At present, large scale electric iron core punch sheet is mainly made of 0.5 mm or 0.35 mm thin electrician Silicon steel sheet. The reason for the large burrs in the process of punching is generally due to the following reasons:
1) The punching gap is too large, too small or uneven.
In these three cases, the quality of the section and surface quality of the hedges have a great influence. From the analysis of the deformation process of the plate, it is found that if the gap between the convex and concave die is too small, the crack near the convex die edge is staggered out of a distance from the normal gap range. When the Silicon steel sheet is finally separated, there will be a burr sandwich in the fracture layer. Due to the extrusion of the concave blade, the punch section forms a second bright band, with an extruded burr or jagged edge and an inverted cone at the upper part, as shown in Figure 1A. If the gap is too large, the shear crack near the edge of the convex die is staggered into a distance from the normal gap range. The material is greatly drawn and the slope of the punch section is increased, so that the Silicon steel sheet is easily pulled into the gap, so an elongated burr is formed, see Figure 1C. In addition, the uneven distribution of the punching die gap will also cause the punching piece to produce a large burr in the local area, that is, a squeeze burr in the small gap and a elongated burr in the large gap.

　2) Blunt of the cutting edge of the work
When the edge of the die work has a round angle due to long-term wear, it can not play a good role in material separation. At this time, the entire section is irregular due to tearing, resulting in larger burrs, see Figure 2. Especially, the burrs are more serious when the burrs are blunt when the bulging edge and the burr edge are blunt.
3) Reasons for equipment
The precision of the guide rail of the punch bed, the parallelism of the sliding block and the bed surface are not good, and the direction of the sliding block and the vertical degree of the table table are not good. Bad punch precision will cause the center line of the convex die and the concave die to not coincide, resulting in burrs, and it will also cause the mold guide column to develop. In addition, when the punch bed has a sinking car phenomenon, there will be secondary punching, or when the punch force of the punch bed is not enough, it is easy to produce a large Burr. 

4) Material Reasons
In actual production, the mechanical properties of Silicon steel sheet material, uneven material thickness, poor surface quality and other factors will also affect the cross section quality of the sheet. The elasticity and plasticity of the metal material determine the stamping properties of the metal. In general, Silicon steel sheets used for electric motors must have a certain degree of elasticity and plasticity. Because of the cold stamping process such as punch, drop, and cutting edge, the use of elastic Silicon steel sheet material is more suitable. This is because materials with better elasticity and high mobility limits can obtain good cross-sectional quality.
I hope that the above introduction can be helpful to your work. The introduction is for your reference only. In the actual work, we must maintain the maintenance and maintenance of the equipment. Thank you for your reading.