What are the causes of workpiece deformation during CNC machining?

What are the causes of workpiece deformation during CNC machining?

1. The material and structure of the workpiece will affect the deformation of the workpiece.
The amount of deformation is proportional to the complexity of the shape, the aspect ratio and the thickness of the wall, and is proportional to the rigidity and stability of the material. Therefore, the influence of these factors on the deformation of the workpiece is minimized when designing the part.
Especially in the structure of large parts, the structure should be reasonable. Before processing, the defects such as hardness and porosity of the blank should be strictly controlled to ensure the quality of the blank and reduce the deformation of the workpiece.

2. Deformation caused by workpiece clamping
When clamping the workpiece, first select the correct clamping point and then select the appropriate clamping force according to the position of the clamping point. Therefore, the clamping point and the supporting point should be made as close as possible, so that the clamping force acts on the support, the clamping point should be as close as possible to the working surface, and the position where the force is not easily caused by the clamping deformation is selected.
When there are clamping forces in several directions on the workpiece, the order of the clamping force should be considered. The clamping force should be applied first to make the workpiece and the support contact, and it is not easy to be too large. The main clamping force for balancing the cutting force Should be applied later.
Secondly, the contact area between the workpiece and the clamp should be increased or the axial clamping force should be used. Increasing the rigidity of the part is an effective way to solve the clamping deformation, but due to the shape and structure of the thin-walled part, it has a lower rigidity. In this way, deformation occurs due to the application of the clamping force.
Increasing the contact area between the workpiece and the fixture can effectively reduce the deformation of the workpiece when it is clamped. For example, when milling thin-walled parts, a large number of elastic pressure plates are used, the purpose is to increase the force-receiving area of ​​the contact parts; when turning the inner diameter and the outer circle of the thin-walled sleeve, whether using a simple open transition ring or an elastic mandrel The entire arc claws, etc., are used to increase the contact area when the workpiece is clamped. This method is advantageous for carrying the clamping force and thus avoiding deformation of the part. The axial clamping force is also widely used in production. The special fixture designed and manufactured can make the clamping force act on the end face, which can solve the bending deformation of the workpiece due to the thin wall of the workpiece and poor rigidity.
What are the causes of workpiece deformation during machining?

3. Deformation caused by workpiece processing
Due to the cutting force, the workpiece undergoes elastic deformation in the direction of the force during the cutting process, which is what we often call the knife phenomenon. In response to such deformation, corresponding measures should be taken on the tool. The precision of the tool is required for finishing. On the one hand, the resistance formed by the friction between the tool and the workpiece can be reduced, and on the other hand, the heat dissipation capability of the tool when cutting the workpiece can be improved, thereby reducing the workpiece. Residual internal stress.

For example, when milling a large plane of a thin-walled part, using a single-edge milling method, the tool parameters select a larger lead angle and a larger rake angle in order to reduce the cutting resistance. Due to the light cutting speed of the tool, the deformation of the thin-walled parts is reduced, and it is widely used in production.
In the turning of thin-walled parts, a reasonable tool angle is critical for the amount of cutting force during turning, the thermal deformation during turning, and the microscopic quality of the workpiece surface. The rake angle of the tool determines the sharpness of the cutting deformation and the rake angle of the tool. The rake angle is large, the cutting deformation and the friction force are reduced, but the front angle is too large, the wedge angle of the tool is reduced, the tool strength is weakened, the heat dissipation of the tool is poor, and the wear is accelerated. Therefore, when turning thin-walled parts of steel materials, use high-speed tools, the front angle is 6 ° ~ 30 °, with carbide tools, the front angle is 5 ° ~ 20 °.
The back angle of the tool is large, the friction is small, and the cutting force is also reduced accordingly. However, if the back angle is too large, the tool strength will be weakened. When turning thin-walled parts, use high-speed steel turning tools, the cutting angle of the tool is 6 ° ~ 12 °, with carbide tools, the rear angle is 4 ° ~ 12 °, when the finishing car takes a larger rear angle, rough Take a smaller relief angle. When the inner and outer circles of the thin-walled parts of the car are taken, take a large lead angle. Proper selection of the tool is a necessary condition for the deformation of the workpiece.

