Engman-Taylor now has access to all the processes explained below in the following blog. Engman-Taylor will work with you on any of your project needs and will find the best solution via 3D printing. Any questions on 3D printing contact us or call 855-382-6349
SLS is known as Selective Laser Sintering. The printer has a bed of powder that it will layer out in thin micron layers. At each layer a CO2 laser will fuse the plastic material to the last layer. Because this is built up in a bed of powdered plastic there is no need for support structures which can lead to more complex parts. In this blog I will be putting together useful information for using and printing with SLS technology. The following bullet points will be described.
- Benefits of SLS
- Post Processing and Finishes
Benefits of SLS
Because of how SLS works the part is built up in a bed of powder, this eliminates the need for additional support [materials], which reduces the cost of the overall parts. Engineers can combine parts and eliminate fasteners and adhesives which also reduces cost. This process uses high powered lasers to melt and fuse the plastic material together. Plastic powders can be made out of materials that are seen in typical manufacturing plants. The mechanical properties of the plastic powders are exactly the same as the actual plastic form. Together the process and materials combine to create very durable functional parts that can be used for a wide variety of applications. Parts can be used for snap-fits, living hinges, and can be water and air tight.
Standard resolution for SLS will be .004″. The surface quality will be a little rougher than SLA parts because of the powdered style material. There is also some warping that may occur on thin walled parts. Build plate for this process will be 28″ x 19″ x 19″ which is an average size. Layer thickness can range from 80-150 microns for the typical machine. This process can save on the left over material not used and it can be recycled and reused for the next build. This process will be discussed in finishing practices as there are certain ways to recycle the left over powder.
There are many patents surrounding FDM and SLS processes. 3D systems controls a lot of the SLS business however there are other companies coming out with new products based on some of the patents are coming to end around now. I will go through 3D systems SLS printers and couple other printers that are made by companies typically outside the US.
3D systems makes 4 different machines. The ProX 500, sPro 60, 140, 230. The ProX has a small build plate at 15″ x 13″ x 18″ and can only use 3 different materials from 3D systems (PA, GF, HST). This machine does have a fully automatic recycling system enclosed with the 3D printer. This means after the print is done the plastic powder that remains will be automatically recycled into the new build. The user will not have to vacuum anything off of the old print, the machine will do it itself. Keeps running the machine at max efficiency 24/7. The next machine sPro 60 has the same build plate, but without the fully automatic recycling system. This machine has a higher Watt output for the laser therefor it can print all the materials that 3D systems makes for SLS. Both of those machines produce a volume build rate of 1.8l/hr. The next two machines are faster at 3.0l/hr. The 140 and 230 are piratically the same except the 140 has a build height of 18 inches and the 230 has 30 inches, they both have a X and Y build of 22 inches. These machines will cost you starting at around $350,000 and can cost up to $1,000,000.
The next few machines will be based off of other compaines that mostly operate in other countries. The first one is the 3D printing systems located in Australia. The printer is called EP 380 and has a build plate of 15″ x 15″ x 20″ and a 55 W CO2 laser. The reuse of material will have to be manual on this machine.
Prodways is a European country and produces 3 different laser sintering 3D printers. They use a open materials strategy for their printers (meaning they can use other companies materials in their machines) and they also make their own materials.
ProMaker P 1000. This is actually a much smaller printer for SLS, but is very affordable. The build plate is 11″ x 11″ x 11″ with a 30W CO2 laser. The volume build is .6l/hour and scans at 3.5 m/s. The scanner is included to insure accuracy of the part. The build chamber holds 10 independent heaters with double IR sensor and intelligent temperature control systems. This printer is priced at only $115,000! Very good deal for a SLS machine.
ProMaker P2000 HT which is an industrial 3D printer. The build plate size is smaller than the 1000 coming in at 9.84″ x 9.84″ x 12.60″ however it does have a 60 W laser and a digital galvo scanning system for high precision. Volume build is 1.2l/hr and the scanning speeds are 10.2 m/s. The build chamber includes shortwave gold-plated twin tube for fast heating and is easily accessible. It also has an eight zone heater and intelligent temperature control systems. This is regulated by a real-time surface temperature monitoring and optimization.
ProMaker 4500 with a build plate of 15.75″ x 15.75″ x 23.62″ and a 100W CO2 laser. The scanner included is a high precision full digital galvo. The volume build is 4.0l/hr and the scanning speed is 15.2 m/s. The build chamber includes shortwave gold-plated twin tube for fast heating and is easily accessible. It also has an eight zone heater and intelligent temperature control systems. This is regulated by a real-time surface temperature monitoring and optimization. The chamber can reach temperatures of 220C which allows the powders to fuse easier.
The materials for SLS machines are very durable and production grade quality. You can use parts made with these materials for long cycles and they are heat and chemical resistant. All the materials will be powder based initially and will be hardened and melted together using the laser. The materials used do tend to leave a fine powder on the finished product.
Stratasys uses mostly Nylon 12 filled with different elements. Could be glass filled or aluminum filled. They also have a plastic powder called NyTek and a couple other unique materials.
- NyTek 1200 – Standard Nylon 12 with good chemical resistance
- NyTek 1100 – Fully dense with material flexibility; Superior chemical resistance
- PA 640-GSL – Like properties of NyTek 1200 CF with and additional benefit of being lighter in weight
- CastForm PS – Used to produce investment casting patterns without tooling
- PA2201FDA – Is in compliance with FDA, 21 CFR, §177.1500 9(b) except for alcohol foods
- FR-106 – Flame, smoke & toxicity (FST) certified
3D systems uses mostly Nylon 12 materials in which they call their powdered materials Duraform. Nylon 12 can be aluminum or glass filled. There is also EX which has a better surface finish, and a HST which is high temperature and high strength.
Post Processing and Finishes
Every sls part will come out in a bed of powder. To get this powder off there are basic finishing techniques that need to be applied. First the part will need to be bead blasted. Plastic beads work fine and even glass beads that are about 70-100 micron large would work. This will leave a matte like finish on the part comparable to a medium size grit sand paper, perfect for painting and coating.
Once the basic finishing is done then you can either tumble your parts for a a very smooth surface. This will also remove all sharp edges and features. This is only to be used on parts that don’t have any small fragile features.
Dying is preferred over painting. The part will soak up the colors about .5mm deep and the dye does not change dimensional accuracy. Many parts can be dyed at once. Spray painting is another option. This will create a nice glossy finish however this can sometimes impact the part dimensions.
More information on our 3D Printing services.