How to choose the right CNC machining material？


The materials are wrong, all in vain! In order to produce satisfactory products, the choice of materials is the most basic step and the most critical step. CNC machining can choose a lot of materials, including metal materials, non-metallic materials and composite materials.

Common metal materials include steel, aluminum alloy, copper alloy, stainless steel and so on. Non-metallic materials are engineering plastics, nylon, bakelite, epoxy resin and so on. Composite materials are fiber reinforced plastic, carbon fiber reinforced epoxy resin, glass fiber reinforced aluminum and so on.

Different materials have different physical and mechanical properties, and the correct selection of the right material is critical to the performance, accuracy and durability of the part. Starting from my own experience, this article will share with you how to choose low cost and suitable materials among many processing materials.




Determine the actual application requirements of the product

First, we need to determine the end use of the product and its parts. For example, medical equipment needs to be disinfected, lunch boxes need to be heated in the microwave oven, bearings, gears, etc., need to be used for load-bearing and multiple rotational friction.


Transform the application requirements of the material into the characteristics of the material

After determining the use, starting from the actual application needs of the product, the use of the product is investigated, and its technical requirements and environmental requirements are analyzed, and these needs are transformed into the characteristics of the material. For example, parts of medical equipment may have to withstand the extreme heat of an autoclave; Bearings, gears and other materials have requirements for wear resistance, tensile strength and compressive strength. Mainly can be analyzed from the following points:

01 Environmental Requirements

Analyze the actual use scenario and environment of the product; For example: What is the long-term working temperature of the product, the highest/lowest working temperature, respectively, belonging to high temperature or low temperature? Are there UV protection requirements indoors or outdoors? Is it in a dry environment or a humid, corrosive environment? Etc.

02 Technical Requirements

According to the technical requirements of the product, the required capabilities are analyzed, which can cover a range of application-related factors. Such as: the product needs to have conductive, insulating or anti-static which of the capabilities? Is heat dissipation, thermal conductivity, or flame retardant required? Do you need exposure to chemical solvents? Etc.

03 Physical Performance requirements

Analyze the required physical properties of the part based on the intended use of the product and the environment in which it will be used. For parts subjected to high stress or wear, factors such as strength, toughness and wear resistance are critical; For parts exposed to high temperatures for a long time, good thermal stability is required.

04 Appearance and surface treatment requirements

The market acceptance of the product depends largely on the appearance, the color and transparency of different materials are different, the finish and the corresponding surface treatment are also different. Therefore, according to the aesthetic requirements of the product, the processing materials should be selected.

05 Processing performance considerations

The machining properties of the material will affect the manufacturing process and accuracy of the part. For example, although stainless steel is rust resistant and corrosion resistant, its hardness is high, and it is easy to wear the tool during processing, resulting in very high processing costs, and it is not a good material to process. The plastic hardness is low, but it is easy to soften and deform during the heating process, and the stability is poor, which needs to be selected according to actual needs.


Find materials that match the characteristics

Because the actual application requirements of the product are composed of a number of contents, there may be multiple materials that meet the application requirements of a product; Or the situation where the optimal selection of different application requirements corresponds to different materials; We may end up with several materials that meet our specific requirements. Therefore, once the desired material properties are clearly defined, the remaining selection step is to search for the material that best matches those properties.

The selection of candidate materials begins with a review of material properties data, of course, it is not possible to investigate thousands of applied materials, and there is no need to do so. We can start from the material category, and first decide whether we need metal materials, non-metallic materials or composite materials. Then the previous analysis results, corresponding to the material characteristics, narrow the selection of candidate materials. Finally, the material cost information is used to select the most suitable material for the product from a number of candidate materials.

At present, Honscn has selected and launched a number of materials suitable for processing, which have been a popular choice for our customers.





Introduction to the properties of metal materials


Metallic materials refer to materials with properties such as luster, ductility, easy conduction and heat transfer. Its performance is mainly divided into four aspects, namely: mechanical properties, chemical properties, physical properties, process properties. These properties determine the scope of application of the material and the rationality of the application, which is an important reference for us to choose metal materials.The following will introduce two types of metal materials, aluminum alloy and copper alloy, which have different mechanical properties and processing characteristics.




