Stamping dies

An auto industry story with a happy ending

It starts in 1956 and ends on Tuesday at 10:15, local time. In that time, auto industry veteran Kenneth Rooth has seen auto industry tooling go from wooden models and plaster molds to CAD manufacturing and efficient 21st century production.

But just when it seemed that engineering couldn’t get any more sophisticated, Kenneth teamed up with Sandvik Coromant to achieve a full 30% reduction of metalworking times on stamping dies.

History being made? Maybe. Money being saved? Definitely.

Automakers typically manufacture over a third of their stamping dies in-house. Making these tools is time-consuming and, with around 750 of them required to build a car, causes a major production bottleneck. Today, shorter lead-times, more models, and tight budgets have made this process even more critical.
Kenneth Rooth knew that much of this cutting and milling work was done by individual operators, with a lot of manual finishing – something that requires great skill and a great deal of time. The result was not only higher costs, but also lower standardization. The quality and fit of a right door could vary from a left door if two different operators were programming the machines.
Sandvik Coromant was given the job of finding a way to bring costs and lead-times down and quality up. Together, a new process was developed with new tools and machining processes. The results: machining times were cut by more than 30%, manual tool polishing was totally eliminated, and other manual machining was reduced considerably.

How did they do it?

First, high-speed steel drills were replaced with indexable inserts drills, a simple measure that gave a considerable boost in efficiency. Then, to improve machining efficiency of parts with long overhangs, silent tools replaced traditional tools and a number of templates were developed for future use.

Kenneth Rooth

Stamping die machining reinvented

Perhaps the biggest savings in machining stamping dies can be found in new methods for material removal. Here are a few examples of measures that helped make Kenneth Rooth a hero in cost cutting.

Round insert milling cutter instead of a ball nose cutter: lead-time savings in 3D roughing

A common rough machining method on 3D surfaces uses a ball nose cutter in a copy milling operation at varying depths of cut. In combination with long overhangs from the spindle nose, this puts excessive stress on the cutting tool and machine spindle.

By switching to a contouring tool path using a round insert cutter, a higher metal removal rate can be achieved by taking advantage of the larger number of effective teeth. A constant axial depth of cut gives a more even and constant load on the spindle, allowing process optimizations to be made.

Faster hole making on die shoes

Holes are traditionally drilled with high speed drills in cast iron die shoes. Since die shoes often contain lots of bolt holes, eyelet holes, etc., the total drilling time is usually long.

By replacing these drills with an indexable drill, such as the CoroDrill 880, huge productivity improvements can be achieved, even in dry machining.

Efficient hole making with plunge drilling in a trimming steel

Traditionally, these oval hole features are made with a high-speed steel drill and then widened with a milling cutter.

CoroDrill 880 replaces this combination by using an intermittent plunge drilling operation to widen the hole.

This method removes 85% of the material in a much shorter time, leaving the rest for a traditional round milling cutter.

Lifter feature

The standard method for lifter features is to make the hole with a high-speed steel drill, followed up by a solid milling cutter to open up the feature.

Instead, however, Sandvik Coromant chose to drill straight down with an indexable insert drill (CoroDrill 880) and then widen the slot with an indexable plunge cutter (CoroMill 210).

A highly efficient trochoidal milling method was then used to quickly remove as much material as possible, at high cutting depths and on the more narrow part of the slot.

Guide bush seats

An efficient and flexible way of machining seats for guide bushes is to use the CoroMill 300 round insert cutter, the CoroMill 390 long edge cutter, and the CoroBore 825 for finishing.

The CoroMill 300 is used initially for the facing operation, then for opening up the hole in a three-axis helical interpolation.

The CoroMill 390 LE machines the seat efficiently, thanks to its large depth of cut capability in combination with a light cutting action.

The finish tolerance is obtained with the CoroBore 825 precision boring tool. This process saves both time and inventory.

Typically, drilling tools, in combination with solid cutters, are used for this kind of feature at much lower productivity levels.

Machining of surface for safety bolts

Plunge milling with the CoroMill 210 can be an excellent alternative to a long-edge milling cutter when accessibility is reduced and a long overhang is required. Standard methods use a high-speed steel long-edge cutter.

The plunging method directs the forces in an axial direction, which is favorable from a vibration point of view when machining with long overhangs.

Taking advantage of the Coromant Capto system with its excellent stability and modularity makes it possible to optimize tool assembly.

CoroMill 300 in roughing 3D surfaces.

CoroDrill 880 in stamping die hole making.

Plunge drilling with the CoroDrill 880.

Trochoidal milling with the CoroMill Plura.

CoroMill 390 LE in guide bush machining.

CoroMill 210 in plunge milling.