The heat generated by the friction between the tool and the workpiece during machining also deforms the workpiece, so high-speed machining is often selected. In high-speed machining, since the chips are cut off in a short time, most of the cutting heat is carried away by the chips, which reduces the thermal deformation of the workpiece. Secondly, in the high-speed machining, due to the reduction of the softened portion of the cutting layer material, It can reduce the deformation of parts processing, and is beneficial to ensure the size and shape accuracy of parts. In addition, the cutting fluid is mainly used to reduce the friction during cutting and to reduce the cutting temperature. Reasonable use of cutting fluid plays an important role in improving tool durability, machining surface quality and machining accuracy. Therefore, it is necessary to use a sufficient cutting fluid in order to prevent deformation of the part during processing.
The use of reasonable cutting amounts in machining is a key factor in ensuring part accuracy. In the case of thin-walled parts with high processing precision, symmetric machining is generally adopted to equalize the stress generated on the opposite sides to reach a stable state, and the workpiece is smooth after processing. However, when a certain process takes a large amount of knife, the workpiece will be deformed due to the unbalanced tensile stress and compressive stress.

The deformation of thin-walled parts during turning is multi-faceted. The clamping force when clamping the workpiece, the cutting force when cutting the workpiece, the workpiece hindering the elastic deformation and plastic deformation caused by the cutting of the tool, and the temperature of the cutting zone is increased to cause thermal deformation. Therefore, when we are roughing, we can take a larger amount of feed and feed. When finishing, the amount of the knife is generally 0.2 to 0.5 mm, and the feed is generally 0.1 to 0.2 mm/r, or even smaller. The cutting speed is 6 to 120 m/min, and the cutting speed is as high as possible when finishing the car, but it is not easy to be too high. Reasonably choose the cutting amount to achieve the purpose of reducing part deformation.

What are the causes of workpiece deformation during machining?

4. Stress deformation after processing
After processing, the internal stress of the part itself is a relatively balanced state. The shape of the part is relatively stable, but after removing some materials and changing the internal stress after heat treatment, the workpiece needs to reach the balance of force again, so the shape is A change has taken place. To solve such deformation, the workpiece to be straightened can be stacked to a certain height by a heat treatment method, and a certain tooling is pressed into a flat state, and then the tooling and the workpiece are placed together in a heating furnace, and the material is selected according to the material of the part. Different heating temperatures and heating times. After the heat is straightened, the internal structure of the workpiece is stable. At this time, the workpiece not only has a high straightness, but also the work hardening phenomenon is eliminated, which further facilitates further finishing of the part. The castings should be aged to minimize the residual stress inside, and then use the method of deformation and then processing, that is, roughing-aging-reprocessing.
For large parts, profiling is required, that is, the amount of deformation after the workpiece is assembled, and the amount of deformation is reserved in the opposite direction during processing, which can effectively prevent deformation of the parts after assembly.
In summary, for the easily deformable workpiece, the corresponding countermeasures should be adopted in the blank and the processing technology. It is necessary to analyze according to different situations, and a suitable process route will be found. Of course, the above method only further reduces the deformation of the workpiece. If you want to get a higher precision workpiece, you need to continue to learn, explore and study.
What are the factors that affect the cost of CNC machining quotes?
You must have a clear understanding of all the issues affecting contract processing and manufacturing costs so that they can provide accurate quotes to customers with guaranteed quality and delivery.
So what are these factors?

As with any type of manufacturing, the materials you are using affect the processing costs. Some materials are more difficult to process than others, and some materials are more expensive as raw materials.

Some materials are processed much more slowly than other materials, even with advances in modern tools and mechanical techniques. Some materials can wear the expensive consumable cutting tools used more quickly, and can vary from one tool that makes hundreds or even thousands of parts to one tool that consumes multiple tools. If you ask the store to handle potentially hazardous materials that require additional safety precautions, the overall cost can increase significantly. Therefore, even before component design, the material choice of your component can be a huge cost factor.

CNC machined part size
The size and overall geometry of the part is of course an important factor in the quotation of the machining operation. Obviously, the larger the physical part, the more material is needed to make it. The more detailed and complex the geometric design, the higher the cost of creation. Very tight tolerances are required, long tool arrivals, better surface finishes, or parts that are difficult to form geometric shapes will cost more for simpler parts. It is surprisingly easy to design a component that cannot be manufactured at all, or that is not expensive at the time of manufacture. It is always wise to consult a knowledgeable manufacturer at the design stage of the component. This knowledge can help you design fully functional, high-efficiency parts.
CNC processing equipment needs
The machines required to create parts can have a significant impact on cost. Can CNC machining centers use a multi-axis machine to complete parts, or do they need multiple machines? How many different machines and operations are needed? What size machines are needed? Modern processing equipment is very expensive, random machine type, brand, quality, size And ability is different. Each of these factors must be considered in the accurate cost determination of the part or product.

