How to Calculate Draw Force

Deep drawing is a metal forming process used to transform flat sheet metal into three-dimensional shapes by pulling the metal into a die cavity using a punch. The procedure entails fastening the metal sheet to a blank holder and then pressing the sheet into a die cavity with a punch. The metal expands and thins out as the punch forces it into the die chamber, eventually fitting to the shape of the die.

Deep drawing is frequently used to make cylindrical or box-like objects like cans, cups, and automotive parts. The process is popular in industries such as automotive, aerospace, and consumer goods manufacturing, where complex shapes must be produced in large quantities. Depending on the complexity of the part and the required production volume, the process can be done manually or with automated machinery.

The deep drawing procedure gets its name from the fact that the depth of the drawn part is usually greater than its diameter. Deep drawing is frequently used to manufacture parts for the automotive, aerospace, and consumer goods sectors, where great strength and precision are required. It is a low-cost method of producing huge numbers of parts with consistent quality and accuracy.

Deep draw calculation Process method

Deep drawing is a metal forming technique that is used to deep draw from flat sheet metal. The following are the basic steps in the deep draw process:

1. Material selection: The first step is to choose the right sheet metal material for the job. The type of metal, thickness, strength, and ductility are all factors to consider.

2. Blank preparation: The sheet metal is cut to the size and shape required for the blank, which serves as the starting point for the deep drawing process.

3. Lubrication: During the forming process, the blank is coated with lubricant to reduce friction and prevent tearing or wrinkling.

4. Loading: The blank is loaded onto a punch, which is a tool that gives the part its initial shape.

5. Drawing: The punch is driven into a die, which is a shaped instrument that gives the part its final shape. The metal is stretched and moulded into the desired shape when the punch is drawn through the die.

6. Redrawing (optional): If more drawing operations are required to attain the desired shape, the portion may be redrawn.

7. Trimming: The extra material on the portion is removed, leaving only the finished shape.

8. Finishing: Further finishing techniques, such as polishing, coating, or painting, may be applied to the part to improve its look or performance.

Top of Form

Bottom of Form

The factor of Calculate The Deep Draw Force

        Deep draw force is calculated using several criteria, including material qualities, component shape, tooling design, and lubrication employed during the process. Following are some of the important factors that influence deep draw force calculation:

1. Material Properties: When determining deep draw force, the strength and ductility of the material being formed are crucial elements. The material's yield strength, ultimate tensile strength, and strain hardening exponent all contribute to the force necessary to draw the metal into the die.

2. Component Geometry: The geometry of the component being generated also influences deep draw force calculation. The force required to draw the metal into the die is influenced by factors such as the diameter-to-depth ratio, the thickness of the metal sheet, and the geometry of the punch and die.

3. Tooling Design: The design of the punch and die used in the deep draw operation can also influence the needed force. The amount of force required to draw the metal into the die is affected by factors such as the radius of curvature, the clearance between the punch and die, and the angle of the die.

4. Lubrication: Using lubricant during the deep draw operation can help to reduce friction and increase metal flow. The type and quantity of lubricant used can have an impact on the computation of deep draw force.

To calculate the deep draw force, mathematical models that account for the aforementioned components are frequently utilized. These models employ equations to connect the required force to material parameters, component geometry, and tooling design. The precision of these models is determined by the quality of the data utilised in their development, as well as the complexity of the component being generated.

Defect of Deep Draw

        The deep draw method is susceptible to a variety of flaws that might impair the quality and performance of the manufactured component. Following are some examples of common deep draw flaws:

1. Wrinkling :  when the metal sheet is not dragged evenly into the die, causing folds or wrinkles in the material. This flaw is frequently caused by inadequate lubrication or poor tooling design.

2. Tearing: Tearing happens when a metal sheet is overstressed, causing it to rip or tear. This flaw is usually produced by too much drawing power or inadequate metal thickness.

3. Necking: Necking happens when the metal sheet thins in specific locations, resulting in a narrow neck in the component. This flaw is frequently caused by insufficient blank holder pressure or poor tooling design.

4. Springback: When a metal sheet returns to its original shape after being forged, dimensional errors ensue. This fault is primarily caused by the metal's elastic recovery and can be reduced by proper tooling design and material selection.

5. Die marks: Die marks are tooling impressions left on the surface of the produced component. These markings are frequently created by insufficient space between the punch and die, and they can be reduced with careful tooling design and maintenance.

        To reduce deep draw defects, carefully design the tooling and choose the proper lubrication, material thickness, and blank holder pressure.

Deep Draw Force Calculation Formula

The deep draw force formula is complex and depends on a number of elements, including material qualities, component shape, tooling design, and lubrication. Nonetheless, the following basic formula can be used as a starting point:

You can calculate Draw Force been required with the help of following step as -

Draw Force = d × π × t × R × n

And

Blank Diameter is (D) = √(d²+4dh)

Where-

d = Punch Diameter

t = Sheet Thickness

R = Tesnile strength

n = Correction Factor

D = Blank Diameter

h = Draw Height

Layout of drawing punch, blank holder

Actual Draw Ratio (ßActual) =D/d

 

n	0.1	0.3	0.5	0.7	0.9	1.1	1.3
ßActual	1.1	1.2	1.4	1.6	1.8	2.0	2.2

Diameter-Wall Thickness Ratio (ßPerm) =d/t

 

d/t	30	50	100	150	200	250	300	350	400	450	500	600
ßPerm	2.1	2.05	2.0	1.95	1.90	1.85	1.8	1.75	1.7	1.65	1.6	1.5

Permissible draw ratio for the draw (ßPerm > ßActual)

I will explained as -

The Actual Draw Ratio

ßActual = D/d = 188 mm/80 mm = 2.35

Diameter-Wall Thickness Ratio

D/t = 80 mm/1.5 mm = 53.3

See the above table and then

ßPerm = 2.35

2.05 < 2.35

 

Result:

 

This part can not be produced in one draw

Deep drawing steps-

1. Draw d1 = D/ßActual = 188/2.05 = 91.7 mm ≈ 94 mm

So that it is not necessary to go up to the deformability limit at the first draw,

ßActual = D/d1 = 188 mm/94 mm = 2.00

2.05 > 2.00

d1 = 94.0 mm is selected.

At the second draw, this then produces an ßActual of

ßActual = d1/d2 = 94 mm/80 mm = 1.17

2.05 > 2.00

d2 will also be safely achieved.