Experienced help with your tube fab and tooling needs
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Experienced help with your tube fab and tooling needs
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297 Tips and TricksWhile debugging, make only one adjustment to the set up at a time. Small adjustments are best. Keep track of the last position so you can go back if a change doesn't work. Proper lubrication in the right amount is important for good performance with mandrels and wiper dies. Establish bench marks for tool wear so that tools are not over-worn when removed for repair:
Establish a pre-shift check list on bender and tube condition, things like:
Playing with the neutral axis
Machine Features That Improve Productivity Multi Radius / Bend Die Stacking: Many manufacturers offer tube benders with the capacity for "stackable" tooling. More than one bend die set can be mounted on the machine. This allows an operator to set up and run a machine with different sets of compound clamp dies, more than one centerline radius, or more than one tube OD. Drop Away Clamp Die / Separate Swing Arm and Bend Die Return: Many CNC benders have drop away clamp dies as a standard feature. As the clamp die moves away from the bend die, it also travels in an arc downward below the plane of the tube groove in the bend die. This allows the swing arm of the machine to return after a bend without interfering with the tube as the carriage feeds it out for the next bend. An improvement on this is allowing the swing arm and the bend die to return after a bend at different times. Sometimes, with compound clamp sets, the tube gets captured between the compound cavity on the bend die and the clamp die if the amount of drop in the clamp die isn't sufficient. The only way to get it out is manually or by holding the bend die stationary while the swing arm return clears the clamp die out of the way. Boost On Pressure Die: Most newer machines are equipped with a pressure die boost cylinder. This is a servo or hydraulic cylinder mounted above the pressure die bolster so as to apply force to the pressure die in the direction of the bend. This is very useful for thin wall and/or tight radius bending. Pressure die boost tends to move the neutral plane away from the center of the bend, putting more of the tube into compression. The proper amount of boost will reduce wall thinning and collapse on the outside of the bend. Too much boost will cause wrinkles on the inside of the bend. The maximum amount of boost that can be applied to the tube is limited by the friction developed between the pressure die and the tube itself, more than that and the pressure die will slip past the tube. Most people set their boost so that the pressure die will just barely creep past the tube during the bend. Boost On Carriage: Some machines are equipped to apply force to the back end of the tube in the same direction as the bend. The boost is applied directly and positively to the tube from the collet at the carriage nose. This has the same effect as boosting the pressure die except that since the force is applied directly to the tube, much more force can be applied without the possibility of slippage. Extra Clearance Under the Bend Head: Most tube fabricators have faced a situation where they need a right and left handed machine to complete a particular bent part. This usually happens because of interference between the last bend and the machine head or some prior bend and the structure of the machine under the bend head. Tube bender manufacturers have responded to this problem with machines that have smaller bend heads, and/or no plumbing or structure under the bend head. These changes don't eliminate the problem, but they do reduce it significantly. Right Hand / Left Hand Capability: Some times there is no avoiding it, repositioning from bend "X" to bend "Y" requires rotating down into the bend head or machine interference. The only solution is to move the part to an opposite handed machine and continue to bend it. OR, several manufacturers offer machines with the built in capacity to make right AND left handed bends. This usually involves a second bend head and additional tooling - not an inexpensive option. Collet Recapture: When bends must be made close to the pull off end of the tube an additional problem occurs, the carriage nose can be hit by the pressure die or bolster as the tools close if the collet remains in position closed on the tube. To get around this problem many manufacturers offer "collet recapture" where the carriage / collet releases the tube and backs away after the clamp die is closed and before the pressure die closes. Once the carriage is clear, the pressure die can close and make the bend. When the bend is complete, the pressure die opens (not the clamp die though) and the carriage moves forward, and recaptures the tube in the collet. The carriage can then position the tube for the next or last bend. Swing Away Wiper Die: When tight radius bends, requiring a mandrel and wiper die, must be made close to the tube ends an additional problem occurs, the carriage end can hit the back of the wiper die. To get around this problem wiper dies can be mounted on a fixture which pivots on the same center as the bend die. When needed, the fixture and wiper dies swing away from the tube centerline keeping the wiper die tips in the tube groove. The carriage can then move right up to the bend die to position the tube for the next bend. Tooling Features That Reduce Difficulty:
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