Elements of 3D printer design

I am putting together a list of things one has to be concerned with and think about when designing a new, original 3D printer or even when modifying an existing design. I am just putting this list here as "food for thought", feel free to contribute and eventually I will add a page in the wiki with the information in this thread.

Apart from print envelope (how large will the printer be able to print, in terms of volume) and basic mechanism choice (Cartesian, linear delta, CoreXY or other), there are in fact quite a few more points one has to think about:

1. IP licenses: How do I comply with the various licenses of the various elements I am reusing from other designs? Which license should I use to cover my own work?
2. Electronics: which controller to use? Does it support all the features I need or plan to use? Where do I put it, how do I hold it to the frame?
3. Steppers: how much torque do I need? How do I mount my steppers?
4. Wiring: how much wiring do I need? how do I route it? strain reliefs? Colors? connectors? Gauge?
5. Heated bed: what size and material? how much power? Can I use the standard MK2 PCB heatbed? How do I level it?
6. Availability of standard parts: Do I have to custom machine any parts or have them machined for me on a CNC? How many standard parts can I use?
7. Power supply: see Choosing a Power Supply
8. Firmware: what are the firmwares supported by the controller I have chosen above, that support all the features I need? Which one to choose? How to configure it?
9. Filament path: Where does the spool of filament go? How does the filament reach the print head?
10. Costs: this thing is going to end up costing me over $1000, how do I keep costs down?
11. Extruder mechanism: choices, choices, choices...
12. Hotend: and more choices...
13. Cooling: my printer now sure prints fast, but the quality of the prints s...ks and it can't do bridges! Oh, wait, you said "cooling"?
14. CAD software: Do I really have to learn OpenSCAD? (yes you do) Bah, no, Google Sketchup is good enough! (no it isn't)
15. Ergonomics (while building or while using): Do I put the LCD at the bottom of the printer or somewhere around eye-level? How easy or difficult is it to move around my printer / transport it to a new location?
16. Safety (again while building or while using): Will the printer chop off my finger if I accidentally leave it somewhere around the moving print head? Will a laser reflection make me blind? Is there any risk of fire? What about toxic fumes?
17. Last but not least, documentation. What 's that? BOM? Plans / Cad drawings / assembly manual / recommended settings? Who needs documentation, I have everything in my mind, anyways...

Edited 4 time(s). Last edit at 03/26/2015 09:24AM by AndrewBCN.

Quote
AndrewBCN

1. IP licenses: How do I comply with the various licenses of the various elements I am reusing from other designs? Which license should I use to cover my own work?
2. Electronics: which controller to use? Does it support all the features I need or plan to use? Where do I put it, how do I hold it to the frame?
3. Steppers: how much torque do I need? How do I mount my steppers?
4. Wiring: how much wiring do I need? how do I route it? strain reliefs? Colors? connectors? Gauge?
5. Heated bed: what size and material? how much power? Can I use the standard MK2 PCB heatbed? How do I level it?
6. Availability of standard parts: Do I have to custom machine any parts or have them machined for me on a CNC? How many standard parts can I use?
7. Power supply: see Choosing a Power Supply
8. Firmware: what are the firmwares supported by the controller I have chosen above, that support all the features I need? Which one to choose? How to configure it?
9. Filament path: Where does the spool of filament go? How does the filament reach the print head?
10. Costs: this thing is going to end up costing me over $1000, how do I keep costs down?
11. Extruder mechanism: choices, choices, choices...
12. Hotend: and more choices...
13. Cooling: my printer now sure prints fast, but the quality of the prints s...ks and it can't do bridges! Oh, wait, you said "cooling"?
14. CAD software: Do I really have to learn OpenSCAD? (yes you do) Bah, no, Google Sketchup is good enough! (no it isn't)
15. Ergonomics (while building or while using): Do I put the LCD at the bottom of the printer or somewhere around eye-level? How easy or difficult is it to move around my printer / transport it to a new location?
16. Safety (again while building or while using): Will the printer chop off my finger if I accidentally leave it somewhere around the moving print head? Will a laser reflection make me blind? Is there any risk of fire? What about toxic fumes?
17. Last but not least, documentation. What 's that? BOM? Plans / Cad drawings / assembly manual / recommended settings? Who needs documentation, I have everything in my mind, anyways...

