Minimum wall (flange?) thickness?

[jagged ben]

I'm starting a 3d model of a spine car.  Don't have a printer yet but will probably get an entry level something like the Anycubic Photo Mono 4 (strongly considering this deal but may want to get farther along in the modeling before biting the bullet). 

I'm seeking advice from your experience on what thickness of detail of wall or flange will print on such a resin printer and hold up to (gentle or not so gentle) handling.    To be clear, none of this is really about structural wall, it's all about detail.   For example, the edges of the top and bottom sheet steel of the central spine, but also various other similar detail edges.  (Hence the 'flange' part of the question, as a lot of this isn't so much about 'wall'.)  Like, the proto has all these edges where 1/2" to 3/4" sheet steel sticks out anywhere from 1" to 6".  In N scale that would be, like, 0.004" thick, sticking out between 0.006" to 0.04".   I'm thinking that sort of thickness won't print and in any case will be way too fragile even if it did, but not sure how much I need to increase that.

For perspective I calipered similar features on a BLMA spine car to about 0.018" give or take a couple thousandths, which is actually quite oversize in scale but obviously those models are considered pretty dang nice in N scale.  But those are also diecast metal, and so I've no idea how relevant that is.  I'm hoping I can do slightly better?

Thoughts?  Recommendations? 

(Hopefully I can figure out how to parameterize all of these edges together sufficiently in Fusion to speed up adjustment if want to push this boundary, but that's a different subject.) 

TIA

[chessie system fan]

First, I recommend working in metric and use three decimal places max (more decimal places get rounded and throws off your dimensions). In metric, .15mm or .2mm should do fine. You may need to thicken in to .25mm for strength, but that won't look terrible.   I'd be more concerned about weight. Prints are very light, and trailers are high above the center of gravity. 

[robert3985]

3D resin printing for N-scale involves several priorities.  First, your printer's spec's on the finest details it will print.  Find this out by looking at the pixel size on your LDC, and at the Z-axis accuracy.  Although LDC pixel sizes are continually getting smaller and smaller, the vast majority of UV resins will not resolve below 30micrometers (roughly).  However, the LCD is not where the UV resin gets cured when printing...where it is cured as the printing process proceeds is on the FEP membrane.  The collimated light from the machine's light source has gone though the LCD, through a protective layer on the LCD, through a glass protective screen, and through another protective screen on top of the glass.  Then, it goes through an air space and then the FEP membrane before it hits the resin.  This means that the collimated light is quite un-collimated by the time it gets to your resin on top of the FEP membrane on the bottom of your resin vat...and where it cures the resin is called a "voxel" and is in three dimensions (X, Y & Z).  This means that the fancy new 17micrometer wide pixel on your 3D printer's LCD translates into about a 45micrometer wide voxel on your FEP membrane...which, in decimal inches, is 0.0018"...or in N-scale... 0.285" or close to 9/32"...a little over a scale 1/4" in 1:160 scale.

This is pretty good resolution...not perfectly smooth with no anti-aliasing applied, but hardly noticeable, especially with LCD printers with relatively fuzzy light defining the voxel in the resin vat, unlike sharper in-focus DLP printers, the LCD machines dulling/blurring any sharp edges a bit.  Applying AA with Anycubic 3D resin printers, actually increases detail resolution while softening layer lines until they virtually disappear.  This may be true with other brands too, but I only have experience with Anycubic printers.

If I were you, I would opt for the next step up in printers...the Anycubic Photon Mono 4 Ultra, which has some distinct performance advantages over the basic Mono 4, such a much better COBB light source and Fresnel Lens light deliver arrangement.  The basic Wash & Cure is on sale also, and you can probably pick up 3 containers of resin for the price of two...a usual deal...all of which won't cause you to spend very much more money...but be well worth it.

Speaking of UV resin, this is the second priority.  Basic "craftsman" resin isn't gonna do the trick, especially with N-scale cars and things that get handled and moved around a lot.  Although there are several options, I am printing ALL of my N-scale detail parts using their Anycubic ABS-Like Resin Pro2, which is giving me excellent detail, low stink, easy printing and durability.  I use their Grey colored version.  Yes, it is a bit more expensive, but if you want detail and durability...this resin works great.

That's about it.  There are some extras you should think about, but...I've gotta get back to work!

Cheerio!
Bob Gilmore