SLS part serialization sounds like paperwork until a batch comes out with defects. In a Formlabs forum thread asking for automatic part numbering, a Fuse operator explained the problem. In a job with 30 identical parts, if 5 come out damaged with orange peel or layer shifting, “it’s nearly impossible to determine how and where the 5 parts were packed in the chamber.”
Why does SLS part serialization matter?
It ties each part back to its build and its position in the chamber, which turns a defect into data you can act on. Without IDs, the operator’s only options were manual serializing or “extremely careful unpacking.”
What did operators ask for?
- The original request asked for auto-numbered text on a chosen face, with set formats, starting numbers, a persistent log so numbers aren’t reused, and a way to release numbers from failed prints.
- Another user suggested multi-part serials, where one section identifies the printer and run and another identifies the part, similar to computer serial numbers.
- One company said it was building its own dashboard on Formlabs’ labeling REST API. Its goal was for operators to pick a part number and press print.
A Formlabs team member said the request had been passed to the development team, with nothing more to share at the time.
Does position really change quality?
It can. A 2025 Polymers study of 45 identical PA12 parts on an HP MJF 4200 found that parts in the center of the build were consistently the least accurate and parts near the edges were the most accurate, regardless of height. You can only find patterns like that if each part carries its position.
How big should printed IDs be?
- HP’s MJF handbook says embossed or engraved text should be at least 1 mm deep or high, and lists 6 pt as the minimum printable font size.
- Rapidobject recommends text at least 4.0 mm tall (about 11 pt) and 0.7 mm deep. It also recommends marking parts that are hard to tell apart.
What should a bureau do?
Put the ID somewhere it won’t affect the part’s function, and get the customer’s approval. Encode the build, the position and the part number, and record them with each job. When a defect shows up, check the IDs before changing settings.
Related on the Solvi blog: MJF Packing Density: How Full Should You Pack a Build?; SLS Orange Peel: Why It Happens and How to Fix It; MJF Elephant Skin: What Causes It and How to Avoid It.
Sources: Formlabs forum automatic numbering and serialization thread; Raz et al., Polymers 17(20):2804 (MDPI); HP MJF Design Handbook; Rapidobject SLS/MJF design guidelines (German).