A stamping die is not finished when the last surface is machined. Until it has formed good panels from production material, nobody knows whether it will split, wrinkle or spring back out of tolerance. Tryout is the stage where the die is run, adjusted and proven. Buy-off is the point where the buyer agrees the die is ready to ship. Hailong Group designs and builds cold stamping dies for automobile body panels and sheet metal parts, and this guide explains what happens in tryout and how buyers can make buy-off faster.
Why tryout takes real time
Forming simulation predicts most problems, but real sheet steel varies in thickness, strength and surface condition, and real presses deflect under load. Small differences in blank holder force, draw bead height or radius size can turn a good simulation into a split panel. Tryout closes the gap between the design and the press shop, so problems are solved at the die maker and not on the customer’s production line.
The tryout sequence
- Die setting and first hits. The die is set in the tryout press and the first panels are drawn slowly, often with trial blanks, to check how the material flows.
- Fixing splits and wrinkles. Draw beads, blank holder pressure, radii and blank size are adjusted until the panel forms without splits, wrinkles or excessive thinning.
- Springback compensation. Panels are measured and the forming surfaces are corrected so the part springs back to the right shape.
- Trim, pierce and flange operations. Downstream dies are tuned so trim lines, hole positions and flange angles fall inside tolerance.
- Surface quality. Outer panels are checked for low spots, skid lines and other surface defects that become visible after painting.
- Measurement. Panels are checked on a checking fixture and measured with a coordinate measuring machine or 3D scanner against the CAD data.
- Run-off. A batch of consecutive panels is produced to show the die is stable, not just able to make one good part.
What buy-off usually covers
- Dimensional results from the checking fixture and measurement reports, compared with the part drawing and GD&T.
- Formability, meaning no splits, no wrinkles in functional areas and acceptable thinning.
- Surface quality on visible outer panels.
- Stability over the run-off batch.
- Die construction against the agreed die standard, including safety features, lifting points, nameplates and spare inserts.
- Documentation, such as final die drawings, the parts list and tryout records.
What buyers should prepare
Many tryout delays come from missing information rather than from the die itself. Share these early:
- Press data for the production line: tonnage, bed size, shut height, stroke, cushion and transfer or tandem layout.
- Material specification, and if possible coils or blanks from the production supplier, since tryout with different steel can give different results.
- Part drawings, 3D data and GD&T, with the critical characteristics marked.
- Acceptance criteria, including run-off quantity, measurement method and surface standard.
- Who attends buy-off, and whether a pre-buy-off review is wanted at the die maker before final acceptance.
Common reasons buy-off is delayed
- Late engineering changes to the part after the die surfaces are machined.
- Tryout material that differs from production material.
- Press data that does not match the actual production press.
- Acceptance criteria that are agreed only at the end of the project.
How tryout works at Hailong
Hailong covers the full chain from die design and model making to die machining, testing, installation and commissioning. Tryout and measurement use a large mould tryout press, mechanical and hydraulic presses, a large laser coordinate measuring machine and a five-axis laser cutting machine. Our quality plan follows each project from quotation and contract through design, programming, machining and assembly to die tryout and delivery, with inspection of incoming material, the production process and nonconforming products.
The group also runs its own stamping lines, including an 8,250-ton closed automatic line and a 3,400-ton automatic line, so our engineers work with dies in production as well as in tryout. Hailong is a member of the China Die & Mould Industry Association and certified to IATF 16949 and ISO 9001.
Read more about how automotive stamping dies are made, why stamped parts need checking fixtures and the die line behind a body panel, or see our vehicle stamping dies.
Talk to our engineers
Send your part drawings or 3D data using our RFQ guide or the contact page. You can also email nora@qdhailong.com or call +86-532-66090318.