The Solution
A slightly more detailed description of the process will more fully explain how the unique features of the Haven Dual-Blade Shear recut machine deliver the advantages and benefits for which Haven is well known. The dual-blade shear process usually begins with an automatic tube loader / unscrambler or a similar mechanical escapement device that lowers tubes individually onto a series of powered V-rollers. The tube is then advanced to a 4-roll variable speed drive system which uses proportional controls to drive the tube into the target stop assembly to insure precise cut control. Once inside the drive system, the tube is rapidly accelerated to the target (which, when depressed, signals the tube clamping dies to close) at high speed and then quickly decelerates to a pre-programmed constant speed to depress the target finger. When setting up for a new production run requiring different cut lengths, Haven's target mechanism uses a motorized lead screw to adjust the length of the cut parts to enable rapid changeover.

The clamping die, which is specifically designed and manufactured for the required tube shape, holds the tube securely to prevent damage to the tube and to maintain close length tolerance. Once the tube is secured within the die clamping area, hydraulics with a dual acting cylinder provides the die clamping function and a separate cylinder controls the stroke for the cutting motion. This unique system uses low pressure to cut thinner wall tubes and shifts to higher pressure when required for tubes with greater wall thickness. Because dual-blade shear tube cutting is a 2-stage process, a mechanical linkage is used to keep the horizontal blade clear of the vertical blade. First, the horizontal cut removes some of the outer material of the tube (penetrating almost, but not quite, the thickness of the tube wall) to prevent the downward pressure of the vertical cut from distorting the roundness of the tube. Then, the vertical blade parts the tube by entering through the scarf on top and shearing the tube clean - the vertical blade basically collapses the tube wall material onto itself and the continuing downward pressure pushes the tube wall material until it clears the tube. This process results in minimal burr and, contrary to rotary saw cuts, leaves no residue of metal filings that must be manually or mechanically removed. After the cut, the clamping die opens and the feed rolls advance the mill length tube, ejecting the cut part and then depressing the target finger for another cycle. Haven's Dual-Blade Shear control system relies on internationally recognized machine control technologies and is easy to setup and operate. The menus are intuitive and commands can be executed or programmed by following a logical series of operations using a touch screen display. The machine includes controls for performing a trim cut on the front end of each mill length tube and scrap separator for trim (crop) and tail (scrap) pieces. This feature allows the tube manufacturer to maximize yield from every tube.

Benefits and Future
The Haven Dual-Blade Shear Recut machine is capable of achieving impressive cycle times - depending on tube diameter and cut length, volume can exceed 4,000 cycles per hour (less than 1 second per cut). And, because the dual-blade shear cut is so clean, no secondary washing operation to remove metal filings is necessary and minimal end-finishing, if any, will be required. In addition, Haven machines enjoy an international reputation for reliability - they have the highest uptime of any competitive system. When combined with their fast service time, they have the highest availability in the industry and the lowest TCO.

Because changeover is very simple (often only a few minutes), tube manufacturers who use Haven's Dual-Blade Shear recut machines can quickly reconfigure their systems and minimize idle time. This means they can now accept small quantity orders with short runs that previously they had to turn down simply because they were not profitable at the prices they were constrained to charge. And, this means not only increased revenue, but more importantly, keeping existing customers whose requirements are now more demanding as well as winning new customers from competitors who can not satisfy their customer's challenging requirements.