Aluminium alloy

There are more than 1000 aluminum alloy grades registered in the world, each brand name and meaning are different, different grades of aluminum alloy in hardness, strength, processability, decoration, corrosion resistance, weldability and other mechanical properties and chemical properties there are obvious differences, each has its strengths and weaknesses.

hardness

Hardness refers to its ability to resist scratches or indentations. It has a direct relationship with the chemical composition of the alloy, and different states have different effects on the hardness of aluminum. The hardness directly affects the cutting speed and the type of tool material that can be used in CNC machining.

From the highest hardness that can be achieved, 7 series > 2 series > 6 series > 5 series > 3 series > 1 series.

intensity

Strength refers to its ability to resist deformation and fracture, commonly used indicators include yield strength, tensile strength and so on.

It is an important factor that must be considered in product design, especially when aluminum alloy components are used as structural parts, the appropriate alloy should be selected according to the pressure under.

There is a positive relationship between hardness and strength: the strength of pure aluminum is the lowest, and the strength of 2 series and 7 series heat-treated alloys is the highest.

density

Density refers to its mass per unit volume and is often used to calculate the weight of a material.

Density is an important factor for a variety of different applications. Depending on the application, the density of aluminum will have a significant impact on how it is used. For example, lightweight, high-strength aluminum is ideal for construction and industrial applications.

The density of aluminum is about 2700kg/m³, and the density value of different types of aluminum alloy does not change much.

Corrosion resistance

Corrosion resistance refers to its ability to resist corrosion when in contact with other substances. It includes chemical corrosion resistance, electrochemical corrosion resistance, stress corrosion resistance and other properties.

Corrosion resistance selection principle should be based on its use occasion, high-strength alloy used in a corrosive environment, must use a variety of anti-corrosion composite materials.

In general, the corrosion resistance of series 1 pure aluminum is the best, series 5 performs well, followed by series 3 and 6, and series 2 and 7 are poor.

processability

The machinability includes formability and machinability. Because formability is related to the state, after selecting the grade of aluminum alloy, it is also necessary to consider the strength range of each state, usually high strength materials are not easy to form.

If the aluminum is to be bent, drawn, deep drawing and other forming processes, the formability of the fully annealed material is the best, and on the contrary, the formability of the heat-treated material is the worst.

The machinability of aluminum alloy has a great relationship with the alloy composition, usually higher strength aluminum alloy machinability is better, on the contrary, low strength machinability is poor.

For molds, mechanical parts and other products that need to be cut, the machinability of aluminum alloy is an important consideration.

Welding and bending properties

Most aluminum alloys are welded without problems. In particular, some 5 series aluminum alloys are specially designed for welding considerations; Relatively speaking, some 2 series and 7 series aluminum alloys are more difficult to weld.

In addition, the 5 series aluminum alloy is also the most suitable for bending a class of aluminum alloy products.

Decorative property

When aluminum is applied to decoration or some specific occasions, its surface needs to be processed to obtain the corresponding color and surface organization. This situation requires us to focus on the decorative properties of materials.

Aluminum surface treatment options include anodizing and spraying. In general, materials with good corrosion resistance have excellent surface treatment properties.

Other characteristics

In addition to the above characteristics, there are electrical conductivity, wear resistance, heat resistance and other properties, we need to consider more in the selection of materials.


Copper alloy

Orichalcum



Brass is an alloy of copper and zinc. Brass with different mechanical properties can be obtained by changing the content of zinc in brass. The higher the content of zinc in brass, the higher its strength and slightly lower plasticity.

The zinc content of the brass used in the industry does not exceed 45%, and the zinc content will be brittle and make the alloy performance worse. Adding 1% tin to brass can significantly improve the resistance of brass to seawater and Marine atmosphere corrosion, so it is called "navy brass".

Tin can improve the machinability of brass. Lead brass is commonly referred to as easy to cut national standard copper. The main purpose of adding lead is to improve the machinability and wear resistance, and lead has little effect on the strength of brass. Carving copper is also a kind of lead brass.

