Performance boost in aluminum forming: enabling cost-effective trimming of aluminum with Tetrabond™ (ta-C)

For companies in sheet metal forming, the generation of burrs and slivers is an ongoing challenge, especially when it comes to forming aluminum alloys. Burrs and slivers can reduce the final product quality and are costly to remove, which drives the search for solutions that prevent them from forming. Ionbond’s solution for this challenge is our Tetrabond tetrahedral amorphous carbon (ta-C) coating – a thin, extremely hard coating with a smooth surface and low sticking.

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High-quality parts need calibrated machining processes

Shearing is one of the most frequently used processes in sheet metal manufacturing and forming operations. This process of stamping parts from sheet metal includes blanking, trimming and piercing, and is widely applied in different industries such as primary metal, automotive or household appliances. The overall quality of the stamped part is defined by the height of the burrs on the sheared surface, the dimensional accuracy of the part and the absence of splitting. To meet quality standards and customer expectations, stamped parts frequently need a manual metal-finish operation for deburring. This is time consuming and adds costs to the stamped part.

Figure 1: Tetrabond™ deposited on trimming dies for sheet aluminum forming

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These days, aluminum alloys are popular because they help reduce the weight of automotive body panels. That means the quality of shearing operations has increasingly come into the spotlight. Aluminum alloys are replacing low carbon steel because they can improve fuel economy while maintaining strength for passenger safety purposes. However, many manufacturing processes were originally designed for low carbon steel, and now need to be adapted for use with aluminum alloys. This is especially true of trimming, as both materials demonstrate different forming behavior due to differences in mechanical and chemical properties and mass density.

Figure 2: Tetrabond™ deposited on trimming dies for sheet aluminum forming

Slivers and burrs – the challenges that arise from trimming

A common defect arising from the trimming process is sliver formation. This is one of the main obstacles preventing the high-volume production of aluminum alloys for automotive body panels. Slivers are highly undesirable as they adhere to the blank surface and get distributed to the dies following the trimming process. The accumulation of slivers on both the die and blank surface can result in an unacceptable surface finish, as the slivers on either side can be pressed into the blank surface during pressing. A second common defect to arise directly from the trimming process is the production of burrs. Burrs can cause a decrease in quality and accuracy of stamped parts and are considered the source of potential splits in following forming operations.

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From defect removal to defect prevention

Many technical solutions have been developed to remove these defects after the trimming process. However, removing slivers from the dies and blanks can be time-consuming and expensive, in particular when cleaning the die requires an interruption of the automated stamping process. Therefore, it is also important to identify technical solutions to prevent defects from occurring during the trimming process.

One approach to minimizing the occurrence of burrs and maintaining acceptable surface quality, for example, is an accurate alignment of the upper and lower shearing edges during the trimming process. A more promising approach to eliminate the root cause of sliver and burr generation is the use of hard, wear-resistant coatings deposited by physical vapor deposition (PVD).

Tetrabond Comparison abrasive wear resistance

Ionbond Tetrabond™ drastically reduces the scrap rate

Ionbond has developed the Tetrabondcoating as part of our forming and molding tool coating portfolio. It is an economical solution that ensures excellent product quality of stamped parts and increases the productivity of highly automated stamping processes by drastically reducing the scrap rate. Tetrabondis a non-hydrogenated tetrahedral amorphous carbon (ta-C) coating that belongs to the class of diamond-like carbon coatings. It was tailored to the specific need of forming tools with a sp3 ratio (sp3/(sp3+sp2+)) between 60 % and 70 % and a hardness above 3,000 HV0.02.

Figure 3: Comparison of abrasive wear resistance of TiN and Tetrabond™

That makes it the perfect match for trimming aluminium alloys:

Thin and extremely hard coating

Abrasion resistance comparable to nanocrystalline diamond coatings (CVD)

(see Figure 3)

Has an extremely smooth surface

(see Figure 4)

Minimum adhesion tendency

(anti-sticking - towards non-ferrous metals)

Very low coefficient of friction

Maximum forming tolerance and edge sharpness

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Compared to conventional hydrogenated DLC coatings (a-C:H), Tetrabondhas an enhanced temperature stability up to 500 °C, which extends the range of forming applications and choice of workpiece materials. Tetrabondcan be deposited on complex tool geometries and on a broad range of tooling materials, including cold-work, hot-work and high-speed steels, stainless steels and cast iron. A proprietary decoating process allows refurbishment of production tools after regrinding, making the best use of expensive forming tools.

Figure 4: Confocal 3D surface image of Tetrabond™ for forming and molding tools (largest scale 1.75 µm)

Exciting news for German and EU customers

Tetrabond is now also available at the Ionbond Germany branch in Saxony. This is in response to the increasing demand from our German and European customers for this innovative diamond-like carbon (DLC) coating. Ionbond Germany has a specialized coating machine in operation that is used exclusively for the production of Tetrabond coatings, ensuring short delivery times. Our team in Germany is looking forward to supplying our existing and future customers with this high-quality coating.

Would you like to know more?

Dive deeper and discover all the technical details of our Tetrabond coating for Forming & Molding Applications in the provided factsheet.

If you would like to discuss your sheet metal forming process and the potential of our Tetrabond coating to improve your productivity and increase product quality, please do not hesitate to contact us via the contact form.

Get in touch

Discuss your challenges with Tobias Brögelmann

Tobias Brögelmann, Global Segment Manager Forming and Molding Tools, will be glad to support you.

We will get in contact with you as soon as possible

Tobias Broegelmann

Dr. Ing. Tobias Brögelmann

Global Segment Manager Forming and Molding