Analysis of the causes and solutions for 11 common abnormalities in hardware molds!

I. Burrs

II. Punch breakage

III. Material skipping

IV. Tensile cracking

V. Pulling cracking and deviation

VI. Unsmooth material removal

VII. Screw breakage

VIII. Deviation in folded edge dimensions and angles

IX. Excessive clearance and warping after flattening

X. Poor riveting

XI. Sliding block malfunction and cracking

I. Burrs
Product burrs are one of the most common abnormalities in stamping dies in our stamping plant. Below, I will explain the causes and troubleshooting methods for burrs in several categories.

1. Burrs from simple punching dies:

Cause Analysis
1>. Severe wear of the punch and die (normal damage)
2>. Punch and die are scraped (including secondary punching of material or foreign objects in the die cavity, etc.)
3>. Excessive clearance between the punch and die.
4>. Misalignment of the clearance between the punch and die.
5>. Cracks caused by material blockage in the die. Improvement Measures:
1. Grind the cutting edges of the punch and die to keep them sharp.
2. Depending on the extent of damage, repairable punches and dies can be ground and welded; severely damaged ones require replacement.
3. Inspect the punch and die, and adjust the clearance between them as needed.
4. Determine the punch or die repositioning based on the correct hole position.
5. Increase the angle of the die blanking hole to ensure smooth blanking.

2. Compound Die and Cutting Burrs:

Cause Analysis:
1. Compound Die 1. Automated feeding misalignment or incomplete positioning leads to one-sided cutting, damaging the cutting edges of the punch and die.

2. Misalignment between the inner and outer guide pillars and the punch and die positioning pins results in uneven clearance.

3. For the cutting punch (punch), the punch end face lacks a shoulder, causing wear on the outer side of the die, resulting in burrs due to the punch being squeezed outwards.

Remedial Measures:

1. Adjust the parallelism and length of the feeding to ensure the above situations do not occur (using a positioning device on the mold to jam the material).

2. Re-close the mold and test the clearance between the punch and die to ensure stability. 3. Add a shoulder to the end of the punch.

3. Other burrs

Cause Analysis
1. The workpiece positioning is too tight, causing burrs.
2. Insufficient positioning leads to burrs (such as burrs in the pre-punch hole, or burrs in the pre-punch hole).
3. Burrs on the pre-punch hole (burrs are present in the pre-punch hole).

Improvement Measures
1. Adjust the positioning (ensure the correct positioning of the workpiece).
2. Increase the clearance.
3. Trim the burrs on the pre-punch hole.

II. Punches Prone to Breakage
Punches should be classified according to their breakage probability, in order: pre-punch, and structurally weak irregular punches. These two types of punches usually break at the working part. However, irregular punches used for cutting materials often break due to the convex positioning part of the punch, which is also a frequent occurrence. Below is a brief explanation of some causes of these punch breakages and general improvements.

1. Pre-punch breakage is prone to occur.

Causes Analysis:
1. Insufficient blanking angle or excessive magnetism in the die causes material blockage, leading to punch breakage.
2. The working part is too long and lacks strength.
3. The punch-die clearance is misaligned.
4. During the second punching, the material is stuck in place (or there are foreign objects in the die cavity).
5. The material has reached its normal wear and tear.
6. The spring inside the stripper plate is broken, causing the stripper plate to deform and break.
7. Misalignment between the clamping plate and the stripper plate.

Improvement Measures:
1. Increase the draft angle or diameter of the blanking hole under the die; demagnetize the die using a demagnetizer.
2. Shorten the working part, generally by 4mm or less.
3. Grind the punch or die and adjust the clearance (depending on the size requirements).
4. Production line personnel ensure that the material is not subjected to excessive pressure.
5. Replace the punch. 6. Check springs, replace springs and punches.
7. Modify the clearance of the through holes in the clamping plate or stripper plate (modify according to the position of the die).
2. Analysis of the causes of other types of punch breakage:
1. The causes and countermeasures for punches with weak structures are similar to those for pre-punching.
2. Different fixing methods for cutting punches can cause them to break at the fixing point.
3. Insufficient tempering of the rivet punch can cause the rivet joint to break and pull off (avoid using rivet punches as much as possible).
4. The hook punch is prone to breakage due to incorrect hook force position or right angle at the hook root.
5. Insufficient countersunk head on the clamping plate.
Improvement measures:
1. Reuse or replace with hooks and use screws for locking.
2. Modify the position of the punch hook to ensure even force distribution.
3. Increase the height of the countersunk head hole.
III. Material Skipping
Material skipping includes small punching skipping and larger cutting waste skipping.
Cause Analysis
1. Excessive die clearance.
2. Excessive punch magnetism.
3. Worn die cutting edge, shiny cutting wall.
4. Insufficient effective stroke of punch into die.
Remedial Measures
1. Adjust die clearance and re-cut the die block.
2. Demagnetize the punch and die.
3. Roughen the die cutting edge with a coating machine.
4. Increase the working length of the punch.
1. Alternatively, for the punch, after lengthening, grind a notch on the working surface to form an R-angle or chamfer the cutting edge.
2. For larger punches, ejector pins or ball screws can be installed inside the punch.

