Date   

Re: Naperville

mwbauers
 

This has reminded me of a 3d printed object I got some 10-15 years ago.

It was a lightweight near-black print of a hand calculator with details to the print. It was a commercial 3d printer sample.

I took it to work in my lunch and misc pack to show the guys at work. When I got to work and unpacked the lunch, the print was in shattered fragments. It was sort of foamy inside and glass brittle.

This weekend I got to handle and bounce some model railroad Dremel 3d printer models. They stood up very well with no damage. [ a large grain silo, a good sized stone bridge, and some palm sized tools and brackets ]

That was from a ‘cheap’ home-user machine printing in PLA. 

The art has progressed enough that even the cheap 3d printed stuff is much improved in durability over the very expensive commercial results of a few years ago.

Best to ya,
Mike Bauers
Milwaukee, Wi

On Oct 27, 2015, at 2:33 PM, 'Jack Burgess'  wrote:

No, 3D models are not "flimsy". I have passed around the frame for the side
dump I'm working on at a number of clinics and no one has broken it yet.
Thin parts are brittle and you need to just be careful with them. You cannot
tap the material for screws to attach the trucks (hence the need to also
print plugs for attaching trucks). And I didn't say that the model
"shattered" when I tried to tap the hole for the truck screw...the bolster
just cracked and could have been glued back together if I wanted to.

As I mentioned in the clinic, this technology is really geared for building
single cars (not a fleet) and replacement parts (where a sprue can be used
to minimize costs). If you want to build a fleet, follow Tom's approach. If
you want to build a single side dump car, 3D printing is the answer.

-----Original Message-----
From: STMFC@... [mailto:STMFC@...] 
Sent: Tuesday, October 27, 2015 9:59 AM
To: STMFC@...
Subject: Re: [STMFC] Naperville

I've handled enough 3-D parts to realize how flimsy they are. Sure they LOOK
like freight car models but they'd last less than…...


Re: Naperville

Tim O'Connor
 

Jack Burgess wrote

>> I didn't say that the model "shattered" when I tried to tap the hole for
>> the truck screw...the bolster just cracked and could have been glued back
>> together if I wanted to.

Shatter ... Crack ... 6 of one, half dozen of the other.

And glue a crack in a bolster strongly enough to hold a screw? That's a bit of
a challenge even with styrene. What kind of glue would you use? Would it tolerate
temperatures between -20F to 100F? (These are typical temperature variations that
models in the northeastern US encounter while being transported.)

Tim O'


Re: Naperville

Jack Burgess
 

Thanks for chiming in Dennis.



I recently had Shapeways print some passenger truck sideframes in wax that I drew up for Rio Grande Models (Valley Brass & Bronze did the lost wax process) and I had four truck sideframes on a sprue and the only problem was that I had the sprues too thin. (I was using the minimum sprue dimensions for Frosted Ultra Detail.) Their concern was that the sprues would break with the weight of the sideframes. (And the parts couldn’t be cast in brass without the sprues needed for pouring the brass.) I also had to add more than a single sprue for each sideframe. Once I fixed that, they went ahead and cast them in wax and they turned out fine. Rio Grande Models will be using the lost wax castings to make high-temperature rubber molds for casting the sideframes in white metal.



Note what Dennis is saying…this only involved brass parts. My last order from Shapeways was in August and it was a sprue of very small queenposts. No problem with spruces for other materials…



Jack Burgess



From: STMFC@yahoogroups.com [mailto:STMFC@yahoogroups.com]
Sent: Tuesday, October 27, 2015 11:02 AM
To: STMFC@yahoogroups.com
Subject: Re: [STMFC] Re: Naperville










---In STMFC@yahoogroups.com, <mwbauers55@...> wrote :

Jack and guys,

People are talking about a problem with Shapeways and multiple parts on a sprue. Something about a set-up fee for each part rather than a single set-up fee for the sprue of parts.

For now, if you sprue in 3d, you better have your own 3d printer.
==========

I should chime in here... That was me. I have a test file I've been sending out occasionally to test the ability of 3D printing to give adequate surface detail (it's a passenger car triple valve) and now that Shapeways is offering brass parts (they print the wax master and subcontract the casting) I decided to try out the new process. My test file consists of twelve valves on a stick, same as CalScale or PSC often do NBWs, valves, and pipe fittings, and Shapeways refused to print it. Their policy FOR BRASS PARTS is no more than a pair of parts together... makes no difference if all the parts are ONE solid model, if they see a repeating feature they will claim it's multiple parts and refuse the job.

