Measuring tubing for bending requires careful calculations to ensure accuracy and prevent material waste. The key factors to consider include bend radius, bend angle, and material elongation. Here’s a step-by-step guide:
Step 1: Identify Key Parameters
Outside Diameter (OD) – Measure the external width of the tube using calipers.
Wall Thickness – Use calipers or a micrometer to determine the thickness of the tubing.
Bend Radius (CLR - Centerline Radius) – This is the distance from the center of the bend to the centerline of the tubing.
Bend Angle – The degree to which the tube needs to be bent.
Material Type – Different materials have different elongation properties, which affect bending calculations.
Step 2: Calculate the Bend Allowance
To determine how much tubing is required for the bend, you need to calculate the bend allowance (BA):
BA=(π/180)×(BendAngle)×(BendRadius)
Step 3: Calculate the Stretch Factor (K-Factor)
When bending, the outer side of the tube stretches while the inner side compresses. The Neutral Axis Shift must be considered. The K-Factor is typically 0.446 for standard tubing but varies based on material.
Step 4: Measure the Total Tubing Length
To measure the required tube length before bending, sum up:
The straight sections
The bend allowances
TotalLength=(StraightLength1)+(BendAllowance)+(StraightLength2)
Step 5: Mark the Tube
Use a tube bending template or layout drawing to mark where each bend starts.
Measure and mark the tangent points, which indicate where the bend begins and ends.
Step 6: Consider Springback
After bending, the tube may slightly spring back. The amount depends on the material and bending method. To compensate:
For steel, over-bend by 1-3 degrees.
For softer materials like aluminum, over-bend by 2-5 degrees.
Step 7: Use a Tube Bender
Set up the tube bender to match the calculated bend radius and angle. Secure the tube and carefully bend along the marked points.
By following these steps, you can accurately measure tubing for bending while minimizing errors and material waste.
