SLS parts come off the machine in a natural off white nylon that might look a little plain at first glance, but is actually an excellent starting point for adding colour. The slightly porous surface of the nylon absorbs dye readily and evenly, giving deep colour that soaks right into the outer layer of the part rather than simply sitting on top of it the way paint does. That is why a dyed SLS part keeps its colour even after a knock that would chip a painted surface.
That property makes dyeing one of the most popular and cost effective finishing options for SLS parts, and we offer it entirely in house through our MJF & SLS printing service so there is no need to ship parts elsewhere for finishing and add to the lead time.
How vat dyeing works
In vat dyeing, the parts are immersed in a heated bath of dye, where the porous nylon draws the colour down into its surface layer over time. Because the colour genuinely penetrates the material rather than coating the outside, it will not chip, flake or peel away the way a painted finish eventually can, and small scuffs and scratches in use are far less noticeable because the colour continues just below the surface.
Black is by a wide margin the most common choice and gives a clean, consistent, professional look that suits almost any product, but a useful range of other colours is achievable depending on the requirements of the job. The bath temperature and immersion time both affect the final shade, so a longer soak yields a deeper, richer colour while a shorter one gives a softer tone.
Beyond a single colour
For a more refined or sealed appearance, parts can be vapour smoothed before they are dyed, or finished with a protective coating afterwards. This is particularly useful when you want a part to look closer to a polished injection moulded product, or when you need the surface to better resist marking and handling in everyday use. A clear lacquer or matte sealer over a dyed part can also lift the colour slightly and give a more uniform sheen across the whole surface.
It is worth bearing in mind that dye colours can vary slightly between separate batches, which is simply the nature of the process, so for any colour critical or closely brand matched work we strongly recommend approving a physical sample before committing to a full production run.
What dyeing cannot do
Dyeing darkens the natural nylon, so it works brilliantly for deep colours such as black, navy and charcoal but cannot produce a pale pastel or a bright white, since the dye can only add colour rather than lighten the base material. If you need a very light or vivid shade, a sprayed coating is the better route, and we can advise on that during quoting.
The depth of colour also depends a little on the surface, so a smoothed part takes dye slightly differently to a raw bead blasted one. Telling us the look you are chasing lets us choose the right combination of smoothing and dyeing from the start.
Practical tips
A few simple choices at the design and ordering stage help you get exactly the colour result you are after on the very first run, rather than discovering a mismatch once parts arrive. Keeping a reference part from an approved batch gives you something to check future orders against and settles any question about whether a shade has drifted.
- Black dye hides surface texture and looks consistent batch to batch.
- Request a sample for colour critical or brand matched parts.
- Smooth before dyeing for a more even, sealed finish.
- Colour penetrates the surface, so everyday wear shows far less.
- Allow for slight colour variation between separate dye batches.