I should stress this is for their BRASS PARTS ONLY (and I suppose bronze, Sterling silver, and gold :-) They did print my multiple valve file in acrylic, although I've yet to find time to clean up, paint, and photograph their latest effort. My problem is this was to be a "proof of concept" for the brass, before I spent the time to model a part a friend wants; solid leaf springs for caboose trucks. Even if the acrylic parts now have adequate detail, they are going to be way too fragile to mount on car trucks, where they would be subject to handling each time someone has to re-rail the car.

So, I wait for more options to present themselves.

Dennis Storzek










[Non-text portions of this message have been removed]


50' box cars with 6' doors

Clark Propst
 

We’ve been curious about the purpose of making 50’ steel box cars with 6’ doors. The C&NW and Milwaukee had this design. Both served the Upper Midwest. We were think of a light, but bulky lading like tin cans?
Clark Propst
Mason City Iowa


Re: 3-D parts

Tim O'Connor
 

Tony

I mentioned that particular small narrow part because that is exactly what was part
of Jack's model. He had some difficulty in getting the part made correctly and other
such parts (handrails, mullions, ladders) would be common in many of our models.

  >> a number of the materials are "cured" by the laser light, no sintering.

Mincing words now -- the "curing" is what physical process? "Absorption of light"
usually means that the energy of the light spectrum heats the material causing it
to polymerize into a solid.

I can't easily find stuff on mechanical properties of photo sensitive resins online,
although clearly the subject is of great interest outside the hobby. Found this bit
of text from an online synopsis:


  "Fractography analysis following tensile or impact tests, after exposure of samples
   to ultraviolet radiation or thermal treatment, was correlated with mechanical properties.
   Brittle fracture behavior was observed in all samples studied and plastic deformation
   was present in some regions of green samples, showing layer ordering in the microstructure
   originating from the stereolithography process. The samples post-cured by conventional heating
   demonstrated improved mechanical properties and low defect susceptibility."


I am convinced that Tom is right -- the best use of the process now is to produce
masters for casting.

Tim O'Connor




The acid test would be a long piece of say, .020 x .020 cross section. Do you
think any current 3-D process material would be as strong and durable as the same
size piece in cast resin or polystyrene or ABS ?

        Not sure why this is "the test" of such a process. A long piece of the size you quote would be simpler, quicker and far cheaper in styrene from Evergreen, so we are not going to make such materials by 3-D printing. Again, your idea that there is some single "strength" for materials such as styrene or resin is a little naive. But yes, I do think comparable strengths can be achieved, though not in inexpensive materials.

Tony Thompson


Re: Naperville

Jack Burgess
 

No, 3D models are not "flimsy". I have passed around the frame for the side
dump I'm working on at a number of clinics and no one has broken it yet.
Thin parts are brittle and you need to just be careful with them. You cannot
tap the material for screws to attach the trucks (hence the need to also
print plugs for attaching trucks). And I didn't say that the model
"shattered" when I tried to tap the hole for the truck screw...the bolster
just cracked and could have been glued back together if I wanted to.

As I mentioned in the clinic, this technology is really geared for building
single cars (not a fleet) and replacement parts (where a sprue can be used
to minimize costs). If you want to build a fleet, follow Tom's approach. If
you want to build a single side dump car, 3D printing is the answer.

Jack Burgess

-----Original Message-----
From: STMFC@yahoogroups.com [mailto:STMFC@yahoogroups.com]
Sent: Tuesday, October 27, 2015 9:59 AM
To: STMFC@yahoogroups.com
Subject: Re: [STMFC] Naperville


I've handled enough 3-D parts to realize how flimsy they are. Sure they LOOK
like freight car models but they'd last less than a week at my train club.
They are as fragile as fine china or art glass. I've dropped resin cars onto
concrete and have been able to repair them. Try that with a finished 3-D
layout model!

And Bruce, it was JACK himself who said the 3-D models will SHATTER if you
try to drill or tap the material. In order to get screws into his 3-D models
he printed the screw holes extra large so he could line them with sleeves.

