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Automatic Stamping Production Line: The Basic Guide

Before we get into the basics of automatic stamping production line, let’s get some knowledge of the press which been used in the auto line first.

Application of Press in Automatic Stamping Production line

Automatic stamping production process

In the traditional stamping production line, the material handling between the front and rear equipment depends on manual operation. With the continuous improvement of production beats, manual picking and unloading not only fails to meet the needs of high beats, but also brings potential safety hazards. Because personnel focus on the speed of picking and unloading, they ignore the dangers of equipment movement, and there are often accidents when the equipment is pressed to human hands and injured. Therefore, an robotic automated production line for replacing manual operations came into being.

Automated production, that is, the use of equipment instead of manual implementation of sheet transportation between the front and rear presses.

This not only avoids the risk of injury, but also improves production efficiency by about 35%.

After 2005, the automated production technology of stamping parts for domestic automobile manufacturers has sprung up, opening the curtain of stamping automation production. Figure 1 shows a schematic diagram of a stamping automation production line.

Schematic diagram of automatic stamping production line

Figure 1 Schematic diagram of automatic stamping production line

Main production process parameters of the press

At present, the mainstream presses are mechanical closed presses, which can be applied to various cold stamping processes such as blanking, forming, bending, correction, and shallow drawing of thin plate parts.

The process parameters of the press are very important, which not only affect the forming quality of the product, but also have a great impact on efficiency, cost and even safety.

The following will briefly explain the important parameters and accuracy of some presses:

Press basics

The foundation of the press should bear the weight of the press and resist the vibration force when the press is started, and transmit it to the ground under the foundation.

The foundation is premised on being able to withstand 0.15 MPa reliably.

The strength of the foundation is designed and constructed by the civil engineering department according to the local soil quality.

The concrete foundation must be poured in one operation without interruption. After filling the foundation concrete, the surface should be smoothed once at a time, and only shovel or sanded afterwards.

Taking into account the need for oil protection, the surface on the bottom of the foundation should be coated with acid-proof cement for special protection.

The basic drawing provides the internal dimensions of the foundation, which is the minimum space required to install the press.

The strength-related indicators such as the cement label, the arrangement of the reinforcing bars, the size of the foundation bearing area and the thickness of the foundation cannot be reduced.

The basic bearing capacity is required to be greater than 1.95MPa.

Guide post synchronization

Guide post: It is used to connect the beam gear box and the slider, and the decelerated motion of the gear box is transmitted to the slider, so as to realize the vertical movement of the slider.

Generally there are single-point, double-point and four-point types, that is, one guide post, two guide posts, or four guide posts.

Guide post synchronization: 

It refers to the synchronization accuracy of the two-point or four-point press guide column in up and down movement. This parameter is generally accepted before the press leaves the factory.

The precision of the guide post synchronization needs to be controlled within 0.5mm. Excessive unsynchronization will have a severe tensile effect on the slider force, and then affect the product quality of the slider at the bottom dead point when the product is formed.

Mold mounting height

The mounting height refers to the distance between the lower surface of the slider and the upper surface of the table. There are maximum and minimum mounting heights.

When designing the die, taking into account the possibility of installing a mold on the press and continuing to use the tool after grinding, the closed height of the mold is not allowed to use the maximum and minimum limit values of the press mold height.

Figure 2 shows a schematic diagram of the mounting height of the press.

Nominal force of the press

Nominal force is the maximum allowable punching capacity that the press can safely withstand in structure.

In actual work, the conditions such as the thickness of the material and the deviation of the material strength, the lubrication state of the mold and the changes in wear should be fully considered to ensure a certain margin of stamping capacity.

Schematic diagram of the mounting height of the press

Figure 2 Schematic diagram of the mounting height of the press

In particular, when performing an impact load operation such as blanking, the working pressure is preferably limited to 80% or less of the nominal force.

If the above limit is exceeded, the connection between the slider and the transmission may cause severe vibration and damage, which will affect the normal service life of the press.

Figure 3 shows the nominal load allowable load curve.

Allowable load curve of nominal force

Figure 3 Allowable load curve of nominal force

Compressed air pressure

Compressed air is the main power source to ensure the smooth operation of the press, and it is also the control loop source of the power source of the press.

