CCD245-Pinciples of Blanking and Piercing Dies

What is a piece part in terms of blanking and piercing dies?

the product - it may be complete or it may need one component that makes up an assembly

what is stock material?

general term for any material from which the piece part is made

what is a die?

a complete production tool, the purpose of which is to produce piece parts consistently to require specifications

• the female part of a complete die

what is a punch

the male member of a die which mates or acts in conjunction with the female die to produce a desired effect upon the material being worked

What is the difference between a blanking and piercing die?

it depends on if you are keeping the material that is cut out or if you are keeping the remaining material

what is a blanking die?

it is when the blanks are the desired products made by the die

• the remaining material is the slug

• the punched part is the part to keep

what is a piercing die?

the purpose if to produce openings of a certain size and shape

• keep the remaining material

• throw out the slug or the small part that was punched

What are the stages of shearing action

1. plastic deformation

2. plastic penetration

3. fracture

What happens to the material during stage 1 of shearing action?

• punch makes contact and exerts pressure on material

• elastic limit of material is exceeded and deformation takes place

What happens to the material during stage 2 of shearing action?

• driving force of ram continues

• punch is forced into the material

• blank or slug is displaced into die opening

  • shearing portion of cutting cycle

What happens to the material during stage 3 of shearing action?

• continuation of punching pressure

• fracture starts at cutting edge of the punching die

• fractures extend toward each other and meet

• blank or slug separates from material

• punch continues on into the die opening

• blank or slug is pushed slightly below the die cutting edge

how are blanked or pierced parts measured?

at the cut band

what is the relationship of part size to punch and die size?

blanks and slugs are slightly larger than the opening in the material from which it was cut due to the cutting action caused it to be compressed

what must be known about the material in order to calculate the forces on the die?

shear strength of the material

what is A?

guide post

what is B?

shank

what is C?

punch holder

what is D?

punch

what is E?

stripper

what is F?

die block

what is G?

die shoe

What is H?

press bed

what is J?

slug or part

what is the press cycle of a blanking or piercing die?

• at rest the ram is at top of stroke

• start - flywheel rotates

• ram is driven toward press bed

• at 180 degrees rotation of flywheel, ram starts to return to rest position

• back at rest position, ready for next cycle

what is the purpose of a stripper on blanking or punch dies?

• after the operation the material wants to stick, and it prevents the material from traveling with the punch

what are the various operations produced in dies?

• blanking

• cutoff

• trimming

• compound (blank and pierce)

• pierce

• bending

• shaving

• forming

• stub press

• progressive

What is the rule for clearances when a slug is produced to be thrown away?

the punch must be made to the size and clearance is applied to the die

What is the rule for clearances when a blank is produced which will be kept?

the die opening is made to size and the clearance is applied to the punch

What are the three types of blank layout?

adjacent

interposed

interlaid

what is the difference between an interlaid and interposed layout?

an interposed layout there is no flipping of the part and it is just fit together

interlaid layout includes flipping the part in order to maximize the space available