Tim O'Connor




Yes......"3-D parts are useless for freight car models -- at least for
bodies"

Just like these useless bodies here:
https://nycshs.files.wordpress.com/2015/09/nycentralmodeler4th2015final
1.pdf
(see pages 65 and 67)

But to be fair, Tom (and Tim) do have a very valid point: even after you
overcome the technology's limitations and the problems with printing through
Shapeways and come up with a good, usable print, it's still FAR cheaper to
use the resulting car as a master for resin duplication (generally, by a
factor of ten or so).

Now we just need to find more people who can do high quality casting in
bulk.

Ray Breyer
Elgin, IL


------------------------------------
Posted by: Tim O'Connor <timboconnor@comcast.net>
------------------------------------


------------------------------------

Yahoo Groups Links


Re: 3-D parts

Tony Thompson
 

Tim O'Connor wrote:

 

All of the methods use some kind of heat-sintering to join beads of material
together. As a physicist and mechanical engineer can you tell me that those kinds
of mechanical bonds are as strong as the polymer bonds of injection molding or
urethane resin?


        Well, actually, a number of the materials are "cured" by the laser light, no sintering. Strength will obviously depend on the chemistry of the curing of that particular material, so there is surely no single answer. And you assume that injection molded parts are strong, which depends very much on the particular material injected, and how much previously multi-injected scrap is in it. (Dennis can comment on that.) The metals parts ARE sintered, and can be nearly as strong as bulk metal (some pores normally remain, but don't greatly degrade strength.)

The acid test would be a long piece of say, .020 x .020 cross section. Do you
think any current 3-D process material would be as strong and durable as the same
size piece in cast resin or polystyrene or ABS ?


        Not sure why this is "the test" of such a process. A long piece of the size you quote would be simpler, quicker and far cheaper in styrene from Evergreen, so we are not going to make such materials by 3-D printing. Again, your idea that there is some single "strength" for materials such as styrene or resin is a little naive. But yes, I do think comparable strengths can be achieved, though not in inexpensive materials.

Tony Thompson             Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705         www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, tony@...
Publishers of books on railroad history





Re: 3-D printers

nvrr49@...
 

For freight and passenger cars, I don't see FDM printers ever getting to the quality we require, but they can be used for structures, when the structure can be designed correctly to fit the printer.  Perfectly flat surfaces just don't seem possible with an FDM type printer.  Here is a link to a Frisco section house, and a two story depot where the main building was 3d printed on an FDM printer.  Bricks and concrete blocks also can be done.  Board and Batten siding...too much flat area, and the layering running the wrong direction.


nvrr49.blogspot.com


---In STMFC@..., <smithbf@...> wrote :

Jon,

These are monofilament extrusion printers,  For model work, they’re crap.  I don’t know how many times we have to say it, but the resolution of “bargain” 3D printers is insufficient to produce satisfactory parts for models.  PERIOD.  Someone will likely chime in with a pie in the sky view of what MIGHT be coming and yes, it might be coming.  But right now, it ain’t here and as Tom Madden and others who actually use this technology repeatedly point out, to get the resolution that modelers need, you need the really really expensive machines...

Regards

Bruce


Bruce F. Smith            

Auburn, AL

https://www5.vetmed.auburn.edu/~smithbf/

"Some days you are the bug, some days you are the windshield."

 


Re: 3-D parts

Tim O'Connor
 

Tony

All of the methods use some kind of heat-sintering to join beads of material
together. As a physicist and mechanical engineer can you tell me that those kinds
of mechanical bonds are as strong as the polymer bonds of injection molding or
urethane resin?

The acid test would be a long piece of say, .020 x .020 cross section. Do you
think any current 3-D process material would be as strong and durable as the same
size piece in cast resin or polystyrene or ABS ?

Tim O'



3-D parts are useless for freight car models -- at least for bodies -- the
material lacks hardness and strength. It has to be sandable, drillable, and
cut-able. Tom has the right idea -- make MASTERS in 3-D, modify them as needed
(e.g. adding rivet details), and then make rubber molds from those. The final
models are cast in urethane resin.

