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Aerospace Applications

Hot Bending - Aircraft

Aviation parts suppliers are often called upon to bend parts of unusual alloys. Some of these cannot be bent in a cold condition.

Pines offers a custom heated tool package to allow bending of these materials. The bend die, pressure die, mandrel and wiper die may all need to be heated depending upon the application.

During operation the dies are electrically pre-heated to the desired temperature (usually between 400 and 650 degrees F). Temperature sensors maintain the correct desired temperature for each tool separately. The tube is positioned in the bender and the dies are closed. The heat is allowed to penetrate the tube for a prescribed period of time and the bend is started. Once the bend is complete the hot part is carefully removed and allowed to cool gradually to room temperature. The bender is immediately ready to bend another part.

Several machine modifications are required to successfully bend this application. The ending machine must have similar options as required for thin walled tight radius bending. In addition the machine needs to modified to handle the heat transferred from the hot bend tooling into the machine. Too much heat transfer will lead to premature bearing failures and component wear. Pines Engineering supplies a water cooling package for the bender when hot tooling is required. (A closed loop cooling system can also be provided to reduce water consumption.)

Hot bending can be added to virtually any Pines Engineering NC or CNC bender.

Tight Radius Bending – Aircraft

The aircraft industry uses a wide variety of tubular material in their products. Tubing is used for seat frames, hydraulic and fuel lines, cabin air ducting, and engine exhaust to name a few. Aircraft design often limits the space available for these so many parts are designed around tight bend radii. Weight is a major concern in aircraft design so tubular products are designed with the thinnest wall possible.

Several machine options are usually required for bending this type of application. A long stroke Mandrel extractor is required when bending thin wall tube to prevent it from collapsing. The thinner the material the more mandrel balls are required to keep the tube round in the bend area. Automatic mandrel lubrication ensures the proper amount of lubrication between the mandrel and the material being bent.

Too little lube and the tube will tear, too much and you may put wrinkles in the bend area. A wiper die is almost always required to prevent wrinkles from forming on the inside of the bend so a Wiper Die Holder is required. A Pressure Die Assist provides a forward force on the outside of the tube during bending. This helps reduce the drag caused by the mandrel and wiper dies. A Direct Acting Pressure Die may also be required.

A direct acting pressure die mounts the hydraulic cylinder (that opens or closes the pressure die) directly inline with the tube centerline. During bending the machine controls the hydraulic pressure in the cylinder and thus the force applied to the tube. As the bend progresses minor variations in the tube OD, wall thickness, and bend die concentricity will move the tube surface towards or away from the pressure die. A direct acting pressure die can “float” in either direction and maintain the correct force during the bend. Since large clamping forces are usually required, an Overhead Tie bar can be used to reduce the deflection of the bend die.

Bending thin wall tube to a tight radius requires a rigid tool mounting surface to hold the dies in proper alignment throughout the bend. If the dies tip or twist wrinkles can form on the inside of the bend or the material can even tear. The bending machine must be mechanically strong and rigid to contain the tooling forces required to make the high quality bends expected in the aircraft industry.

The Pines NC tube bender line is built to withstand these forces. Because of this Pines benders are the industry standard for bending tight radius, thin walled parts.

CNC machines are used in some applications in the aircraft industry as well. These machines must have the same strength and rigidity to ensure high quality parts. The Pines CNC line is derived directly from the popular NC line and features the same strength, and rigidity. And, of course, all the necessary machine options are available on the CNC line of tube benders.

Commonly used bender sizes in this industry

NC #1, #2, #4
CNC 040, 075, 150


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