Drag Marks

2024-09-25 by Cherry

Introduction

In modern manufacturing, die-casting machines are widely 

used in automobiles, electronics, aviation, and other fields

as an efficient metal forming equipment. And drag mark 

technology is one of the key factors to improve die-casting

machines' performance and product quality. 

This article will explore the application of drag marks in 

die casting machines in depth to help readers understand 

its principles and practical value.

What is a drag mark?

Drag marks, as the name suggests, are uneven marks on the 

metal surface formed during the die-casting process. This 

phenomenon is usually caused by factors such as mold design, 

material flow, and uneven cooling. Although in some cases, 

drag marks are regarded as defects, proper application of

drag marks can improve the performance of die castings.

Causes of drag marks

1. Die-casting process parameters

1.1 Die casting speed: When the die casting speed is too fast,

 the impact force of the molten metal on the mold increases,

 and drag marks are prone to occur.

1.2 Pouring temperature: Too high or too low pouring temperature

will affect the fluidity of the molten metal, resulting in

the appearance of drag marks.

1.3 Mold temperature: Uneven or inappropriate mold temperature

will also change the flow state of the molten metal in the 

mold, resulting in drag marks.

2. Mold design and manufacturing

The geometry and surface treatment of the mold has an important

influence on the formation of drag marks. Unreasonable mold

design may lead to uneven metal flow, resulting in obvious

drag marks.

2.1 Mold structure: Complex mold structure may lead to poor 

flow of molten metal, resulting in drag marks.

2.2 Mold surface quality: Factors such as the roughness and 

hardness of the mold surface will affect the friction between

the molten metal and mold affect the formation of drag 

marks.

2.3 Gate design: The gate's position, size, and shape  

have an important influence on the flow direction and speed 

of the molten metal. Unreasonable gate design is prone to 

drag marks.

3. Cooling rate

During the die-casting process, the cooling rate of the metal 

will directly affect its solidification state. If the cooling

rate is uneven, it may cause drag marks in local areas.

4. Material properties

The fluidity and solidification characteristics of different

metal materials will also affect the appearance of drag 

marks. For example, aluminum alloys are more prone to drag 

marks than zinc alloys because of their greater fluidity.

Positive Applications of Drag Marks

Although drag marks are often considered defects, their 

presence can bring positive effects in some cases:

1. Enhance Adhesion

Appropriate drag marks can increase the adhesion of coatings 

or other surface treatments, and improve the wear resistance 

and corrosion resistance of products.

2. Improve Appearance

In some designs, drag marks can be designed as aesthetic elements

to make the product more visually attractive. For example, 

the surface treatment of some high-end home appliances deliberately

retains slight drag marks to highlight their handmade characteristics.

3. Reduce Production Costs

By making reasonable use of drag marks, the requirements for

mold surface finishing can be reduced during the design 

stage, thereby reducing production costs.

How to Control Drag Marks

To effectively control the generation of drag marks 

during the die-casting process, the following methods can be

adopted:

1. Optimize mold design

When designing the mold, the metal fluidity should be fully 

considered to ensure that the internal structure of the mold 

is reasonable and avoids the formation of dead corners and 

stagnation areas.

2. Adjust the cooling system

Reasonable configuration of the cooling system to ensure uniform

cooling of the mold can effectively reduce the generation of

drag marks. Check the cooling pipes regularly to ensure that

there is no blockage.

3. Choose the right material

When selecting materials, metal materials with moderate 

fluidity and solidification properties should be selected 

according to product requirements to avoid drag marks caused

by material characteristics.

Application of drag marks in die-casting machines

1. Quality control

1.1 As one of the important indicators of casting quality,

the presence and severity of drag marks can reflect the 

stability of the die-casting process and the quality of the

mold. 

Through the observation and analysis of drag marks, 

problems in the die-casting process can be discovered in 

time, such as too-fast die-casting speed, inappropriate pouring 

temperature, mold wear, etc., to take corresponding

measures to adjust and improve the quality of castings.

1.2 For some castings with high surface quality requirements,

the control of drag marks is particularly important. By 

optimizing the die-casting process parameters and mold design,

the occurrence of drag marks can be effectively reduced, and the 

surface finish of castings can be improved, and customer needs

can be met.

2. Mold maintenance and improvement

2.1 The appearance of drag marks can provide an important basis 

for mold maintenance and improvement.

By analyzing the location, shape, and severity of the drag mark,

it can be determined which parts of the mold have problems 

such as wear, deformation, or unreasonable design. In response

to these problems, the mold can be repaired, replaced or 

improved in time to extend the service life of the mold and 

improve production efficiency.

For example, if the drag mark mainly appears in a specific 

part of the mold, it may be that the mold surface in that 

part is severely worn and needs to be repaired or replaced.

