News – Page 8 – CNC Machining & Turning, Milling, Metal parts

The influence of temperature on the process of precision parts

As for our precision machinery parts processing industry, sufficient accuracy is often a more intuitive reflection of the processing strength of the workshop. We know that temperature is a major factor affecting the processing accuracy. Here is a brief introduction from Xiaobian:

In the process of essential machining, under the action of various heat sources (conflict heat, cutting heat, environmental temperature, thermal radiation, etc.), the temperature change of machine tool, cutter, workpiece to be processed will generate thermal deformation, which will affect the relative displacement between workpiece and cutter, form machining deviation, and then affect the machining accuracy of parts. For example, if the linear expansion coefficient of steel is 0.000012 / ℃, for steel pieces with a length of 100m m, the elongation will be 1.2 μ m when the temperature rises by 1 ℃. In addition to directly affect the expansion and contraction of the workpiece, temperature transformation also has an impact on the accuracy of machine tools and equipment.

In precision machining, higher requirements are put forward for the machining accuracy and the stability of the precision. According to the statistics of related materials, the machining deviation caused by thermal deformation accounts for 40% – 70% of the total machining deviation in the precision machining. Therefore, in the high-precision machining, in order to prevent the expansion and contraction of workpieces due to the temperature change, the reference temperature of the environment is usually strictly regulated, and the deviation boundary of the temperature change is formulated. The constant temperature machining at 20 ℃ ± 0.1 ℃ and 20 ± 0.01 ℃ still appears.

In general, for the constant temperature and humidity test room for precision processing, in order to prevent the expansion and contraction of the processed workpiece due to temperature change during processing and measurement, the reference temperature in the chamber is usually strictly regulated, and the deviation boundary of temperature change is formulated, while the requirements for air relative humidity are not as strict as the accuracy requirements for textile testing. For example, a national ultra precision machining laboratory requires a temperature of 20 ℃ ± 0.2 ℃ and a relative humidity of 45% ± 5%.

In the future, with the development of society and the progress of technology, precision parts processing temperature control technology will be more and more developed.

The principle of CNC process division

There are two different principles that can be used to distinguish CNC process, i.e. process set principle and process distribution principle.

(1) Process set principle

The principle of CNC machining process set is that each process contains as many machining contents as possible, so as to reduce the total number of processes. The principle of CNC machining process set is applicable to the machining of workpieces on high-efficiency special equipment and CNC machine tools. The advantages of selecting the principle of process set are: increasing the production efficiency; reducing the number of processes, reducing the process route, simplifying the production plan and production organization; reducing the basic number, the number of operators and the floor area; reducing the number of workpiece clamping, not only ensuring the mutual position accuracy between the processing surfaces, but also reducing the number of clamps and the auxiliary time of clamping workpiece. However, the investment of CNC processing equipment and industrial equipment is large, it is difficult to adjust and maintain the control, and the production planning cycle is long, which is not conducive to the transfer of production.

(2) Distribution principle of CNC process

Process distribution is to distribute the processing of workpieces in more CNC processes, and the processing content of each process is very little. The principle of CNC processing procedure distribution is applicable to simple processing equipment and process equipment. The advantages of selecting the principle of process distribution are: simple operation of processing equipment and process equipment, simple adjustment and maintenance, and easy conversion to production; it is conducive to selecting the correct cutting amount and reducing the maneuvering time. However, the process route is long, the floor area is large, the number of equipment and workers is large, and the processing accuracy is greatly affected by the skill level of the operators.

Six strict tolerance requirements in CNC precision parts machining

The CNC machining machinists are quite fond of seeing such equipments as + / – 0.005 “, which are the six techniques to maintain strict yamen service requirements in CNC precision parts processing. Five thousandths of an inch is a workout for any good mechanic – they might as well close their eyes and grind. But those jobs are more demanding. Add another zero, now you have: 0.0005 “. Holding five tenths of you is a completely different story. This is the difference between the thickness of a person’s hair and white blood cells. When it comes to strict yamen runner, here are some suggestions to maintain your part specifications.

