Another Rejection: "detail Too Fine"

Another day, another rejected customer order, and this time for the excuse that makes the least sense for scale models:


I design scale model airplanes for sale on Shapeways. Though most of my models are in the 1:144 to 1:288 scale, I do have some that range as high as 1:72 and as small as 1:600. I also offer models in three materials: Versatile, Professional, and Modeling plastics, and each of those materials have different parameters.

Imagine I model a cover plate with six nut-heads visible¹, emulating the same feature on the real-life plane. Those nut heads do not protrude far enough from the surface to be considered "wires" -- instead they are classified as surface details.

When I resize a model to smaller and smaller sizes, I realize I may need to thicken walls or increase wire diameters to meet material minimums, but I do not try to remove detail. Going back to those nut heads, I would have to realize that they work at 1:72 and 1:144, but at 1:285 they slipped below the minimum size limit and need to be removed. Oh, wait, perhaps at 1:144 they meet the limit for one material but not for another, so I have to have one model for one material and a different model for another. Easy enough for six nut heads, but there might be hundreds of details on the plane that need to be examined for each material and each scale and removed or retained depending on the scale and material. That would be quite impractical.

Instead, if I leave the nut heads there all the way down to 1:600, no one is ever going to complain if they are not visible in a print at such a small scale. The printer software doesn't care; the customer doesn't care; I don't care. For every model, in every material and at every scale, the actual output of the printer is only an approximate copy of the original digital model, and everyone knows that.

I don't know if there are cases where "Detail Too Fine" is something you really need to enforce for someone somewhere. But for the entire class of scale models, I doubt there is a designer or customer anywhere that would say, "thank god you didn't try to print that because I couldn't see the nut heads at that resolution". Instead, it pops up now and then as a lame excuse not to print a model.

My recommendation to Shapeways is to either eliminate of that criteria or let designers mark their designs with "please don't enforce 'Detail Too Fine'".


¹ I use this example because it's easy to visualize.

Unfortunately, that is NOT the case.

The engineers don't know whether you expect that level of detail or not, and they're trying to tell you what expectations that the customers might have. If the customer doesn't get he level of detail that they expect, they are likely to ask for a refund. As unfortunate as it is, a rejection is much cheaper than a refund. And, yes, I've had several such customers.

I've had a few such rejections. I simply emailed service@shapeways.com and explained that the loss of detail was acceptable. For most of them, they were eventually accepted and the item has been printed without further incident.

For years, I've advocated that a "Message To Production" be added to the database.. I would immediately add "Loss of Detail Acceptable" on about half my models <grin>

That would be a superb addition and -- from a programming standpoint -- seemingly straightforward. I will try the method of telling service that the loss of detail is acceptable and expected.

Followup: no luck here, despite my recommendations. Shapeways refuses to print the model because of the "detail too fine" issue, resulting in a lost sale for both the designer (me) and the printing service (them). And there's a non-zero chance that they've also lost a customer permanently. That's not good for anyone involved.

Someday maybe this 3D printing thing will be more of a science.

Have you considered creating separate files without detail for smaller prints? Another thing I've found that seems to work is to smooth out details with a smoothing function. Sure it might end up looking worse than SW just printing the scaled down parts but they seem to prefer that. Basically they really don't like anything with a sharp corner and would prefer something rounded below the detail height/depth specs.

Look at what CustomMaker produces (when it works). Vertical surfaces get angled and edges get rounded. If you end up with something like a pyramid or acute angle ridge that peak also gets rounded to avoid rejection issues, although I sometimes get the feeling they give more latitude to what CustomMaker produces in terms of not generating rejections. It might be as simple as there being a minimum radius on edges/points for each material process. Maybe.

Aren't CustomMaker artifacts due to (de)voxelization?

I don't know about artifacts but what I'm saying is that when you use a pure black and white image for customization in CustomMaker (CM) the walls are slightly sloped and the sharp edges are smoothed or rounded. It's very different than what you might get from plain vanilla subtraction in applications like Tinkercad. Whether that's a result of devoxelation or some other function I don't know. Here's an example where you can kind of see the sloping and edge "softening" that results.



Another interesting thing about CM is that the font isn't really optimized for spacing to avoid things like thin wall errors. For example between the bottoms of the letter S and the number 3 in the above example. That makes me think the sloping and rounding of edges gives such things immunity from the rejection department, unless of course they have been instructed to give CM details a free pass. If you noticed you can't actually run a 3D tools check on CM customized models so who knows what the heck is actually happening under the hood.

I've had detail rejection issues ranging all the way back to 2012ish. At the time I had identical designs fabricated in plain wsf and polished/dyed sf. The plain (natural) wsf was rejected while the polished was not and the explanation was that a customer would expect a polished print to not have the detail highly visible. Of course I think I also had rejections go the other way and this was all before the print-it-anyway option was established, and possibly before the detail rules were posted on the materials pages. But the whole thing has always been a pain in the butt. All I can say is that it appears that walls sloped at least 5 to 10 degrees or so and having no super sharp edges seems to mostly solve this problem-particularly for details that are shallower than the minimum detail requirements.

Here's another embossing closeup where it's a bit easier to see the sloping.


I'm not sure what would happen if you set up a CM embossing or engraving depth that was less than detail height/depth for that material. Would you get a rejection? Who knows! It might be worth an experiment. You certainly can't independently adjust those settings for different materials either.

Thinking about this some more, wasn't the whole point of creating the rotatable material renders to give customers a better idea of what they would see on a print? Do the rotatable material renders show more detail than is realizable in any particular material? If the point of rejections is to manage customer expectations why isn't this handled by the render process? While the designer might see the detail, and folks in the rejection department might see the detail, why would the customer see it in a render for a model that has been scaled down to 1:600?

Do you have any aircraft uploaded at various scales so we can see any differences in SW detail rendering?

Usually people prefer Versatile Plastic for 1:200 and larger and Detail Plastic for 1:285 and smaller, and that is what I use for test prints, so I don't have many examples of the same plane in the same materials and different scales.

I have hundreds of models in up to five scales each, sometimes offered in as many as five different materials. I'm used to upscaling certain features to meet minimum dimensional requirements -- that's a fairly mechanical operation. But removing detail at each down-scale and for each material is just not practical.

Shapeways and I will just have to sacrifice a sale each time they arbitrarily choose to enforce "detail too fine". I doubt that I have a single model that would pass their criteria if it were rigorously applied, because I do not model with a particular scale as a target (beyond dimensional limitations): the pilot's nose is there whether it's 1:72 or 1:144 or 1:285 or 1:600 or Versatile Plastic or Detail Plastic or Professional Plastic. It may or may not be visible on the print. That is no shock to any buyer.

I agree, it's silly and it's not like this is a new thing. It's literally been a problem basically forever at Shapeways and I never see any meaningful effort on Shapeway's part to solve it or to comprehensively explain all the whys and whats about why it can't be fixed on their end. Seriously, what are the actual difficulties here? I'm not a render guru but you'd think that it would be possible to apply some kind of smoothing filter for too small details on renders that somewhat reflects the real world printing results you get in any material. That's assuming the fundamental problem is one of managing customer expectations with respect to what they see on the renders prior to purchase.

From a production standpoint I could see too small details like rivets falling off white strong and flexible natural versatile plastic prints and contaminating the powder when they recycle it in another batch. However I don't think I've ever seen them make that claim and it certainly wouldn't apply to resin type materials. Oh well, maybe it's just one of those on-demand manufacturing issues that will never be solved by Shapeways.