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Custom tooling and die design · Lesson 4 of 4

Custom tooling and die design: defects, verification and case study

Reading marks, creases, multi-breakage, collisions, overloads, galling and punched-hole faults back to their tool causes, three case studies, and the first-article checks and records that prove the fix.

You will be able to: Diagnose a tooling defect from what it leaves on the part or the tool, choose a corrective option the tool makers publish, and document the evidence for review.

10 min · 12 slides · 7 questions

All lessons in this module
Slide 1 of 12

Read the defect back to the tool

Every tooling fault leaves evidence: on the face, in the angle, in the slug or on the tool itself.

Write down what you see and where, measure it, then match it to a published cause. Change one thing at a time and recheck.

Correct and incorrect press brake tool choicesFour rows, correct on the left with a green tick and incorrect on the right with a red cross. Tip radius: a tip near the natural radius gives a smooth bend; a tip far too sharp creases the sheet. Return flange: a gooseneck clears the formed flange; a straight punch collides with it. Prefinished face: the die shoulders bear on the underside of the sheet, so the film is drawn under the sheet, between it and a die with large shoulder radii, and the face stays clean; with small sharp shoulders the underside is marked where it rides over each shoulder, circled. Load: an even load along full segments; a horned end segment whose horn, drawn dashed, deflects under load, with the corner circled where its angle can deviate and must be checked.Correct and incorrect (press brake, industry)ABCDEFGHNot to scale; deflection exaggerated.

Four rows, correct on the left with a green tick, incorrect on the right with a red cross. A tip near the natural radius bends smoothly; a tip far too sharp creases the sheet. A gooseneck clears the formed flange; a straight punch collides with it. A die with large shoulder radii, with protective film under the sheet where the shoulders bear on it, leaves the face clean; small sharp shoulders mark the underside of the sheet where it rides over them. An even load along full segments; a horned end tool whose horn, drawn dashed, deflects under load, with the corner circled where the angle may deviate and must be checked.

A
Correct: tip radius near the natural radius, smooth bend
B
Incorrect: tip far below the natural radius eats into the bend (about 2/3 of it in WILA's steel, 90 degree, V = 8t example)
C
Correct: a gooseneck relief clears the return flange
D
Incorrect: a straight punch collides with the flange
E
Correct: large shoulder radii, with protective film on the underside of the sheet, between the sheet and the die
F
Incorrect: small sharp shoulders mark the underside of the sheet where it rides over them (circled)
G
Correct: load spread evenly along full segments
H
Incorrect: the horn deflection is not checked; WILA notes horns can deflect and the corner angle may deviate
Press brake, industry practice from WILA and Mate; not AFS equipment. Not to scale; deflection exaggerated. WILA rates horned tools like regular ones and leaves it to the job whether a corner deviation is acceptable, so it is checked.

Sources

Videos for this lesson

What this video shows: Bystronic, a machine maker: per its description, pressure sensors compare tool load with the permissible loads stored in its database and interrupt the bend when they are exceeded. One maker's feature.

Video: Bystronic Pressbrake features: Xpert Pro Automatic tool protection (English) by Bystronic, on YouTube. AFS checked its description against this lesson.

What this video shows: Wilson Tool: per its description, galling as metal buildup on tooling, and how to identify it, remove it without damaging the tool, and prevent it.

Video: Galling on Press Brake Dies | Bending | Technically Speaking by Wilson Tool International, on YouTube. AFS checked its description against this lesson.

Glossary

Galling
Small particles of sheet material or milling scale sticking to bottom tools (WILA), or metal adhering to a punch tip under pressure and heat (Mate).
Burnish zone
The smooth, sheared band on a punched hole or slug; Mate reads its size to judge die clearance.
Rollover
The rounded edge where the sheet is drawn down before it shears; dull tools increase it (Mate).
Multi-breakage
WILA's term for a non-circular bend that is tighter in the centre: when the punch tip radius exceeds the natural inside radius, the centre of the sheet separates from the punch and forms a smaller radius. A larger die opening reduces it.
Tool protection
A press brake feature that compares measured tool load with the permissible load stored for the tool and stops the bend when the measured load exceeds it (Bystronic).