Most brasses have good color, processability, ductility, and are easy to electroplate or paint.

Red copper



Copper is pure copper, also known as red copper, has good electrical and thermal conductivity, excellent plasticity, easy hot pressing and cold pressure processing, can be made into plates, rods, tubes, wires, strips, foil and other copper.

A large number of products that require good electrical conductivity such as electrocorroded copper and conductive bars for the manufacture of EDM, magnetic instruments and instruments that must be resistant to magnetic interference, such as compass and aviation instruments.

No matter what kind of material, a single model basically can not meet all the performance requirements of a product at the same time, and it is not necessary. We should set the priority of various performance according to the performance requirements of the product, the use of the environment, the processing process and other factors, reasonable selection of materials, and reasonable control of costs under the premise of ensuring performance.


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As a machine tool mainly used to process box and shell parts, the machining center is worth hundreds of thousands to millions. It is generally the key equipment in the key processes of the enterprise. Once the machine is shut down, the loss is often great. Therefore, in order to give full play to the benefits of the machine tool, we must pay attention to the maintenance and repair work. Because most of the daily electrical faults of CNC machine tools are electrical faults, electrical maintenance and repair are more important.1) CNC system control part2) Servo motor and spindle motor


Focus on noise and temperature rise. If the noise or temperature rise is too large, find out whether it is a mechanical problem such as bearing or the parameter setting of its matching amplifier, and take corresponding measures to solve it. For example, if there is abnormal sound during the movement of the servo shaft, and there is no obvious parameter change after verification, it is suspected that the mechanical noise may be caused by the lead screw, coupling and non concentricity with the servo motor. Disconnect the motor from the coupling and operate the motor separately. If the motor still has noise, adjust the speed loop gain and position loop gain appropriately, Make the motor silent. If there is no noise, judge that it is the concentricity between the lead screw and the coupling, re correct the concentricity, and then connect with the motor. The problem can be eliminated.
3) Measurement feedback elementIncluding encoder, grating ruler, etc., check whether the connection of detection elements is loose and whether they are polluted by oil or dust.4) Electrical control part
Check whether the three-phase power supply voltage is normal; Check whether the electrical components are well connected; Check whether various switches are effective with the aid of CRT display diagnosis screen; Check whether all relays and contactors work normally and whether the contacts are in good condition; Whether the thermal relay, arc suppressor and other protective elements are effective; Check whether the temperature of components inside the electrical cabinet is too high. For poor contact of contactor contact, the contactor can be disassembled, the high-temperature oxide on the contact surface can be scraped off with a small file, then the sundries can be wiped out with absorbent cotton and alcohol, reassembled, and then the contact can be conducted with a multimeter.
5) Improve utilization
If the machining center is idle for a long time, when it needs to be used, first of all, each moving link of the machine tool will affect its static and dynamic transmission performance due to grease solidification, dust and even rust, reduce the accuracy of the machine tool, and the blockage of the oil circuit system is a big trouble; From the electrical point of view, the electrical control system hardware is composed of tens of thousands of electronic components, and their performance and life are very discrete. If it is not used for a long time, when power is suddenly transmitted, the components will be damaged in high current and strong voltage. Therefore, in a period of time without machining task, it is best to run the machine tool at a low speed, and at least power on the NC system frequently, or even every day.
I have encountered this situation: a horizontal machining center, using FANUC system. After running the warm-up program, it processed and found that the qualified parts were processed in the morning, and the processed parts were unqualified by noon. After inspection by the on-site processing personnel, the positioning and fixture on the machine tool are not deformed or loose. However, when the spindle box is not processed and stationary, it will deviate downward by 0.1mm along the direction of the gravity axis. The technician judges that the temperature compensation fails or the temperature sensor has poor contact. However, the phenomenon still occurs after replacing the temperature sensor and temperature module and re entering CNC parameters and temperature compensation parameters. After expert consultation, it was finally found that it was not the sensor problem, but that there was a 2-meter-long and 1-meter-wide skylight facing the main shaft and column on the machine tool. At noon, the sun directly shines on the main shaft and column, resulting in thermal deformation. After the skylight is covered, the spindle box returns to normal. This is a typical maintenance error caused by improper maintenance. Therefore, proper daily maintenance provides convenience for overall maintenance in the future.

