Frequently Asked Questions (FAQ) About the Tube ...

1. What Makes Material Selection Essential?

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When selecting tubing for your project, keep in mind that opting for the lowest price may lead to compromised quality. Bending subpar tube or pipe can result in inferior bends, increased scrap rates, and potential failures. Even state-of-the-art machinery cannot compensate for inferior tube materials.

The quality of the material determines the tooling options and its composition; hence, ensure that the tooling aligns with your material specifications to avoid conflicts. For instance, utilizing stainless tube with a steel counter bend die may lead to issues.

When deciding on the right material for your project, factors to consider include strength requirements, visual quality, and centerline radius specifications. Request material specifications from your steel supplier to confirm its suitability for bending applications.

2. Can You Explain Rotary Draw Bending?

A rotary draw bend is made by pulling the workpiece around a rotating bend former. The leading edge of the material is secured to the bend forming die, while the material is situated between the die groove and the counter bend or pressure die. The bending die rotates to the specified angle to complete the bend.

This process can vary in cost ranging from economical to quite pricey, hence its applicability largely depends on your project needs and financial plan.

3. Understanding Centerline Radius

Centerline radius (CLR) is frequently mistaken for bend angle. CLR refers to the distance from the center of the forming die to the centerline of the material being bent. This detail is often ignored but is essential for achieving high-quality bends.

Several factors influence the CLR, including the grade of material, wall thickness, the bender's type, the intended application, and desired appearance. Generally, precise CLR measurements lead to aesthetically pleasing and high-quality bends.

It’s important to note that bending materials to a CLR less than double the material’s diameter requires the use of a mandrel to prevent collapse. Thus, rotary draw mandrel bending often entails higher costs for machinery and tooling compared to non-mandrel approaches. Therefore, be diligent when assessing CLR during the design phase and factor in manufacturing costs.

4. What Is the Maximum Bend Angles Achievable?

This query may sound straightforward; however, it can become complex without blueprints for reference while trying to replicate components using sample pieces.

Typically, rotary draw bending tools are designed for a maximum bend angle of 180 degrees. When choosing a bending machine, ensure the programming permits slight overbending to account for springback effects during the bending cycle. Opting for a machine with programmable bend angle settings enhances accuracy and usability.

The degree of bend significantly impacts the quality of the bend. When experimenting with new materials, conduct two test bends, one at 45 degrees and another at 180 degrees. Variations in results may occur, as larger bend angles can lead to more wall thinning and deformation.

5. What Is Springback?

Springback is the tendency of materials to revert slightly after bending due to the release of pressure from the counterbend die. This phenomenon means that materials are often overbent slightly during the bending cycle to counter this effect.

The extent of springback is affected by factors such as the material's tensile strength, the degree of the bend, and the CLS of the forming die.

Higher-end bending machines often enable operators to adjust for springback in each bend across the sequence.

6. Why Should Minimum Bend Distances Matter?

Rotary bending tooling necessitates a straight section of material to ensure that the workpiece is securely clamped, preventing movement during the bending process. Applications should always review the shortest distance between bends, and tooling should ideally be designed to accommodate this.

More economical bending machines may not achieve the required distance, possibly necessitating cutting and welding of the workpiece post-bend to reach the necessary space between bends.

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7. How Many Bends Can Be Produced?

The productivity requirements can vary significantly, whether in a job shop setting or a high-production environment. The actual time taken for each bend often becomes minor compared to the overall cycle time.

For a realistic assessment, account for the following aspects: operator expertise, material loading and unloading, positioning time between bends, machine speed and features, and any secondary processes like cutting, deburring, or welding. Set practical productivity targets and choose a bending machine that meets your required duty cycle.

8. What Type of Tooling Is Necessary?

Rotary draw bending tooling shows a wide variance in quality, availability, and cost among manufacturers. Trusted manufacturers are usually ready to discuss your tooling needs and provide suggestions on the most suitable options.

Standard tooling is generally more economical, so adjusting your part's CLR slightly to fit stock tooling could save considerable time and money.

Specialty tooling often requires upfront payment. If your job demands unique tooling, prepare for increased costs and longer lead times. It’s wise to provide a material sample and an application print with the special tooling order to avoid misunderstandings.

9. What Bender Suits My Workshop Needs?

This can be a challenging selection process, as no single bending machine fits all operators. When choosing a bending machine, reflect on the aspects covered in this article prior to purchase. Consider potential future requirements as well; selecting a low-cost machine now could become more expensive later as new applications arise.

Other factors include the machine's versatility, features, tooling options, parts availability, and access to qualified support in your local area.

Essential Bend Terminology

CLR - centerline radius, the distance from the center of the forming die to the tube's centerline.

DOB - degree of bend, denoting the bend angle.

Sch. - Schedule, representing the wall thickness of the pipe.

Ga. - Gauge, indicating the wall thickness of the tube.

O.D. - outside diameter, the measurement of the tube.

I.D. - inside diameter, the measurement of the pipe.

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