Recent Adventures in 3D Printing - PULLMAN PROJECT · 2020. 9. 19. · 3D Printing Technologies •...

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Recent Adventures in 3D Printing

Prototype RailsJanuary 2020Tom Madden The Hype Cycle

The Hype Cycle The Hype Cycle

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• Yarmouth Model Works boxcar

It’s not new to the hobby

• Resin Car Works boiler load


• Resin Car Works insulated tank car


•Shapeways parts sold by K. Kadwell


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•D&RGW/UCR gons sold by Corey Bonsall


•Smoky Mountain Model Works CofGventilated boxcar kit - 2005


3D Printing Technologies

• Jet Printing


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• Jet Printing

• Stereolithography


• Jet Printing


• Jet Printing

Multijet Modeling (3D Systems)


• Jet Printing

Multijet Modeling (3D Systems)

Shapeways “Fine Detail” (formerly Frosted Detail) material


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• Jet Printing

Think of it as 3D inkjet printing on a build platform that drops after each pass of the print head.


• Jet Printing

Jet printers lay down support material (wax) and model material in the same pass.


• Jet Printing

Jet printers lay down support material (wax) and model material in the same pass.

Both are UV curable.


• Jet Printing

UV lamps attached to the trailing edge of the print head cure the resins as they are deposited.


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• Jet Printing

The wax support material is melted and dissolved away after printing.

3D Printing Technologies Video of Jet printing

Video of Jet printing 3D Printing Technologies

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• Stereolithography (SLA)



Uses a laser to “paint” the pattern, layer by layer, on or in a UV curable liquid resin.



Part is supported by a honeycomb structure. That structure is extended to support overhanging features.



Conventional


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Conventional

Inverted



Conventional



3D Printing Technologies Animation of SLA printing

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Animation of SLA printing Video of SLA printing

Video of SLA printing



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Inverted



Inverted

Resin is exposed from below, through the bottom of a transparent resin tray.



Inverted

Requires much less resin than conventional stereolithography…



Inverted

Requires much less resin than conventional stereolithography…

…so the machines can be much smaller.


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Inverted



Inverted

Layer thickness is determined by the space between the platform (or previous layer) and the bottom of the resin tray.



Inverted

Layer thickness is determined by the space between the platform (or previous layer) and the bottom of the resin tray.

Part peels off the bottom of the resin tray after exposing a layer.



Formlabs Form2 Printer


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Resin tray is transparent silicone rubber.




Resin tray is transparent silicone rubber.

Formlabs recommends that parts with flat surfaces be tilted slightly so they will peel away more easily.


Video of Form2 Video of Form2

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Video of Form2

These videos demonstrate two things:

Video of Form2


1.Printed parts need a lot of post-processing before they are ready to use.

Video of Form2


1.Printed parts need a lot of post-processing before they are ready to use.

2. Stereolithography is a very slow process.

• Inverted resin printing


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3D Printing Technologies Issues

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• All processes

Issues

• All processes

Layering/stairstepping

Issues

• All processes


Issues

• All processes


Issues

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• Jet printing

Issues

• Jet printing

Material properties

Issues

• Jet printing

Jet printing material is brittle, will cold flow if not supported, and softens under moderate heat.

Issues

• Jet printing

Most of my jet printed parts become resin casting masters.

Issues

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• Jet printing

I’ll only use jet printed parts as-is if they are n ot castable, or if they will not be subjected to handling once they are on the layout or model.

Issues

• Jet printing

Banding

Issues

• Jet printing

Banding

Issues

• Jet printing

Banding

Issues

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• Jet printing

Surface degradation under overhangs

Issues

• Jet printing


Issues

• Jet printing


Issues

• Jet printing


Issues

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• Jet printing


Issues

• Jet printing


Issues

• Jet printing

No degradation between layers, only within layers.

Issues

• Stereolithography/DLP/LCD

Issues

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Material is expensive

Issues


Stereolithography is slow

Issues


How slow?

Issues


How slow?

The Form 2 was taking 18 seconds to print each layer.

Issues

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How slow?

If it takes 15 seconds per layer, that’s 240 layers per hour.