1 Tool change of hat type magazineThe fixed address tool change mode is mostly adopted, and the tool number is fixed corresponding to the tool seat number. The tool change action is realized by the lateral movement of the tool magazine and the up and down movement of the spindle, which is referred to as the spindle tool change mode for short. Because it has no tool change manipulator, the tool selection action cannot be preselected before the tool change action. The tool change instruction and tool selection instruction are generally written in the same program segment, and the instruction format is as follows:M06 T


When the command is executed, the tool magazine first turns the tool holder corresponding to the tool number on the spindle to the tool change position, and switches the tool on the spindle back to the tool holder, and then the tool magazine turns the tool specified in the command to the tool change position and changes the spindle.For this tool magazine, even if TX x is executed before M06, the tool cannot be preselected, * the action of final tool selection is still executed when M06 is executed. If there is no TX X in front of M06, the system will give an alarm.2 Tool change of disc and chain magazine
Most of them use random address tool change mode. The corresponding relationship between tool number and tool seat number is random, but its corresponding relationship can be remembered by NC system. The tool change of this tool magazine depends on the manipulator. The action of the command and tool change is: the tool command TX controls the rotation of the tool magazine and turns the selected tool to the tool change working position, while the tool change command M06 controls the action of the tool change manipulator to realize the tool exchange between the spindle tool and the tool change position of the tool magazine. The tool selection command and tool change command can be in the same program segment or written separately. The actions corresponding to tool selection and tool change command can also be operated simultaneously or separately. The instruction format is as follows:
Tx x M06;When the command is executed, the tool magazine first turns the TX tool to the tool change position, and then the manipulator exchanges the tool of the tool magazine with the tool of the spindle to realize the purpose of changing the TX tool to the spindle.After reading the above two methods, it can be seen that method 2 overlaps the tool selection action with the machining action, so that when changing the tool, it is not necessary to select the tool and change the tool directly, which improves the work efficiency.
As mentioned earlier, the tool change command of the tool magazine is related to the machine tool manufacturer. For example, some tool magazines require that not only the Z axis must return to the tool change point, but also the Y axis must return to the tool change point. The program format is as follows:
When writing the instructions of tool selection and tool change in the same program section, the execution rules of tools from different manufacturers may also be different. If any, regardless of the writing order, the rules of tool selection and tool change shall be followed. Some rules stipulate that the tool selection command must be written before the tool change command is executed. Otherwise, the action is to change the tool first and then select the tool, as shown in the above program. In this case, if the tool selection command is not written before the M06 command is executed, the system will give an alarm.

Nowadays, smart phones have changed from plastic back cover to thin metal body. Although the smart appearance attracts consumers, the production process of mobile phone case parts suppliers is more difficult. Only because the cutting and processing of the case requires quite high precision, even if it is only a small deviation, it may cause workpiece scrapping and erode profits.


