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Analysis On The Large-Scale Stamping Workshop Design For Automobiles Covering Parts

The stamping production of cover parts has the characteristics of large-scale, mass production and multi-variety.

Advanced and reasonable stamping workshop process planning and design should fully reflect the improvement of automation level, the improvement of the production cycle, the reduction of stamping parts cost, and the improvement of stamping parts quality.

This article combines the planning and design of a stamping workshop of a stamping factory to explain how to determine the production process and equipment according to the production program and carry out the workshop process layout.

And on this basis, the requirements for supporting civil engineering and public facilities are proposed for reference by process designers.

Stamping process and equipment selection

Prerequisites for stamping line planning

With the production and rising output of new models, as well as the increasing quality standards of the stamping industry, the stamping production conditions of the plant are facing several major problems that need to be solved urgently.

(1) The production load of large stamping parts.

According to the production program, the production load problem of large stamping parts will intensify in the next few years, reaching or even exceeding 150%, which is far beyond the scope of production capacity.

However, there is no mass production capacity for large-scale stamping parts in the surrounding areas, so large-scale stamping production lines must be added to solve this problem.

(2) Product quality assurance ability.

With the market’s increasing quality requirements for medium and heavy-duty commercial vehicles, factories urgently need to improve their stamping quality assurance capabilities to support quality standards, improve production efficiency, and reduce production costs.

The improvement of quality assurance ability is the overall improvement project corresponding to the whole process of stamping.

It is necessary to change and improve the production conditions and improve the management level from the comprehensive layout of raw material preparation, stamping production, warehousing and logistics.

(3) Insufficient press tonnage

The introduction of high-end commercial vehicle models has not only increased the production load of large-scale parts in the factory (an increase of 20 streams), but also the demand for press tonnage exceeds existing conditions.

At present, the rated tonnage of the company’s largest press is 1600t, and the actual demand for the largest part exceeds 2200t.

According to the actual situation of the factory, the economic efficiency of comprehensive accounting comes to a conclusion:

It needs to introduce a larger tonnage press, combined with the company’s product development plan and industry rules, it is defined as the maximum rated tonnage of 2400t.

(4) The production efficiency is low and the labor intensity of workers is high.

The stamping production lines in the factory are manual production lines, the efficiency of large parts is low, and the SPH does not exceed 240 times.

At the same time, workers’ labor intensity is greater,

The handling quality of a single shift exceeds 10t, and the maximum exceeds 15t.

Based on the above analysis, combined with the factory’s demands for improvement of safety technology, environmental protection, inventory management, and technological advancement, the following construction contents need to be completed:

(1) The existing conditions need to be cleaned up, transformed and integrated to meet the needs of the phased construction of the “Stamping Center” project.

(2) One 630t uncoiling blanking line needs to be updated.

(3) One new 2400t stamping automated production line is needed.

(4) It is necessary to complete the supporting facilities such as mold transformation, scrap line, lifting equipment, logistics equipment, and station appliances at the same time.

Production process and equipment

The production process of the stamping workshop mainly includes the production of stamping blanks and stamping parts. There are other auxiliary tasks such as mold trial, mold repair, stamping parts repair, and waste transportation.

⑴ Blank production.

Blanking is the processing of coils into blanks required for the production of stamping parts.

The production process is: coil feeding → uncoiling → cutting head → cleaning → leveling → feeding → blanking or shearing → stacking.

In order to meet the production of blanks, the workshop needs to be equipped with a fully automatic uncoiling blanking production line or a fully automatic cutting production line.

The former can be used for both blanking and shearing, and the latter can only be used for shearing.

An example of the uncoiling blanking line is shown in Figure 1.

Uncoiling blanking line

Figure 1 Uncoiling blanking line

Since the price of the uncoiling blanking line is relatively high, it is necessary to consider the economy of configuration.

Usually, the output of one uncoiling blanking line can match the output of three fully automatic mechanical stamping production lines.