If the shape of the drag mark is irregular, it may be that 

the structural design of the mold is unreasonable and needs 

to be optimized.

2.2 Process optimization

The study of drag marks can provide a reference for the 

optimization of the die-casting process. By analyzing the 

changes in the drag mark under different process parameters,

the best combination of die-casting process parameters can

be determined to improve the quality and production efficiency 

of the casting.

For example, by adjusting parameters such as die-casting 

speed, pouring temperature, and mold temperature, the changes

in the drag mark can be observed and the most suitable 

process parameter range can be found. At the same time, the 

flow state of the molten metal can be optimized and the 

generation of drag marks can be reduced by measures such as

improving the gate design and adding an exhaust system.

Detection and evaluation of drag marks

The detection of drag marks usually relies on professional 

testing equipment and technology. Common methods include:

1. Visual inspection

By visually observing the surface of the product, the presence

and the severity of the drag mark can be preliminarily determined.

2. 3D scanning

Using 3D scanning technology, the depth and distribution of 

the drag mark can be accurately measured to provide data support

for subsequent quality control.

3. Surface roughness measurement

By measuring the surface roughness, the impact of the drag

mark on the surface quality of the product can be quantified.

Drag mark control method

1. Optimize die-casting process parameters

1.1 Reasonably adjust the die casting speed: Select the 

appropriate die casting speed according to the shape, size

and complexity of the casting. For thin-walled castings 

or castings with complex shapes, the die-casting speed should

be appropriately reduced to reduce the impact of the molten 

metal on the mold.

1.2 Control the pouring temperature: Determine the appropriate

pouring temperature based on the characteristics of the metal

material and the requirements of the casting. Generally 

speaking, the pouring temperature should be within a certain

range above the liquidus temperature of the metal material to

ensure the fluidity of the molten metal.

1.3 Stabilize the mold temperature: Keep the mold temperature 

within a suitable range through heating, cooling, or insulation. 

For large castings or castings with complex shapes, equipment 

such as mold temperature controllers can be used to accurately 

control the temperature of the mold.

2. Improve mold design and manufacturing

2.1 Optimize mold structure: Design a simple and reasonable 

mold structure to avoid poor flow of molten metal in the 

mold. For example, use reasonable parting surfaces, gates 

and exhaust systems to reduce turbulence and eddy currents 

of molten metal.

2.2 Improve mold surface quality: Perform surface treatment

on the mold, such as polishing, chrome plating, etc., to reduce

the roughness of the mold surface and reduce the friction 

between the molten metal and the mold. At the same time, improve

the hardness and wear resistance of the mold and extend 

the service life of the mold.

2.3 Reasonably design the gate: According to the shape and 

size of the casting, select the appropriate gate position, 

size and shape. The design of the gate should ensure that 

the molten metal can flow smoothly into the mold to avoid

impact and turbulence.

3. Strengthen production management

3.1 Strictly control the quality of raw materials: Select

metal materials with stable quality and good fluidity 

to avoid the generation of drag marks due to raw material

problems.

3.2 Regular maintenance and care of the die-casting machine:

Keep the die-casting machine in good operating condition 

and ensure the stability of the die-casting process parameters.

At the same time, regularly clean and lubricate the die-casting

machine to reduce the impact of equipment failure on the 

quality of castings.

3.3 Train operators: Improve the technical level and quality 

awareness of operators and operate in strict accordance with

the operating procedures. Operators should be familiar with

the adjustment methods of die-casting process parameters and

the maintenance points of the mold, and promptly discover and

solve problems.

Case analysis of drag marks

Taking the die-casting process of a certain automotive 

part as an example, in the early stage of production, due

to unreasonable mold design, obvious drag marks appeared,

resulting in product scrapping. After optimizing the design

and adjusting the cooling system, the generation of drag

marks were successfully reduced and the product qualification

rate was improved.

Conclusion

Although the application of drag marks in die-casting machines 

is often regarded as a defect they can add value to 

the product under certain conditions.

The application of drag marks in die-casting machines is a 

complex and important issue. Through in-depth research and control 

of drag marks, the quality and production efficiency of castings

can be effectively improved, the service life of molds can be 

extended, and production costs can be reduced.

In actual production, we should take into account factors 

such as die-casting process parameters, mold design and 

manufacturing, and production management according to specific 

circumstances, take effective measures to control the generation 

of drag marks, and contribute to the development of the 

die-casting industry.

Through reasonable design and control measures, manufacturers

can effectively manage the generation of drag marks, thereby 

improving the overall quality and competitiveness of products.

I hope this article can provide readers with valuable references 

and help the development of the manufacturing industry.

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