Introduction: You-SLS: DIY Laser Sintering

This project is not finished.

This is the project page, where I share the progress I have made with the DIY open scource laser sintering printer You-SLS.

for more information please check out my Indiegogo campaign aimed at sourcing the funds for the prototype, thank you all for checking it out!

I have started working on this project a little over a year ago, because ever since I finished my Reprap 3d printer (which I think is a genius design), I was never really satisfied with the consistency of the prints. Sometimes they looked really good, but then the hot end clogged and sometimes I caught bad filament yielding inconsistent layers. I also disliked the design constraints that one has to deal with when using an FDM 3D printer, and the removal of support material was simply annoying. So ever since that, I wanted to address the problems of Fused Deposition Modeling on affordable 3d printers. Therefore I started looking at other processes of additive manufacturing and figured that Selective Laser sintering would be Ideal for the task, as it produces Parts without design constraints and support material from powder, which also eliminates the clogging problem, as nothing other than light touches the molten material. The only problem was, that machines that use this process are found in a price range of tens of thousands of Dollars to millions.

And this is why we are here, because during the past year I designed a SLS 3D printer that can be built for the price of a Makerbot (about 2000 Dollars).

This is where I need help, as a student I simply cannot afford to build the printer I have designed. Therefore I started an Indiegogo campaign where one can support this project.

I hope you can forgive me selling the design files, as I am seeking the funds to build the first prototype. Once that has been achieved I will share all the design files and bill of materials right here, and hope this project becomes something the Open Source community can engage in and build upon.

Step 1: Introduction to SLS

Selective Laser sintering works by scanning a Laser over the surface of a thin layer of powder. The powdered particles fuse where the laser hits. This way, one cross-section of the model is created. After this first cross-section is finished, another thin layer of powder is deposited and another cross-section is sintered by the laser beam. This process repeats until the model is completed

What are the advantages of the SLS process?

Laser sintering allows you to build parts without any design restrictions or the need of support structures, as the powder supports itself. Therefore overhangs of any degree will be built perfectly in unreachable resolution. This is a huge advantage over FDM and SLA machines that are currently popular for home-use. Another huge advantage of SLS over other 3d printing processes is the variety of materials that become printable. Anything that is available as powder, ranging from sugar to professional grade sintering nylon, can be printed. The strength of nylon sintered parts is also well beyond anything that can be created with FDM or SLA machines.

Step 2: Design Guidelines

What are the challenges of making a working SLS printer?

While the process seems simple and not too hard to reproduce, there are many challenges involved when you try to make a DIY SLS-Printer:

To counteract warping of freshly sintered layers, the print chamber must maintain a temperature that is just 10 degrees Celsius lower than the melting-point of the material that is sintered. In order to achieve this You-SLS employs a three way heating system: each of the two pistons will be equipped with two 300W heating cartridges. In addition, the chamber will be heated by two powerful optical heaters. Each of these heating systems will utilize independent temperature feedback for accurate temperature control.

All this heating power now leaves us with another huge
problem: Lasers, stepper motors and electronics like to be cool. It is absolute unacceptable to run a two watt laser in a 150 degree Celsius hot environment. To solve this, You-SLS is designed in two parts: the lower segment, which contains the two pistons and the recoater, and the upper segment, that hosts the XY-stage and the laser diode. In order to access the print-chamber, the upper segment simply folds away. The laser light passes through a laser window into the build-chamber. This way, the hot and the cold parts of the machine are nicely separated. Obviously there will be a security switch prevent the laser from turning on while the system is opened.

Step 3: Electronic's and Major Design Decisions

You-SLS will be controlled by the regular trustworthy Ramps 1.4 board in collaboration with a regular Arduino mega. Both of which can be aquired for less than 50 Euros. If you are into 3d printing, and maybe have played around with a rep-rap, there is no way you don’t know Ramps. It is the most common solution to control 3D printers. The firmware will also be the known and good marlin firmware that is proven to work reliably. However, controlling a SLS machine is a more complex task than controlling a FDM printer, therefore another Arduino that is in control of driving the recoater will support the Ramps-board. Using commonly available parts is one of the main goals of You-SLS, and will allow you to build your own without having to acquire custom circuit boards, or experiment with complex programming.

Gantry X-Y System vs. Laserscanners

Many of you have probably wondered why You-SLS uses an X-Y gantry system over the more common laser scanner. The reason for this is, that the open-source hardware and software for Cartesian robots is sound and broadly available. Laser scanners use a completely different driver circuit and accurate ones are quite expensive. Therefore I decided that it would be best to stick with the Cartesian X-Y system, as the software is hassle free, it allows the use of a standard RAMPS board, which again is very common with open source printers, and the hardware is available all over the world from different suppliers at a low cost.

What kind of laser will beused in the printer?

I will be employing a Laser-diode with 2 watts of power at a wavelength of 445nm (approximately the kind of laser you would find in a Blu-ray burner. It is visible and blue). At first, that doesn’t sound like a lot of power, but considering that most of the melting job is already done by the powerful heating units, the laser is only responsible for heating the powder up 10 more degrees to the melting point.

Step 4: Dimensions

Its outer dimensions are about 90 by 50 by 55centimeters, the build piston size will be 20 by 15 centimeters and the Z hight will be about 10 centimeters. This allows big parts to be printed diagonally, jet small parts can also be printed without using too much powder to fill the bed. it has a print envelope that will be a bit smaller than the one of a regular Reprap printer.

Step 5: Currently

At the current stage, the design work is almost done: all difficult problems have been addressed. At this stage, there are only minor cosmetic decisions to be made. Therefore, there may be slight variations in the final design, but again, everything important is done. Now it has to be build an tested!

To create and verify the design, I went through countless experiments and tested many subsystems, such as the powder distributer.

Step 6: What Is Going to Happen:

should i exceed my funding goal on indiegogo, this project will make a giant leap forward: i will instantly order all teh custom aluminum and frame parts and start building, as this will be after i finnished school, this will project will be something of a full time commitment. i will work hard on building my first prototype. Once that is done, all the cad files will be released for free and it will finally become fully open-scource!