The selection of this equipment should be based on the products and output of the workshop.

(2) Stamping production.

The stamping production process of large-scale covering parts mainly includes deep drawing, trimming, flanging, forming, punching, shaping, etc.

Adjust and combine according to the shape and structure of stamping parts,

The typical production process of some products is:

1) The overall door frame.

Unstacking and feeding device → drawing forming → trimming and punching → oblique wedge trimming and punching → flanging shaping → offline.

2) Top cover.

Unstacking and feeding device → drawing forming → trimming and punching → oblique wedge flanging and shaping → shaping and punching → offline.

The press connection arrangement for stamping production, the number of presses needs to be determined according to the forming process of the stamping part and the form of the stamping die.

There are three, four, five, and six orders, and the four orders are generally the most used.

It should be said that the fewer the processes, the fewer the corresponding presses, and the lower the fixed investment in the workshop.

But at the same time, it is necessary to consider the feasibility of mold design and the cost increase caused by the complex die.

The parameters of the press equipment such as nominal pressure, table size, closing height, etc. need to be determined according to the product process.

The selection of the number of press lines depends on the product, output, and press line productivity.

The formula is:

the number of press lines = ∑ (number of mold sets × production program) ÷ press line productivity (ASPM) ÷ equipment annual time base.

Among them,

1) The number of mold sets and production guidelines has been determined at the time of planning.

2) The press line productivity is related to the operating speed of the press itself and the conveying mode of the stamping parts.

The operating speed of the press is the inherent value of the equipment, and there are generally two forms of stamping parts conveying.

One is manual loading and unloading, the other is fully automatic loading and unloading (divided into robot and manipulator).

The conveying speed of the manipulator is the fastest, followed by the robot conveying, and the manual is the slowest. Accordingly, the investment is from high to low.

3) The annual time base of equipment can be obtained from the “Design Standards for Annual Time Base of Machinery Factory“, or obtained from relevant documents and regulations according to the company system.

The 1×2400t+3×1000t fully automatic stamping production line is shown in Figure 2.

1×2400t+3×1000t automatic stamping production line

Figure 2 1×2400t+3×1000t automatic stamping production line

(3) auxiliary area.

1) Die repair

Simple machine repair equipment is generally set up in the stamping workshop for daily minor repairs of the die.

If the load rate of the press production line is high, it is necessary to set up a trial press in the mold repair area.

The parameters of the tryout press are the same as those of the largest equipment on the production line.

2) Waste transportation

Punching waste will be produced in the stamping production,

On the basis of the press line, a waste conveying line can be set up to collect and discharge waste.

3) Repair of stamping parts

The stamping parts that are loaded and unloaded online need to set up a trim area for trimming the burrs and surface defects of the stamping parts.

Workshop layout and logistics

The layout of the workshop is based on the production process of stamping parts.

The stamping workshop is generally composed of coil storage area, uncoiling blanking production area, blank stacking area, mold stacking area, mold maintenance area, stamping production area, stamping parts temporary storage area and stamping parts maintenance area etc.

In addition, there are waste materials room, forklift storage area, workshop office area and living area etc.

Figure 3 shows the layout of the press shop.

Schematic diagram of the layout of the press shop

Figure 3 Schematic diagram of the layout of the press shop

The logistics route of the logistics stamping workshop is relatively clear, mainly the following routes.

(1) Stamping production, production logistics route is shown in Figure 4.

The logistics route of stamping production

Figure 4 The logistics route of stamping production

(2) Mold, the mold logistics route is shown in Figure 5.

Logistics route of stamping die

Figure 5 Logistics route of stamping die

Civil engineering and public supporting requirements

After the production program, technology and equipment of the stamping workshop are determined, the corresponding requirements for civil engineering must be put forward to meet the production needs.

Civil works

(1) Workshop size

1) Workshop span.

