Tube bending is a vital tool for industrial design. It is critical to consider the limits of tube benders and the information the technician requires. To avoid the need for reengineering, new tooling or equipment costs requires planning. Below are the common considerations to keep in mind to make your project manufacturable.
1. Space Between Bends
One of the most common oversights in custom tube bending is not leaving enough room between the end of one bend and start of the next bend. A CNC tube bender uses a clamp to secure the tubing for bending. If bends are too close together there’s no room for the clamps. At Seaborn we recommend you leave at least 3.5” – 90mm between the end of one and start of the next bend This is a common clamp size for tube benders.
2. Design Using Stock Tube Bender Dies
To avoid tooling costs, and increased lead times it is recommended to create your design with bend radius your tube bender of choice has. Seaborn Manufacturing can provide you with a complete list of our stock bender tooling. Custom tooling especially for small runs can be prohibitive costing $3-5,000 USD. The use of stock tooling for your custom tube bending is faster to market also.
3. Minimum Bend Radius Limit
Every tube material, shape and size has a minimum bend radius that can not be reduced. Attempting to bend tighter just ends in significant deformation and torn tubes. Custom tube bending still requires designs that do not surpass the material limits.
4. Bending Square Tubes
The flat walls of square make them far more vulnerable to distortion, especially on a small radius. Custom tube bending projects that need to maintain the tube’s structural integrity and visual appeal need an adequate radius. Square tube will tear sooner than round.
5. Preventing Tube Collision with the Bender
Common challenge with custom tube bending is avoiding collision with the tube bender and floor. When tubes have multiple bends and bend plains (reorientation of the tube) the chances of collisions increase. There is machine to consider and even the distance to the floor. CNC tube benders have to bend end to end sequentially from one end to the other. Tube benders can not bend tubes so their ends meet. Seaborn Manufacturing can look at your deign and offer work arounds if required.
6. Holes and Feature Near Bends
Holes and cutouts in or close to the bend area can become distorted during tube bending from the material stretching. If holes need to be placed near a bend, additional allowances should be made for distortion. It is possible to add the holes after tube bending but this requires more steps. Planning ahead can minimize the need for secondary operations.
7. Lead and Tail Sections to Avoid Trimming
To avoid post forming trimming, tube designs should incorporate lead and tail sections. These sections need to extend beyond the bend area, ideally at least 3.5 times tube diameter. This allows the bender to operate and reduces tube deformation. Material can be trimmed off after bending when required but adds cost and material losses.
8. Communicating the Required Information
Key bending parameters:
- Bend angle: The angle at which the tube is to be bent to.
- Bend radius: The centerline radius of the bend.
- Orientation angle between bends: The rotational relationship between bends.
- Distance between bends: The linear distance from the end of a bend to start of next, not the distance to the radius centers.
This is the information required for tube bending.
9. Tube Length Limits
Most CNC tube benders have a maximum tube length capacity, typically around 10 feet. Longer tubes may not fit within the machine’s working area. Part of the tube before the first bend may over hang the machine. For example if there are two feet straight before the first bend starts the 10ft capacity tube bender can bend the 12ft tube.
10. Number of Bend Radii in a Tube
CNC tube benders use hard fixed radius tooling. Designs using multiple radii need advanced tube benders like Seaborn’s double stack bender which permit you to use two radii. These tools need to be made to work together even on a multi stack bender.
Summary
These are the most common design considerations custom tube bending has and Seaborn Manufacturing can help you navigate them. Planning ahead makes tube bending a viable and cost-effective option.