Heatbed vs 3d printer size

I'm trying to figure why there are printers so big (like makerbot) with 200x200 heatbed and then some, like prusa, that are smaller.

I'm asking this because i want to build a 3d printer, but i can't really understand the differences.

Is there any rule for heatbed vs 3d printer size?

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I started out with a prusa that had a 200x200 bed. I've since rebuilt it to a different design that also has a 200x200 bed, and I have designed and built a second printer that has, you guessed it, a 200x200 bed.

I think the 200x200 size just came about because of the size of the frame that can be built without moving up to sturdier parts - like 10mm bars and such. It has evolved into a "de-facto" standard. The main factors affecting bed size are frame size (as I've already said) and the ability to attain and the necessary temperature and to consistently maintain that temperature. The larger the bed, the higher the amperage needed to ready the necessary temps, so this starts to affect the power supply and, possibly, the controller board.

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jbernardis
I started out with a prusa that had a 200x200 bed. I've since rebuilt it to a different design that also has a 200x200 bed, and I have designed and built a second printer that has, you guessed it, a 200x200 bed.

I think the 200x200 size just came about because of the size of the frame that can be built without moving up to sturdier parts - like 10mm bars and such. It has evolved into a "de-facto" standard. The main factors affecting bed size are frame size (as I've already said) and the ability to attain and the necessary temperature and to consistently maintain that temperature. The larger the bed, the higher the amperage needed to ready the necessary temps, so this starts to affect the power supply and, possibly, the controller board.

I think that you didn't understand my question or misexplain myself. What i wanted to know is, having a heatbed, how to calculate size of the printer. Because there are a lot of 3d printers with the 200x200 heatbed but with a lot of different sizes.

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The footprint of the printer is determined more by the mechanical design rather than the build envelope. What it appears to me you are asking is why something like a Replicator is a larger machine than an i3 but both have the same build envelope. There is no fast and hard formula for printer footprint compared to heated bed size. The size of the machine footprint is dictated by how the motion design of the machine is implemented and the orientation of the bed more than any formula. Once you add any control panels or filament feeder/storage then enclose the device it's going to appear to be much larger than an open frame printer with the same build envelope.

I have a 12"x12.5" bed with a 24V, 450 Watt heater. There is no effect on the controller- a standard, unmodified RAMPS board. I power the heater from a 24V transformer and switch power into the transformer using an SSR connected directly to the RAMPS board. The SSR doesn't even get warm, and the bed heats to 105C in about 7 minutes.

I used to use a switching power supply but burned it up in short order and decided to go with AC power via a transformer for greater reliability. The transformer I use is an old 500VA "buck-boost" transformer that I picked up on eBay for $30 (less than the cost of a much less reliable switching supply). It's quite a bit heavier and bulkier than a switch mode power supply, but worth the extra effort to haul it.

If you use a RepRap type architecture, the base of the machine has to be at least twice the length of the printbed. Rep Rap has the advantage of a very simple mechanism. If you want a smaller footprint, build something like a Makerbot machine that moves the printbed only in the Z axis. In that case the base of the machine needn't be much larger than the printbed, but the mechanism is much more complicated.

One reason for the printer size variations is the hardware used to drive the extruder and bed. There are different designs for similar sized printers because the designers chose different motors and locations for them. If you're planning to build a printer, I recommend you design it to be completely enclosed to contain the heat and help prevent delamination of prints. If I were going to design such a machine now I would put the motors and electronics outside of the closed box to prevent them from having problems operating at the elevated temperatures inside the box.

Edited 1 time(s). Last edit at 06/13/2014 11:38PM by the_digital_dentist.

I've read this thread. Currently I am building the tantillus t-slot variation. I want to go to a 200mm x 200mm build area. I real new at this so bear with me.
I've been trying to figure out the lengths to cut the I have 2000mm of extruded aluminum and calculate I can get 8x 250mm lengths for the horizontal sections. If I understand correctly, since the bed will be on the z-axis 250mm x 250mm should be fine for XY axis and still give me the overall 200mm x 200mm desired build area?

Additionally I will be putting the electronics in a space below with the build area with a covered top. There will also be an additional cooling fan in that space.

Thanks

Edited 1 time(s). Last edit at 06/24/2014 04:18PM by Damonh.

Putting the electronics under the printbed sounds like a good way to keep the printer small, but you might want to reconsider. You are making a pretty big printbed, so I assume you are going to want to make big prints. If you try to make big prints with ABS and you don't enclose the printer your big prints are going to delaminate even as they are printing. I suggest that you enclose the printer and make sure the electronics are outside the enclosure. The electronics can still be located under the printer. I would also try to design it so that the X, Y, and Z axis drive motors are outside the thermal enclosure. That way everything stays cool except the print, the printbed, and the extruder.

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Damonh
I've read this thread. Currently I am building the tantillus t-slot variation. I want to go to a 200mm x 200mm build area. I real new at this so bear with me.
I've been trying to figure out the lengths to cut the I have 2000mm of extruded aluminum and calculate I can get 8x 250mm lengths for the horizontal sections. If I understand correctly, since the bed will be on the z-axis 250mm x 250mm should be fine for XY axis and still give me the overall 200mm x 200mm desired build area?

Additionally I will be putting the electronics in a space below with the build area with a covered top. There will also be an additional cooling fan in that space.

Thanks

I was thinking about a 400x300mm heatbed and in z axis only, that was why i'm asking if there is any rule, so i can buy the best materials to do it.

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the_digital_dentist
Putting the electronics under the printbed sounds like a good way to keep the printer small, but you might want to reconsider. You are making a pretty big printbed, so I assume you are going to want to make big prints. If you try to make big prints with ABS and you don't enclose the printer your big prints are going to delaminate even as they are printing. I suggest that you enclose the printer and make sure the electronics are outside the enclosure. The electronics can still be located under the printer. I would also try to design it so that the X, Y, and Z axis drive motors are outside the thermal enclosure. That way everything stays cool except the print, the printbed, and the extruder.

Thanks for the suggestion. I will keep it in mind. All electronics and motors outside the printer. But for a 300x400mm heatbed, what is the size that you suggest for the printer? Based on my calculations (based on cartesio printer) it would have to have 900x800mm. What do you think? To big for the size of the heatbed? I was thinking about having 2 extruders + tools (something like in cartesio, which has 4 tools).

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