Resin 3D Printing

Some parts I've printed so far.

I recently finally bit the bullet and got a resin 3D printer, a Phrozen Sonic Mini. https://amzn.to/3h76Pvw Three main things came together that made me finally take the plunge: cheaper prices, water-washable resin https://amzn.to/2OxjEDq , and mono screens for faster printing. The mono screen leading to faster prints is why I went with the Phrozen Sonic Mini. The only thing I really don’t like about the Phrozen Sonic Mini so far is the flat-backed build plate which is messy. But I remedied that somewhat by printing out an angled back in PLA plastic using my FDM 3D printer.

Anyway here is everything I’ve learned so far.

Level the built plate to the FEP film https://amzn.to/3fMs3hW with the vat on the machine instead of using paper. Also I give the FEP film a coat of 3in1 PTFE lubricant https://amzn.to/30icoR5 whenever I clean out the vat. https://youtu.be/NYK_8aEpUCY  

I have my printer set up in my garage and that means when the garage door is open plenty of light can get in. So, when the printer is not in use but I know I’ll be using the machine again in a few days I’ve been leaving the leftover resin in the vat and storing the vat and the build plate in their own tin containers which keeps them totally free of light. Doing that not only assures no light starts curing the resin but keeps me from having to empty/clean the vat; it also eliminates any potential resin leaks onto the screen. You do not want resin on the screen, especially since it can leak down into the machine. When going to use the stored resin vat again, I carefully stir up resin before starting a new print.

Use a 1 or 2 layer sheet file that fills up most of the build plate on every print. It uses up very little resin, makes for more reliable adhesion for all the parts on the build plate, makes clearing off the build plate easier when the print is done, and better assures nothing sticks to the FEP film instead of the build plate. So, for instance, I like to put a 0.05 mm or 0.1 mm sheet down when printing with a layer height of 0.05. Printing objects directly to the build plate is often problematic due to the first several layers needing to be overexposed to assure the parts adhere to the build plate; that translates into the parts being too thick (over-sized) the first few layers. 

Watch this video to see the technique I used to figure out the best resin exposure settings for my printer. https://youtu.be/r9GwPEJ8Lq8  My only issue with this technique is that the stl file used has some details so fine that they can cause floaters to break off into the resin until the settings are dialed in just right.

I’ve only been using water washable resin (Phrozen Water-Washable Rapid Resin Gray), so I can’t compare it to anything else. All I know is that it has worked well enough for me as long as the model is not hollow; hollow prints eventually crack; light has to be able to reach every surface for the final curing. Other than water for cleaning the prints, I use Sprayway glass cleaner https://amzn.to/2CL0Bm4  for cleaning the vat and build plate. And I also use Mean Green for cleaning, which can also be used as a substitute for isopropyl alcohol (IPA) for alcohol wash resins. I use lots of paper towels and shop towels. And I reuse lightly used paper towels and shop towels by setting them in the sun for a few minutes to cure any resin they have on them. Gloves are needed but you can often avoid using them if you set up a neat cleaning procedure. I use needle nose pliers to touch the uncured resin, so I rarely need to put on gloves. I grab a razor blade with needle nose pliers to get the prints to start peeling away from the build plate. Then I hold the print with needle nose pliers and spray the print down with compressed air. I use a compressor tank but canned duster air works too. Then I swish the print around in a container of water for a minute; I remove it, rinse it again in a cleaner tub of water, remove it, spray with air again and let it dry. I mostly cure prints in the sun but have an LED UV light https://amzn.to/3h5pFDl  for cloudy days and nights and for getting into crevasses. Sometimes I cure the prints in a clear jar filled with water to get better light refraction and spread.

I use 190 micron paper paint strainers https://amzn.to/2ZyNxJw for pouring resin from the vat back into the resin bottle. I just strain the resin from the vat to a temporary container if I’m just going to put it back in the vat. I do a strain like that every time I know or suspect that a part broke off while printing and is floating around somewhere in the vat. Floating cured resin pieces are recipes for problems. The paint strainers can be used multiple times. I just give the mesh section a quick swish in water and then set the filter out in the sun for a few minutes to assure any remaining resin cures. That starts to turn the paper strainers into plastic strainers.