Issues


How slow?

If each layer is 0.002” thick*, that’s 0.480” per hour.

Issues


How slow?

If each layer is 0.002” thick*, that’s 0.480” per hour.

* The Form 2 can print layers from 25 to 300 microns (0.001” to 0.012”) thick. If the part has 1” diameter dome-shaped rivets (HO), they will be less than 0.006”tall. You need 0.002” layers for them to print reliably.

Issues


For consistent results room temperature and humidity must be tightly controlled.

Issues

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Supports are the same material as the part so for complex parts there will be lots of “nubbins”to be sanded away.

Issues

All of my earlier projects were printed by conventional stereolithography.

Background

I later had access to a jet printer that was good f or printing shapes, like roof blanks, and added surface details by hand.

Background

For the past three years I’ve used Shapeways jet printing exclusively….

Background

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…..with one exception.

Background Project #1

Project #1A Very Complex Small Part

Truck Mounted Generators

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This complex part can’t be cast – and even if it cou ld, it would be too fragile if cast in conventional resins .


I designed a pair hoping they could be 3D printed i n a material tough enough to withstand handling.


The tensioner was placed within the brake beam.


The tensioner was placed within the brake beam.

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It would be cut out, the collar drilled for a short bit of wire for the operating handle…


…and epoxied to the support.


Shapeways’ inverted DLP High Definition Black Acrylate process looked perfect for the job….


…and it was!

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…and it was!


Went together as planned, material is tough and resilient, perfect for the application.


Shapeways approved it for sale to others, and I ord ered two dozen sets.


But then they reneged, claiming they were too diffi cult to trim, and not only couldn’t they be offered for sale…

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…they would not make them for me at all, unless I wanted them untrimmed with all supports in place.


So I ordered a dozen, untrimmed.


So I ordered a dozen, untrimmed.


I had to admit, they did have a point!

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So that project is in limbo for now.


The printer was an Envisiontec Perfactory machine using their Pro Gray Acrylate material.

Project #2 Project #2Large Parts with Flat Surfaces

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3D Printed Pullman Sides 3D Printed Pullman Sides

I’ve been working on this for years, beginning with conventional stereolithography.

3D Printed Pullman Sides

The build platform in our high resolution machine w as too small to print full sides in one piece.


Not a problem, as my designs, like Pullman’s, were modular and could be split.

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So I printed sides in sections…


…made cast resin duplicates…


…milled the mating edges and…


…proved “the best laid plans” etc. etc….

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The parts were smooth but not flat, so even though the milled faces mated perfectly, the edges did not.


I then tried jet printing.


Ours was an early machine and the parts had very pronounced striations.


Shapeways had better printers, but was not an optio n until customers could specify build orientation.

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Even after that changed, results were mixed. Some s ide pairs were acceptable, …


…some had regular banding striations…


…while others were smooth but had strange surface artifacts.


As it turned out, the poorer sides were from a Shapeways “partner” shop in Utah...

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…and the better sides were from Shapeways own facility in Long Island City.


Once that problem was resolved, results have been very consistent.


Once that problem was resolved, results have been very consistent.


But is “consistent” good enough?

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Printed parts won’t be as smooth as injection molde d parts from polished dies.


Banding tracks are will be evident, especially unde r strong oblique lighting


All printed surface irregularities really stand out on glossy surfaces.


Once painted with a flat, or at worst, matte, finis h, jet printed sides from Shapeways are quite presentable.

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This has been a 15 year project (so far).


During that time I’ve designed 21 sets of side pair s…


And since Pullman used three different rivet patter ns…


I’ve created a library of 178 different window modu les…

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…and 263 different pier panels!

Etc. etc.


And despite all this “modularity” and large library, I have yet to design a side pair that didn’t require at least half a dozen new pier panel or window modules.

Project #3 Project #3Sloped surfaces and a family of common parts

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3D Printed Passenger Car Ends 3D Printed Passenger Car Ends

This is another 15 year project that started with stereolithography.

3D Printed Passenger Car Ends

The challenge is all those sloped surfaces with lot s of rivet detail.


