Selective Laser Sintering
Selective Laser Sintering is our flagship process. We feel that the technology is adaptable enough to hold promise now and in the long run.'
The reasons for this choice are as follows:
- It allows us the ability to print any geometric structure
- It is a relatively simple process
- Laser sintering is the main process used in commercial 3D Metal Printers
The Selective Laser Sintering process works this way. A 3D model of the part that will be printed is virtually sliced into many cross sections by a computer program. The printer takes the first cross section and prepares to sinter the first layer. The build platform drops a tiny amount (typically less than 100um). The powder spreader then pushes a tiny amount of powder in front of the spreader, which then pushes the powder over the work surface. This thin layer of fine metal powder is then sintered or melted by the laser beam. The area that is sintered forms one cross section of the part being made.
After the area has been sintered, the whole process happens again and again until, layer by layer, the whole part has been 'grown' from the ground up. The actual fusing of the metal powder is caused by a laser beam which is guided down onto the surface of the powder bed by mirrors. Unfortunately, one of the most expensive parts of a 3D Metal Printer is the laser.
Laser sintering (also called Direct Metal Laser Sintering) is an additive manufacturing technology. It is a simple process which involves the use of a 3D CAD model which is created and sent to the 3D Printer.
This process allows for highly complex geometries to be created directly from the 3D CAD data - fully automatically - in hours and without any other skills required.
A DMLS machine such as the Metalbot can be split up into subsystems that work together. Generally there are four main subsystems to consider. Please click on the linkes below for much more information on the Metalbot printer subsystems...
Laser sintering holds many benefits over standard manufacturing methods. One benefit is speed because there is no requirement for setting up special tooling paths. Objects can normally be fabricated in a matter of hours. Since most alloys can be sintered, printed parts can have a wide range of strengths equal to forged parts!
Perhaps a bigger benefit is the ablity to print any geometry imaginable. Internal structures that were previously unheard of (because traditional machining can not reach) can now be made in one piece. Internal cooling channels in a turbine blade for example, or honeycomb structures that would be impossible to make traditionally.
The only physical constraints on the parts are 1) their size and 2) their resolution.
If it can be designed on the computer, it can be printed.
3D Printing most likely will not replace all current manufacturing methods (such as injection molding or milling). 3D Printers are best suited to manufacturing very complex parts. The more complex a part, the more sense it makes to print it.
This will translate directly into more efficient parts and therefore more efficient machines in the future.
Laser sintering does not require special tooling like castings.
The main challenges inherent to the process of selective sintering are as follows.
- Warping of the printed part due to shrinkage after cooling
- A powdery finish
- Removing powder from enclosed spaces
The build area of a part also limits us to the printing of small parts only, measured in centimeters.
Other issues are to do with build speed. When building a part with such thin layers it can take a considerable time to finish. To calculate how long it will take to print a part multiply the amount of time it takes to sinter one cross section and multiply that by the number of cross sections the part is made up of. As hobbyists however this is not our main concern.
For a more compete list of the challenges posed my lase sintering please see our challenges section.
What Needs to be Done
The Metalbot community is developing an open source laser sintering system. We have to start from the ground up. As you can see, designing and building a 3D Metal Printer is no small task and the Metalbot project is one of the more ambitious projects in the history of open source. The subject covers a wide range of disciplines and requires many skills. Therefore the more information we have on laser sintering the better.
Please see the Challenges page for a rundown of the challenges we face...