I am currently working with my colleagues on a a project of building a

3D Printing
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I am currently working with my colleagues on a a project of building a 3D printer

I want to ask if it is possible to make a customized heat bed as all the beds that we found on the internet are 200*200 and we want our printer’s build space more than that

I also want to ask about the stepper motors used for x,y,z do we need to make a complete stress analysis to calculate the torque needed?

Thanks in advance :slight_smile:

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  1. Many far-east vendors on Aliexpress will make custom-sized silicone heater pads for you at a pretty good price point.
  2. It depends on what kind of speed you want to achieve with what kind of bot architecture (H / Z-X stacked + Y independent / X-Y stacked with Z independent, also bowden or no bowden). Generally, though, standard NEMA17 40 to 48Ncm bipolar steppers will suffice for normal printing, and once you go beyond that torque class, you’ll need more expensive NEMA23 motors and beefier drivers.
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1)thanks for the information about silicon heater pads … i want to ask whether it will work normally with the ramp 1.4 like the reprap heated bed or not ( imean does it have the same ratings) ?

  1. our bot architecture will be (x-z stacked + y independent) with no bowden (standard extruder)… the NEMA17 48Ncm bipolar stepper is available… do you recommend to use it (1 for x, 2 for z and 1 for y)?

thanks again

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The RAMPS’ output connectors are rated for 10A max, which is already exceeded with a standard PCB heater. The vendors will make any power rating you request, so, for ABS, i’d shoot for a bit more power per area than the standard PCB (which is about 0,35W/cm²) and make a separate driver board with a couple IRLZ44N and beefy connectors (or soldered-in wires).

If you use a larger bed, it’ll inevitably end up heavier.
A 300300 bed assembly is already more than twice as heavy as a 200200 one which will most likely work with one motor, but don’t expect any great acceleration from that. I’d start with one and set acceleration values low to start out with and then add a second motor (and driver, sharing ENABLE, DIR, STEP, MS0, MS1 and MS2 with the main driver) if you feel that you need more power.
One motor for X and one on each side of Z is the de-facto standard setup and should be ok.

For longer axes, i’d go with wider and therefore stiffer belts, too. The standard 5mm wide T5 will give some serious overshoot artifacts on the edges of your printed objects. I’d say go with a at least 10mm wide HTD, GT, GT2 or GT3 profile (they are all compatible) with a 2 or 3mm pitch.

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i’m sorry but i really can’t understand what you have said in your previous comment

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Ok, to recap that post:

  1. The RAMPS is already at its limits with a normal heated bed. You’ll need to use an external, beefier driver MOSFET for a larger heated bed.

  2. For now, the standard motor setup will work.

  3. I would suggest using wider belts with a better profile for the longer axes. Normal 5mm wide T5 belt flexes too much, a GT-type 10mm wide belt would be better for your printer.

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thanks very much for your help … it became clear now :slight_smile:

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I made my own heated bed for my Reprap Mendel. It’s not that effective, but at that time it was the only option. What I did was that I took some constantan (not sure if it’s the correct English word) wire. It’s wire that heats up when powered. I made a zigzag pattern on the back of an aluminum plate and secured it with kapton tape + a thermistor for controlling the temperature. Then a layer of insulation material to keep the heat from escaping. It takes 5 minutes to heat up, but it works.

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@Jesper_Krog_Poulsen that’s one of the ways the early heated beads were done before the PCBs came along. It’s a valid technique to use resistor wire to make one, and 5 Minutes actually is pretty fast for a heated bed.
Still, I’d prefer a silicone heater - last time I looked them up, a 30x30cm bed ran in the ballpark of $30 and you can simply stick that to a glass sheet and it’s done. I’ve had a hard time finding really straight aluminum plates that size, and once you factor in the cost of that plate and the resistor wire, you’re pretty much even.

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@Tim_Rastall ordered a custom silicone heater from http://aliexpress.com. Cant find the book mark though. As for motor torque, a stress analysis is not needed, just a dynamic analysis. Good Ole’ F=ma. Just keep your moving weight down, and this lowers the required motor torque. Generally it’s the step controller that’s the limiting factor though, as these will overheat before the motors, unless the motor’s are crazy under rated.

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Also, for the Z stage, you can gear things down - Z movement needs to be nothing like as fast as X/Y movement. I’m running a very heavy 300x300 stage with 4mm aluminium plate and T-Slot supports, the whole thing must weigh a couple of kilos. I’m driving 2 x 32 tooth GT pulleys with 6mm belts via a common shaft with 4:1 Herringbone gearing off a nema 17. It’s slower than direct drive but the resolution is very high - eg. 0.08mm per full step.

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thanks for your help :slight_smile:

i want to ask another question what is the best ( in terms of quality and price) internet store to get abs/pla filaments from ?

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I get PLA and ABS from protoparadigm. The PLA works better than some cheap Chinese crap I bought, but that’s the only comparison. The ABS, I’ve only used on a Replicator 2X at work, and isn’t tuned to the Makerbot temperatures, so we’re switching back to makerbot filament. Protooparadigm shipping is 15 bucks, pretty steep.