For stereolithography I designed the end patterns s o all the detailed surfaces could be printed flat.

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Vestibule end patterns have open frame bodies and separately applied side panels.


Vestibule end patterns have open frame bodies and separately applied side panels.


The open frame lets me glue the panels from the bac k.


Blind end patterns have solid bodies.

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Decent ends can be made with stereolithography.


Post-retirement I no longer had access to that, so I recently submitted some end designs to Shapeways.


Post-retirement I no longer had access to that, so I recently submitted some end designs to Shapeways.


They were designed like the SLA ends.

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The 16 micron layers of their Smoothest Fine Detail process left the sloped areas fairly smooth.


So I designed ends complete with rivet detail.


So I designed ends complete with rivet detail.

Six in all.


Like the sides, the ends are of consistent quality but shouldn’t be given a high gloss finish.

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Those were photos of actual 3D printed patterns, cleaned and primed,

Here’s my current portfolio of cast resin ends.


Here’s my current portfolio of cast resin ends. Here’s my current portfolio of cast resin ends.

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Here’s my current portfolio of cast resin ends. Here’s my current portfolio of cast resin ends.

Wide clerestoryVestibule end

Narrow clerestoryVestibule end

StreamstyledVestibule end

Curved topVestibule end



Sun room end withBlanked windows

Narrow clerestorySun room end

Wide clerestorySun room end

Inner wall for Sunand Solarium ends



Solarium end, no brake housing

Solarium end with brake housing

Wide clerestory blind end,no brake housing

Wide clerestory blind endwith brake housing

Narrow clerestoryblind end

Streamstyledblind end

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I also did two types of hand brake apparatus.






The ends look pretty good with the hardware added.


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Project #4 Project #4A sampler of small parts

3D printed model

1/3 HP water pump for York AC systems

Illustration from Pullman’s AC manual


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B&O blueprint of pump


B&O blueprint of pump


3D printed model

18” UC brake cylinder

Roughness on underside acceptable considering where part will be located on model.

18” UC brake cylinder

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Roughness not acceptable if part will be more visib le.

21” diameter belt-driven generator

Generator split into parts that can be printed clea n.


Design includes keyway to align parts.


Completed generator.


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Sometimes a rough vertical surface can work in your favor.

Sometimes a rough vertical surface can work in your favor.

Housing has fine mesh screen on face.

Air conditioning condenser Air conditioning condenser

First attempt – scratch built pattern.

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Air conditioning condenser

Second attempt – 3D CAD design.

Air conditioning condenser

Second attempt – printing orientation

Castings from 3D printed & scratch built patterns

Air conditioning condenser Air conditioning condenser

Castings from 3D printed & scratch built patterns

Compared to the prototype

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COST????? COST?????

Shapeways prices reflect material usage and machine time, with a minimum charge per part.

For Smooth Fine Detail, the minimum is $7.50

For Smoothest Fine Detail it’s $10.00

COST?????

A pair of sides is one part. Printed with Smooth Fine Detail plastic it costs about $40.

COST?????

That is a bargain for resin casting patterns.

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COST?????

These six ends each count as one part. They were printed with Smoothest Fine Detail

plastic and cost $10 each.

COST?????

That is also a bargain.

COST?????

These little water pumps in Smoothest Fine Detail would cost $10 each.

COST?????

That is not a bargain, but parts like these can’t be cast.

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COST?????

Gang small parts together or put multiples on a base plate. This set of 6 pumps costs $10.

Takeaways

Takeaways3D printing is a useful tool, with some amazing

capabilities and significant limitations.



Don’t impose your hopes and desires on the present technology – work with what it can do,

not with what you wish it could do.

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Stay away from highly detailed side walls –break your projects down so they can be

printed as flat pieces and assembled later.





Stay away from highly detailed side walls –break your projects down so they can be

printed as flat pieces and assembled later.

3D printing is just getting started – enjoy the ride!!

Prototype RailsJanuary 2020Tom Madden

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Recent Adventures in 3D Printing - PULLMAN PROJECT · 2020. 9. 19. · 3D Printing Technologies •...

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