Under Tested’s Fuse 1 demo, one viewer asked how long it takes to print something small compared with something large. Another guessed the printed glove took 15 to 20 hours and doubted SLS could ever be a production process. Both are really asking how SLS print time works, and the answer surprises most people.
What drives SLS print time?
Mostly build height, because every layer costs time whether it holds one part or fifty. Formlabs’ figures from its PreForm 3.21 speed update show it. A run of belt buckles only 114 layers tall printed in 2 h 58 min on a Fuse 1. A drill case 1,921 layers tall took 13 h 52 min, at just 7% packing density.
Formlabs also said the update’s savings were “constant per layer.” That only makes sense because layers are the basic unit of cost.
Do more parts add much time?
Some, but less than you’d guess. In a Formlabs comparison on the Fuse 1+ 30W, one three-part gaming controller assembly printed in 3 h 52 min, and five of them took 9 h 38 min. A single two-part electrical connector took 3 h 30 min. Fifty of them, 100 parts, took 12 h 59 min.
Extra parts add laser time on the layers they share. The recoat and heating on every layer happen regardless.
How does MJF compare?
HP quotes the Jet Fusion 5200 at up to 5,058 cm³ per hour. The footnote says that figure assumes PA 12 at 0.11 mm layers and 8.45 seconds per layer. By my arithmetic, a full 380 mm build height at that pace is about 3,450 layers, or a little over 8 hours of printing. Use that as a sanity check, not a quote.
What about the wait after printing?
That’s what customers forget. Formlabs’ same comparison lists 6 h 52 min of cooling for the single controller and 13 h 47 min for five. For the connector run it’s 13 h 49 min, longer than the print itself.
How should you quote lead time?
Read the layer count from the slicer before you look at the part count. A short part dropped into a tall build that’s already running costs very little machine time. Make it the only tall part in a build, though, and it sets the height, and the cooling time, for everything packed around it.
Related on the Solvi blog: SLS Cooldown: How Hot Can You Unpack a Build?; MJF Packing Density: How Full Should You Pack a Build?; MJF Cooling: Natural or Fast, How Should a Bureau Decide?.
Sources: YouTube: Formlabs Fuse 1 SLS 3D Printer Demo (Adam Savage’s Tested), viewer questions; Formlabs: Fuse 1 is now printing 15-30% faster; Formlabs: FDM vs SLA vs SLS comparison; HP Jet Fusion 5200 Series brochure (PDF).