Drop-in Andrews trucks for Bachmann tenders from Keystone Details

[Lemosteam]

@peteski what I mentioned had NOTHING to do with dimensional accuracy. I made no mention of holding a dimensional range (accuracy).

All trucks have details that small on them, i.e., rivets, hex heads, small socket access holes, tiny spring details, coils, etc.

THIS is what I am referring to.  So far I have not been able to print these types of details with any visibility much less accuracy.

[Dirk Jan Blikkendaal]

Hi John,

Its unfortunate (in view of home/cheaper/better 3D printing) but so far I am inclined to take your side.
I had some trials done with a Form 3 resin printer and even that one did not give me the details Shapeways can do in Smooth or Smoothest.
The surface smoothness and model rigidity of the Form 3 is much better but small detail is simply lacking.
Also 3D printed model accuracy versus my/your plans is not always 100% with Shapeways but that also goes for the (home) resin printers .... can be a pain in the a.. with dedicated etchings but you can design around that and nobody will notice the discrepancy...... (read my comment about accuracy of the Kato E8/9 truck) .
Happily we live in a free world and everybody is entitled to his/her opinion......

You are right about my truck pickups..... phosphor bronze etchings with small holes to hold the axle cones ... no dimples..... all parts move freely.
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[peteski]

@peteski what I mentioned had NOTHING to do with dimensional accuracy. I made no mention of holding a dimensional range (accuracy).

All trucks have details that small on them, i.e., rivets, hex heads, small socket access holes, tiny spring details, coils, etc.

THIS is what I am referring to.  So far I have not been able to print these types of details with any visibility much less accuracy.

Hmm,  maybe members like @Chris333 or @Mark W (among others) can chime in and let us know what is their secret for producing small, yet detailed parts on their printers.  I've seen some fine examples of things their printers.

[Chris333]

Well John is right about dimensional accuracy. You have to scale up or down certain items to get them to come out how you want. Sometimes this takes a few prints to keep taking measurements off of and go change the drawing to get what you want. Some things may never come out perfect.

I made HOn30 trucks that take FVM metal wheels and it can take 2 or 3 tries to get the drawing just right so the wheels pop in and spin free right off the printer. You can't just measure the axle length and make the drawing based off of that. Print one, nope too tight- change the drawing. Print one, nope too loose- change the drawing. Ahhhhh just right. Now print a whole bunch. Same thing with small details.

Also John's 3D designs are like a Picasso compared to my kids crayon drawing on the fridge. So he may just not want to compromise. As much as I hate Shapeways I still see why John wouldn't want to go into production. And if he did the costs may go way up. There are things I see on Shapeways and wish the owner would just sell me the file. But it is their file so I can't complain.

[Lemosteam]

Here is one comparison:





Here is a truck comparison:

My recent print:


Same truck, from shapeways:


And thanks for the compliment @Chris333.

[Dirk Jan Blikkendaal]

John, thats clear!
Can I make one suggestion?
If you blast your Shapeways print with the (simple/cheap) AirEraser (see previous posts) using alu grid all the "white fuzz" will disappear and you will have a clean/sharp print.
This treatment will not visibly affect the small details (if not heavily overdone of course).
I give almost all my Shapeways prints a couple of swipes from close range (2 inches) with the pressure set at 40-45 psi.
Check progress regularly to see if/when all the fuzz is gone......

[Lemosteam]

John, thats clear!
Can I make one suggestion?
If you blast your Shapeways print with the (simple/cheap) AirEraser (see previous posts) using alu grid all the "white fuzz" will disappear and you will have a clean/sharp print.
This treatment will not visibly affect the small details (if not heavily overdone of course).
I give almost all my Shapeways prints a couple of swipes from close range (2 inches) with the pressure set at 40-45 psi.
Check progress regularly to see if/when all the fuzz is gone......

Yes, I already do that- this came right our of my stash with only light prep to show that even then the SW print has more detail.  Everyone always gets hung up on the part before prep.  You should see what prep I had to do just to get the supports off the resin truck...  IMHO, the effort is identical, so when push comes to shove, and the part is painted, the SW version will win on detail every time.

Even with a delrin truck, if you really want the paint to stick, you have to air erase that. Its a matter of picking your poison.

[SkipGear]

I'm not sure I agree with the dimensional accuracy issue any more. The pressed steel trucks I printed only took two prints to get right, and the axle cup was not the problem, I forgot to leave clearance for the flanges.




I just printed a replacement drive coupler for an Athearn HO steamer; measured, copied, and printed exactly as is, fully expecting to need to ream the 2mm hole for the motor shaft. Snapped the first print off the raft, slid it snugly on the motor shaft and put the loco back together. Measured another to compare and it's spot on. Yes filling really small holes is an issue but I've been getting better results each time.

[Lemosteam]

What resin are you printing in? Is that really low viscosity? Is this the sub 2 second layer cure time?

[reinhardtjh]

Two quick thoughts came up, maybe not practical

1)  Experiment with resin temperature.  Warmer resin has lower viscosity.  Maybe it would flow out of the holes quicker so it doesn't get cured?

2)  Some way to increase the lift time or the pause after lifting so that the part is held out of the resin pool longer so that it drains out of the holes?

[SkipGear]

What resin are you printing in? Is that really low viscosity? Is this the sub 2 second layer cure time?

1. Anycubic green - just cleaned the vat and new FEP to try gray.

2. 1.4 sec exposure. .025mm layer height. 100% UV strength.

Oddly enough, the motor coupler parts were in a cold room so I had a small ceramic heater blowing warm air on the vat for 10 minutes or so before I printed. I hadn't been down to the hobby room for a few days before and the room was around 60 deg. Viscosity is definitely a concern.

[Chris333]

I bought a small ceramic heater this last winter. I leave it on the whole time. Still don't think that will fix the light bleeding.