It is no secret that CNC machining shops form the backbone of the mold making process, tool-and-die making and precision machining the world over. The same technology is available in Zurich or Hong Kong, the difference is how it is used.
When I was an injection mold making apprentice, in 1978, CNC milling was just entering the shop. Now, the bulk of the work in any modern machine shop is done this way. Personally, I do not miss the tedious, complicated setups required to machine compound angles, conical radii and adding draft to all the core features. What was once very time-consuming is now an everyday humdrum event, thanks to CNC machining centers.
Much of what is routinely done in CNC machine shops would have been extremely difficult in the not-so-distant past.
CNC Machining Shops Are Versatile
|Cores And Cavities
|Mold Base Work
A quick list would include insert pockets, the core and cavity pockets, interlock pockets, slide openings, many water-lines, ejector pin holes and counterbores, and much more.
Cores and cavities for plastic injection molds
The mold cores and cavities are roughed out and semi-finished with CNC machining, often at the steel supplier. Once in the shop they might be detailed in a 5 axis milling machine, CNC lathe, wire EDM, sinker EDM, CNC surface grinder or CNC gun drill.
Machining graphite and copper EDM electrodes
There are times when it is advantageous to manually machine a graphite or copper EDM electrode, but typically it is much faster to process these by CNC machining. Most molds are multi-cavity, thus requiring many identical electrodes, which presents the perfect CNC machining application. Also, cutting EDM copper is much easier with the flood coolant and high speed milling on a machining center.
Life before the VMC
Machining before CNC machining went very slowly. Operations that are taken for granted on a CNC mill were once very complicated to do on a manual machine. It is like the olden days to look back, sometimes with a touch of nostalgia.
Personally, I found it quite annoying that a setup on a manual machine could take an hour, and the actual cutting only a minute or two! It just didn’t seem fair! Many, many errors have just disappeared because of the positioning accuracy of these versatile machines.
CNC machining applications
There are numerous applications for CNC machining; ranging from micro machining parts so small you can’t believe it is possible, to gigantic aerospace components. I once applied for a mold making job at Boeing, only to discover they were making room sized molds for graphite aircraft wings.
What is the best CNC milling machine? That all depends on your application, obviously.
There are so many machine tool companies producing varying quality of machines that the choices seem endless.
You can get a very basic knee-type CNC milling machine quite reasonably. Many shops begin with such a small investment and build up from there. This is also a good way to gain experience, if that is lacking. These rather simple machines are actually capable of an amazing amount of work.
From there you can invest in a CNC bed type milling machine. These are much heavier, more rigid, and have a much greater capacity. They are more precise and come with automatic tool-changers to keep things running 24/7, if that is what you want. Many companies have worked with moldmakers to design VMC’s especially for moldmaking.