IV. Deep Drawing Failure

Causes of Deep Drawing Failure
1. Insufficient clearance between the punch and die (including overall clearance and local clearance due to punch-die misalignment)
2. Excessive roughness due to lack of fillet radius in the die.
3. Material that is too hard and has poor plasticity.
4. Height exceeds the material's plastic deformation limit (one drawing cycle).
5. Insufficient material in the second drawing cycle.
6. Insufficient blank holder force, causing wrinkling or depression at the edge of the boss after deep drawing. Improvement Measures:

1. Adjust the clearance between the punch and die to the normal value.

2. Grind and polish the corresponding radius according to product requirements.

3. If the material is significantly out of specification, replace the material. Alternatively, increase the radius and gloss of the die accordingly to avoid this.

4. Deep drawing can be performed in several stages.

5. Adjust the positioning to ensure correct positioning.

6. Add elastic force to the stripper plate of the punch and die to increase the blank holder force.

V. Brushing, Breakage, and Deviation

Analysis of the Causes of Brushing, Breakage:

1. The pre-punch edge of the brushing punch breaks off.
One-time brushing:
2. Punch and die misalignment.
Pre-punch hole brushing: 3. The clearance between the punch and die is too small.

4. The burr on the pre-punch hole is too large or the punch is broken, and the hole is not punched out.

5. The punch is broken (the working part of the drawing punch is chipped).

Solutions:
1. Replace the drawing punch.
2. Adjust the position of the punch and die.
3. Adjust the clearance between the punch and die to a suitable level.
4. Replace the pre-punch punch.
5. Replace the drawing punch.

2. Analysis of the causes of insufficient drawing height:
1. The pre-punch hole diameter is too large.
2. The working part of the drawing punch does not enter the die deeply enough.
3. The diameter of the drawing punch is too small, and the clearance with the die is too large (or the diameter of the die is too large).
4. The material for the pre-punch hole is misaligned when it arrives at the drawing station, resulting in one side being higher than the other after drawing. Low

Improvement Measures

1> Modify the pre-punch hole to an appropriate diameter (if the pre-punch hole is too small, it will cause the bud to be too high after drawing).

2> Lengthen the working length of the drawing punch.

3> Modify the drawing punch to the required diameter, and the same applies to the die.

4> Adjust the positioning of the two stations for drawing or pre-punching, depending on the position of the drawing hole.

VI. Unsmooth Stripping
Unsmooth stripping is mainly caused by the following reasons:

1. The template is too magnetic.

2. The positioning is too tight.

3. The stripper spring is faulty (also the stripper plate).

4. There is no stripper on the stripper plate.
5. The material is squeezed by the pressure line, increasing the width and causing poor positioning in subsequent processes.

6. The material is deformed and has poor flatness.
7. The die has insufficient clearance after the product is folded or formed.

8. The slider is stuck and its movement is not smooth.
9. For compound molds, the material and scrap are not completely separated.

Improvement measures:
1. Demagnetize the mold plate.
2. Adjust the positioning according to the correctness of the product positioning.
3. Replace the ejector spring (the same applies to the stripper plate).
4. Add ejector pins to the stripper plate.
5. It is best to use internal positioning, or positioning in a position without variation.
6. Adjust the flatness of the material.
7. Increase the clearance on the mold.
8. Adjust the slider to make it slide smoothly.
9. Add ejector pins to the upper and lower molds to ensure smooth separation of material and scrap.
VII. Screws are prone to breakage.
Screw breakage: Damage and abnormal damage.
I. Causes of normal damage:
1. The screw itself... 1. Insufficient load-bearing design (incorrect specifications or insufficient quantity)

2. Poor material of the screws themselves

3. Screws break due to normal wear and tear after a few punches

Improvement Measures

1. Increase the screw size, such as using M8 or M10 and increasing the quantity (depending on the actual situation)

2. Replace with screws of new material

3. Maintain the mold for replacement

Abnormal Damage

1. Misalignment between two plates leading to forced tightening

2. Insufficient clearance between the punch and die (especially forming molds)

3. For molds with air cushions, the ejector pin is too long, causing excessive air cushion pressure, resulting in the lower mold screw breaking

4. Folding, forming molds, stamping two pieces of material or stamping twice

Improvement Measures

1. Enlarge the hole or re-drill the hole

2. Punch and die clearance

3. Standardize the ejector pin and mold air cushion plate

4. Minimize stamping twice or two pieces of material

VIII. Poor Folding Dimensions and Angles

I. Reasons for Poor Folding Dimensions:

1. Incorrect material unfolding length during design

2. Loose positioning

3. Folding angle deviation affects dimensions

4. 5. Material not fully compressed, resulting in an excessively large radius (R-angle) (die height, air cushion pressure, etc.), leading to dimensional deviations.

