©2008 Mate Precision Tooling Punch Press Tool Maintenance & Ordering Recommendations

©2008 Mate Precision Tooling

Punch Press Tool Maintenance & Ordering

Recommendations

Punch Press Tool Maintenance & Ordering

Recommendations


Punch Press Tool Maintenance & Ordering Recommendations


Punching Knowledge– Punching Cycle

– Quality hole

– Die clearance

Maintenance– Tool sharpening

– Spring maintenance

– Turret alignment

Troubleshooting & Tool Ordering Recommendations– Punch shear

– Slug Pulling

– Punch non-metallic material


Punching CyclePunching Cycle

Material Punch

Die

Impact Penetration

StrippingFracture

Slug


Anatomy of a Quality HoleAnatomy of a Quality Hole

Material Thickness

Burr Height

Rollover Depth

Rollover Width Burnished

Length

Slug


Die ClearanceDie ClearanceDefinition: The size of the gap between the punch and the die.

Total Die Clearance (TC)

Dependent on material type and thickness

Thinner material requires less clearance

Thicker material requires more clearance

Total clearance = Die Clearance 1 + Die Clearance 2


Correct Die ClearanceCorrect Die Clearance

Optimum Die Clearance – Shear cracks join, balancing punch force, piece part quality and tool life.


Tight Die ClearanceTight Die Clearance

Clearance Too Small – secondary cracks are created, raising punching force and shortening tool life.


Excessive Die Clearance

Excessive Die Clearance

Large BurrBurr is not compressed and is easily removed

More Rollover & Less Burnish


Calculating Die ClearanceCalculating Die Clearance

Total Clearance = Material thickness x Total Die Clearance % (shown on chart)

Die Clearance is based on type and thickness of material being punched.



0.079” x 20% = 0.016” Total Die Clearance



2.0mm x 25% = 0.50mm Total Die Clearance


Benefits of Proper Die Clearance

Benefits of Proper Die Clearance

Longer tool life

Better stripping

Smaller burr height, minimum rollover

More uniform holes

Fewer shavings

Reduced galling

Flatter work pieces

More accurate hole location

Less wear on the machine


When to Re-sharpen Punches and Dies

When to Re-sharpen Punches and Dies

R = .010” (0.25mm)

Sharpen when

a .010” (0.25mm)

radius forms on the punch or the die

Sharpen when

a .010” (0.25mm)

radius forms on the punch or the die


Sharpening RulesSharpening Rules

Sharpen frequently.

Provide proper face geometry.

Use coolant.

Coarse wheel(46).

Soft wheel. (G) (Norton SGB46KVX)

Radius on wheel.

Minimal surface contact.

Observe proper set-up practices.

Establish written maintenance procedures.


Inspect Tools Before SharpeningInspect Tools Before Sharpening

Fractures on dies or punches

Damaged guides or slots

Grind life


Calculating Grind LifeCalculating Grind Life

Grind Life = SBR - (Stripper Thickness + Material Thickness + Die Penetration)

Stripper

Material Thickness

Die Penetration

Usable Grind Life


GallingGalling

Fractured or broken punches

Stripping problems

Poor quality holes

Fast tool wear

Punches with galling cause:


GallingGalling

Remove galling from punches

Consider Nitride or Maxima

Run machine at slower speed

Lubricate the sheet

Check die clearance

Causes: Heat, tight die clearance, lack of lubrication

Solutions:


Special Punch TreatmentsSpecial Punch Treatments

Nitride Maxima™


Die Land InspectionDie Land Inspection

Inspect die for material build up.


Proper Wheel DressingProper Wheel Dressing

Correct Wrong

Improper dressing

can shatter the wheel


Orientation of WheelOrientation of Wheel

Wrong Right


Importance ofFrequent Maintenance

Importance ofFrequent Maintenance

Improper Sharpening Proper Sharpening Total Holes Produced

Radius Formed

Total Holes Produced

Radius Formed

100,000 0.25mm 100,000 0.25mm 50,000 0.50mm 100,000 0.25mm 25,000 0.75mm 100,000 0.25mm 10,000 1.00mm 100,000 0.25mm

185,000 Total Hits

1.0mm Total Removed

400,000 Total Hits

1.0mm Total Removed

More than DOUBLE the tool life when sharpened frequently!

Note: Theoretical example only. Tool life will vary.


Sharpening ProblemsSharpening Problems

Waves on surface are due to overheating.

