Newbie questions about print layout (Photon Mono)

[GaryHinshaw]

I'm super excited to have my own Photon Mono in the house now: it's really going to transform my approach to a number of modelling tasks.  But getting there is a learning process, so I'm here to learn, starting with a few specific questions about part layout when printing with resins.  But please excuse a long-winded introduction first, or skip this post and go right to the second post, where I ask my questions. 

The first project I'm trying is a set of functional replacement parts for Kato well cars:
1. a new end sill with a built-in coupler pocket and a standard bolster to accommodate body-mount couplers and MTL trucks,
2. a new articulated coupling system to replace the overly-complex and poorly functioning Kato design.  (The Maxi-I cars, especially, are prone to uncoupling under load, at least on my heavy trains.  The slot & pin articulated joint is just not reliable enough for me.)

To the extent possible, I am trying to make them snap-in replacements because I have a lot of these cars and I want the retro-fit process to be fast, easy, and reliable (then I can spend more time weathering these cars).  Below are some photos of the first draft prints, which are, in fact, the first parts I have designed, and the first parts to come out of the printer, aside from the test cube, which printed brilliantly.

An overview:

L-R: end sill, "A side" articulated coupling loop, snap-on post to replace the slot & pin Kato part.

Test fit of the end sill:

(Sorry you can't really make out any detail in the white resin parts.)

Test fit of the A side loop:


In the first photo, you can also see how the truck part snaps over the bolster of the Kato 125T truck.  The centre-post is also compatible with the Deluxe and N Scale Kits Maxi-III cars, so I can use proper 125T trucks on those cars as well.

I was really happy with the way these parts fit on the first try.  I still have some minor tweaks to make to the dimensions, and then some details to add, but all in all this will be a quantum leap in my ability to upgrade these cars.  (I'm also planning to draw up some replacement etched walkways, but that's another story.)

Issues and questions coming next.

[GaryHinshaw]

Now for the issues.  Since this was my first print, I didn't do anything special with the print setup: I just used the default exposure settings for the basic Anycubic resin, used default support posts with a fairly low density (I think around 20%), and had the parts oriented horizontally.  The main issue I encountered was that the first large flat layer to be printed (the bottom surface of the part) was very unstable, causing it to drift or feather away from subsequent layers.  Some examples shown here:





The truck adapter turned out pretty well, but had a few similar issues:



The top (later) surfaces turned out beautifully though:



Are there any general guidelines for how to manage this?  Add more support? Reorient the parts?  Change the exposure parameters?  I also noted that these parts came out of the printer much wetter than the test cube.  I think some uncured resin was not draining off of large horizontal surfaces very well, so I should probably avoid situations like that.  Any other general tips?  Thanks in advance!

[C855B]

I'm no expert - just mostly lucky - but I can't recall success printing anything with a 0° orientation. There's always been an issue. The peeling thing is new to me, must be something peculiar to the Mono, or at least a different manifestation of the print sticking to the FEP. At any rate, try 45° and see what emerges from the soup.

[Chris333]

Way more supports and even more so in corners.

[GaryHinshaw]

Ok on both fronts.  I'll report back.  Thx.

[SkipGear]

Printing flat is just fine. Supports on all the corners and maybe a tenth or two more exposure time. Remember that each layer has to peel off of the FEP sheet each time. The resin is still soft so it can stretch and distort with out support.

I've been pretty happy with 1.4 seconds on the green resin. Haven't printed white or gray yet, have it, just don't want to mess with what is working for me.

[GaryHinshaw]

Thanks Tony.  Do you have any issues with resin pooling on horizontal surfaces?

I'm tweaking the drawings this afternoon, then I'll try a new print run tonight, with a range of new supports and part angles, and a slightly longer exposure.

[SkipGear]

Not at all.

[GaryHinshaw]

Bit of an update here.  I played around with various part orientations and support structures and I think I have a better understanding of the issues.  After trying a few runs with horizontal and 45 degree orientations:



I tried a run with vertical, and ±10 degrees off vertical orientations:



The obvious winner for these parts is vertical with the supports on the inboard side of the part (the left part in the above picture).  In the course of doing so, I've been tweaking the design to improve the fit of the parts, so it's now starting to look like something:





Pardon the pizza cutters...    Still some adjustments and improvements to make to the design, but once those are finalized, I can mass print these for the fleet and really make some progress.  Thanks for the tips.

To say that I'm pleased with this printer would be a gross understatement.

[ednadolski]

Fantastic progress, Gary!    Nice too seeing the design incorporating the LEZs

Ed

[ednadolski]

BTW are those the GMM etched parts?

Ed

[GaryHinshaw]

Thanks Ed,  I thought you'd appreciate the coupler pocket.    The end walkway is indeed a GMM part, from set 160-54 for the Husky Stack.  Unfortunately, the interior walkways will need to be custom made.  Here's a bit more on the pocket as it currently stands (I'll post more thoughts in my old body-mount thread when I get further along).  The underside at the moment is a simple open channel with an integral post that the coupler attaches to:





I haven't drawn up a bottom cover yet, but I'm thinking I'll redo this design with a detente in the top cover and an integral post in the bottom cover that press fits or snap fits into the channel. 

Unlike the etched pockets (which are great, Ed), with 3-d printing, trying out different ideas has a turnaround time of hours rather than weeks, and costs pennies rather than dollars.  And the possibilities for custom pockets with integral support hardware are virtually endless.  My mind is positively racing with ideas for covered hoppers parts, tank car end frames with custom saddles, etc.   

[C855B]

A man possessed! Great to see the huge progress happen so quickly. 

Looks like I need to get off my tuckus and do those dwarf signal edits.

[Chris333]

Soon you'll be 3D printing ballast! 

[GaryHinshaw]

LOL, that's hilarious Chris.  Maybe not quite that far, but definitely turnout parts... and dwarf signals, Mike.