APHS-31120-large-revisedBottom bending is a delicate art requiring precise calculations and careful handling. Adding aluminum to the mix – a material prone to fracturing – makes it even more challenging. But bottom bending can bring rewards. When done correctly, it helps operators increase production by stabilizing the bend angle, resulting in fewer angle and dimensional variations and errors.

Check out these seven tips for successfully bottom bending aluminum with your press brake:

1.     Be Aware of the Aluminum’s Grade

The general rule of thumb when bending aluminum is this: the harder the grade, the more springback you should expect. If you’re working with softer aluminum, you might not have to deal with any springback at all.

2.     Be Vigilant for Creasing Along Bend Lines

Aluminum will lose its integrity when it’s creased. Depending on the types of parts you’re producing, this can have a major impact. If you’re making aircraft parts, for example, creasing along the bend line will deem parts unacceptable.

To avoid creases along bend lines, ensure your piercing tonnage is greater than your forming tonnage – remembering to exercise caution as working with higher tonnages will increase risks for damage.

3.     Don’t Use a Punch Tip That’s Too Narrow

Ideally, you should choose a punch tip as close to the material’s thickness as possible. Be careful you don’t coin the aluminum, which happens if the punch’s nose punctures the material thickness’ neutral axis.

To guarantee the best results, you need to make sure you’re using tooling suited to your press brake and the materials you’re working with. WILA tooling, for example, provides a range of benefits for press brake operators – including fast setup, maximum accuracy, and versatility across applications.

4.     Watch out for Cracking or Spreading

Especially with sharp bends, bottoming can make the aluminum’s grain even more prone to fracturing. The nearer you can get to a 1-1 radius between the material thickness and the inside bend, the less likely you’ll see cracking on the outside of the bend.

5.     Don’t Compensate for Springback with the Crease

When you’re bottom bending aluminum, you need to work with the 88-degree punch. Using an 85-degree punch will extend the bend too much, which means you won’t be able to achieve enough springforward to get the bend back to a 90-degree angle.

This means that:

  • When bottom bending material with springback of more than two degrees, it’s important that the operator is highly skilled.
  • For less experienced operators, bottom bending is ideal when you’re working with light-gauge aluminum and 90-degree bends.

6.     Take into Account Angular Clearance

With bends that have different amounts of springback than what the angular clearance will allow for, you’ll need to cheat a little bit:

  • Purchase 1/8-inch wide vinyl pinstriping tape (you can also use masking tape, but you’ll have to replace it frequently).
  • Place a piece high on the punch’s face, which will change the punch angle.

Remember, you’ll rarely be able to tape both sides. It simply doesn’t work. You also shouldn’t cover the whole punch face with tape, as that will change the tool’s centre instead of the punch angle.

7.     Work with Caution when Bottom Bending Aluminum

It’s important to understand the risks associated with bottom bending. These include ram upset being five times more likely and mistakes – no matter how small – being exaggerated.

Before making your first bend, make sure you:

  • Centre the punch into the die, even if you need to check it multiple times.
  • Start with no tonnage load, positioning punch faces touching, before stroking the press brake slowly. If the tooling moves even a little bit, you’ll need to the re-centre the load. Check alignment at each end, and continue making tweaks until there’s no more movement.
  • Make sure the bed/bolster screws have been removed or backed out, which will prevent you from trying to centre your tooling using a distorted or curved bolster.
  • Know the press brake’s centerline load limit, as exceeding it can upset the ram and permanently bend the bed

Bottom bending can be challenging, especially when working with delicate materials like aluminum. When done correctly, however, it can help operators increase their productivity and create quality parts.

Westway Machinery is the Canadian leader in press brakes, proudly distributing SafanDarley electric models and Baykal hydraulic press brakes. Contact us to find out more about our products and services.

For a complete guide to press brakes, click here.

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