In my experience with resin, you can get misshapen parts for a bunch of reasons:

1. Resin will change size a bit during and after curing. Not by a large amount, and of course it depends on the type of resin you use etc - but enough. And of course if your design has some thick bits and some thin bits, one might shrink more than the other.

2. Every time the machine exposes the resin, it sticks to the previous layer and to the projector screen/LCD. The machine then lifts the model, to unstick it from the projector screen. This applies force to the model, and can cause it to bend by a tiny amount - which can gradually build up over several layers.

3. Resin has to be somewhat UV transparent, for each layer to cure all the way through in a short exposure time. Because of that, UV curing later layers can pass through the part and cure resin that shouldn't be cured, on earlier layers. This is particularly the case if the shape has areas resin can pool up and won't run off.

> PLA is brittle as well, about the same as standard resin. Just like with FDM, there are other formulations, but the materials are different, and perhaps there are no good analogs for FDM materials.

For many printers, resin has to be brittle because of the way the printing process works.

You cure a layer, it sticks to the previous layer and the projector screen/LCD, then you raise it to unstick it from the screen.

If the resin is flexible, the unsticking process would cause the layer to bend, giving poor dimensional accuracy. So resin is formulated to be stiff and unyielding.

FDM can print flexible materials like TPU - common 'print upside-down' designs of resin printers simply can't. Although you undoubtedly could engineer a printer that could, such as a resin equivalent of an SLS printer, which doesn't face the unsticking issue.

1. Resin shrinking tends to be uniform, which is something to be taken into account if you plan on making parts that fit into holes, like screw mounts.

2. Peel force is absolutely a problem, that's why you need to minimize contact surface with the print film. With 28mm minis, this tends to be not a problem, but for large models, its recommended you hollow them out. This saves resin and prevents partially cured resin from being trapped inside. Bending tends not to be an issue.

3. Again not a huge problem in practice. If you look at a sliced model, you will see, that below each layer the layer below is almost the same, with most pixels shared between the 2, and with overhangs that stick out by 1-2 pixels. This means that leaking light will likely hit parts of the model that are supposed to be solid anyway. But both underexposure and overexposure can happen, with the former meaning that resin doesn't properly cure, leading to thing features disappearing, and the latter meaning that light leaking will cure unintended resin, which leads to thin cavities disappearing. This can be fixed by dialing in the exposure.

4. PLA in my experience is just as prone to shattering as resin is. While truly TPU-like rubber resins might not exist (at least I've never used them), there are ton of resins with a slightly rubbery texture, which are solid, but are flexible enough that thin features don't break when you manhandle the models. Most official wargaming and board game minis tend to be made of a similar resin (which is probably not UV resin but has a similar feel)

I experienced every issue I mentioned first-hand, in practice.

I suppose it's possible I was uniquely naive in attempting to get engineering quality prints out of a consumer resin printer? It seems there's a good reason every resin 3D printer promotes itself with pictures of figurines rather than anything more demanding.

My experience was that getting good results when printing something like a plastic bottle cap wasn't just a matter of dialing in the exposure - I had to dial in the exposure, the room temperature, the conditioning of the resin, the support placement, the orientation, and design the item geometry with printing in mind. Even then the results were adequate rather than impressive.

Engineering prints are certainly possible I think, but you'd need some specialist resins.

Personally I'd stick with FDM for making functional prints.

Did you try engineering resins, like Siraya Tech's "Build", "Sculpt", etc.?

I make some small parts that I FDM print, then CNC mill for accuracy. Was hoping to switch to resin printing, instead.

Resin is also much less prone to size changes than standard FDM filaments. If you've printed FDM you should know how much tolerance you have to have in your parts (ex. hole diameters) to account for shrinkage post-print, not to mention the difficulty of printing things like ABS.

Resin has MANY drawbacks and in my opinion kind of sucks as a general user experience, but warping, material quality, and material options are not worse than FDM.

OK, you make a fair point. People will sell you such resin.

But look at the video at the 4m40s mark - the dimensional accuracy is trash.

The makers of these printers will all claim they have 0.01mm layers and 0.03 mm x/y resolutions and stuff like that but the dimensional accuracy of the parts coming off them is far, far, far below that no matter what the marketers claim. That cube barely has 1mm dimensional accuracy.

At that price point you might as well outsource it or at least print a negative and use a real silicone pour.