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For years, I have always wanted these modeled on the layout.  I have never seen them for sale.  I  received an Ender 3,  3D printer for Father's day, and have been playing around with using Tinker CAD and Fusion 360 after the last couple of months (both were free software packages from AutoDesk).  I finally made enough progress in drafting these up to print them on my 3d printer, but these were a disaster as they were just too small, where the engineered supports were too much and obviously very grainy.

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My local library allows use of their FormLab Resin printers which has allowed me to get allot more detail in the prints.


Some background on what electric locks are.  They are used for locking hand throw switches not in dark territory, typically between signal locations, until it is determined safe to throw the switch.   When the Engineer stops short of coming out of the siding ( or on the main waiting to get into the siding), they would request the dispatcher permission to come out, but this device provides an extra layer of protection beyond the dispatcher giving permission, as it ties into the Vital part of the signal system.  There is handle on electric lock, that when pulled (wired to the closest signal house) communicates to closest signal interface, which then changes the Signals red both directions and then starts a timer waiting for any potential trains that maybe be already coming with prior cleared signals enough time to get stopped and potentially pass this location if they cannot get stopped.  Once the timer expires, the signal system sends a control to the electric lock where the engineer can then pull the rod preventing the the switch from being hand thrown.  I don't know allot about the 9A, but I assume it is predecessor to the 9B.  9B electric locks are easily identifiable and still in use today on railroads.  Alstom Signaling sells the former GRS 9B electric locks.

In working to draft these up I used Fusion 360.  While I really liked Tinker CAD, it didn't seem to have enough tools to do what I want to do (although my exposure to Tinker CAD was so much fun, I started my kids who are in grade school on using it and they have had a blast making things).  The 9B especially, is tough as the round cavity on the back of it was really difficult (for me) to recreate.  I drew these estimating dimensions, in an effort to learn the software.  I still have allot to learn in fusion 360, and my drawings are not an exact representation in O scale, but they are close, easily identifiable as an electric lock and the right height.

Fusion 360 has some really cool rendering capabilities.  Below are some images from my drawings and the renderings it can produce.



9A Ver 2.0 20220729 v3

9B Ver 2.0 20220729 v3

When using the Resin printer, it is interesting as instead of building objects from the ground up like I have seen on traditional 3D printers, instead it produces the objects upside down, as they are pulled out of the Resin, each small layer at a time.  As an experiment, I start with the 9A to see how the print works when rotated in different directions in the same batch.  What I found was that the Resin printer really struggled with starting to produce the initial part of the plane when creating horizontal surfaces and it actually rounded them.  Image below showing this.  So for any surfaces that needed to appear “up”,  i made sure their “up” face was up side down when printed so they looked flat when they came out.  I also saw there seemed be an issue with printing the smaller pipe on the 9A, and I am not really sure why.  I initially thought I may have drawn it hollow on accident, but not the case.  The resin printer takes forever to print, for example these items that are roughly 1' tall with base, are about 9 hours to print. After which they needed to be cured and cleaned.



Example of printing upside down and one can see how rounded the base was made when the design file had it flat.  Also, the underside of the of the cabinet on top of the pipes, have the same issue, where it has been rounded even when the design file had it flat.

Rounded Print Edge

Below are the finished prints.  I was not able use the same resolution on my second set of prints which included both 9A and 9B models as it exceeded the time slot for the library.  I instead opted for the program to optimize the layer height, which in the end did not come out as well.  The image above showing the non-flat base, was printed with the highest resolution, and the ones below are the optimized resolution.   I did show the sprues before and after I cut them and painted them black.  It seems easy to criticize the grainy detail, until you realize there are only 3/4' of an inch tall.

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Images (17)
  • 9a
  • 9b
  • 9A Ver 2.0 20220729 v3
  • 9B Ver 2.0 20220729 v3
  • Rounded Print Edge
  • FormLabPrinter
  • Slicer
  • FirstPrint
  • image8 (1)
  • image9 (2)
  • image10 (2)
  • image5 (1)
  • image1 (1)
  • thumbnail_image0
  • thumbnail_image1
  • thumbnail_image2
  • thumbnail_image0 (1)
Last edited by Hump Yard Mike
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YES  great difference with a FormLabs 3 over an Ender.

the side closest to the build plate is not going to be printed great; so orient the unseen side toward the build plate.

As you discovered. Also use the smallest support with about 75 density.  I rearrange the supports to minimize supports.

Mini-rafts work well with smaller prints and really speed up the print. The higher (more layers) the slower the print.

Last edited by AlanRail

I should know the layer height and forgotten.  The first batch I did at the highest resolution possible on the printer.  The second batch, I was trying to print a higher quantity of the electric locks which was driving up the print time.  The slicer software provided an option to optimize the layer height for features and allow me to stay in allot window time of use.  I hope to be back at the library in a couple of weeks and will capture the height.

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