Heat changes the metallurgical base fo the material and speeds up tool wear.


Sharpening ProblemsSharpening Problems

•Undressed wheel

•Lack of coolant

•Excessive material removal

•Wrong grinding wheel choice


Spring MaintenanceSpring MaintenanceNote: springs have a finite life and require maintenance.

Be aware of the different type springs used in various tooling lines and their maintenance requirements.


Broken Disc SpringsBroken Disc Springs• Disc springs require

lubrication.

• Stripping problems and guide damage can occur if springs are not maintained.

• If one disc spring is broken replace the entire stack.

• Maintain proper spring count and pattern.


Fatigued Coil SpringsFatigued Coil Springs

Throw away length = 75% of new length.

A & B station Original Style coil springs

New Length

Throw away length


Misalignment-PunchesMisalignment-Punches

Uneven punch surface wear on any one side of the tool (marking and or galling).

More evident on long, narrow shapes but can happen on any shape or size tool.


Die MisalignmentDie Misalignment

©2000Mate Precision Tooling

Damaged side has marks and abrasion, evidence of being hit.

Undamaged side is sharp and has no evidence of being hit.


Thick Turret Alignment ToolsThick Turret Alignment Tools


Mate Pilot Calibration System for Thick Turret

Mate Pilot Calibration System for Thick Turret

LED color indicator

– Red – not aligned

– Yellow – Aligned within 0.030mm

– Green – aligned within 0.008mm

Electronic Sensor

Upper Tool

Lower Tool

Surface Contact Sensor


Benefits of ProperTool MaintenanceBenefits of ProperTool Maintenance

Flatter sheets

Cleaner holes

Less stress on tool and machine

Longer tool life

More accurate hole locations


Troubleshooting and Tool Ordering

Recommendations

Troubleshooting and Tool Ordering

Recommendations


Prevent Slug PullingPrevent Slug Pulling

Use Slug Free® dies.

Eliminate magnetism in tools.

Lightly dull recently sharpened tools.

Increase die clearance.

Maximize die penetration.

Use shear.

Use urethane ejectors.


Mate Slug Free® Die Cycle

Mate Slug Free® Die Cycle

Punch penetrates the material. Slug fractures away from sheet.

Punch retracts and slug is free to fall down and away through exit taper of the Slug Free die.

Material held securely by stripper before punch makes contact.

Pressure point constricts slug. Punch stroke bottoms out as slug squeezes past pressure point.


Advantages of Punch ShearAdvantages of Punch Shear

Tonnage reduction (up to 60%).

Noise reduction.

Slug control.

Reduced shock loads -- tooling and machine.

Flatter sheets.

Improved stripping.


Punch ShearPunch Shear

One-way & Whisper Cup

Concave RooftopFour-Way


Punching Non-Metallic Materials

Punching Non-Metallic Materials

Use sharp punches and dies.

Reduce die clearance by 5%-8%.

Run the machine on slow cycle.

Lubricate hard plastic if possible.

Use Maxima™ or Nitride treated punches.

If marking occurs use urethane pads.

Support thin material when possible.


Punching Thick Material +4mm

Punching Thick Material +4mm

Sharp punches and dies.

Clearance of 25-30% of material thickness.

Extra back-taper on punches.

Punch to material thickness ratio of 1 minimum.

0.5mm radius on all punch corners.

Inspect tools frequently for wear.

Lubricate the sheet, punch and guide.

Run machine on slow cycle.

Use Heavy Duty tool configuration.


Overcoming Stripping Problems

Overcoming Stripping Problems

Use additional back-taper on punches.


Check stripping springs for fatigue.

Use sharp tools.

Use Heavy Duty tool configurations.

Remove galling.

Lubricate sheets.

Use sharp punches and die.

With spring tooling use larger station.


Standard Back-taperStandard Back-taper

1/8 degree per side(1/4 degree TOTAL)

Punch Size


Reduce GallingReduce Galling

Sharp punches and dies.

Lubricate work piece.

Use Maxima™ or Nitride treated punch.


Adjust machine hit rate (slower).

Use tool lubrication if available.