It is mainly determined by the type of die change of the press.

Generally, the press has three upper die forms: front upper die, side upper die, left and right upper die.

Among them, the front upper die occupies the smallest area, and the workshop with a span of 15m is enough;

The side upper die is second, and the workshop span requires 24m;

The left and right upper mold occupy the largest area.

At present, the stamping workshop usually adopts fully automatic production lines.

In order to improve the production efficiency of the whole line, the left and right upper molds are mostly used, which also determines that the span of the stamping workshop is generally 30m or 36m.

The span of the stamping parts warehouse is generally required to be more than 24m to facilitate forklift transportation.

2) Workshop length

According to the layout of the press in the span, the length of the automatic stamping production area is generally about 60m, and the length of the die stacking area needs to be measured according to the number of dies.

If only one stamping line is arranged for a span, the length of the workshop is generally about 120m.

If the number of dies is large, the workshop needs to be extended appropriately.

The length of the corresponding unwinding blanking span is also 120m.

3) Column distance

Considering the transportation requirements of large presses and the economy of the plant for mold transportation and equipment maintenance between spans, the column spacing of the stamping shop is generally set between 9-12m.

4) Workshop height

The height of the press shop depends on the height of the press.

Since the press for producing large covering parts is generally a maximum of 2400t press, the height above the ground is about 11-11.5m.

After considering the safety distance, the height of the rail top of the crane in the workshop is generally 13 to 14m, and the lower chord height of the roof truss of the stamping workshop can be determined to be about 17m according to the height of the selected crane.

Among them, the selection of presses and cranes has an important influence on the height of the workshop.

The height of the uncoiling blanking span is affected by the press on the uncoiling blanking line, and the height of the rail top is 12m.

The height of the stamping parts warehouse is determined by the height and number of layers of the stamping parts stack.

The warehouse that only considers forklift transportation is generally 7m.

(2) Architectural form

The building forms of the press shop generally have three forms: concrete structure, steel structure, and steel-concrete structure, depending on the specific project.

In the past, the stamping workshop was mostly made of concrete.

Now, because the cost of steel structure is almost the same as that of concrete, and the production and installation of steel structure are simple and convenient, and the construction period is short, most stamping workshops currently adopt steel structure.

The workshop floor is required to be clean and wear-resistant.

Both epoxy resin floor and high-strength wear-resistant floor can be used, and the steel sand floor can also be used for more demanding ones.

(3) Load requirements

1) Press load

It depends on the load of the press, the weight of the die change cart, and the weight of the die.

Since a mechanical press will generate a large impact load when it is working, the dynamic load needs to be considered when calculating the load of the press.

2) Crane load

The crane used in the stamping workshop generally needs to use 32t and 50t cranes, and the deadweight, wheel pressure, wheelbase and other parameters should be proposed according to the crane product specifications.

3) Floor load

Except for the press line area, most of the stamping workshop area is used for stacking molds.

Generally, the number of mold stacking layers is two, so the floor load of the workshop is about 100kPa.

The coil or sheet stacking area should be determined according to the stacking form.

If the special rack is used for stacking and exceeds the second floor, the floor load needs to be considered at 150kPa.

4) Pipeline load

There will be pipes for water, electricity, gas, wind, and fire fighting on the pillars of the press shop, and their loads need to be considered in the calculation.

In addition, on the column near the press line, an electrical cabinet platform is generally required to place the press and the power distribution cabinet of the automation device, and the load of the column also needs to be considered.

(4) Press foundation

The foundation of the automated press line in the press shop is a very important civil engineering content, which has three types including independent foundation, through foundation and basement foundation.

An Independent foundation means that each press on the press line is an independent foundation, and they are not connected to each other.

This basic form has the cheapest cost, but each press equipment needs to be separately discharged and transported in the workshop.

Relative to mass production, it will have a great impact on workshop production and logistics, so this form is currently rare.