     Tim, nowadays there is no such thing as saying "the material." You can choose from a wide variety, from the soft and brittle stuff you seem to have seen, to material which is much like urethane resin, and even metals. The Hart convertible gondolas we talked about, a week ago, are a really nice material -- there is one in front of me as I speak, and I have been drilling and sanding, no problem.

Tony Thompson


Re: Naperville

Dennis Storzek
 




---In STMFC@..., <mwbauers55@...> wrote :

Jack and guys,

People are talking about a problem with Shapeways and multiple parts on a sprue. Something about a set-up fee for each part rather than a single set-up fee for the sprue of parts.

For now, if you sprue in 3d, you better have your own 3d printer.
==========

I should chime in here... That was me. I have a test file I've been sending out occasionally to test the ability of 3D printing to give adequate surface detail (it's a passenger car triple valve) and now that Shapeways is offering brass parts (they print the wax master and subcontract the casting) I decided to try out the new process. My test file consists of twelve valves on a stick, same as CalScale or PSC often do NBWs, valves, and pipe fittings, and Shapeways refused to print it. Their policy FOR BRASS PARTS is no more than a pair of parts together... makes no difference if all the parts are ONE solid model, if they see a repeating feature they will claim it's multiple parts and refuse the job.

I should stress this is for their BRASS PARTS ONLY (and I suppose bronze, Sterling silver, and gold :-) They did print my multiple valve file in acrylic, although I've yet to find time to clean up, paint, and photograph their latest effort. My problem is this was to be a "proof of concept" for the brass, before I spent the time to model a part a friend wants; solid leaf springs for caboose trucks. Even if the acrylic parts now have adequate detail, they are going to be way too fragile to mount on car trucks, where they would be subject to handling each time someone has to re-rail the car.

So, I wait for more options to present themselves.

Dennis Storzek


Re: 3-D models

Tim O'Connor
 


I wish to see an evaluation of the mechanical properties of 3-D models
compared to cast urethane resin, i.e.

What is the crush strength (side pressure)? What is the bend strength (how much force
to break the car in half by bending in the middle? How much weight can be placed on
the coupler before it pulls out?

I suspect that in all of these mechanical properties, cast resin (including
injection molded) will significantly outperform current 3-D technology.

Tim O'





      Some of you may not realize that the era of the home 3-D printer is not so far away. Sure, Shapeways may have $100,000 machines, but Robert Bowdidge has a home machine costing less than 5 percent of that number, and he is producing pretty darn nice car bodies for sale. Most of us may still not be ready to spend even 5 percent of a Shapeways machine, but costs are still falling. Keep your eyes open.
       Please note, if you didn't before:

http://www.drycreekmodels.com/

Tony Thompson 


Re: Handling RR Claims

Tim O'Connor
 


Alternate interpretations of hearsay factoids:

  (1) PFE claims department was more proficient at re-directing blame to the PRR (i.e.
       that's why they call it a "settlement" and not just a "bill for damages")

  (2) PRR had .0001% more claims per ton-mile, rendering it a statistically meaningless
       "worst" but very handy in employee pissing contests of "who has the worst record?"

  (3) PFE agents told customers to send apples and lemons via the Erie, but lettuce via
      the PRR, in order to induce higher damage claims on the PRR to settle a bet they
      made over dinner with a bunch of annoying PRR sales agents...

History is both fun, and fungible !

Tim O'Connor



The PRR might have recorded more claims, but I don't think anyone here would believe they were the cause of the claim. and they handled more perishable freight beyond the gateways than any other eastern carriers, but not so with livestock. The PRR gets the bad wrap because they are the delivering carrier. It has little or nothing to do with any perception of the PRR's service.

       Greg, PFE was not a railroad. They did not operate on ANY miles of mainline track. They were owned by, and supplied cars to, UP and SP (and managed cars for WP). My understanding from the PFE people I interviewed is that claims were settled EITHER by identifying a mistake (car wasn't iced when scheduled, missed a connection, etc.), in which case the maker of the mistake was liable, OR by pro-rating the claim according to miles handled by each railroad en route. Assuming for the moment that the PFE report is true, that PRR had the highest perishable claims PER TON-MILE of any railroad, I don't see how you can say they get a "bad rap" as delivering carrier, because the claims either reflect a mistake or are pro-rated. I'm aware that PRR talked a lot about service, but this perishable claim issue suggests that maybe they talked the talk but didn't walk the walk. (Heresy, I know, to Greg and others.)

