Gripflow is a metal stamping process developed in the United States by Edward Bennett in the late 1970’s. It has the ability to produce precise stampings with fully-sheared, straight-cut-edges and tight tolerances for the entire thickness of the part. The characteristics of the Gripflow stampings are similar to fineblanking, but what is different is the method and cost.
Unlike fineblanking, Gripflow tooling does not utilize an impingement ring (V-Ring) and the ram of the Gripflow hydraulic press is down-acting, similar to traditional blanking presses. The fineblanking press is typically a hydraulic, triple-action, up-acting press (the press piston is on the bottom and pushes upward).
Like that of traditional blanking, the Gripflow slugs drop through the bottom of the die and bolster. Fineblank tooling is not able to have an opening on its bottom (this would be the press ram) due to the press piston and hydraulics beneath the ram --- they must eject all slugs out with the stamped parts and, if any of these slugs stay within the tool, there is the possibility of tool damage.
The high quality of Gripflow stampings is achieved by the rigorous control of tolerances between and within the Gripflow tool and press... there is almost zero clearance between the Gripflow punch and die which leaves no room for error (punch & die clearance is the dimensional difference between the punch & die which is based on a percentage of the material thickness --- traditional tooling will normally have a punch & die clearance of 10% to 25% of the material thickness).
The design and manufacturing methods for Gripflow tooling are streamlined and efficient, as compared to its competitor’s cumbersome and antiquated design, which provides a tremendous cost savings --- Gripflow tooling typically cost 30% to 50% less than fineblank tooling.
The same is true with Gripflow presses --- their design is not as complex as that of fineblanking and so their cost is less than the fineblank presses. Because the fineblank V-Ring requires separate and additional tonnage (as much as 40% of the blanking tonnage), the fineblanking process necessitates more tonnage (larger presses) than Gripflow. Typically, Gripflow presses will cost 40% to 50% less than fineblank presses (less capital investment for Gripflow).
Gripflow is a hybrid metal stamping process that is an economical alternative to fineblanking and, at times, traditional stamping --- when post-secondary machining is required. The special combination of press and tooling creates stampings whereby many secondary operations can be eliminated, such as drilling, reaming, countersinking, counterboring, milling, straightening, shaving, hobbing, and broaching.
Gripflow can also produce holes smaller in diameter than the material thickness (at times piercing hole diameters as small as 35% of the material thickness) and thin web-sections, on occasion, making web-sections as small as 30% of the material thickness.
The typical Gripflow stamping is characterized by smooth, fully sheared, straight-cut-edges and consistent high accuracies (tolerances down to 0.0005” and part flatness to 0.001” per linear inch) allowing parts to be made to the print tolerances out of the die. The Gripflow process has excellent dimensional controls and repeatability throughout a production run providing stampings with improved quality and reduced costs.