so i will be watching this for a report. If the SSR are as inefficient as it sounds a separate power supply may be needed. My voltage already drops from 13v to 10.5 or so when the heated kicks in and the LED lights flicker quite badly. How much amp draw would just the board and motors take. 10amps? 15?

[printbus]

...My voltage already drops from 13v to 10.5 or so when the heated kicks in and the LED lights flicker quite badly. How much amp draw would just the board and motors take. 10amps? 15?

Both RAMPS and RUMBA are protected to 5 amps on the 12V input that supplies the logic, motors, and extruder heater. RAMBO is a little different in that it separates the power for the extruder heater and fan outputs to an additional 12V input (also limited to 5A).

Having a power supply that fluctuates with load like that is not good.