MISCELLANEOUS DIESAswin s10mi31ME-CIM

INTRODUCTION Miscellaneous dies include

Marking and numbering dies Straightening or flattening dies Horn dies Cam dies Hemming dies Crimping dies Assembly dies Sub press dies.

CONTD… Marking and numbering dies are used for

stamping numbers, characters, and symbols on metal parts.

Straightening or flattening dies will bring a part to size, or a drawn shell within the drawing dimensions by striking it without allowing for its walls to become thinner.

Horn dies are equipped with a horn, which is a sort of protruding stake, or a mandrel, the shape of which conforms to the inner configuration of the part.

Cam dies transform the vertical motion of the die movement into a horizontal (or angular) movement. With the aid of cam dies, many side-piercing operations can be performed.

Fig 1. Cam and Horn die

Hemming dies can fold an edge of a sheet-metal piece back onto itself, which is often used as an edge reinforcement

Fig 2. Hemming operation

Crimping dies are used to create additional surfaces to be used for retention of other parts and assembling them together. These dies operate by bending, denting, louvering, or otherwise forming the retaining shape.

Fig 3. Crimping dies

Assembly dies are built to assemble various parts, and they utilize riveting, staking, forming, press-fitting, and similar operations.

Sub press dies, or self-guiding dies are valued for their great accuracy in punching out minute, precise parts, such as watch hands, geared wheels, and watch dials.

There are two types of these dies cylindrical sub press pillar-type sub press

pillar-type sub press die uses pillars for the support and guidance of its movement.

cylindrical sub press die the up-and-down moving plunger is guided by a bearing surface, which is firmly attached to the sturdy casting of its body.

Fig 4. Pillar type sub press

Fig 5. Cylindrical sub press die

FORCES FOR CUTTINGFor Cutting: In general ferrous stamping materials, shear

strength is 70-80% ultimate tensile strength Force=Shear Strength*Perimeter of

Cut*Thickness When calculating tonnage required it is

recommended that ultimate tensile strength be used instead of shear strength to compensate for die wear.

Tonnage=(UTS*Perimeter*Thickness)/2000

FORCES FOR CUTTING Take caution in what number is used for

shear strength or UTS. Consideration must be made for prior operations that may affect the material properties. Work Hardening Annealing or Tempering Other processes that affect the mechanical

properties of the material

WORK AND ENERGY In terms of metal cutting:

Work=average force*distance Force: Since the force/displacement curve

for cutting sheet metal is nearly rectangular use the maximum force prior to fracture as the average force

Distance: The distance used in this calculation is percent penetration (see earlier slide) multiplied by material thickness.

This calculation assumes no secondary shear, which will require additional energy during cutting.

COST OF INDIVIDUAL DIE For each type of die the cost includes a basic die set:

Cds = die set purchase cost, $ Au = usable area between guide pillars, cm2

Mfg point system to estimate cost of tooling elements such as: die plate Punch punch retaining plate stripper plate, etc.

The system includes time for: mfg die elements Assembly tryout of die

Assembly includes custom work on die set: drilling and tapping of holes fitting of metal strips or dowel pins to guide sheet metal stock in die

COST OF INDIVIDUAL DIE Basic mfg points are determined by:

1. size of punch2. complexity of profile to be sheared

Profile complexity is measured by index Xp as

P = perimeter length to be sheared, cm L,W = length & width of smallest rectangle

surrounding the punch, cm

COST OF INDIVIDUAL DIE L and W:

Blanking die, or a cut-off and drop-through die: length & width of smallest rectangle surrounding the entire part.

Part-off die: L is distance across strip while W is width of zone removed from between adjacent parts.

Cut-off die: L and W are dimensions of a rectangle surrounding end contour of part.

for either cut-off or part-off, min punch width W of about 6 mm should be allowed to ensure sufficient punch strength.

COST OF INDIVIDUAL DIE Recommendations on die plate thickness hd

fit quite well with the relationship

U = ultimate tensile stress of sheared sheet metal

Ums = ultimate tensile stress of annealed mild steel

V = required production volume, thousands h = sheet metal thickness, mm value of hd is usually rounded to nearest one

eighth of an inch to correspond with standard tool steel stock sizes.

COST OF INDIVIDUAL DIE Mfg points in were determined for the condition

Or hd = 25 mm cost of dies changes with die plate thickness according to a thickness factor fd:

Or fd = 0.75 Whichever is the larger.Mfg points Mp for a blanking die:

Mpo = basic mfg points f1w = plan area correction factor fd = die plate thickness correction factor

REFERENCES Handbook of die design by Ivana Suchy 2nd

edition. Brallia: Design for Manufacturability

Handbook, 2nd ed., McGraw Hill