In actual sheet metal fabrication, product surface quality is evolving from a “hidden indicator” into a “visible standard,” especially when processing materials with high surface requirements such as stainless steel, aluminum sheets, decorative panels, and coated sheets. As a critical forming process, bending inevitably creates contact and sliding between the sheet metal and the tooling, making surface marking one of the most representative process defects. These marks not only damage the original gloss, texture, or coating integrity of the material, but also directly reduce the product’s visual appeal and perceived quality.

During the press brake bending process, the root cause of surface marking is usually excessive localized pressure or severe friction between the sheet metal and the tooling. Common causes include: improper V-die opening selection, which concentrates stress on specific contact points during bending; excessive bending pressure, causing permanent indentation beyond the material’s elastic deformation range; rough tooling surfaces that scratch or wear the protective layer of the sheet; unreasonable tooling design, such as improper hardness matching or insufficient relief structure; in addition, the lack of necessary protective measures during bending can significantly increase the risk of surface damage.

So, what measures can be taken to effectively reduce surface wear and marking during the bending process?

Select the Proper V-Die Opening

Choosing the correct V-die opening is one of the most effective ways to reduce material marking. A V-opening that is too small increases the pressure applied to the sheet surface, resulting in obvious indentation marks.

When selecting the V-die opening, the following recommendations are commonly used:For mild steel, the V-opening is typically selected at 6–8 times the material thickness. For stainless steel, a larger V-opening should be used whenever possible to reduce the risk of surface marking. For aluminum sheets, wider V-dies are preferred to effectively minimize scratching.

Sharp die shoulders create concentrated pressure points that can easily damage the material surface. Using radius tooling helps distribute pressure more evenly, significantly reducing indentation marks.

In addition, polishing the tooling surface can effectively reduce friction and improve overall bending quality.

For materials with high surface-finish requirements, such as stainless steel or coated sheets, protective layers can be added between the tooling and the material to reduce direct metal-to-metal contact.

Common solutions include protective films, PVC tape, nylon film, and polyurethane pads. These materials can effectively reduce marking and surface scratches during bending.

Modern press brake tooling has developed specialized non-marking solutions for sensitive materials. Examples include nylon insert dies, roller dies, polyurethane dies, and ball-bearing non-marking dies.

These tooling solutions can greatly reduce friction and surface damage during the bending process.

        Keep Tooling Clean and Perform Regular Maintenance

Recommended maintenance practices include:

      Regular polishing of tooling surfaces

      Timely removal of metal debris and chips

      Inspecting die shoulder wear conditions

      Proper tooling storage and protection

      To reduce material marking, proper bending parameter settings are essential. Excessive pressure should be avoided, and machine accuracy must be maintained throughout production. Key factors include:

       Proper control of bending tonnage

       Correct crowning compensation

       Accurate backgauge positioning

       Maintaining good machine alignment and parallelism

Especially in industries with high surface-finish requirements, such as elevators, home appliances, and decorative products, professional non-marking press brake tooling is becoming the industry standard.

Golin continues to innovate in this field by introducing a variety of high-performance non-marking tooling solutions. More importantly, we are committed to providing customers with complete support, from tooling selection to process implementation, helping manufacturers achieve high-quality and cost-effective bending production.