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Current projects for SLS / SLA / powder printers and what I've learned so far

Posted by Dejay 
Current projects for SLS / SLA / powder printers and what I've learned so far
April 07, 2015 05:57AM
I've been reading up on the possibility of SLS selective laser sintering DIY 3D printers the last days. I just wanted to write down what I've found out so far plus a few thoughts and a list of what project there are out there (which will likely be outdated very quickly!). If you know any other projects please let me know. From what I've read a SLS printer with a gantry and a 2.3W laser diode for sintering dark nylon PA12 powder should be possible for below $1000.

First the excellent DIY Selective Laser Sintering FAQ.


Sintratec.com
Price: ~4500€
Nylon PA12 ("less than $150 per kg")
Fine resolution
Optical surface heaters and heating coil with and sensor
2.3W laser 445nm (visible blue) laser Speed: 70+ mm/s
Galvo
130x130x130mm


You-SLS (on instructables.com)
Price: ? Open hardware. Currently on indigogo for prototyping.
Gantry
2W laser 445nm (visible blue)


Ester (on github)
Price: ???
1 Watt laser diode
Polyester (so far)


The PowdrKeg (Website)
Price: ~$3400
Nylon PA650
40W CO2 laser


Matterfab
Metal printer (stainless steel etc)
Price: Probably professional price of >> 10k


Pwdr 0.1
3DP / inkjet cartridge
Gantry
last update 2012?


OpenSLS
Wax, Nylon, Sand
Gantry (laser cutter, mirror?)
40W CO2 laser



Plan-B
3DP / inkjet cartridge
Gantry
Gypsum


SLA printers: [formlabs.com] [www.peachyprinter.com]


--------------

Some thoughts:
  1. A cheap laser diode will only be able to sinter (dark) colored nylon. Possibly other colors like orange might work well too. For white nylon you need far infrared light and the cheap near IR laser diode don't provide that. The Nichia 445nm 3W seem a good pick.
  2. Professional nylon powder is hard to get in small quantities (<500kg). Potentially the price can be as low as $4-$10 per kg.
  3. Galvo setups often used for light shows are a different kind of tech and you need closed loop galvo with a motor, mirrors, a driver and also a digital to analog interface in order to be used from a typical reprap micro controller board. An additional problem with galvos is that the focus distances needs to change depending on the angle you are firing.
  4. Metal needs far higher laser strength and even professional SLS machines don't preheat the metal powder. So in order to sinter stainless steel you'll need a very expensive 400W laser. Metal powders are also more dangerous e.g. combustible or toxic. Additionally you'll need inert gas like argon.
  5. A surface heater (using IR diodes?) for heating the most recent layer of powder seems like the way to go. You'll need an IR thermometer which apparently can be had for something like $20 and constantly control the surface heater as seen in some SLS videos. Plus a heat bed might be good too.
  6. Thermal insulation against rest of printer
  7. A gantry is easier and cheaper for our reprap experience, and also should be fast enough for sintering using a diode laser. Sintratec mentions their laser is moving 70+ mm/s and they use a galvo. A delta can do 300mm/s and so should a CoreXY gantry. Eliminating mirrors might help with costs and wear and tear also. Potentially you could also use a inkjet cartridge in parallel to first color a layer and then sinter it for full color printing.
  8. Theoretically you could design a printer that does SLS, SLA or FDM by simply exchanging the print head and print bed.

Edited 2 time(s). Last edit at 04/07/2015 11:45PM by Dejay.
Great collection you have come up with, i just wanted to add the OpenSLS project to the list and maybe introduce those of you who don’t know it to the CandyFab. Whilst the work on the project has come to a stop I think they delivered some remarkable results with heat-sintering sugar.

