Discussion on Fixture Design Challenges in CNC Machining


The selection of high-quality CNC fixtures can largely improve the efficiency and machining accuracy of CNC machining. When selecting fixtures, the compatibility between the size of the fixture, machine, and the size of the machined part should be considered.

On the other hand, we should ensure the tightness of the fixture. Otherwise, displacement will cause declined machining quality or defective parts. It affects the efficiency and wastes machining materials.

At present, commonly used fixtures of CNC custom machining services are completed by way of component assembly. It can realize the repeated use of fixtures, thereby improving economic efficiency, and also conducive to the reduction of waste. CNC fixtures must have good mechanical automation matching, and reduce manual operation and intervention in the machining process, so the design of CNC clamping requires higher quality. In the design process, the main attention should be paid to the following aspects.

Achieving Precision in CNC Fixture Positioning

Fixtures play a crucial role in the quality of workpiece machining. Accurate positioning is the original purpose and basic premise of fixture design. The CNC machining program needs to prioritize the origin of the coordinate system of the parts, match the fixture with a suitable coordinate system, and minimize the workpiece movement.

CNC Machining

After the fixture is removed and then installed, any movement of the fixture leads to a change in the position of the workpiece, which will seriously affect the quality of the workpiece. Also, it causes prolonged adjustment time, increased work steps, and reduced processing efficiency.

To achieve accurate fixture positioning, it is necessary to strengthen the tool and control measures. During CNC programming, first accurately grasp the machining process diagram of the part, and understand the basic origin of the workpiece.

Once the fixture is securely installed according to the tightening requirements, the deviation value is gradually reduced by adjusting the basic origin. By establishing the relationship between the two coordinate systems through tool operation, CNC machining precision and accuracy can be ensured.

Adapt Fixture for Versatility

In the fixture design process, different types of workpieces and parts often require unique fixtures. However, frequent tool and fixture changes will not only affect the work efficiency but also lead to the risk of human negligence, thus affecting the data accuracy and quality.

To solve this problem, clamping design and development should comprehensively consider the characteristics and shape of the workpiece, aiming to make the fixture that can adapt to a wide range of workpieces. By minimizing fixture replacements and downtime, production efficiency can be improved, increasing comprehensive economic benefits for the enterprise.

Ensure Fixtures Rigidity

In CNC machining, workpieces often require different levels of rigidity, so abundant materials are often used for processing. Therefore, the fixture design must prioritize rigidity to meet the demands of different workpiece types.

However, in the process of CNC machining, the same set of fixtures may be applied to two modes of finishing and roughing at the same time due to operating steps and modes. This places demands on the tool feed rates and can accelerate fixture aging and damage, thereby increasing the cost of CNC custom machining services to a certain extent.

CNC Machining

For example, high precision and high-strength materials such as titanium alloys are common when machining aerospace components. In such cases, fixtures must withstand high forces and vibrations during roughing, and ill-fitting fixtures can wear out quickly. When these fixtures are also used in finishing operations, their rigidity is significantly reduced. Surface roughness and dimensional accuracy are also reduced, which increases scrap rates and rework costs.

During the processing, insufficient rigidity of the fixture can lead to the stress concentration of the holding part. And long term use will probably cause edge collapse, posing a risk to production and operator safety. Therefore, we must first ensure sufficient rigidity.

CNC Machining

Replacing CNC Fixtures

In CNC machining, several complex workpieces are more difficult to hold, requiring very complicated and special fixtures. A monolithic fixture needs to be completely replaced when there is local damage in the application process, leading to increased machining costs.

In addition, fixture models or parts are discrepant, which is challenging to replace the appropriate components. It takes a long time for the fixture parts to be replaced, seriously affecting the efficiency of CNC machining.

To solve this problem, the most commonly used fixture method of component organization replacement is very suitable. The fixture itself is not a whole but is composed of multiple components. According to the clamping demands of different parts, adjust the number of components and combination mode, which can improve the fixture applicability and production efficiency.

CNC Machining


Fixture plays an important part in CNC machine processing. It impacts processing accuracy, quality and efficiency. Therefore, the fixture design should focus on the adaptability of the production. So that the fixture matches the operation of the machine tool, and assures the quality of CNC custom machining services.



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