3D printing through which digitized printing of products which are light, durable and versatile has grown in the last 10 years at an annual growth rate of 20%. The products range includes automobile and aviation parts, medical implants and engineering polymers. Through selective laser sintering, micro-scale powders are printed and fused together to create an item.
3D printing has been hailed as the key to economic resilience according to Hop Lipson who further adds that most people believe this technology will save us if well utilized. That said one of its setbacks is that selective laser sintering (SLS) can only printing using one material at a time. This according to Lipson has hindered the industry from achieving its maximum potential since many products are usually made of more than a single material.
In a bid to address this, Lipson and John Whitehead employed their robotics knowledge to counter these challenges of SLS. Through changing the laser to point upwards, they were able to have the laser use multiple materials simultaneously. The prototype of this invention together with a printed sample having two different materials in the same layer has been published and will appear on Additive Manufacturing’s issue for December 2020.
Whitehead who is the study’s lead author, says there is a lot of promise and he foresees a future where it shall be possible to “produce both simple tools and complex systems at the touch of a button minus the need for assembly.”
Selective laser sintering typically works through combining material using a laser pointing downwards into a heated print bed. An item is produced from the bottom up in a process that has powder deposited to a bed and fused using laser to form a layer and this is repeated over and over until a part is formed. When using one material, the process works smoothly, however if two or more materials have to be used in a single print, it’s extremely challenging since the powder layer can’t be replaced or removed.
This process according to Whitehead makes it hard to gauge the quality of the product being printed until you get to the end of the printing cycle. So in cases of print failure, there is a waster of resources. This setback served as their motivation to do away with the powder bed.
By setting up a series of transparent glass plates lined with a thin film of different plastic powder, they lowered the print platform unto the top of one of these powders and had a laser beam both on the upper and bottom part of the plate. This allows for selective sintering of powder unto the print platform via a pre-programmed virtual blueprint. Next the platform is then moved with the fused material into another plate and a different powder coated and fused and on goes the process until a single layer has been formed.
+2The team successfully produced a 50-layer sample using their prototype machine and Lipson believes this innovation will enable laser sintering to be applied in multiple industries where production of complex multi material integrated systems shall be possible. Their next project is working on metallic powders and resins to produce parts with varied mechanical, electrical and chemical properties.