How are model kits designed / manufactured?

[shaunmza]

So I get that plactics kits are done using injection molding machines, I am wondering if anyone has insights as to how it gets to that point?

Do car manufacturers send CAD files to model companies? Do the model companies re-draw everything in a CAD/CAM program? Do they build a mock of it and do 3d scanning?

Would appreciate insights!

[Modelbuilder Mark]

Correct,  most are now CAD. you can see some of the in progress cad work of the new Moebius Ranger pickups here on the forum.  A couple years ago when they were announced there was a lot of shared information in advance. 

They used to make/carve wood bucks and then use a machine where the manufacture would run one arm across the buck,  then another work copy that in the correct scale to create the mold. There are pics and video out there on the web,  but I have not seem them in a long time. 

[Luc Janssens]

Some interesting info here...

[Ace-Garageguy]

Some interesting info here...

Acceptable article, but full of inaccuracies and severely math-challenged. The author's equating the 2000 PSI injection-pressure with the "weight of 400 compact cars" means absolutely nothing. The description of alignment pins for two halves of the mold as "steel support rods (that) keep the steel mold for [sic] warping as plastic explodes into the channels" is wrong. The '30 Ford on the CAD monitor screen is incorrectly identified as Revell's '29. Later there's the .003" written-out by the author as "one three-thousandths of an inch" (it's actually three one-thousandths of an inch...an ENTIRELY different number). And then comes a biggie. The industry is described as being "uniquely American", which we all know is not right...at all. Anybody remember seeing kits from Japan? England? Western Europe? Russia? Czechoslovakia? 

Rowlett is also quoted as saying (referring to the ability of Americans to cut tooling) "We no longer have those types of skill sets in the States". That's just flat out incorrect. The problem is that the Americans who can do it also think they should be paid well for highly specialized work. Go figure.

The article also fails to explain that 3D-printed first-generation "test-shots" are part of many manufacturer's processes now, or the fact that metal tools have to be actually cut to get to the later test-shot phases.

So many factual errors and omissions (I quit counting at that point) in a single article are unacceptable, so when you read it, even though it's an OK general overview, be sure to have your internal BS detector switch in the ON position.

The author says he'd like to see a scale model of Lady Gaga wearing a meat-dress, so I guess you just have to consider the source sometimes. 

Edited September 11, 2016 by Ace-Garageguy

[Art Anderson]

Ace, the art and science of injection-molding plastic did have its beginning here in the US, way back in the 1930's, and the start of the plastic model kit industry was here as well, with injection-molded detail parts being included in otherwise wood and card-stock model car kits shortly after WW-II, so in a very real way, it began as a uniquely American thing.

Now, as for test shots of model kits being done by 3D printing, that is not true at all.  When we see a 3D printed version of a model kit, that is what is called a "tooling mockup" which is not unlike the old hand-carved 1:10 scale mockups that used to be used as patterns to be reduced with a 3-axis milling pantograph when creating the actual steel tooling.  Today, with everything about model kit tooling being done in CAD, the same CAD files that will ultimately be used to cut steel can be used in to create a 3D printed set of parts, which mockups are then sent to the person(s) responsible for checking out the correctness and accuracy of the model kit itself, BEFORE any tooling begins.  As such, the 3D tooling mockups are done 1:1 with the scale of the final model kit.  Test shots, on the other hand, are literally the plastic kits themselves, being molded from tooling that while basically done, has yet to be approved, the tooling polished, hardened to be ready for mass production.

Even the process of cutting the steel tooling is no longer one of a toolmaker moving the stylus of a 3-axis pantograph mill over and over again, on the tooling mockup of the actual mold (which used to be done in wood and resin in 1:10 scale, to be reduced to 1:25 scale in blocks of steel--today that is all CAM (Computer Aided Machining) and virtually no rotary cutters are used--it's almost ALL done by EDM (Electro-Discharge Milling), controlled by the final-approved CAD files.

As for all the reference work going into such projects--that does involve a ton of human input--the soon-to-be-available '65 Comet Cyclone came about from several hundred photo's of a real car, with only perhaps a dozen pics showing the complete car--the VAST majority of those hundreds of pics were taken of small areas of the car in question, many as closeups with a measuring tape, even a common, ordinary ruler in the picture to illustrate the important dimensions of that area of the body shell, as well as the even smaller details needed to be reproduced, such as scripts, badging, and the like.  Such simple techniques as photographing, with measuring instruments in the scene, of the edge of an open door happen, to get the curvatures of the side of a body.  It's not simply a matter of shooting a few pics, and somehow magically have a perfectly scaled model kit magically appear with a few keystrokes.

Art

 

[Ace-Garageguy]

... it began as a uniquely American thing.

...Now, as for test shots of model kits being done by 3D printing, that is not true at all....

Just semantics, really. The operative word here is "began".

And semantics again concerning what I referred to as "first generation" 3D-printed "test-shots". The production-scale 3D-models, when they're even made, are made BEFORE any tool steel is cut and have a function very similar to later-phase test-shots pulled from pre-production-ready tooling. They are, as I noted, production-scale positives, used to evaluate part fit and fidelity of the scale model  to the original BEFORE any tooling is cut.

So they technically aren't "tooling mockups" either, but production-scale pre-tooling design-evaluation models. 

Otherwise, we're in complete and total agreement.  

[CometMan]

Since promo models have long since disappeared as a demonstration tool for the salesmen at the dealerships, I wonder how much, if at all, the auto manufacturers get involved with the model companies? Or, do the model companies simply wait until a car is available to them to start their work?