What are the sheet metal parts defects in manufacturing?

Sheet metal parts are the parts that are produced by stamping operation by sheet metals. During stamping operation, there are many sheet metal parts defects such as burrs, dents, scratches, wrinkles, fracture, crack & wrong dimension etc. So below are the operation-wise defects, their causes & remedies.

These are the defects which increase increase internal rejections. Increase in internal rejection increase cost of poor quality. So below root cause and action will help in rejection analysis during red bin analysis.

Punching, Blanking & Trimming operation:

Defect: Burr on blank or punching parts

Burr sheet metal parts defects
Credit: Google
Cutting edge bluntDo grinding of punch & die face
More clearance between the die & punchMaintain adequate clearance
The punch position shifted as per dieMaintain uniform clearance between die & punch
The top of the tool shifted from its bottomReplace guide post or pillar bush
Die part shiftedSet the die part in the socket & use the dowel pin

Draw operation:

Defect: Wrinkle

Wrinkle in sheet metal
Credit : Google
The wrong lubricant usedChange the lubricant
Blank holding pressure lowIncrease the blank-holding pressure

Defect: Fractured Rim & bottom in the draw

Blank holding pressure too highReduce the pressure

Puching Operation:

Defect: Dent on cutting edge

More play of posts in bushingsReplace bushings
Cutting element shiftedMaintain uniform clearance in die & punch
Press slide not parallel with bed surfaceRepair the press
Tool shoes not parallel ( Spacer below tool)Grind the shoes

Blanking operation:

Defects: Press jerks when blanking:

Cutting force too large
No taper on die cutting edge
Grind die face & make taper on die cutting edge

Defect: Stripper fail to remove stocks:

Spring too weakReplace spring

Beding & Forming operation:

Defect: Wrong dimension:

Locator worn outRepair or replace locator
Locator shiftedRectify the locator position
Workpiece shifted as operation startsMake provision for blank holding
Spring backChange tool working part to allow spring back

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