United States sourced tube-bending production and tube fabrication for 500 to over 100,000 tubes annually can be bent using several different technologies. Each has its own economics but almost all utilize rotary draw bending although some utilize dedicated high volume benders for usages over 250,000 annual. This is used for furniture, equipment handles, lawn and garden carts, and machinery; exercise equipment, grab handles, chair legs, etc.
Rotary draw bending can be done in a CNC Bender or a rotary draw bender without CNC control. Both use a bend roll or die which forms the inside of the bend. A clamp in front of the bend die holds onto the tube and pulls the tube around the bend die. The tube is pushed into the bend die with the pressure die. To improve the perfection of the bend a wiper die is often placed behind the bend die. For tighter bends and thin wall tube a pressure die may also help push the tube into the bend.
Most commercial steel tubes with a centerline bend radius of 1.5 times the tube OD can be bent without a mandrel. i.e. inside bend radius equals tube OD. This is known as empty bending. Up to 15% flattening is allowed for this process. Whether done on a CNC bender, rotary bender or in a specially built dedicated bender, this is one of the most economical tube-bending production processes. Some tube fabricators can supply secondary operations to complete a tube or produce a complete tube fabrication. End forming is a complimentary process and is often used to reduce or swage a tube to allow a tube to fit inside a mating tube. Press work is required to flatten or pierce tubes to allow for holes and connections.
If volumes are very large a specially built tube-bending production machine can be built that can make many bends at the same time but up-front costs can be high while processing costs can be a fraction of those formed one bend at a time.
A bender with capacity from under ½” tube to 2” tubing is often used for his work. Exercise equipment like Arc Trainers, Stationary Bicycles, strength and gym equipment handles, lift bars, curl bars and grab bars are produced to very high quality. Lawn and garden spreader frames are also made with this process.
Designing parts for the most economical production requires a couple of considerations. Try to keep the bend radii all the same as this allows for bending without a change in bend tooling and in a single radius machine which is the most available capacity. Design bends at 2- 3 times the tube diameter for most economical processing. Try to allow a straight between each bend equal to one or two times the tube diameter. A compound bend is a bend running into another bend with no straight. It can be accommodated but special tooling is often required.
All bends are flat plane bends, spirals cannot be made on a rotary draw bender.
For professional tube-bending production and tube fabrication, contact Ever-Roll.