Page 16 - MetalForming Magazine September 2022

Tooling by Design
Coin Location
Camber
Camber
into the die or during work on the strip, look for a few things.
First, verify that the straightener and feed unit have been maintained properly and are free from wear and damage. A bent or unevenly worn roll or a loose roll bearing can cause the roll(s) to tip in one direction. This causes uneven roll pressure across the width of the coil, which can induce camber in narrow materials and edge wave in wider coils.
Fig. 2—When coining to assist in running cambered coils, position the coin feature on the concave side of the camber. Adjust the coin depth until camber is minimized.
Fig. 3— Adding a half-round notch in the carrier between the pilots can help balance camber-inducing stresses in progressive- die operations.
pressure on the concave side of the coil to slightly elongate the edge and help reduce coil camber before the coil enters the feeder. This may work—assuming a feedline equipped with a roller leveler—on relatively thin coil strip, when incoming camber does not snake side to side, and on nar- row-width coil.
Unexpected Sources of Camber
When incoming coils fall within their specified camber limits, but camber appears or worsens as the material feeds
Some die operations cause the progressive-die strip to camber due to cutting stresses and the relieving of internal stresses in the strip—prevalent in strips that carry parts on one-sided carriers requiring large amounts of gutting or cutouts. Adding a half-round notch in the carrier between the pilots can help balance the stresses (Fig. 3). The notching station should be adjustable for the initial die tryout, enabling movement of the notch depth inboard or outboard to achieve the desired results. The station then can be doweled per- manently in place or left adjustable.
Another option for controlling stamping-induced camber: Add an adjustable coining station in the die that imparts a small chisel-point depression in the carrier (Fig. 4). This method proves useful in dies that run thin materials, such as those used to stamp electrical terminals.
Narrow, thin-gauge coils represent the most camber- prone materials. Incorrect packaging and storage of these coils also can induce camber, such as with several coils stacked vertically and banded together on a wooden pallet or skid. In production, the operator must lift the coils indi- vidually during coil changes, usually using coil separators between each coil. The separators must align properly. Mis- aligned separators and multi-skid stacks can cause coils to camber, even after a perfect slitting process. MF
Half-Round Notch
Stripper
Anvil
Locking Screw Adjustable Slide
Coin
Coin Insert
Fig. 4—Adding an adjustable coining station in the die can help control stamping-induced camber.
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Adjustable Location