The demand for compressed air pressure is different at each location. The compressed air pressure value delivered by the factory is based on the maximum demand value of the press.

The other parts with lower demand values are equipped with pressure reducing valves for pressure regulation.

The function of compressed air in stamping automation production process can be divided into two categories: product quality and action function.

Product quality category is used for product quality shaping, such as air cushion pressure. The action function category is involved in the action control of the press, such as clutch pressure.

Taking the press of one fabrication company as an example, the compressed air pressure values required for each functional module of the press are shown in Table 1.

The press parameters are far more than the above five. The following is a brief summary and display of the press parameters of the company (Table 2) for your reference.

Table 1 Required compressed air pressure value of each functional module

No. Item Supply air pressure MPa Pressure regulating valve position Note
1 Total air supply ≥0.5
2 Clutch 0.32 Beam walking platform
3 Balancer 0.47 Inside left front post Calculated value without mold
4 Hydraulic protection Air pump 0.29 Inside slider Calculated
5 Unloading valve 0.32 Inside slider Calculated
6 Stretch pad 0.04 ~ 0.8 Inside left front post

Table 2 Summary of press parameters

No Item Value Unit
1 Nominal force 10000 kN
2 Nominal force stroke (before the bottom dead center) 12.5 mm
3 Slider stroke length 1000 mm
4 Number of slide strokes (during dry running) Continuous 8-12 Times / minute
Maximum single 8
Fine-tuning 3
5 Maximum loading height 1350 mm
6 Loading height adjustment 500 mm
7 Rail distance L*R 4970 mm
8 Slider bottom surface size L*R 4600 mm
F*B 2400 mm
9 Worktable size L*R 4600 mm
F*B 2400 mm
10 Worktable thickness 300 mm
11 Movable worktable Moving way Move left and right
Quantity 2 Pcs
Height of moving table 700 mm
Carrying weight 50 t
12 Slider Rail type Right-angle guide
Beating type /
Beating force / kN
Beating stroke / mm
Number of beater / Pcs
13 Stretch pad Type Pure gas single crown
Quantity 1 Pcs
Ejection force 4500 kN
Blank holding force 4500 kN
Stroke 0 ~ 300 mm
14 Balancer balance force (at 0.62MPa air pressure) 200 kN
15 Inlet air source pressure 0.7 MPa
16 Free air consumption 1 m³ / min

Conclusions

The press is the main equipment in the stamping production process. With the rapid development of the automotive industry, the demand for various high-precision equipment in the automotive industry has also increased.

During the development of the stamping process, it has experienced three processes: manual production line, automated intermittent production, and automated high-speed continuous production. In each update iteration of the model, the production equipment plays an important role in it.

Now we have know the key point of the press, let’s dive into the automatic product line now.

Types of automatic stamping production line

The automatic stamping production lines mainly include: progressive die stamping, multi-station stamping, and tandem stamping.

automatic stamping production line

Because of their own characteristics, they are used to produce different automotive sheet metal parts. With their own unique advantages, they play a huge role in automotive automation and efficient production systems.

This article compares and analyzes the respective characteristics of these three stamping automation production lines, and explains the selection method of production lines based on their characteristics.

Therefore, it is convenient for enterprises to combine their own characteristics of parts and make reference in the selection of automatic production lines.

With the rapid development of the automobile industry, the four major stamping industries of car manufacturing have also flourished.

In order to adapt to the ever-increasing output, various automated production lines have emerged as the times require, and with the characteristic requirements of different products, different production methods have been given.

In order to facilitate enterprises to choose different production methods according to their product characteristics, this article classifies common stamping automation production lines: progressive die stamping, multi-station stamping, tandem stamping, and briefly analyzes the characteristics and selection methods of each production line.

Progressive die stamping production line

(1)Overview:

The automatic production line of progressive die stamping is a production line that uses progressive die stamping, which generally consists of an uncoiling feeder, a punch, a progressive die, and an automatic blanking line. Realize the automatic process of unwinding the coil, flattening the strip, oiling the strip, stamping into pieces, and collecting finished products offline.

The important part: Progressive die, consisting of multiple stations, up to more than 20 stations. Each station is related to each other in order to complete different processing contents. Generally speaking, it is punching, trimming, flanging, shaping, blanking and so on. A series of different processing contents are completed in one stroke of the press. After one stroke is completed, the feeder moves the material strip in the direction of the material in a fixed step, so that multiple processes can be completed simultaneously in a reciprocating punch of a press. As shown in Figure 1.

