Currently, many metal stamping factories often experience high scrap rates in the processing of stampings. High scrap rates increase production costs and go against the principles of energy conservation and environmental protection. The stamping industry itself is already highly competitive, and profit margins are declining significantly. If the scrap rate remains high, a batch of orders may not only fail to generate profit but could also result in losses. Therefore, solving the problem of high scrap rates in stampings is particularly important. To address this issue, we need to understand what causes the high scrap rate. Only then can we apply the right remedy. What are the reasons for the high scrap rate of metal stampings? Let's take a look with the editor below.
1. Raw materials do not meet standards.
Raw materials are the first guarantee for processing qualified stampings. If the hardness and surface quality of the raw materials cannot meet the requirements, the scrap rate of stampings will be excessively high. Especially for stampings with significant deformation, if the raw materials are unqualified, cracks and damage may occur. Therefore, when purchasing raw materials, we should not be tempted by low prices but should seek reliable and reputable raw material suppliers.
2. Stamping dies are not installed as required.
If the stamping die installation does not comply with specification requirements, it can result in poor matching between the upper and lower dies, leading to a high scrap rate. The stamping die is the foundation of stamping part processing. If the die itself is not the issue, installation is very important. Do not assume that stamping die installation is simple—even a very small error can cause the stamping parts to be scrapped during production. The concentricity, clearance, and flatness between the upper and lower dies have a significant impact on the die installation.
3. Die wear.
Long-term use of stamping dies, wear, or loose parts can also cause product scrap. Many stamping factories, after installing production dies, do not carry out routine inspection and maintenance. Only when burrs become relatively large do they remove the die and simply sharpen the cutting edges. We know that die wear is not just about blade wear; as the die is used, some die components also wear out. Once these components are worn, the precision of the entire die is affected.
4. Improper worker operations.
Workers operating the press must follow the instruction manual; otherwise, feeding errors may occur.
5. Incorrect positioning device.
During the loading process, if the die positioning device is inaccurate, it can cause improper coordination between processes and even lead to scrap.
For metal stampings, since each stamping part requires different stamping processes, there must be specific causes and specific analysis methods. If the scrap rate of stampings is too high, it is advisable to identify the causes from these five aspects.
However, the processing industry often demands high precision for hardware punched and drawn parts, and requirements for suppliers are increasingly stringent. Yet, not all metal stamping factories meet high-precision standards. Issues to note in the production of die-cast parts:
1. Regularly inspect the mounting seats of the punch, die, and punch holder to ensure consistent precision of the upper and lower turrets.
2. Metal stampings should be strictly cleaned before installation and use. Carefully check that the guide bushings and die lubrication are in good condition on the stamping parts.
3. To ensure proper drawing and pressing of parts, replace die springs regularly to prevent fatigue damage that could affect the use of drawn and pressed parts.
4. When installing dies, stamping operators should use metal working tools to prevent damage to stampings from impact and compression during installation.
5. If the edges of the punch and die on stamping parts become worn, they should be stopped immediately and reground. Otherwise, edge wear will rapidly expand, accelerating die wear and shortening stamping quality and die life.
6. According to the die installation steps, install the punch and die on one turret to ensure consistent punch direction. In particular, strictly install the punch according to orientation to prevent misinstallation or reverse installation.
6. How to calculate the scrap rate of stampings
1. The calculation methods are as follows:
a. Calculated by weight: Casting scrap rate = (Weight of scrapped castings / Total weight of castings) x 100%
b. Calculated by quantity: Casting scrap rate = (Quantity of scrapped castings / Total quantity of castings) x 100%
2. Scrap Rate, Scrap Factor
The probability that a component becomes defective during the process of being used to manufacture its parent item. The same component may have different scrap rates when used to produce different parent items; therefore, the scrap rate is defined in the Bill of Materials (BOM). When MRP uses the BOM to explode a material's POR (Planned Order Release) to calculate the gross requirements (GR) of its components, it divides by (1 - scrap rate) to inflate the component's GR (Gross Requirements).