Heat-Sintering is also something that really interests me because it does not use an expensive laser system. There is a commercial machine that uses this process, the only drawback would be the limited choice of material, as it cannot process nylon powder and they use their own thermoplastic. They did not tell me more about their material other than that its melting point is much lower than nylon.
Btw: I just asked around companies that sell sintering powder, the first one I talked to was very helpful and answered a lot of questions regarding their material. They also allowed me to purchase 2kg of their powder for the price of quality filament (I think it was around 30 euros per kilogram)

I also wanted to give a few quick thoughts on the coloring of the sintered object with inkjet technology:
I believe that coloring before sintering would be problematic, because the different colors would vary the heat absorption. While this could be counteracted by programming the laser power to match the absorption of the specific color, there might be an even bigger challenge: the temperature inside the build chamber of an SLS machine might melt the plastic ink jet cartridges. This immense heat is also the reason why I separated the laser and XY gantry from the print chamber by a sheet of glass in my design.
Re: Current projects for SLS / SLA / powder printers and what I've learned so far
April 08, 2015 12:28AM
Quote
Lukas Hoppe
just wanted to add the OpenSLS project to the list

Of course OpenSLS! What an omission smiling smiley That's why I needed a list. And the CandyFab with hot air melting sugar is quite interesting too.

But the Blueprinter is very impressive for sure! How does the thermal print head work? It looks like a copier or something. I wonder what powder / material they use? It seems they have filed a patent for it sad smiley But it seems there are tons of patents filed in this field all the time. I hate patents!

They use an interesting "scoop" mechanism to get the powder out of the powder containers using some kind of ramp to shovel out the powder. I also like that they use dual powder vats. They have a nice and clean looking system to remove the print inside the powder in a box from powder. It also seems the powder is pretty much baked afterwards. Removing the powder requires first a heat gun and then air. But they do have a grinder in their cleaning station and the powder is recyclable. I would guess they use a very precise and quick surface heater to bring the material very close to the melting point so the imaging element doesn't need to use much power. From what I can glean from the patent they use a kind of "sheet" to separate the thermal heating element from the thermal print head. (good article on 3ders)

Quote
Lukas Hoppe
I also wanted to give a few quick thoughts on the coloring of the sintered object with inkjet technology:
I believe that coloring before sintering would be problematic, because the different colors would vary the heat absorption. While this could be counteracted by programming the laser power to match the absorption of the specific color, there might be an even bigger challenge: the temperature inside the build chamber of an SLS machine might melt the plastic ink jet cartridges. This immense heat is also the reason why I separated the laser and XY gantry from the print chamber by a sheet of glass in my design.

Some very good points. I would guess a far infrared laser would have no problems with the colors (since white nylon is already opaque in the far infrared spectrum). But the heat might be a big problem for sure. Even with an "all metal" inkjet print head the nozzles might dry out and get blocked.


Maybe the ideal powder printing would be an inkjet printhead that uses some kind of chemical to create a kind of epoxy reaction / thermoplastic without using any heat?

Edited 2 time(s). Last edit at 04/08/2015 12:43AM by Dejay.
Hi All,

I'd like to add the printer that i'm working on, the Polyforge Selective Laser Sintering printer:

Polyforge (www.polyforge.com)
20W CO2 Laser
Laser speed 120+ mm/s
Variety of build materials (and colours), so far tested with Nylon from several suppliers
195 mm x 195 mm x 195 mm build volume

I will be showing off the printer at Makerfaire Bay Area 2015 (http://makerfaire.com/) so if you're attending please stop by!

Patrick Lie
Founder & CEO Polyforge, Inc
Re: Current projects for SLS / SLA / powder printers and what I've learned so far
April 25, 2015 04:13AM
Your project looks very nice! I wish you the best of luck.

Do you use a gantry with mirrors? Or galvos?

Unfortunately I cannot edit the original post anymore (time limit). Maybe an admin could unlock editing feature again? Or maybe the wiki would be a better place. I really just wanted to write down a current list of what I've found smiling smiley

Quote

Polyforge (www.polyforge.com)
20W CO2 Laser
Laser speed 120+ mm/s
Variety of build materials (and colours), so far tested with Nylon from several suppliers
195 mm x 195 mm x 195 mm build volume
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