1. The spindle warms up to maintain the critical tolerance

Run a warm-up program – although it’s a standard program for a lot of CNC machines, it’s more difficult to study and run. A typical program only warms up the spindle, which is essential for applying grease to prevent premature bearing wear. However, you also need to allow internal components to reach a safe operating temperature to cope with thermal expansion. Now, if you only want to maintain strict yamen service on the z-axis, all of these are accurate, but if you integrate the preheating of the spindle with the movement of the machine tool on all the axes, this will help further. The machine is allowed to run for 10-20 minutes, and all parts move to the desired temperature, which will help reduce the impact of thermal expansion of milling time. No matter what, at the end of the warm-up, make sure to measure all the equipment accurately and maintain strict yamen service.

Tool selection may be a factor in maintaining strict government service. Rough machining is carried out with rough machining equipment, so as to reduce the wear of finish machining tools and maintain the accuracy.

2. Equipment selection for maintaining tight yamen service

Choose your equipment carefully – when you deal with these intolerant yamen runners, make sure it is suitable for you. You need to ensure that you have specific equipment for roughing and finishing, so that the roughing tool can receive wear, while the finishing tool only saves one process, so as to ensure the repeatable process of creating accurate parts.

3. Strictly tolerated compensation

Compensation for your equipment – the equipment manufacturers are not happy, so they design the equipment with a little tolerance. They know that if you want to use their equipment to do something, you will be more happy if its reduction performance goes out of too large size instead of too large size. It’s like shaving: you might as well take a rest, but you can’t put it back. Knowing this, you need to make sure that the first thing you do when configuring an accurate job is to dial your essential equipment diameter. You can finish it in many ways, but my preferred way is to mill a feature, and then use accurate equipment to verify the size. Very simple – if you insert a 0.250 inch hole with a 0.236 inch tool, and only a 0.248 inch measuring pin can be inserted, then your tool size will be reduced by 0.001 inch (because the size of each side cannot be small, so use half value).

4. Maintain the temperature of tight yamen service

Thermal stability – this is one of the important things in the list, because it can make a huge difference, and you may not even pay attention to it. Please pay attention to the location of your machinery. Is it close to the window? If so, at some time of the day, is the sunlight reflected on it? Is the air conditioning system started in the afternoon and blowing cool air in the cabin? Are your raw materials stored in a stuffy warehouse, and then enter the cold 68 ° environment? These seem innocent, but will cause huge difficulties in your process. The thermal expansion or contraction of a milling machine or cutting material can vary greatly in your processing. Put all of this in place – keep your machinery and materials in a temperature controlled climate, protected from the sun, and you’ll be rewarded – in the totality of your process.

5. Maintain the calibration of government officials

Calibrate your device – when you’ve done all of the above, all you need is * that * is more stringent, research calls at the manufacturer. After a machine is built, transportation, falling off the truck, moving, stabilizing, using thousands of hours, things will be transferred and handled. This is not preventable. Fortunately, there are several pieces of equipment, whether granite block or Renishaw ballbar, that can help maintain the reins on the loose machinery of the marathon. We like to have a club test and adjust it as part of our annual care so that you can maintain a close relationship with the accuracy of the machine. In the rest, the implementation of these annual services can ensure that the bearings are tight and smooth, the belts are properly tensioned, and the drive motors operate well – these are important factors for accurate machining machinery.

6. Linear scale for maintaining tight government service

If it all fails, scale! – if you still finish all the work on this list, and still try your best, it’s probably time to study using linear scale to obtain machinery. Your typical CNC machine will use the drive motor encoder as the key way to track its absolute position, but this may be due to the shortcomings of the ball screw or the formation of temperature difference. The linear scale changes all of this – usually installed in the workshop, they are composed of two key parts – the scale and the reading head.

Analysis of hardening factors in CNC parts

Many CNC machining enterprises have encountered the problem of hard parts. Next, Xiaobian explains why CNC parts are hard to process. CNC hardware parts processing technology in order to reach the accurate surface of processing parts, it needs to choose the dream processing principle and precise forming activities. But beside the essential work, it is very difficult to finish the accurate machining principle of mechanical numerical control, and there is a big gap between it and the dream value. If we only seek for accurate comments, it will affect the machining efficiency and fail to achieve the expected economic benefits.

The key factors that affect the hardness of CNC parts are as follows:

Factors of raw materials to be processed: the hardness of raw materials to be processed is small, and the more plastic the raw materials are, the more important the level of hard cold working is.