The through-type foundation is to lay out the foundation of each press, and set up a waste conveying line in the foundation to collect stamping waste and transport it to the waste room.

Because this form completely separates the waste logistics from the production logistics, and at the same time increases the convenience of press maintenance, it is currently more commonly used.

The basement foundation is to make a basement within the range of the press or arrange the press line on the second floor.

Because of this form, the press foundation becomes a large space. In addition to the press equipment and waste conveying line, public power, power distribution facilities and some maintenance areas can also be arranged, which greatly increases the use area of the workshop.

However, due to the high cost, it is currently not used much.

The foundation of the through-type press depends on the equipment, and the product data of different suppliers will be different.

Usually, the 4-station press line pit has a net width of 9.5m, a depth of 7m and a length of about 35m.

In addition, it is necessary to set up a pit for the main line of the waste conveying line.

It is connected to the press pit and arranged vertically, the depth is the same as or shallower than the press pit, and the width is about 4m.

Public power auxiliary facilities

The public supporting facilities of the press workshop are generally relatively simple.

Water, electricity and gas are necessary for the equipment,

The other is to decide whether to send cold air, heating, dehumidification and other facilities according to the project situation.

(1) Electricity.

Electricity is the main source of energy used in stamping plants.

The use area is mainly concentrated in the automatic stamping line and the uncoiling blanking line, so the workshop transformers are arranged as close to the equipment as possible.

(2) Compressed air.

The air points in the stamping workshop are mainly in stamping equipment, mold repair, stamping parts repair and other areas.

The quality requirements of compressed air are: the air source pressure is 6bar, the oil content in the compressed air is 25mg/m3, the particle diameter is 40μm, and the particle content is 10mg/m3.

(3) Circulating cooling water.

Circulating cooling water is mainly used for press equipment,

The inlet water temperature is 32°C, and the outlet water temperature is 37°C.

Soft water or pure water is required to prevent scaling damage to the equipment.

(4) Others.

1) Fire protection.

The stamping workshop belongs to Category E production, and it has no special requirements for fire protection and smoke exhaust.

2) Environmental protection.

The environmental impact of the press shop is mainly noise caused by press production, vibration and noise caused by waste conveying lines.

Therefore, the doors and walls of the press shop need to use sound insulation materials, and the windows use double vacuum glass windows.

Vibration isolation pads must be installed under the press to reduce the impact of noise and vibration on the surrounding environment.

Of course, in the layout of the general plan, consideration must also be given to reducing residential, school, hospital and other civilian facilities around the stamping workshop.

Workshop personnel planning

Compared with manual lines, the number of people in each shift is significantly reduced for automatic lines.

Staffing changes from stamping workers with high labor load to automation operators with high skill requirements, and the physical labor intensity of workers is reduced, as shown in Table 1.

Production mode

Type of work

Automatic line staff structure manual line staff structure Note
Monitor 1 1 single line

single shift

Acting monitor 1
Stamper 18
Underpaid staff 1
Site management 1
Stamping operator 1
Automation preparation 1
Engineering quality 1
Crane operator 2 1
Check 2 1
Packing 3 3
Repair 3 1
Hand in 3 3
Warehousing 2 3
Total 22 31

Compared with the automation line, the main reason for the large difference in staffing is the degree of emphasis on production stability and quality stability:

For large parts, the production capacity of the automated line is more than 3 times that of the manual line.

Naturally, there are more people in equipment maintenance and die maintenance to maintain stable production.

At the same time, increase a large number of online inspectors to detect quality problems early and maintain stable quality.

It should be noted that the skills and qualities of the newly added processing species require training reserves.

Conclusion

The press shop has a heavy load and has high requirements for civil engineering and public configuration.

From the perspective of engineering design, this article gives a unified explanation of several aspects involved in the design of the stamping workshop, hoping to serve as a reference for the process technicians responsible for designing this type of workshop.

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