designing large area printer

Hey all,
I'm Luke from the UK and by day build custom kit cars. Have been thinking for a while that a large 3d printer would be excelent for making non structual body panels.
The main issue is that there are no really big designs off the shelf and the ones that have turned up are hundreds of thousands of pounds to buy, some over a million!

The plan is to design and build a printer that can make panels LxWxH 2000mm x 1500mm x 4-500mm. The height is less of an issue due to the nature of car body panels.

basicly I need pointing in the right direction on where to learn how to design a 3d printer and then how to scale that up for my needs. so questions..

What resourses are out there to learn how to design a printer?
what changes when you start to scale up the design?
have other people already built these sort of printer, who and where are they?
can a system be designed to use autocad drawings as a design input?

thanks for reading.

With a printer of that size you will soon run into stability problems if you try to apply current 3D printer mechanics.
You will need a frame and bearings that are able to remain riggid over a length of 2meters. This increases the mass, which in turn increases the need for power, larger motors, more powerful drivers etc.
Basically you end up with a pretty big CNC gantry that holds an extruder instead of a router. Converting an existing CNC setup should be a lot easier for you than building a printer from scratch.

Once you have resolved those problems the next thing you will not be happy with is speed. Current printers usually use nozzles up to a diameter o 0.5mm. For you this means that the small size of the nozzle and the weighty mechanics will make this a very slow printer for parts the size of a car panel. Keep in mind that the nozzle diameter will have a roughly cubed impact on the print time, since it defines the maximum layer widht and height.
Alternatively you can increase the nozzle diameter, but this reduces the print quality.

If you are looking to create prototype panels i think it might work, but it will be much to ineffcient to be used for production.

Good luck
Björn

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I would start with building a proven design of a smaller printer. If you are designing a larger one a printer to print your parts will be essential.
In the UK [www.think3dprint3d.com] sell kits for reliable design and give excellent customer service.

Printing body panels flat will tend to accentuate the layer lines on the gently sloping surfaces. Sanding out these lines is a total pain in low-temp plastics because the material wants to pill-up rather than sand cleanly. And I'm imagining that each panel will need supports under the entire print area. Printing flat also means that you need a great whopping print area, and then you have the attendant stiffness issues Srek mentions. However, what if you printed the panels on edge? This would give you really nice looking surfaces and reduce the amount of support material. Most importantly, though, if your panels are not very deep (say, less than 300mm) you can construct the printer mechanism with the moving support for, say, the Y axis only spanning 300mm or so. The rest of the structure can be pretty heavy and stiff and you'll only have to move the 300mm wide carriage.

Commonly, the way to do this is to print the contour pieces for use in a vacuum forming table. This way you can print your contour in several smaller pieces and then assemble them to form one smooth piece of plastic on top of the assembled contour (and still be able to pull out the same contour to vacuum mold more of the same piece later if desired.) Only tricky part I guess is to make sure that your printed parts are well protected from heating up and sticking to the sheet plastic, perhaps by coating with a layer of plaster or gypsum after assembly.

(there's dozens of DIY vacuum forming table plans on the internet, it's one of the easiest plastic-working projects you can find.)

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logiprint
What resourses are out there to learn how to design a printer?

In terms of a formal guide, nothing I've found. Your best resource is to take an existing design and scale it up. Given what you're trying to accomplish, scaling up something with a box frame, as opposed to a rostock or a prusa i3, seem to be your best bet. To be more specific, taking a 3D printer design that uses extruded aluminium for its frame will be easier to scale.

Take a look at this reprap wiki page. There's a bunch of designs on there; not all of which will scale well. The i3 relies on a lasercut frame to give it stability, which will be expensive to scale. Something like the Solidoodle will be easier to scale as it would be a relatively straightforward matter of scaling up the extruded aluminium parts, the smooth rods, etc. I'm using the word relative here not to imply that scaling up is simple, but that scaling the Solidoodle might be easier than scaling the i3 or Rostock.

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logiprint
what changes when you start to scale up the design?

Do a search in the forum for "large format". There are loads of threads on this, but basically, you'll need to scale up the nozzle size to get anything close to a decent printing time, the motors will need to be scaled up significantly, which means the power requirements will go up; the stiffness of the structural components and smooth rods will have to be scaled up according to a specific formula to prevent flexing (don't know what this is off-hand, but it's in the forum somewhere). Some useful threads here and here. You'll need a gantry design as large scale precludes having a moving bed.

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logiprint
have other people already built these sort of printer, who and where are they?

Take a look around the forums, but these guys have built one they used to do what you're thinking of.

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logiprint
can a system be designed to use autocad drawings as a design input?

To get a printable object from Autocad, you must have a solid 3D object in Autocad first. The software toolchain goes from 3d-design (e.g. Autocad) to stereolithography file (STL) to gcode (via slicing software) to print. Autocad is capable of creating STL files from a solid 3D object (google for the specific process). From there, you use slicing software such as Slic3r or Kisslicer to create gcode specific to your printer and you/re ready to print.

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for prototyping parts can you CNC in MDF and vacuform?

don't forget that the floor you will be working on may not be level, may need to look at adjustable feet for the bottom of the printer, take a large spirit level and lay it on the floor space you are looking to use to get an idea of what I mean.

as said above an Aluminium extrusion frame is more likely to keep it's dimensions for a large format printer, basing this on something like the I3 or a Delta does not sound like a good idea. the Delta will take up a lot of room you can see a few examples of these large format deltas in videos on youtube from this years makerfaire (I forget which one but one of the recent fairs had 2-3 different ones on display)

I would suggest looking at the Hbot and CoreXY designs, I think there have already been a few that have built bigger versions of these.

Consider your filament material. to print with ABS in a large format you will potentially come across lifting and warping issues, you'd be looking at a heated build chamber to try and get around this, and large format heated build plate. with PLA this is less of an issue but may still want to look into an HBP which is likely to be custom.

as said above nozzle size will have a dramatic effect on time and quality, look at the 3D printed car that was printed with a large diameter nozzle, it's not so pretty.
If you are just wanting to print out the structure so that you can lay fibreglass overtop then it wont be as bad as you can print it thinner and it wont take as long to lay down all of the material.

and Please, Please, make a project blog, I would like to see how it goes and perhaps build a slightly larger than standard printer my self.