Supports are tricky. You want your model well supported but don’t want the model overwhelmed with leftover bumps from supports. Angling models on both the X/Y and Z axes at 30-45 degrees usually reduces the need for supports, especially on rectangular objects. But the smoothest edges come from flat planes perpendicular to the screen. The curing screen is made of pixels and straight lines only come at 90 degree angles. That means that if you are printing a freight car with flat sides, you’d want to keep those sides un-angled and at 90 degrees to the screen, parallel to the screen’s pixels. Otherwise, the pixels create a fine grain texture on the model; the texture can be easy to sand down though so it isn’t always an issue. I use the free program Chitubox for making supports but also sometimes design my own supports into models for more exact supports. You don’t want islands and long unsupported layers. To learn more about making supports that won’t result in failed prints and floating parts in your resin vat, I recommend this video. https://youtu.be/sBAlZwZtiEQ

Overall, you won’t be able to avoid a certain amount of trial and error before you get well versed in resin 3D printing. I’ve found dimensional accuracy is hit and miss, so don’t expect parts to fit tightly together perfectly without tinkering. If you don’t print a lot and don’t do your own designs, Shapeways is still way easier, even with the less than ideal price structure, waxy detail plastic (the wax supports are actually great compared to resin supports and cleaning resin in my opinion), and shipping costs. Overall, home resin printing is useful but it is nowhere near as great as I was hoping.

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N Scale Flex Track Comparison Guide

Here is a breakdown of the main N scale flex track options available as well as some other options. I personally most often use Micro-Engineering code 55, not because it is perfect but because it has the most features I want relative to what is available. Recently, I’ve started using Central Valley Model Works (CVMW) N Code 55 Curvable Mainline Ties with Micro-Engineering code 55 rail when appropriate. CVMW ties are pretty much the best bet available currently for nice looking N scale track. I’d probably use Peco code 55 if the tie spacing was prototypical for the United States. Atlas code 55 is nice but the spikes cause issues with some of my older locomotives. The ideal track for me would be code 40 Peco style track (where the rail is actually code 80 but half of it is embedded in the ties and thus very sturdy) with prototypical US tie spacing, prototypical tie width, and small spikes. Kato Unitrack is also nice track just not very prototypical. I like to use Kato Unitrack for hidden track when appropriate and practical. If Kato made code 55 Unitrack with prototypical US tie spacing and spikes plus also left the ballast off the roadbed allowing users to paint the track and apply their own ballast I’d likely use a lot more Unitrack than I do. At the very least, I’d use more Unitrack if Kato made some little Unitrack code 80 to code 55 flextrack transition tracks. Those would be easier and more reliable than fabricating transition tracks out of Peco code 55 track (see below).

Micro-Engineering code 55
Pros:

• Long 36”
• Small spikes
• Prototypical US tie spacing and tie width (close enough anyway)

Cons:

• Somewhat hard to bend into smooth curves
• Plastic flashing is somewhat common
• Somewhat fragile

Atlas code 55
Pros:

• Easy to bend into smooth curves
• Prototypical US tie spacing and tie width

Cons:

• Short 30”
• Spikes are too big and interfere with wheel flanges on older equipment. But not really an issue if you just have newer equipment made in the last decade or so.

Atlas code 80
Pros:

• Cheapest
• Easiest to find
• Easy to bend into smooth curves

Cons:

• Not prototypical US tie spacing or spikes
• Short 30”

Peco code 55
Pros:

• Long 36”
• Uses code 80 rail embedded in the ties…making it sturdy

Cons:

• Not prototypical US tie spacing or spikes

Peco code 55 track can be used to make transition tracks from code 55 to code 80. All that is required is a file.

Central Valley Model Works (CVMW) N Code 55 Curvable Mainline Ties.
Pros:

• Unlimited length
• Ties can be painted and ballasted before the rails are applied making variation in tie color easier to achieve (especially if a masking template is constructed) and the rail can easily be painted a slightly different color than the ties
• Long stretches of Micro Engineering code 55 rail can be soldered together before being applied to the ties
• No glue required to attach the rail

Cons:

• The ties vary a bit in length which is true to a lot of prototype track (especially older track) but not necessarily true in all cases
• You still have to buy Micro Engineering code 55 rail

 


Kato Unitrack
Pros:

• Reliable
• Reconfigurable

Cons:

• The rail is code 80
• Not prototypical US tie spacing or spikes
• The ballast is part of the track which can be a pro or a con, but it is a con if prototype accuracy is the objective.

Kato N Unitrack vs. Micro-engineering code 55 Flex

3D Printed Track?
Finally, I just wanted to mention that I played around with 3D printing some code 40 track. I did this because there is some track I wanted to put on my layout to make it true to the prototype, but I didn’t need it to be functional. So, at about 10 cents a foot, this 3D N scale code 40 track does the trick just fine, especially since it allows me to make custom track such as very long turnouts in code 40 rail that aren’t commercially available. As technology gets better, dead rail battery powered locomotives on cheap 3D printed track may be a viable solution for some applications.

Code 40 N Dummy Track 3D Printed in PLA

Originally posted 1/10/16. Updated 3/19/18.