• Granulated sugar, 25lb
• Wilton's Meringue Powder, 8oz
• Diamond 10-X Powdered Sugar, 64oz (super fine sugar powder + corn starch)

• Print at 0.2mm per layer.
• Cure 'in bed' for at least 8 hours before removal (or 4 hours, if you can heat the chamber to 35C-40C)
  
  • Shell will be hard enough to handle air depowdering and manual brushing
  • Inner core material will still be soft.
• Part will continue to harden for 48 hours (depending on temp & humidity)
  
  • Shell will be hardened in about 12 hours
  • Core material fully hardened after 48 hours
• Make sure to *thoroughly* clean the roller/spreader with a dry paper towel after each print.

mx(x) = -0.5 * x2 / (z - x)

btb5jRq.png

FD = z - LX;
A : (z - mx)^2 = z^2 + (x - mx)^2;
B : solve (A, mx)[1];
mx(x, z) := ''(rhs(B ));
plot2d(mx(x, 25), [x, -15, 15], [y, -6, +6]) $

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.