When considering the relationship between the form of production of a product and the cost of production, do you struggle with the following questions: What kind of tooling and production method can be used to achieve the best price/performance ratio? What logic should be used to make a decision, and what factors should be considered? How to compare the advantages and disadvantages and how to make a choice is a big topic, but as long as we sort out the logic and define the criteria for benchmarking, then the advantages and disadvantages between different options will be obvious, and making a choice will be easy. This time let’s run through the forms of stamping production together.
According to the type of tooling and equipment used for stamping, we can divide stamping into the following two main types of production: manual stamping and automated stamping production. The common automated presses can be divided into Tandem, Transfer, Progressive, and Tandem, depending on the product’s characteristics.
Manual Single Process Stamping
A single machine executes a single process, and loading and unloading operations are performed by hand.
High flexibility, no need to consider automation-related factors in die structure, and low investment in dies required for simple structure.
The investment in equipment is also very low, the maintenance cost of the equipment is low, and the single machine has a small footprint because there is no automated auxiliary mechanism.
Separate shears or drop-in equipment are required for sheet pre-production, and one more sheet turnover cost.
The sheet does not need a complex positioning area, the contour shape is less restricted, and the material utilization rate is higher.
Very high labor cost, the operator-to-machine ratio at least 1:1. 1-2 persons each for loading and unloading of larger-size parts.
Production efficiency is low, SPM: 5~10.
Knowledge: SPM is called “strokes per minute,” which means the number of strokes per minute and simply the number of strokes per minute.
Because of the simple equipment and dies and more manual participation, the production stability is poor, and the quality cost is relatively high.
The general life cycle usage is less than 20w strokes, especially for products with less than 10w strokes. The savings in tooling and automation investment are generally greater than the increase in production costs caused by inefficient labor.
Automated single-process tandem stamping
The main differences between automated stamping production and manual stamping production are
The use of automated production system equipment, including in-line (or not) sheet feeding systems, automatic sheet cleaning, and oiling systems for large covered parts, automated loading systems, automated transfer of parts in the die process parts, and automated unloading and even parts collection systems.
To ensure the continuous movement of the production system, the mold needs to be equipped with a top material mechanism linked to the equipment, a sensor system to detect the position of the product, detect whether the mold structure is in place or even whether the mold is damaged, and an auxiliary structure on the mold to assist automatic loading and unloading.
It is necessary to consider the interference between the mold structure and the automatic pick and place mechanism, the mold design is more complicated, and the design cost, manufacturing cost, and later automation commissioning cost are much higher than the manual mold.
Stable operation of equipment and mold, less personnel involvement, high production stability, and stable quality.
A single machine executes a single process, and the transfer beam or robot is used to complete the transfer of parts between different processes. Generally suitable for large parts, such as cover parts of automobiles, larger structural parts of body-in-white chassis, etc., some small parts will be made in the form of an automatic single mold, such as seat slides, etc.
An automatic single die is still a pair of molds and a machine, so the mold structure has more room to play, good process flexibility, and can be processed in complex shapes.
Need to invest in additional automation equipment; the drop molding process is often separate, so additional drop molds and process costs for drop molding need to be considered, but material utilization is relatively high.
The ratio of operators to production units on the machine is usually 2:1 or more. Large stampings require at least two people for product collection and another for in-line visual inspection. In addition to the operator, another sheet material stacker is needed for loading.
The SPM is usually 12~20 due to the large transfer distance between processes and the lower production efficiency compared to other automated stamping production modes.
Life cycle usage of 20w or more, large or medium-large products, such as automobile cover parts, body chassis parts, shells of large home appliances, etc.
Automatic transfer die stamping
All processes are completed on one machine, and the parts are transferred between processes by robotic arms.
The robotic arm can be turned over, and the structure of the die is relatively flexible. Still, it is limited by the size of the punching machine table, so in case of too many product processes, two machines may be required for in-line production.
Limited by the punching equipment table size, it is not recommended to produce too great products.
Additional investment in each die’s robotic arm and the corresponding robotic arm is required.
It is possible to produce inline dropouts with rolls or separate dropouts with depalletizers.
The ratio of the operator to the machine is about 1:1~2:1. One person can watch more than one punching machine. Under stable production, only the operator is needed for loading and unloading coils, sampling products, collecting products, etc. If it is larger, two people are needed to collect products.
SPM is usually 16~60. Body chassis parts such as the front longitudinal beam, front subframe, etc. SPM 16 or more.
Life cycle usage of 20w or more, medium or small and medium-sized products, such as A, B, and C pillars, longitudinal beams of auto body-in-white, basin surfaces and side panels in seat skeleton, motor shells that need a deep drawing, etc.
Automatic progressive die stamping
The material belt consists of multiple processes (automotive stampings generally have 10 to 25 processes), and the parts of each process are formed in sequence by connecting materials called carriers. The products are cut off and separated in the final process.
Due to the limitation of the carrier, it is difficult to reverse the product, so it is difficult to use the progressive die for complex shaped parts and parts that are too large, and the tonnage of the stamping equipment used in the progressive die is generally below 1000 tons.
An unwinding and unloading system is required.
Online uncoiling and unloading require more material for connecting parts and pieces (carrier), and the material utilization rate is low.
The operator-to-machine ratio is usually 1:3~1:1. One person can watch more than one punching machine. Under stable production, only the operator is needed to load and unload the rolled material, sample the products, and collect the products.
SPM is usually 18~2000. 18~60 for general automotive structural parts; 100~200 for stator and rotor; 800~2000 for terminal connectors.
Life cycle dosage above 20w, small and medium or small products, such as small connection parts on the car body, motor core laminations, terminal products, etc.
How to choose the right stamping？
Stamping cost analysis is not just a narrow sense of the cost of a single piece of a stamping product but a broad consideration. We analyze the total costs incurred during the entire project cycle. In the case of stamping, the factors that affect the cost are the total project life cycle, the cost of the individual stamping product, the tooling cost, the inspection cost, and the quality cost of the project cycle.
As you can see from the above chart, stamping cost is a systemic cost. If you analyze the stamping form and focus only on a single cost, the conclusion will not be objective. The more conclusions that are not objective, the further away from the real situation the analysis will be. The value of the variables in this formula depends on the form of stamping used for the product, so it is important to analyze the relationship between the various variable cost items for each form of stamping.
Comparison table of different forms of stamping production
Manual single mode
Automatic single mode