Tony Thompson 


Re: Naperville

Charlie Vlk
 

While this comment may be true for many HO and larger bodies it is not so for N Scale.  While we would certainly like to get better materials and resolution there are many very credible printed model freight car, passenger car, and locomotive bodies ccurrently being sold that make up to nice models.   At Naperville Bill Denton was showing a partially completed FM H-10-44 and Keith Kohlmann had a PRR gondola that will  be the subject of an upcoming Model Railroader article.

Going on 13 years ago a friend made a CB&Q one piece SM-18 body for me which was totally 1/160 scale.   It was printed using the Prefactory process and the surfaces could not be distinguished from injection molded plastic except for the fact that the framing, slats, roofwalks, free standing grabirons, etc. would be impossible to tool.   That technology was very expensive but we are close to seeing such results being commercially available at reasonable prices….and in print areas that will accommodate larger scales.

Charlie Vlk


3-D parts are useless for freight car models -- at least for bodies -- the
material lacks hardness and strength


Re: 3-D printers

mwbauers
 

If you don’t mind putting on your own rivet/NBW detail, wire steps, grab irons and ladders, the extrusion made models are just fine.

Like the real thing, you’ll need to put on stand alone brake wheel parts and on bracket tag boards.

But those details I mention above are the meat and potatoes of this Yahoo list RR car modeling anyway. You already do it that way.

I got to handle scale models made from the Dremel 3d printer this Sunday. Once you are in tune with the limitations of the process, and work within those restrictions, you’ll do just fine with it.

We don’t have to fret about future advances of the 3d print method that aren’t yet here. What is here can be well and wisely used, as is.

Best to ya,
Mike Bauers
Milwaukee, Wi

On Oct 27, 2015, at 10:42 AM, 'Bruce F. Smith' wrote:

Jon,


These are monofilament extrusion printers, For model work, they’re crap. I don’t know how many times we have to say it, but the resolution of “bargain” 3D printers is insufficient to produce satisfactory parts for models. PERIOD. Someone will likely chime in with a pie in the sky view of what MIGHT be coming and yes, it might be coming. But right now, it ain’t here and as Tom Madden and others who actually use this technology repeatedly point out, to get the resolution that modelers need, you need the really really expensive machines...


On Oct 27, 2015, at 10:28 AM, Jon Miller wrote:



Monoprice has a couple of 3-D printers, one at $399 and one at $599. Not sure if these are the normal price range or good prices.


Re: USRA

Armand Premo
 

Ray,The question was rhetorical.Armand Premo

----- Original Message -----
Sent: Tuesday, October 27, 2015 12:50 PM
Subject: Re: [STMFC] USRA

 

>>Which begs the question; How many double sheathed cars were still around in the 50s?
>>Armand Premo


Hi Armand,

"The Fifties" is a ten year long span of time with a VERY significant marker stuck in about one third of the way through. Are you talking before or after the K-brake ban? Because the numbers will look VERY different.

(Roughly, and ONLY going off of memory here, there were around 40,000 double sheathed cars in 1950, and less than 4,000, mostly all ventilated boxcars or shortline cars, in 1959).

Ray Breyer
Elgin, IL

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2014.0.4842 / Virus Database: 4447/10898 - Release Date: 10/27/15


Re: Erie version of a "surrey with the fringe on top"?

Tim O'Connor
 

Scott

According to the 1959 ORER, "cars in series 15800 to 15899 are arranged for
handling crates for export".

Tim O'Connor




http://rr-fallenflags.org/el/frt/erie15850lba.jpg
Anybody have any idea what this was used for? 
Scott Chatfield


Re: USRA

 

Armand – Almost all freight cars were heavily used in WW2.  The oldest were replaced first in the late 1940s – 36’ cars, truss rod cars.  The 1950s saw virtually all USRA cars except the ones upgraded with steel sides gone by 1960.  1953 seems to be the turning point for most roads. – Al Westerfield
 

Sent: Tuesday, October 27, 2015 11:50 AM
Subject: Re: [STMFC] USRA
 
 

>>Which begs the question; How many double sheathed cars were still around in the 50s?
>>Armand Premo


Hi Armand,

"The Fifties" is a ten year long span of time with a VERY significant marker stuck in about one third of the way through. Are you talking before or after the K-brake ban? Because the numbers will look VERY different.