2. The form factor of the tool: the front angle, the edge fillet and the wear amount of the back edge of the CNC machining tool have a great influence on the cold working hard layer. The hardness and depth of the hard layer increase with the decrease of the front angle and the increase of the wear of the edge and the back edge.

The change of cutting speed and feed rate has a great influence on cold work hardness. When the cutting speed increases, the contact time between the cutter and the workpiece is short, the plastic deformation level is small, and the hardness and hard layer are reduced. As the feed speed increases, the plastic deformation level increases, and the surface cold hardening level increases.

Therefore, as long as the correct prevention of the above factors, there will be no problem of CNC machining parts.

On the commonly used fixture materials

Common fixture / fixture materials: (A3, 45, P20, Cr12MoV, S136, SKD11, tungsten steel)

These raw materials are used for making fixtures and jigs, but different raw materials have different uses. Each raw material has different characteristics. Let me make a general comment on the usage of each raw material;

1. A3, 45, cheap raw materials, usually used in the main board without auxiliary fixture;

2. P20, Cr12MoV, usually an important part of the fixture, because the selected raw materials can be wear-resistant, will strengthen the service life of the product, and ensure the application accuracy;

3. S136 raw materials, mainly for wear and rust resistance. Generally used in welding fixture is a common raw material;

4. SKD11 raw materials are usually used in inspection tools and some sophisticated and wear-resistant tools;

5. Tungsten steel, the raw material used less, because the cost of raw materials is quite expensive, usually used in a thorough inspection tool, mainly if wear-resistant and rust proof high;

What kind of influence will be caused to the parts when CNC machining is very rough

This article will introduce the influence of rough machining on CNC parts

1. Influence on wear resistance: the rougher the CNC product processing surface, the smaller the useful contact area between mating surfaces, the greater the pressure, the greater the conflict resistance, and the faster the wear.

2. Affect the stability of fit: for clearance fit, the coarser the surface is, the easier it is to wear and make the middle gap gradually increase in the working process; for interference fit, because the meso convex peak is squeezed flat when it is equipped, the essential useful interference is reduced and the connection strength is reduced.

3. Influence on fatigue strength: there are large grooves on the surface of rough parts, which are the same as sharp corner notches and cracks, and are sensitive to stress sets, thus affecting the fatigue strength of parts.

4. Impact on corrosion resistance: rough part surface is easy to make corrosive gas or liquid penetrate into the inner layer of metal through the surface micro concave Valley, forming surface erosion.

Kunshan CNC processing

5. Influence on sealing: rough surfaces can not be well fitted, and gas or liquid leaks through cracks between contact surfaces.

6. Influence on contact stiffness: contact stiffness is the strength of the part fusion surface to resist contact deformation under the action of external force. The stiffness of the machine depends on the contact stiffness between the parts to a great extent.

7. Affect the measurement accuracy: the surface roughness of the measured surface of the part and the measuring surface of the measuring equipment will directly affect the measurement accuracy, especially in the careful measurement.

Other factors, such as coating, thermal conductivity and contact resistance, reflection strength and radiation function, flow resistance of liquid body and smooth current on conductor surface, will be affected by surface roughness at different levels. Therefore, Suzhou CNC processing plant should pay close attention to this aspect, and do not make the same mistakes in the production process.

How to reduce the scrap rate of parts in precision machining

How to reduce the scrap rate of workpiece in precision machining? I hope I can help you with the understanding of precision workpiece processing.

In the process of precision machining, the design of workpieces should be correct. In the process of design, we should study whether the processing is simple, whether the process and requirements meet the nature of the workshop and market supply. Precision machining enterprises need to provide improved equipment, high-precision processing equipment and inspection equipment. In terms of material use, it is also important to calculate the required raw materials, process placement, and processing methods for each workpiece, and comply with strict process requirements.

In precision machining, the first step of the processing staff is to see the technical requirements of the drawings clearly. It is the basic of precision machining to follow the process. Check whether the drawings of the parts are intact and accurate, and analyze whether the accuracy, surface integrity and technical requirements of the key surfaces of the parts can be reached under the existing manufacturing conditions. Therefore, in time-honored and wonderful machining experience, some people with machining experience may also reduce the scrap rate of workpieces.