Simplified diagram of progressive automatic production line

Figure 1 Simplified diagram of progressive automatic production line

(2) Features:

The production cycle of the progressive die stamping automation production line is relatively high, generally up to 30 times / min.

  1. High production efficiency.Progressive die is a multi-tasking process die. Within a pair of die, it can include punching, bending forming, and drawing, which has high productivity. Progressive die layout process, as shown in Figure 2.

Figure 2 Progressive die layout process

Figure 2 Progressive die layout process

  1. Easy to automate.It can realize automatic operation from loading, feeding, processing, and lowering parts, thereby reducing labor costs and improving production efficiency. At the same time, abnormalities caused by inconsistencies in manual operations are prevented.
  2. Can use high-speed punch production.Depending on the product status, a high-speed punch can be considered to achieve higher production efficiency.
  3. Safeoperation.Progressive press equipment has safety doors to enable the work to improve material utilization. The work area is isolated from the personnel operation area to form a relatively closed work area, which provides safety guarantee for high-speed production. Traditional series production lines can achieve higher production efficiency.
  4. Save production plant area.A machine tool constitutes the processing part of a production line, which can complete the production of a product. It has a small footprint, and also simplifies the transportation status detection of the bottom material and semi-finished products, and has high safety.
  5. Material utilization is not high.Because of ensuring the continuity of the tape and various requirements, in order to ensure the stability of the feeding, it is generally necessary to ensure the uniform distribution of the process content in each process state, and sometimes a part of the material is sacrificed, so that a higher material utilization rate cannot be achieved.

Multi-station stamping automation production line

(1)Overview: 

A production line with multiple independent station molds (usually 4 to 5 molds)  placed on a large tonnage press table. Use destacker or unwind feeder to load, transfer of process parts with automatic feed bar, and use an automatic conveyor belt to collect offline products. As shown in Figure 3.

Multi-station stamping automation production line

Figure 3 Multi-station stamping automation production line

(2)Features

  1. The bottom material can be a roll material or a blank, which has great flexibility and is conducive to improving the material utilization rate.
  2. Using automatic rod feeding, the punching times are lower than the progressive die production line and higher than the traditional tandem production line, which can achieve higher production efficiency.
  3. It can add loading and unloading sensors, dual material detection, grip sensor, in-mold sensor, etc., to detect the position and status of the material piece and the product in production, with high safety.
  4. There are high requirements on the feeding height and stamping direction of the molds at each station. In order to ensure the stability of the feeding, generally the states of each process must be consistent.

Tandem Stamping Automation Production Line

(1)Overview: 

Multiple presses are arranged one after the other and connected in series to form an automated production line. A pair of molds (that is, a process of the production process) is placed on each press table, and the automatic mechanical arm or robot completes the loading, transfer of process parts, and the unpacking and packing work. As shown in Figure 4.

Automatic production line for tandem stamping

Figure 4 Automatic production line for tandem stamping

(2)Features

  1. It has a wide range of applications and can be applied to the production of various stamping parts.There is no high requirement on the size, shape and thickness of stamping parts, and it can be applied to the production of large-scale cover parts with great flexibility.
  2. The production efficiency is low. Due to the use of robotic arm feeding, the cycle time cannot be higher. Compared with the progressive production line and multi-station production line, the production efficiency is lower.
  3. Facilitate mold maintenance and debugging. Because each mold belongs to each press, the clamping is independent, and the working parameters are independent. The maintenance and debugging of each mold process can be performed independently without affecting each other.
  4. Occupy a large production plant area, a traditional series production line generally includes 4 to 5 presses, covering a large area.

How to select stamping automation production line

Generally the following factors should be taken into consideration while choosing the type of stamping production line.

(1) Product material: Including the type of material, forming performance, hardness, etc. to measure the selection of coil or sheet forming.

(2) Material thickness: Consider together with the material to choose the tonnage of the punching machine and the supporting form of the feeding mechanism.

(3) Monthly supply and demand: Evaluate the production capacity, determine the production cycle, and weigh the type of automatic line.