(Roughly, and ONLY going off of memory here, there were around 40,000 double sheathed cars in 1950, and less than 4,000, mostly all ventilated boxcars or shortline cars, in 1959).

Ray Breyer
Elgin, IL


Re: Naperville

Tim O'Connor
 

I've handled enough 3-D parts to realize how flimsy they are. Sure they LOOK
like freight car models but they'd last less than a week at my train club. They
are as fragile as fine china or art glass. I've dropped resin cars onto concrete
and have been able to repair them. Try that with a finished 3-D layout model!

And Bruce, it was JACK himself who said the 3-D models will SHATTER if you try
to drill or tap the material. In order to get screws into his 3-D models he
printed the screw holes extra large so he could line them with sleeves.

Tim O'Connor

Yes......"3-D parts are useless for freight car models -- at least for bodies"

Just like these useless bodies here:
https://nycshs.files.wordpress.com/2015/09/nycentralmodeler4th2015final1.pdf
(see pages 65 and 67)

But to be fair, Tom (and Tim) do have a very valid point: even after you overcome the technology's limitations and the problems with printing through Shapeways and come up with a good, usable print, it's still FAR cheaper to use the resulting car as a master for resin duplication (generally, by a factor of ten or so).

Now we just need to find more people who can do high quality casting in bulk.

Ray Breyer
Elgin, IL


Re: Naperville

Tony Thompson
 

Lester Breuer wrote:

 

Guessing most are still recovering from travel time home or still processing and digesting all the information gathered from seminars or exchange with others or being fired up from the event have headed for the railroad modeling bench to finish or start a new project preventing them from posting regarding the event.
I as other attendees I have talked to had a great time.


      I had a good time too, and have summarized some features of the meeting in a post to my blog. If you'd like to see it, here is a link:


Tony Thompson             Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705         www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, tony@...
Publishers of books on railroad history





Re: Naperville

mrprksr <mrprksr@...>
 

Saying 3D parts are useless for freight cars ...you need to take a look at Seaboard Shops on the Shapeways site.....Several ACL and SAL pulp wood flats and chip cars.....I just got the AC L H1 chip hopper to build and while not cheap I'll put it up against a resin kit any day.....Larry Menn ie



On Tuesday, October 27, 2015 12:43 PM, "Ray Breyer rtbsvrr69@... [STMFC]" wrote:


 
Yes......"3-D parts are useless for freight car models -- at least for bodies"

Just like these useless bodies here:
https://nycshs.files.wordpress.com/2015/09/nycentralmodeler4th2015final1.pdf
(see pages 65 and 67)

But to be fair, Tom (and Tim) do have a very valid point: even after you overcome the technology's limitations and the problems with printing through Shapeways and come up with a good, usable print, it's still FAR cheaper to use the resulting car as a master for resin duplication (generally, by a factor of ten or so).

Now we just need to find more people who can do high quality casting in bulk.

Ray Breyer
Elgin, IL

--------------------------------------------
On Tue, 10/27/15, 'Bruce F. Smith' smithbf@... [STMFC] wrote:

Tim,

Perhaps you need to read Jack’s latest article in the current Model Railroad Hobbiest ;)
(Which also features Clark Propst’s LDE layout) While 3D printing is not for every car, it is my
experience that in fact it is hard enough, sandable, cutable and drillable.  No, it isn’t resin or styrene, and
it is a new medium that requires some adjustment of technique, but in fact cars can and are being made this way
that are very nice.  It may not be appropriate for every car (for example a smooth sided steel carbody might show
very fine build lines) but it a workable direct solution.

Regards
Bruce F. Smith  
         

On Oct 27, 2015, at 11:02 AM, Tim O'Connor
timboconnor@... [STMFC] wrote:

Jack

3-D parts are useless for freight car models -- at least for bodies -- the material lacks hardness and strength. It has to be sandable,
drillable, and cut-able. Tom has the right idea -- make MASTERS in 3-D, modify them as needed (e.g. adding rivet details), and then
make rubber molds from those. The final models are cast in urethane resin.



54341 - 54360 of 192652