Factors affecting the accuracy of punching (cutting) molds
It is divided into seven major parts: mold design and manufacturing, assembly guidance, heat treatment, punching equipment, punched materials, production wear and tear, and environment and operation.

1、 Mold design and core structure
The clearance size and uniformity of the convex concave die punching gap (the most critical) directly determine the precision of the cutting edge and the quality of the cross-section. Large gap: large burrs, large collapse angles, and dimensional deviations of the workpiece; Small gap: The cutting edge is prone to breakage, overheating, rapid wear, and easy to gnaw on the mold. The gap needs to be matched according to the material thickness and material (soft steel/stainless steel/high-strength steel).
Guidance system guide column guide sleeve (ball guide column has higher accuracy), mold frame parallelism. Excessive clearance and wear between the guide column and guide sleeve can cause a deterioration in the alignment of the convex and concave molds, resulting in offset during punching, uneven clearance, and dimensional drift. Progressive molds also need to consider the positioning accuracy of guide plates and guide pins, as multiple workstations can result in accumulated errors.
Wear and looseness of positioning pins/plates in the positioning and unloading structure, and inaccurate positioning benchmarks; The unloading plate is uneven, the pressing force is unbalanced, the material moves and tilts during punching, and the hole position and external dimensions are offset.
The thickness of the rigid mold template is insufficient, the template has too many hollow holes, and the arrangement of fastening screws is unreasonable. After stamping, the template undergoes elastic deformation and the cutting edge is misaligned, which affects the accuracy.
2、 Machining precision of die parts
Processing equipment accuracy: positioning/repetitive positioning accuracy of slow wire, grinding machine, CNC; The clearance between the machining machine tool guide rail and the lead screw will directly affect the size, parallelism, perpendicularity, and coaxiality errors of the convex and concave molds.
Processing technology and cutting tools: unreasonable arrangement of rough and fine machining, residual cutting stress; The wear of the cutting tool causes the contour and size of the cutting edge to exceed the tolerance.
Blade profile and positional tolerance: parallelism, perpendicularity, and flatness of convex and concave molds. Once there is warping, the gap around the edges will be uneven.
3、 Heat treatment and materials
Heat treatment deformation: Improper quenching, tempering, and cryogenic treatment can release internal stress, causing warping, shrinkage, and deformation of templates and convex and concave molds. Dimensional drift after precision machining is an important reason for the loss of accuracy in many molds after installation.
Mold steel: material wear resistance and hardness. Poor steel quality, the cutting edge wears and breaks shortly after stamping, and the accuracy deteriorates rapidly; Precision punching commonly uses Cr12MoV, SKD11, hard alloys, etc.
Residual stress: Processing and heat treatment stress, slowly released during batch stamping process, causing the mold to slowly deform.
4、 Mold assembly accuracy
Parallelism of mold frame assembly; Coaxiality of convex and concave mold assembly;
The fixed plate, unloading plate, and concave mold are not properly fitted, and there is pre tightening deformation during assembly;
The fastening screws are subjected to uneven force, causing the template to twist after locking;
The assembly cleanliness is poor, with iron filings and debris trapped between the templates, causing the plane to not fit properly.
5、 Stamping equipment (punch press) factors
Insufficient rigidity of punch press: The opening of the C-type frame opens elastically during stamping, causing the slider to flex downwards, resulting in dynamic clearance changes; The tonnage is too small and deformed due to overload.
Sliding accuracy: The gap between the sliding block and the guide rail is large, the parallelism is poor, the sliding block moves obliquely, and the downward movement is not perpendicular.
The levelness of the workbench and the unevenness of the cushion plate; The mold is not securely clamped, the pressure plate is loose, and the mold is displaced due to stress.
Repetitive positioning accuracy and impact vibration of punch press; Vibration will amplify the gap error of mold guidance.
6、 Raw materials for the punched workpiece
Fluctuations in the thickness tolerance of the sheet metal, changes in the actual material thickness, and equivalent changes in the punching gap;
Fluctuations in material hardness and tensile strength, material rebound and tensile deformation, elastic recovery of the workpiece after punching, and dimensional deviation from the mold edge;
The board is uneven, warped, the coil has waves, burrs, and oil stains, and the positioning is inaccurate during feeding. The material belt deviates (especially for progressive molds).
7、 Production, use, wear and maintenance
Blade wear: During mass production, the blade gradually wears out and the size slowly deviates; The blade is directly scrapped if it breaks or falls off.
Wear of guide components: The gap between the guide column and guide sleeve increases after long-term use; The positioning pin is worn.
Insufficient lubrication and increased wear due to heating; Iron filings get stuck between the cutting edge and the template, crushing the cutting edge and causing local deformation.
Mold disassembly and assembly, lifting and collision; Shutdown for storage and rusting.
8、 Environment and Others
Temperature changes cause thermal expansion and contraction of molds; Workshop vibration; The heat accumulation during high-speed punching causes the mold to heat up and deform.

Quick troubleshooting sequence (practical on-site)
Check the wear of the guide column guide sleeve and positioning pin → 2 Check the uniformity of the clearance between the convex and concave molds, as well as the wear and breakage of the cutting edge → 3 Template parallelism, presence of foreign objects on the cushion → 4 Parallelism and rigidity of punch slider → 5 Incoming board thickness and flatness → 6 Heat treatment induced stress deformation.