6. Misalignment occurred during punching.

7. Loose or broken screws caused dimensional instability.

8. Deviation in the pre-folding edge pressure line position.

9. Material deformation and poor flatness affected positioning.

Remedial Measures:

1. Change the blanking length of the material or add a pre-folding edge pressure line to correct the issue.

2. Adjust positioning.

3. Adjust the folding edge angle to within specifications.

4. Adjust the die height and air cushion pressure or spring to ensure the material is fully compressed.

5. Adjust the front punch and cut to ensure the correctness of the previous workpiece.

6. Replace and tighten the screws, then adjust positioning.

7. Adjust the pre-folding edge pressure line position.

8. Adjust the material flatness.

Analysis of Causes of Poor Folding Edge Angle:

1. The gap between the punch and die is too large, resulting in an excessively large angle.

2. The air cushion pressure is too high or too low (the die spring force is too high or too low), resulting in an excessively large or small angle.

3. The radius (R-angle) of the punch is too large.

4. Loose or broken screws.

5. Material deformation and poor flatness

6. Incorrect position or uneven depth of pre-folding crease

7. Punch crease too high or too low, resulting in an angle that is too small or too large. Solutions for poor folding angle:

1. Adjust the clearance between the punch and die

2. Adjust the air cushion pressure of the die

3. Adjust the punch radius (R) or negative angle to reduce springback

4. Tighten or replace the folding block screws

5. Adjust material deformation and flatness

6. Adjust the position and depth of the pre-folding crease.

7. Adjust the crease height on the punch.

IX Excessive gap and warping after flattening

Analysis of excessive gap:
1. Pre-folding line too deep or misaligned.
2. Folding angle too large or outward deformation.
3. Insufficient clearance of the pusher block.
4. Gap of the pusher block too high or too low, or the mold closing height too tight or not tight enough.
5. Insufficient clearance of the pusher block.
6. Gap of the pusher block too small or too large.
7. Material too hard.

Remedial measures:
1. Modify the height or position of the pre-folding line.
2. Adjust the folding angle and material deformation.
3. Adjust the height or position of the upper mold pressure block. Mold height.

4. Increase the clearance of the push-flat block.

5. Adjust the gap of the push-flat block. Analysis of the causes of edge warping during push-flattening:

1. The pre-folding edge crease is too shallow or incorrectly positioned, or the folding punch has no crease or the crease is too shallow.

2. The height of the push-flattening die block is insufficient and not fully pressed down (including insufficient mold height).

3. The gap of the push-flattening blocks is too large.

4. The material is too hard. Improvement measures:

1. Adjust the depth and position of the crease.

2. Increase the height of the push-flattening block.

3. Adjust the gap of the push-flattening blocks.

4. Changing the material or adjusting the width and depth of the pre-folding edge crease can overcome the problem. Poor Riveting

Causes of Poor Riveting

1. Riveting punch radius (R-angle) is too large or too small.

2. Misalignment between the drawing hole and the riveting hole (during hemming).

3. Insufficient drawing height.

4. Poor product positioning within the riveting die.

5. Damaged riveting punch.

6. Misalignment between the riveting punch and the die hole.

7. Excessive or insufficient clearance between the riveting punch and the die.

8. Insufficient depth of the riveting punch into the die.

Improvement Measures

1. Adjust the riveting punch radius (R-angle).

2. Adjust the position of the drawing hole and the riveting hole during hemming.

3. Adjust the drawing height.

4. Adjust the positioning.

5. Replace the riveting punch.

6. Adjust the riveting punch and the die.

7. Adjust the clearance between the riveting punch and the die.

8. Lengthen the riveting punch.

XI Slider Malfunction and Cracks

Analysis of Causes of Slider Malfunction and Cracks

1. Insufficient clearance between slider and template

2. Broken spring inside slider

3. Slider pressing on two pieces of material or foreign objects in the mold cavity causing cracking or deformation

4. Insufficient radius (R) angle inside the slider mold causing cracking

5. Incorrect ejection position inside the slider mold, resulting in uneven stress

6. Rough contact between slider and template

7. Weak structural design

Improvement Measures

1. Adjust the clearance between slider and template.

2. Replace slider spring.

3. Repair slider by welding and grinding.

4. Ideally, change the radius (R) angle of the grooves inside the slider and template.

5. Adjust the slider and ejection position to ensure even stress distribution.

6. Polish the contact surface between slider and template.

7. For structures that cannot be modified, consider a quick-change insert type.