I was building some freight cars today and it raised my curiosity again, so I’ll ask. Same question arises on styrene structure kits. The question: how do they create such detail? I was building Accurail & Bowser freight cars (recent manufacture) and have built structure kits such as Cornerstone, Woodland Scenics DPM, etc. I’m amazed at the extent of detail and wonder how they do it, especially since it’s 3 dimensional. If different from when I was first in the hobby in the 60’s, how did they do it then (even an old Athearn BB kit ain’t so bad)? Surely someone does not hand carve a mold???
Anyway, I’m impressed by the current models and also wonder how they did it in the “old” days (i.e., with less computing power if that’s the key today). Sorry if it’s an old topic, but I’m curious!
I was at an N scale layout today where the guy showed me vehicles that were made on 3D – for lack of a better word – printers. There will be more of this. Imagine being able to email a vehicle to a friend. The technology is here now. Already I know guys who have their own laser cutters.
These days there is technology which can reduce drawings on a computer (where you can cut and paste and copy and duplicate) to dies and molds.
But back in the day – the earliest Blue Box, and the Revell structures, and so on – yes there was a lot of hand work involved. Highly skilled artisans. For that matter, consider the Lionel NYC Hudson of the mid 1930s.
If you can find older MRs that have the O scale freight cars of Bill Clouser who did all his own work on molds from which resin castings were made. Astounding detail then or now.
Not exactly hand carved, they did use power tools. Nodays though, it’s likely made on some sort of CNC machine, so someone draws it with a CAD program, converts it to machine tool code with a CAM program, and off it goes. Depending on the shape and complexity of the dies, they may be cut with electrical discharge machining instead of physical grinding and milling.
High pressure plastic is quite good at filling all the little details, as long as proper reliefs and flow paths are maintained.
Smaller production items may very well be hand done - master model scratch built and a mold taken from that to produce the kit parts.
Plastics have changed a lot also in the past 50 years. The plastic handrails and brake rigging we have today, if produced in the plastics of yesteryear, would have been too fragile to last through the installation process. They probably could not be pumped into the fine molds either.
But you do have to admire the craftsmanship of some of the old mold makers who didn’t have computer aided tooling. I think many of those original molds are still in use, maybe new versions of the original mold.
For example, I recall reading at some point that the old Varney HO scale molds wound up at the company that made Life-Like trains. I compared my original Varney caboose shell from 1958 to a Life-Like caboose shell from maybe 20 years ago and it was identical. When I look at pictures on the internet of Life-Like cabooses - now made by Walthers - it still looks like it’s still the same body. That’s more years in service than the USS Enterprise!
Basically you use lathes, milling machines and drill presses to cut the reverse image of the part into steel plates, one for the front of the part/sprue and one for the back. Its called “machining” and was done by machinists. The same technology was used to make all sorts of things.
Once the molds are cut, the steel plates are clamped together and molten plastic is injected into the molds at high pressure. After the plastic solidifies the molds are separated and the plastic part is ejected.
Modern CNC machines automate the actual cutting/milling process for the steel plates.
Model making has also improved. Every model starts as some kind of idea (let’s make an XXX". Then someone does the research, gets basic measurements and this is usually translated into a master model. Traditionally the master might be considerably larger sized than the finished item. They used to be pantographed down - a mechanical scaling process. Now it’s done via computer. With modern CAD drawings supporting CNC and other automated tooling I don’t even know if they do “master models” anymore.
A big improvement is in research. Back in the days of Varney and Irv Athearn there were “boxcars”, now we have researchers that can tell us that the car is an ACF design with 10-panel sides made in 1953. Basic research and translating drawing led to rather egregious errors, like the Athearn boxcar/reefer/stock car having their underframe brake gear “mirrored”, or the Athearn stock car having the roof panels in inverse arranngement. Both of those were from working from a traditional freight car drawing that looked “down” through the car, not up at the bottom. We have far fewer such silly mistakes these days (some things get through). With better research comes the fidelity of detail that we now take for granted.
So a multi-layered process that runs from the library and camera to the CAD drawing to the mold maker to checking test models for errors, on to marketing and sales.
Molds are comonly machined as was mentioned earlier. Finer details though are EDM machined. This is a process of burning the cavity with electrical current. Commonly called sinking the mold. This EDM process uses a carbom “plug” machined to match the part being made. This is then burned into the cavity using a high current electric charge. Once the cavities are don, a machinist then goes into the mold cavitied with small polishing burrs and buffs to clean up the mold. After this is done the cavity blocks are mounted in a mold block (2 halvs) and alligned to properly match up. Any undercut details have to have a core pull component built into the cavity. Now-a-days most model molds are made from aluminum as it is easier to build. Unfortunaly the life expectancy of these tools is considerably shorter than their steel counterparts.
Here is a link to a youtube vid of some EDM work being done