Exploring Cost-Saving Measures in Tube Bending Tooling

TL;DR: We experimented with using 1.25-inch tooling to bend a 1.5-inch steel tube, aiming to save on tooling costs (which can reach $15-20k per size). At a 6-inch radius, the collet couldn't grip the tube, so bending wasn't possible. At a 3-inch radius, the tube collapsed during a 90-degree bend, suggesting a mandrel might prevent this but was untested. Ultimately, while mandrels might allow low-angle bends with mismatched tooling, scaling operations likely require the correct, size-specific tooling for reliable, quality results.

Introduction

In metal fabrication, tube bending is a precise art and science, where accuracy in tooling plays a critical role. Traditionally, tooling for each unique tube size requires a significant financial investment—often ranging from $15,000 to $20,000 per tube size. This necessity for bespoke tooling has motivated fabricators to explore potential cost-saving measures. In this study, we hypothesized that tooling for similar-sized tubes could potentially be cross-utilized, which, if successful, could lower costs associated with tooling acquisition. Here, we present our methods, findings, and recommendations based on an experiment using 1.25-inch tooling on a 1.5-inch tube.

Experiment Setup and Objectives

The objective of this experiment was to determine if tooling designed for a 1.25-inch outer diameter (OD) pipe (1.66 inches OD in actuality) could be used effectively on a slightly smaller tube size of 1.5 inches OD. The specific focus was on assessing whether the existing collet could securely grip the tube and, if so, whether the tube could be bent effectively without structural collapse or significant deformation. We conducted tests at two different bending radii: a 6-inch radius and a smaller 3-inch radius.

Methodology

1. Bending at a 6-Inch Radius:
   Initially, we attempted to bend the 1.5-inch OD tube at a 6-inch radius using a standard collet designed for the 1.25-inch pipe. The collet failed to establish an adequate grip on the tube, making it impossible to initiate a bend. This suggested a fundamental limitation in using the oversized tooling, as proper grip is critical in initiating controlled bending.

2. Bending at a 3-Inch Radius:
   Next, we attempted a 3-inch radius bend using a smaller bend die, opting for a 90-degree angle as a preliminary test. While we achieved partial bending, the material collapsed under pressure. This outcome highlighted a potential issue with structural integrity when using undersized tooling for larger tubes, especially at tighter radii.

Discussion of Results and Observations

The inability to secure the tube at the 6-inch radius underscored the importance of precision in collet fitment. Tooling that is marginally too large may not adequately grip the tube, leading to slippage or failure to initiate bending. In the 3-inch radius bend, material collapse suggests that for tubes at this size, structural support from a mandrel might be necessary. Mandrels are inserted inside tubes during bending to prevent flattening or buckling, and we hypothesize that using one might prevent collapse during tighter bends, although this remains untested for this tube size.

These findings indicate that while slight deviations in tooling size may be feasible for small angles or less demanding applications, achieving precise, high-quality bends may require tooling that is specifically tailored to the tube diameter. For critical applications, in

vesting in the correct tooling remains a sound practice to ensure safety, accuracy, and consistency.

Final Insights and Practical Recommendations

This experiment demonstrates the limitations of using oversized tooling on slightly smaller tubes and provides insights into potential cost-saving measures:

1. Mandrel Use: For bends at or under 90 degrees, a mandrel might offer enough internal support to prevent collapse, especially with smaller radii.
2. Right Tooling for Scale: For consistent, scalable results, investing in tooling that matches the exact tube size is recommended. While initial tooling costs are high, they ensure quality outcomes, reduce rework, and provide reliability in performance.

Conclusion

Although cross-utilizing tooling sizes may seem appealing for cost reduction, our findings suggest that proper tooling remains essential for achieving high-quality bends in tube manufacturing. This experiment underscores that while mandrels may help alleviate some issues for lower-angle bends, the best practice for scalability and quality is to invest in size-specific tooling.