Processing outside the CNC
Many processed products require additional processing such as heat treatment, special processing operations, surface treatments and specialty coatings. All of these requirements will increase the cost of the base product and should assess its necessity and value.

CNC mechanic skills
More complex machining requires the expertise of more trained and skilled mechanics. The skills and experience of talented mechanics are not without cost – and there are reasons. No matter what formal training program, there is nothing to replace on-the-job experience and on-the-job training. But many modern mechanics have relevant formal education and on-the-job training. Even with a lifetime of processing experience, the industry changes and develops so fast, the mechanic must be a lifelong learner to keep his/her skills at the forefront. The competitive Louisiana machinery store offers ongoing training and cross-training opportunities, and most growing stores offer extensive experience on a staff basis. A simple component that runs on a basic CNC machine, often experienced people can operate effectively, reducing tuition. As the complexity and difficulty of the components increase, the mechanic’s experience and capabilities are also running, so you can see that the cost will increase accordingly. The greater the number of CNC machine tools, the difference between quotes and costing methods.
Number and frequency of operations
One of the important cost influencing factors that is often misunderstood is the amount of operations. Many components require multiple operations and steps to complete, sometimes even many. Each of these operations must be set up and processed. From a basic manual finishing operation, you must centralize the tools and consumables you need to perform very complex machining operations with many tools that can be loaded, dialed in and adjusted to produce Required tolerances. Personal operation settings may be completed in minutes to days or even weeks. Prototype samples can be run if all the required settings are required – all relevant costs must be assigned to the sample and can therefore be very expensive. If you perform the same settings to run 10,000 sheets, you can allocate the same setup cost on 10,000 units, which greatly reduces the cost per piece. The frequency of these runs can also work. If a customer needs 50 deliveries per week, many custom machine shops can run 200 or even a full year, so they also allocate high cost setup costs. Therefore, providing machine tool rework guarantees and accurate demand estimates can often be used to reduce component costs. Many custom machine shops run a 200-piece or even full-year quantity requirement at a time, so they also allocate high-cost setup costs. Therefore, providing machine tool rework guarantees and accurate demand estimates can often be used to reduce component costs. Many custom machine shops run a 200-piece or even full-year quantity requirement at a time, so they also allocate high-cost setup costs. Therefore, providing machine tool rework guarantees and accurate demand estimates can often be used to reduce component costs.

Inspection standards
If the likelihood of failure and the associated consequences are negligible (taking into account the fishing reel components), the level and level of inspection checks can be greatly reduced, thereby significantly reducing the cost associated with component inspection. Therefore, when considering the cost of processing parts, a clear standard of appropriate inspection levels should always be given.
Tax, environment and regulations
Other costs may not be so obvious, but they are crucial. Processing parts requires the use of many different materials, lubricants, coolants, chemicals and safety issues. Any special requirements of the components or materials may seriously affect the cost.

Parts made of materials such as magnesium or tantalum may require special handling and safety equipment. Most parts and modern machines require synthetic oil or oil-based coolant for efficient processing. Local and federal regulations stipulate that proper disposal and handling of these items can affect the overall cost of running a particular component. Revenue, property, inventory, and sales taxes, as well as local, regional, and federal costs and regulations that affect virtually every business unit, vary widely from one area to another and can significantly impact cost variances.

CNC part processing design
Is your CAD drawing accurate, detailed and complete? You may need the help of an experienced engineer or mechanic to complete your design plan to ensure that your finished product is discharged as expected. A tolerance analysis is easily overlooked and can also cause assembly or functional problems at random. This design consultation phase can add some initial cost to the project, but it can save a lot in the long run. Make sure your drawings and CAD models communicate with what you are looking for before manufacturing begins, rather than making it twice to get what you need. The lack of size or size may prevent the production process and result in excessive loss of efficiency while seeking this information.

For more information about CNC precision machine parts processing, you can contact DEYUCNC at any time, we will work with you to solve CNC machining problems in a professional way. Don’t hesitate to get in touch with DEYUCNC as soon as possible.