Sharpening Cutting Sections

Cutting sections and punch edges break down over a period of time, resulting in part defects such as burrs, feeding problems, and safety issues, to name just a few. For this reason, these die sections and punch must be sharpened periodically.

• Use the right grinding wheel—Remember that when you grind tool steel sections such as D2, M4, and powdered metals, you actually are grinding small carbide pools (Fig. 1). Carbide is a very hard metal to cut. Use a wheel that breaks down and does not load up during the grinding process. Wheels that load up can cause excessive heat to build up in the die’s sections, resulting in softening, heat checking, or cracking of the die section or punch. Using flood coolant methods will help keep your die section as cool as possible. Think of your grinding wheel as millions of single-point cutting tools, like sand, held together by a bonding agent. Once the small granules of sand get dull, they must fall off the wheel. If they do not fall off, they will no longer cut smoothly and will begin to load up and burn the die section. 

There are just a few of the basic maintenance items that need to be addressed. Create your own list based on your needs, but be sure you’re setting a true die maintenance program and not a die repair program. 

Consult with your grinding provider to determine the best grinding wheel for your application. Keep in mind that there is no single miracle wheel that can be used for all tool steel and low-carbon applications.

• Grind the proper cutting shear. Angularity ground on the cutting sections helps to reduce the necessary cutting force and helps quiet down the die. The correct cutting shear also reduces the shock loading of the die and press, prolonging press and die life.
• Grind shear angles so the cutting action is balanced. This will help to maintain punch-to-button alignment and prevent excessive shifting of the piece part (Fig. 2).
• Grind your die section so that small, weak appendages enter the die last. This help prevent impact shocking and possible breakage of a small, weak cutting feature (Fig. 3).

Shimming Procedures

Shimming die sections be necessary to maintain the timing of each die station. Following are some guidelines for shimming:

• Avoid using multiple thin shims. An excessive number of thin shims placed under a die section creates a spongy die section, which may have a greater tendency to breathe and move. Use fewer, thicker shims instead.
• Make sure that there is sufficient clearance for screws, dowels, and slug drop holes. Inspect all pierce holes to make sure that there is no shim interference in the slug drop hole.
• Avoid shimming die sections crookedly and avoid shim overhang on die sections.
• Remove all burrs from your shims.
• Make sure all sections and shims are free from debris before mounting.

Cleaning and Inspection

Clean your dies regularly ad inspect them for loose dowels, screws, and ken springs. Following are some guidelines for die inspection:

• Look for loose fasteners. Check all screws to make sure that they are tight

• Look for missing dowel pins
• Look for broken springs
• Determine why the spring broke. If the springs are close to the end of their normal life cycle, replace them.
• Look for galled die sections.
• Inspect wear plates and cam surfaces. Regrind and fit as necessary.
• Lubricate all necessary mating die surfaces.
• Inspect the die to make sure all safety guards are in place.
• Clean all debris such as slugs, slivers, and lubricant buildup from the dies.
• Dry the die to ensure that it does not rust.
• Look for dulled, chipped, or cracked die sections and replace as needed.
• Make sure all cutting punches are secure in their retainers.

Technologies: Tooling

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