CNC Hole Making Without A Programmer
Speak of die machining, and most people think of the CNC milling used to arrive at a die's smoothly flowing form. But this is only part of the job. The typical die is an assembly of many machined parts, and some of those parts are simple enough that CNC may just get in the way.
Consider a progressive stamping die, for example. Building dies of this variety is one of the specialties of Brenner Tool, a 400-employee contract manufacturer based in Croydon, Pennsylvania. Each progressive stamping die includes not only a series of milled 3D forms, but also various interlocking plates. These plates feature milled-out 2D pockets and cavities, as well as numerous holes for components like jack screws, fastening screws, dowels and springs. And the need to machine all of these holes is what makes CNC problematic.
Brenner's shop runs a large quantity of these plates—about 40 per day. However, for the most part, this is a large quantity of one-off parts. The typical plate is a unique component designed for one particular die. That's why the shop has historically relied on toolmakers working at milling machines to make these parts, instead of using CNC machining centers. CNC would not have been effective because the one-off work offers no chance to amortize the work of a programmer creating each hole-making move in CAM software. In the time it would take the programmer to think his way through to the right tools and machining strategies for each hole, the toolmaker could perform this same thinking himself...and complete the part as he does so.
But now that obstacle to using CNC effectively has been overcome. Alert to the decline in the number of skilled toolmakers for hire, Brenner Tool has put in place a system that makes machining centers efficient for die plate work. The key was to skip the programmer.
That's not to say there's no CAM software; there is. However, in Brenner Tool's die plate machining area, CAM software will take on an increasingly less visible role. Here's how:
In the past, what made CNC prohibitively time-consuming was the need for a programmer to apply his machining knowledge during CAM programming. For each hole, the programmer had to select an appropriate series of tools—drill, tap and chamfer, for example—then have the software define the right moves for each of those tools.
But recently, the shop switched to CAM software that permits a different approach. Called PartMaker (from PartMaker Software, Fort Washington, Pennsylvania), this "knowledge-based" CAM software automates the programming of hole-making operations by storing and remembering the sequences that define how specific holes are machined. With the right sequences in place in its database, this software can generate an NC program for a complex series of holes automatically, requiring the "programmer" to do no more than identify the holes using a small number of mouse clicks.