Dimensional defects of seam

Introduction

Following key dimensions that can detect abnormalities through an examination dimensional seam.

Excessive depth of cuvette

The excessive depth of cuvette (or excessive seam-cons) appears when the cup depth exceeds the limits specified in the standard and results in a shortening hook cover and overlap (Figure 31). This defect can cause as:

1. Excessive pressure compression plate;
2. Poor calibration: Insufficient height of the crimping head;
3. Chuck improperly installed;
4. Wrong height of the lip of the chuck;
5. Lip of the chuck inconsistent with the arrow first pass.

Body hook too long

This defect occurs when the body hook length exceeds the limits specified in the standard (Figure 32). Possible causes are:

1. Compression (pressing the compression plate) excessive;
2. Insufficient distance between the mandrel and compression plate (chuck is too low compared to the compression plate);
3. Crimp edge down (lip fungus).
4. 1st pass insufficient clamping.

Hook cover too long

It speaks of the lack of cover when the hook is longer than the specifications (Figure 33). This may be due to a tightening in the first pass.

Body hook too short

The hook body is considered too short when its length is below the specified limits (Figure 34). Possible causes are:

1. Insufficient compression;
2. Excessive distance between the mandrel and compression plate;
3. Excessive tightening in the first pass;
4. Insufficient torque in 2nd pass;
5. Crimp edge too short;
6. Insufficient penetration of the chuck in the cup cover (sinking incomplete);
7. Excessive height of the lip of the chuck.

Hook cover too short

The hook cover is shorter than the specifications (Figure 35). This defect may be due to:

1. Lid not hemmed;
2. Insufficient tightening in the first pass;
3. Excessive compression;
4. 1st pass worn wheel;
5. Cup depth excessive
6. Excessive height of the lip of the chuck.

Set with loose

We talk about the defect when the thickness of the seam exceeds the specified limits. A loose seam could produce a seam that will flee because the folds of metal have not been pushed each other hard enough and the seal has not been compressed to fill the interstices of the seam (Figure 36 ). Possible causes are:

1. Bad adjustment of the wheel 2 ^nd pass;
2. Wear of the wheel 2 ^nd pass;
3. Wear of the cam wheel;
4. Wear of bearings and bolts.

Overtightening

Excessive pressure during the second pass creates a risk and movement serves to flatten the metal, to lengthen the seam (in height) and reduce the overlap (Figure 37). This defect can also occur by cutting and crimp to seal the overflow (creep). Possible causes are:

1. Poor adjustment knob 2nd pass;
2. Thickness of body and / or abnormal lid.

Insufficient overlap

The lack of overlap occurs when the hook body and lid are not sufficiently embedded into each other (Figure 38). This defect may be due to:

1. Edge of the body outside the norm;
2. Hem of the cover extraordinary;
3. First set with too loose;
4. Excessive tightening during the second pass.