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Toolmaker meets material, tolerance challenges with CNC technology

CNC grinding machine helps achieve consistent, quality results

Situation

Bridge Tool & Die, Buckley, Mich., was experiencing industry pressure to increase die life and to lower costs. The company had been increasingly using carbide grades and ceramics and tighter tolerances to meet this demand. However, this shift of materials and tighter tolerances created the need to improve its machining techniques.

Carbide is an extremely hard material to grind. It requires diamond grinding wheels and more finesse in terms of speeds, feeds, and material removal rates.

The tool and die shop relied on manual grinders and experienced machinists to roll radius and blends to print specifications manually. Manual grinding is somewhat of an individual operation because machinists rely on feel and noise in grinding the dies. Although not consistent or repeatable, this approach had worked well enough with standard tooling materials and tolerancing.

As the tooling tolerancing tightened up and materials became harder, it became more difficult for Bridge Tool & Die’s toolmakers to hit the mark and maintain consistency from order to order and part to part using manual grinders.

The company sought technology that would resolve these challenges.

Resolution

Bridge Tool & Die invested in precision CNC technology to improve its ability to grind the harder tooling materials with greater precision and repeatability.

The CNC technology it invested in was a Studer CT960, which includes software that allows the programmer and operator to visually define the grinding parameters while building the program. Alternatively, the user can import a DXF file of the tool or die. Then, the areas to be ground are defined and process parameters are added.

Next the machine can simulate the grinding, using wheels from the database the company has developed over time. This ensures that the tool- and diemaker grinds to the designed profile features off the print.

The process has proven to be repeatable and accurate. The machine employs glass scales for absolute positioning accuracy, and a rotating diamond dresser ensures that the wheel geometry is accurate and compensated for in the grinding program.

To further enhance the productivity, an automated, calibrated probe locates the die component’s face and measures the radius. Locating the face is essential to verifying that all of the internal geometries tie back to the front face of the part. The calibrated probe can measure the ID and assess whether the die component is complete or if it requires an additional finish pass. This prevents the operator from having to worry about removing and then attaining clamp repeatability.

Using a coordinate measuring machine, the company compared the components it machined using a CNC and its previous method and found the smoothness and accuracy of the grinds to be better than manual grinding.

Using CNC technology, Bridge Tool & Die has been able to expand its market opportunities and materials. It can now offer complete grinding services for the manufacture of carbide tooling for deep drawing, can, extrusion, cold heading, and end forming applications.

Studer, www.studer.com