3d Printing – SLA vs. FDM

These 3d printed vehicles are all 1/285 scale, so the largest of them is only about 25mm (an inch) long. I thought these tiny little models would do best to compare the merits of FDM and SLA printing.

All of the SLA prints were done by Shapeways, and all in their "Smooth Fine Detail Plastic" material, which is the lower of the two detail options they offer in resin printing.

The two FDM prints were done by me on my Ender 3 with a 0.4mm nozzle at 0.08mm layer height in PLA.

  1. Vickers Medium Mk.III — SLA
  2. Burford Kegresse — SLA
  3. Carden-Loyd MG carrier — SLA
  4. Vickers Medium Mk.II — FDM
  5. Vickers Medium Mk.II — FDM. Printed with no gun barrel, and a brass pin added later.
  6. Vickers Medium Mk.II** — SLA

SLA uses a UV laser to selectively cure a photopolymer, layer by layer, within a wax support medium, so requires no additional supports and is capable of rendering very fine surface detail. The sloping panels are cleaner owing to its finer layer discrimination. Shapeways used to have information on the exact layer heights on their website, but they no longer do now that they've "improved" their site design again.

DLP is another process that uses a photosensitive resin, but in a different manner: it employs a LCD screen to expose each layer in one go. It has the advantage that the amount of build-plate coverage has no effect on its print speed, but the disadvantage that its horizontal resolution is dictated by the resolution of the LCD exposure screen it uses. The finer screens now available, and antialiasing technologies, have improved this substantially in just a few years, but it is still likely that pixelation effects might be seen on curved surfaces. Nevertheless, like SLA it is generally capable of much finer layer heights than FDM printing. DLP printing uses printed support structures in much the same way as FDM.

The two FDM examples I've shown here, for all the limitations of that medium, are really not too bad as wargaming models. Both of these have been printed at 0.08mm layer height; my machine will go as low as 0.04mm, but with only a slight improvement in visual quality, and at the cost of doubling the print time. The surface detail is much lower than SLA (or DLP) is capable of, though this could be improved by printing with a smaller nozzle — 0.2mm or 0.25mm — though this once again increases print times substantially.

I'm unlikely to do any more 1/285 scale printing myself, as my eyesight has grown too poor to easily distinguish the different models on the wargames table without a lot of leaning and peering. However, as you can see, it's certainly a viable prospect to print usable 6mm wargames vehicles, even on a cheap entry-level printer.

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