As for electronics, I'd reccomend a Smoothieboard, or a "MKS SBASE" which is a $70 clone. They're powerful, capable, and easy to configure.

For the steppers, that depends on size. For a normal-sized printer, NEMA 17s should suffice. If it's big enough, you might want 23s, but that'll require abnormal drivers.

For the bed, use a sheet of borosilicate over a PCB heated bed. If you want faster heat times, get a 110v silicone heater and use a relay to power it.

Costs are, of course, a huge consideration. To keep them down, use cheap Chinese electronics, and use V-slot or OpenRail instead of ground rods or linear guides.

I'd recommend a Bowden extruder, because the lower moving mass allows for faster, more accurate prints with less ghosting/vibration. This is especially true of a coreXY or delta machine.

For the hotend, th E3D-lite6 is cheap and high quality. If you want higher temperatures, use an E3D-v6 or a clone (if the latter, take it apart and clean it before use).

CAD: I'd recommend ImplicitCAD. It's an expansion of OpenSCAD which can be used with Haskell, among other benefits.

If you get a Smoothie or clone, you can print over the internet with no LCD at all!

Add to 9... Filament thickness

18. Structure: materials, rigidity, mechanicals

0. Quality: which drives many of the others... design, steppers, structure, wiring, power supply. e.g. Bigger build volume requires more rigid structure, bigger motors, therefore better wiring and power supply.

Its a very thorough list you created. I kept going back to it with ideas but you'd already covered them. Good additions Frank.

Some items are hardware and some are personal decisions - ie Extruder machanism is hardware choice, learning cad or creating a BOM is personal.

Having access to machining services or a 3D printer is personal. It will influence the design a printer.

Some issues cross reference one another - style of printer may determine what kind of hotend/extruder or controller.

Cost is personal and cross references almost everything, usually directly proportional to Franks '0.Quality' but not if you get free machining/ lasercutting/ materials.

Maybe break it into and/ or cross reference machine areas - filament travel from spool to hotend is one chunk, motion drive and motion guidance is another chunk but both cover electrical and mechanic but electrical control and electrical power can be considered a separate chunk in itself.

I started writing this a while ago but my PC rebooted for updates and I lost what I wrote on the subject and lost the will to get back to it.
I forgot a lot of what I said now

A big caveat about personal abilities, expectations and understanding of the 3D print process and mechanical design would be worth adding for the ' I've never seen a reprap before but I'm going to build a monster printer' brigade.

It would be a useful wiki to bring together a lot of the existing pages as the way you put above; the link to 'choosing a power supply', is a good format for the document.

Happy typing and hyperlinking, Andrew. It's a good idea.

-a

Thanks Alan, and your expression the ' I've never seen a reprap before but I'm going to build a monster printer' brigade made me chuckle! So very true...

I fully agree that many design decisions are personal choices while many others are purely technical constraints. And I also agree that many design decisions are cross-dependent.

I have been thinking about these matters a lot these days because I am considering embarking on the design of a small CNC router, which poses similar problems to the design of a 3D printer, with sometimes completely different or even contrary constraints. For example, when designing a 3D printer, weight is a major consideration as we want maximum acceleration potential for all our moving parts. This contrasts with the design of a CNC router where weight is not a critical constraint and can actually be desirable to minimize vibrations.

I have also come to further appreciate the design of some "classic" RepRap 3D printers these days for the brilliant solutions found by their designers (Josef Prusa for the Prusa i3, Johann C. Rocholl for the Rostock and Kossel). It is actually very difficult to improve on these classic 3D printer designs in terms of ease-of-build, cost, performance and print quality.

Evidently it must be easier to build a massive printer to print large parts, than to design parts well to assemble into a larger part.

Good list though...

On point 12, hotends, you have a choice of one nozzle, two nozzles, one nozzle and two filaments (ie Chimera or Diamond)... or even four nozzles, like the Kraken.
If you have two nozzles you need to be able to level one against the other one.
Filament size, 1.75 vs 3mm...
Bowden vs Direct drive...
On the Extruder, consider what it takes to be able to push soft rubber filaments succesfully (ie have no gap between the hobbed wheel and the hotend where the filament can escape and buckle)

I would add another point: open vs enclosed print area, for retaining heat and keeping out air drafts.

Also the mechanics of it, cartesian vs corexy vs hbot vs delta dynamics.

Nice list!

Paucus