Small Diameter or Narrow Holes

Small Diameter or Narrow Holes

When punching small diameter or narrow holes, maintain the following ratio ofpunch size (minimum) to material thickness:

Material

Aluminum

Mild Steel

Stainless Steel

Punch to Material Ratio

.75 to 1 (.5 to 1 Fully Guided)

1 to 1 (.75 to 1 Fully Guided)

2 to 1 (1 to 1 Fully Guided)


Perim

ete

r Calc

ula

tion

s

Calculate diagonals to

determine station size

Calculate perimeters for

tonnage calculations

A = Diagonal Dimension

(Station Size)

L = Hole Perimeter


Tonnage Formula:Punch Perimeter x Material thickness x Material Tonnage Value x Material Multiplier

L dimension from chart

on previous slide Material tonnage values:

Metric tons = 0.0352

Imperial tons = 25

Tonnage CalculationsTonnage Calculations

Material Type Material Multiplier

Aluminum (soft sheet) 0.3

Aluminum (1/2 hard) 0.38

Aluminum (full hard) 0.5

Brass (soft sheet) 0.6

Brass (1/2 hard) 0.7

Copper (rolled) 0.57

Mild Steel 1

Stainless Steel 1.5

30mm round hole

3mm stainless steel

Metric Tons Example: 30mm round hole in 3mm stainless steel:

Tonnage = (30 x 3.14) x 3 x .0352 x 1.5 =

13.93 metric tons

BlankingBlanking

Blanking --When the slug

becomes the

“good” or the

“saved part”

Punch 3.0-5.0mm flat

1.5-3.0 degreeone-way shear can be used

Blanking Punch Configuration

Blanking Punch Configuration


Blanking OperationsBlanking Operations

Extremely sharp punches and dies.

Reduce die clearance by 5%.

Determine which blank dimensions and tolerances are critical.

Notify tooling provider that tooling required will be used for blanking.

Use non-slug free or straight taper dies.

Punches should be flat faced or with slight one-way shear.

Inspect tools for wear frequently.


Ordering Punches and DiesOrdering Punches and Dies

Punching a Hole

Punch Size = Hole Size

Die Size =

Punch Size + Clearance

Blanking a Part

Die Size = Blank Size desired

Punch Size = Die Size - Clearance (determined by material thickness)


Minimum Spacing Between Holes and Forms

Minimum Spacing Between Holes and Forms

Spacing between forms

Minimum = 2 x Material Thickness between holes

Minimum = 2 1/2 x Material Thickness to sheet edgeTo

p v

iew

of

sh

ee

t


Making Straight Walled Holes Without Drilling

Making Straight Walled Holes Without Drilling

Finished hole size is the starting point. Order Punch for Hit #2 to the finished hole size. The punch for Hit #1 equals finished hole size less 20% of material thickness. The die size equals finished hole size plus 0.1mm.


Large Holes Without Exceeding Press Tonnage


R =2.0

The customer has a Thick Turret machine with a C station auto-index.

He should pierce a hole 47.0mmdiameter in mild steel T=6.0mm

• Suggested Solution: 1st hit-pre-pierce in the center of the 47mm hole a punch with a 25.0mm diameter. Hits 2, 3 &4-Special shape punch finish 47mm diameter with three hits.

• Tooling characteristics: Punch-roof top shear, Die-HD with 30% die clearance

2nd Hit

4th Hit 3rd Hit

1st Hit

Special Punch Shape For Hits 2,3 & 4

R=23.5

Overlap

140 Degrees


Customer wants to pierce a 50.0mm diameter hole in mild steel T=8mmThe customer does not want to buy a special shape radius tool but wants to use standard tooling.

Tool 1 Use one Square 10mm and pre-pierce along the 50mm periphery 8 holes with equal pitch.

Tool 2 Finalize the hole with a 50mm flat punch

8 hits 10mm sq.

Final Hit 50mm round




Large Holes Without ExceedingPress Tonnage

Large Holes Without ExceedingPress Tonnage


Forming ToolsOrder Recommendations

Forming ToolsOrder Recommendations

Material Type & Thickness

Accurate Dimensions

Spacing between forms

Tool Style

Punch press model

Other useful information

– If tool is replacement, provide Mate etch number.

– Has tool been manufcatured by another supplier?

– Is the design flexible?

– Is the tool required for a specific station?



Summary


SummaryPunching Knowledge

– Punching Cycle

– Quality hole

– Die clearance

Maintenance– Tool sharpening

– Spring maintenance

– Turret alignment

Troubleshooting & Tool Ordering Recommendations– Punch shear

– Slug Pulling

– Punch non-metallic material

Documents

©2008 Mate Precision Tooling Punch Press Tool Maintenance & Ordering Recommendations