To sum up, see through the technical requirements of the drawing; follow the process processing; select the appropriate speed feed; accurately select the tool angle; process the workpiece cutting amount to meet the requirements to complete the processing mission; accurately use all kinds of measuring tools, and follow the strict process requirements. The quality of products is the key to the success or failure of enterprises, so it is not too late to reduce the scrap of precision machining parts and improve the quality of workpieces for every precision machining plant.

After the above understanding of precision workpiece processing, I hope to be able to help you.

The identification rule of coordinate direction for CNC machine tools

In order to simplify the way of programming for CNC machining and ensure the exchange of recorded data. The naming of the coordinates and targets of CNC machine tools has been formulated in the world for a long time. Jb3051-82 “naming of coordinates and targets of CNC machine tools” was formulated in 1982 in China.

In the CNC machining rules, the right-hand Cartesian coordinate system is selected to name the coordinate system of the machine tool. X, y and Z are used to represent the linear feed coordinate axis, and the relationship between X, y and Z coordinate axes is decided by the right skill:

The circular feed coordinate axis rotating around the X, y and Z axes is represented by a, B and C. according to the right-hand spiral rule, the targets of + A, + B and + C are confirmed, as shown in the figure.

Some of the feeding activities of CNC machine tools are completed by the spindle to start the cutter activities, some by the worktable with the workpiece activities. In normal programming, no matter whether the machine tool moves during machining or the workpiece is still moved, if the workpiece to be machined is relatively stationary, and the cutter is moving, and the object that the cutter is far away from the workpiece is the positive target Z axis of the coordinate coincides with the axis of the spindle, and the object that the cutter is far away from the workpiece is the positive target (+ Z); The x-axis is perpendicular to the Z-axis and parallel to the clamping surface of the workpiece. If it is a single column milling machine, the right moving target is the positive target (+ x) of the x-axis when facing the tool spindle to the column target; the y-axis can be confirmed according to the selected x-axis and z-axis according to the right technique..

How to improve precision machining?

Facing the penetration of high-tech such as artificial intelligence and big data into mechanical parts processing enterprises, the traditional precision mechanical parts processing plants are more distant. On the one hand, a large number of people are still not allowed to learn CNC parts processing and programming from scratch. On the other hand, these skills are brilliant, but it is difficult to land them. If a mechanical parts processing factory wants to invest in these skills, it may lose all its energy and cause the previous achievements to be wasted.

Now, precision machine parts processing plant is facing a big dilemma, that is, the profit margin is too low and the technology content is lower. The workshop of machine parts processing is still the traditional assembly line. In such a production mode, the new generation of employees are also defined as equipment and cost, and the subjective initiative cannot be developed. The old model is really out of date, and the new generation of employees are more and more disgusted with these mechanical work. Therefore, the automatic and intelligent machining of mechanical parts is highly sought after in order to completely free the hands of human beings. The manufacturing of some large products, such as automobiles and home appliances, is still basically automated. However, the manufacturing of Zhihao mobile phones, iPads and other products requires high precision. If the current automation equipment is unable to correctly install a soft cable, it is still necessary to ask for help In precision machine parts processing plant.

What should be paid attention to in the processing of non-standard fixture accessories

The following points should be paid attention to for grinding of non-standard fixture accessories:

1. Abrasive grain size for grinding shall be changed from coarse to fine in sequence. When changing abrasives, the grinding trace of the previous process should be completely removed. Grinding should be carried out until the grinding trace can only be seen this time. It is very important to prevent the “relief” phenomenon by punching the thimble.

2. The abrasive of the same size can only be used for the same grinding tool. Before changing the size, the workpiece must be completely cleaned to prevent coarse abrasive or other dirt from being brought to the next process to form scratch on the grinding surface.

3. Each time the next grain size is changed, the grinding shall be carried out at an angle of 30-45 ° with the last grinding target. If there are deep scars, it is not allowed to only grind the one-sided position, otherwise, the one-sided position will be pitted, and full trimming shall be carried out to remove the pit. It is necessary to pay attention to average grinding for simple grinding and not simple grinding stations

These are the articles shared today. Do you understand? If you want to know more about or need non-standard fixture accessories, please call our company or pay attention to our official website. We will sincerely serve you.