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CHOOSING A PRESS

Mechanical presses are available in many configurations so it is important to choose a press that has the features and capabilities that meets your unique production needs. The typical criteria used to choose a press include:

  • Die Size
  • Force (Torque) Capacity Required
  • Energy (Work) Capacity Required
  • Actuation Means
  • Work Handling Methods

To assist in the determination of which press is right for you, Kenco has provided a list of criteria to consider.  The following five questions will provide you with your basic press requirements.

What work is to be done on the press?

Consider what parts you want to make now and in the future. Don't short change yourself. Allowing for additional capacity now can provide you with production flexibility that will eliminate capital expenditures in the future.

What tonnage is required to make the parts?

The tonnage limit tells you the range of material thicknesses you can punch, blank, or process. When estimating the required tonnage, be conservative. Presses in production should operate at no more than 70 to 75% of capacity. This will provide a safety margin in the event of material misfeed, operator error, snap through, etc. and greatly reduce downtime and repair costs. It is also recommended to have at least a 10 percent higher tonnage margin to allow for tool wear, which increases tonnage requirements as the tool dulls.

The industry standard for rating tonnage force on presses 35 tons or less, is to establish the rating at 1/32" from the bottom of the stroke. As the point at which the work to be performed increases from the bottom of the stroke, the available tonnage force of the press decreases.

The general formula to determine the tonnage required to punch a blank is shown below:

Tonnage = ( [linear cutting edge] x [material thickness] x [shear strength] ) / 2000  

Example:

A 3/4" diameter circular blank is to be punched in 16 ga [0.060"] mild steel [sheer strength = 50,000 lbs]

Tonnage = ( [0.75" x 3.14] x [0.060] x [50,000] ) / 2000 = 3.53 tons

* Using a safety margin of 25%, the minimum tonnage required to perform this operation is 1.25 x 3.53 tons = 4.4 tons.

 

Tons of Pressure Required to Punch Mild Steel

Hole
Dia.

Gauge

Inch

20

.036

18

.048

16

.062

14

.075

12

.105

11

.120

10

.135

3/16"

.188

1/4"

.250

5/16"

.312

3/8"

.375

1/2"

.500

1/8"

 

.4

.5

.6

.7

1.0

1.2

1.3

-

-

-

-

-

3/16"

 

.5

.7

.9

1.1

1.5

1.8

2.0

2.8

-

-

-

-

1/4"

 

.7

.9

1.2

1.5

2.1

2.4

2.6

3.7

4.9

-

-

-

5/16"

 

.9

1.2

1.5

1.8

2.6

2.9

3.3

4.6

6.1

7.8

-

-

3/8"

 

1.1

1.4

1.8

2.2

3.1

3.5

4.0

5.5

7.4

9.2

11.1

-

7/16"

 

1.2

1.6

2.1

2.6

3.6

4.1

4.6

6.4

8.6

10.7

12.8

-

1/2"

 

1.4

1.9

2.3

2.9

4.1

4.7

5.3

7.4

9.8

12.3

14.8

19.7

9/16"

 

1.6

2.1

2.6

3.3

4.6

5.1

5.9

8.3

11.1

13.9

16.5

22.0

5/8"

 

1.8

2.4

2.9

3.7

5.1

5.9

6.6

9.2

12.3

15.4

18.5

24.6

11/16"

 

1.9

2.6

3.2

4.0

5.7

6.2

7.3

10.1

13.5

17.0

20.2

26.9

3/4"

 

2.1

2.8

3.5

4.4

6.2

7.1

7.9

11.0

14.7

18.5

22.1

29.5

13/16"

 

2.3

3.1

3.8

4.8

6.7

7.6

8.6

12.0

16.0

20.0

23.8

31.8

7/8"

 

2.5

3.3

4.1

5.1

7.2

8.3

9.2

12.9

17.2

21.5

25.8

34.4

15/16"

 

2.6

3.5

4.4

5.5

7.7

8.8

9.9

13.8

18.4

23.0

27.5

36.8

1"

 

2.8

3.8

4.7

5.9

8.2

9.4

10.6

14.8

19.7

24.6

29.5

39.4

1 1/2"

 

4.2

5.5

7.0

8.8

12.3

14.0

25.9

22.0

34.4

43.0

51.5

68.8

2"

 

5.6

7.5

9.5

11.7

16.4

18.8

21.0

29.5

39.3

49.0

59.0

78.5

2 1/2"

 

7.0

9.4

11.7

14.7

20.5

23.5

26.5

36.8

49.0

61.5

73.6

98.2

3"

 

8.5

11.3

14.0

17.6

24.5

28.2

31.7

44.2

60.0

76.5

88.4

118.0

3 1/2"

 

9.9

13.0

16.5

20.5

28.8

32.7

37.0

51.5

68.7

86.0

103.0

137.0

4"

 

11.3

15.0

18.8

23.5

32.8

37.6

42.2

60.0

78.5

98.0

188.0

157.0

 

The capacity of a press is determined by its work capacity, torque capacity, and component strength. The work capacity is the energy or sustained force that the press can generate. The torque capacity is the ability of the press to transfer the energy of the flywheel through the drive train to the die. The component strength is the physical strength of the press components needed to handle the load and deflection generated by the performed work. Each Kenco press is engineered so that the torque and component strength is of an ample magnitude to safely generate the designed work capacity.

What are the die/tooling dimensions?

The tooling weight and dimensions may necessitate selecting a higher tonnage press to physically accommodate the die. Other tooling specifications that the press must dimensionally match are: stroke length, shut height, and shank size.

What type of clutch is required for the work?

There are two classifications of clutches: full-revolution and part-revolution. When engaged, a full-revolution clutch (roller or pin clutch) can only be stopped after making a complete stroke cycle. A part-revolution clutch (air clutch) can be stopped and started at any point in the stroke cycle.

Full-revolution clutches can be used where:

  1. the operator does not have to place his hands in the tooling area to position parts, and
  2. the work area can be hard guarded, and
  3. press speed is not excessive (less than 220spm in continuous operation, less than 40 spm single stroking)

If any of these conditions do not exist then a part-revolution clutch should be considered.  Additional criteria that would warrant a part-revolution clutch include use of safety light curtains and use of die protection equipment.

How will the press be actuated?

Two popular methods of operator actuation include dual palm buttons and footswitch.  Dual Palm Buttons require the simultaneous pressing of both buttons to initiate a stroke. These can be supplied as standard pressure or the more ergonomic "light touch" switches.  With a footswitch, proper hard guarding is essential. Alternatively, presses can be actuated by the operator by a remote source such as PLC or from a feeder.

Contact Taber Industries today to determine which Kenco Press is right for you!