(4) Volume and difficulty of stamping products: Through modeling complexity and product quality requirements standards, you need to comprehensively consider the mold design methods and corresponding stamping automation production methods.

Selection and Application of Stamping Automation Production Line

Progressive die stamping automation production line

According to the process characteristics of each process distributed on an overall strip and the higher process punches that can be reached and According to the process characteristics of each process distributed on an overall strip and the higher process punches that can be reached, it can be applied to the production of small parts on the car body and can meet a high supply.

Multi-station stamping automation production line

It can be applied to the rapid production of medium-sized parts and is not easily deformed. Symmetrical parts with more complicated left and right common shapes, as well as products that can be held by the gripper on the automatic lever, can be applied to the production of the automatic line.

Tandem stamping automation production line

Because each process is independently distributed on each press, this production line has the highest flexibility. It is suitable for large-scale covering parts with complicated production processes, which is conducive to the debugging of a single process and independent production, and is convenient for the high quality control of products.

The characteristics of the three production lines are shown in Table 1

Advantages Disadvantages Applications
Progressive ① High impact times, high efficiency and high output

② Small footprint

① Low material utilization

② Only applicable to small parts

③ The single-piece mold is large and difficult to debug

① Small structural parts with high demand
Transfer ① High automatic efficiency

② There are many types of products that can be produced

③High material utilization

④Many automated safety detection devices

① The joint installation of molds has higher requirements on the design process of the product

② Combined installation of molds, inconvenient debugging and maintenance of molds

③ The interchangeability of production lines is low, and special molds are designated for production on a single production line.

① Beam parts, reinforcement parts, baffle parts, etc. are regular in shape and easy to clamp, and the whole process can be distributed on the same workbench.

② Parts with larger demand

Tandem ① Most applicable product types

② Flexible delivery methods for loading and unloading and process parts

③ High interchangeability of production line

④ Easy debugging and maintenance

⑤ High material utilization

① Large footprint

② Low production efficiency

① Large parts and covering parts

② Parts with complicated technology and high quality requirements

The selection of each stamping automation production line can be based on two trends: high output and high flexibility. For a large number of parts, you can choose an automated production line with high efficiency and high output. If the part is more complex and requires higher production technology, a flexible production line can be selected. A simple illustration is shown in Figure 5.

Special intention of 3 production lines

Figure 5 Special intention of 3 production lines

Relying on their own characteristics, stamping automation production lines are used in major automobile plants, providing a strong guarantee for the development of the automotive industry and the rapid growth of automobile output. The analysis and understanding of the stamping automation production line facilitates the selection of the production method of stamping parts, and makes full use of the advantages of their respective automatic lines to serve the automotive field.

  • Progressive
  • Multi-station Transfer
  • Tandem

Abbreviated abroad::P.R.G /T.R.F/T.D.M

Which stamping automation production method should be selected is generally considered from the following factors:

  • Material (Material hardness and whether coils are needed)
  • Material thickness (Punch specifications and supporting considerations for leveling feeders)
  • Monthly production quantity (For large number, continuous molds are available, general or less can use multi-station or tandem mode)
  • Difficulty of stamping product shape (select the corresponding stamping automation method according to the product design mold)

Progressive die automation method

Progressive die refers to a cold stamping die where the press uses a strip-shaped stamping raw material in one stamping stroke to complete several stamping processes at the same time using several different stations. Each time the die is punched, the strip moves at a fixed distance until the product is completed.

Progressive die automation method

Progressive die automation method

Multi-station automation method (Transfer)

The multi-station punching method is to arrange the molds of multiple processes on a punch press, and use the one-time reciprocation of the punch slider to make multiple pairs of molds installed on the machine tool blanking, punching, bending, stretching, trimming, etc. at the same time, and in a round-trip cycle, the robot transfers the work piece from the previous station to the next station to obtain a complete part. It can be divided into two-dimensional and three-dimensional manipulators.

Multi-station automation method

Three-dimensional handling method

Three-dimensional handling method

Tandem Automation Method (Tandem)

Multiple punches are arranged in series to form a whole stamping production line, and the die of each punch corresponds to an independent forming process. The loading and unloading between the punches is a robotic automation method. It is mainly suitable for product lines with small output requirements, few processing steps and relatively independent production lines with strong flexibility.

Tandem Automation Method

Tandem Automation Method

-END-

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