How SLS 3D Printing Works

Overview

All types of 3D printer work by taking a digital 3D version of an object and slicing it up into thin horizontal cross sections and laying material down layer by layer on top of each other. This is different from other methods of manufacture which generally use moulds or subtract material to produce a product. There are many advantages and disadvantages to this process, and also many types of 3D printer which in turn have their benefits and drawbacks of their own.

We specialise in Selective Laser Sintering (SLS)

This process uses top end machines which require a great working knowledge to run properly.

The process works using a print bed covered with white Nylon powder. Using a laser the machines melt certain areas of the print bed ‘colouring in’ the areas to be printed. The bed then drops by 0.1mm and is re-coated ready for another print layer.

The benefits of this process are that the laser blends layers together meaning there are far fewer visible layer lines than found when using alternative printing methods. The material is really strong and durable and can be post processed and finished to like like almost anything.

To learn about the other 3D printing processes click here.

The generic process for all 3D printers

All (well most) 3D printers follow the same process for making an object. This is made up for six main stages – these are: Design (CAD), fixing, slicing, printing, post processing and finishing.

Stage 1 – CAD

This is the creation of the digital version of the object you want to print. All 3D prints require this to produce a object. The digital version can either be created using Computer Aided Design packages (CAD) or 3D scanning if you already have an object. These files need to be in 3D format and not 2D elevations or photographs. Once the design is done, it must be converted to STL format to print from. We have links to recommended CAD packages and if it is all a bit to much… we have an in house CAD service here too!

Stage 2 – File fixing

Once the 3D file has been converted into STL format it needs to be checked for errors. You’d be amazed at how many there are, even from the most experienced designers. For the file to be printable, it needs to follow a certain set of rules. In a nutshell, the printer needs to read each layer as one continual outer shell of a part or it will not be able to tell where it needs to lay the material and where not to lay material. The good news is we have a free file fixing service for all 3D print orders taken though us.

Stage 3 – Slicing

Once the STL file has been designed, checked and fixed it is imported into a slicing software package. This takes each file and cuts it up into hundreds or thousands of slices that range from 0.3mm thick on the cheaper FDM machines to 0.01mm thick on ultra high detail SLA printers . As a rule of thumb, the thinner the layer, the longer it takes to print. These slices tell the machine where to put the material on each layer. And don’t worry – we do all this for you!

Stage 4 – Printing

This is when the product starts to get physical! The machine will take each of these slices and lay/melt/cure the material one layer at a time so that it bonds with the lower layer. This layer building process is repeated hundreds, if not thousands of times until the product is made. Some printers can print single items in minutes, and some can build in mass (like ours) where they can take up to 48 hours, but will produce much higher quantities from the same batch (our record is 2,500 in 24 hours!). Printing can be done in a range of materials, though generally in one material at a time.

Stage 5 – Post processing

Once the print is completed you may be surprised to know that there is still work to do! Depending on what machine you have used, you generally have to remove some support material. With our process – SLS – the powder is the support material – this needs to be brushed off and blasted with compressed air. Other processes require the removal of uncured Resin (SLA) and support structures (SLA and FDM).

Stage 6 – Finishing (optional)

3D printed parts do not look like traditionally manufactured parts when they come off the machine – many of them have layer lines in them, are and a single colour and may have a matt/rough texture as well as other imperfections. These don’t really matter for prototypes, but if you want the item for a display or end use it is advisable to add a finish to it – this can be as simple as a polish to give a smooth surface, or full on painting, chroming or detailing. We do not offer a painting service but we do have a FREE polishing service for a premium finish to your models.