In order to improve the yield of CNC processing, mobile phone box manufacturers are often forced to change tools frequently to ensure that CNC machines maintain a normal production beat, but this leads to an increase in the cost of consumables and also affects profits. In addition, the mobile phone case processing industry attaches great importance to the production rate, for fear that the sudden failure of CNC cutting machine will lead to negative chain reactions such as production capacity decline and delivery delay, which will damage customer satisfaction and goodwill. Therefore, it allocates manpower to carry out regular inspection and entrusts outsourcers to provide second-line maintenance support, but these methods are passive, It is difficult to effectively deal with abnormal conditions at the first time.
Mobile phone case is one of the cases of CNC machine application. CNC cutting is widely used in various processing and manufacturing, and various suppliers are facing a similar profit defense war. Xu Changyi, manager of Linghua technology measurement and automation products division, believes that whether you want to improve the machining accuracy or increase the productivity, the axe bottom salary drawing plan is to monitor the cutting process, especially the vibration monitoring, mainly because once the vibration value of the machine rises beyond the reasonable range due to imbalance, resonance or misalignment, It is easy to affect the operation of the machine, resulting in fault shutdown.
PC based monitoring solution is better than PLC solution to capture fine vibration signals
If the CNC processing machine can be endowed with intelligence and built with a set of full-time vibration monitoring mechanism, it can diagnose the health state of the machine at any time. Instead of waiting for the output of the final finished product and judging the cause of the abnormality afterwards, it can detect the unusual state of the processing machine in real time through preventive detection in advance and take corresponding treatment measures quickly, Including optimizing and adjusting processing parameters (such as changing spindle speed), or changing tools, etc. to solve small deviations immediately and avoid causing major disasters in the future.
It can not be denied that the cutting vibration monitoring of CNC machining machines is not a new topic at this moment. In the past, there were some PLC solutions with the demand of simplicity and convenience, which boasted that as long as the CNC machine was connected, it could produce utility quickly; Therefore, it is inevitable that some people wonder why PC based monitoring scheme is needed since PLC is available to assist in cutting vibration monitoring?
The so-called devil lies in the details. Some subtle vibration signals or high-frequency signals reflect some facts to some extent. It may be that the connecting mechanism begins to be unbalanced, the rotating spindle bearing ball breaks and affects the transmission power, or the fasteners become loose, which means that the CNC machining machine begins to "get sick", and the symptoms are different with the different machine characteristics; These subtle and changeable signs are not easy to capture by virtue of the PLC solution with the characteristics of low sampling rate, supporting limited bandwidth range and fixed algorithm. If the CNC monitoring solution can capture small changes and help users quickly grasp the key factors that may lead to reduced accuracy or capacity decline, they can respond as soon as possible.
In view of this, Linghua launched a cutting vibration monitoring scheme called mcm-100, which boasts that it can carry out 24-hour continuous data acquisition and vibration measurement for rotating transfer machinery and equipment under the condition of high precision and high sampling rate, and integrate the functions of data collection, vibration analysis and calculation, operation, Internet access and so on, Assist CNC machine users to successfully solve various challenges faced by traditional cutting process, and endow CNC machine with intelligence in the most relaxed and burden-free way.Achieve the wonderful effect of preventive maintenance through high-precision monitoring
Xu Changyi explained that generally speaking, there are three detection situations that CNC machines most want to establish. One is "spindle vibration detection", which aims to monitor the vibration of the spindle during cutting. The method is to directly measure the RMS value of the time domain signal. If it exceeds the critical value, reduce the speed or stop running; The second is "bearing quality diagnostic tic", which is intended to diagnose the health status of bearings. It is carried out when CNC does not perform cutting and only idles at high speed; The third is "spindle collision detection", which is used to detect the spindle collision. When the vibration wave pattern meets some default conditions, it is judged that the collision has occurred, and the spindle movement is stopped immediately.
The above situations 1 and 2 are closely related to the accuracy and bandwidth range of vibration signals. PLC solutions can capture very little information, which is difficult to help users establish contingency strategies; In contrast, mcm-100 not only has 24 bit high resolution capability (generally falling in the range of 12 or 16 bit), but also can capture high-frequency signals with a sampling rate of up to 128ks / S (generally only supporting 20Ks / s or even lower), so as to provide users with more vibration analysis materials.New business opportunities for CNC machine equipment manufacturers
On the other hand, the cutting vibration monitoring scheme can also create new business opportunities for CNC machine equipment manufacturers. As CNC machine equipment suppliers are exposed to a large amount of vibration information, once combined with big data analysis, they have a more thorough understanding of the correlation between signal changes and machine failures. CNC machine equipment suppliers can make good use of the accumulated knowledge assets, give birth to value-added services, and even adjust their business model from selling out equipment to selling machine operation hours, Establish long-term stable income. According to Linghua technology, the operator of PC based cutting vibration monitoring scheme, the vibration monitoring scheme has entered the landing stage and has been adopted by various well-known CNC tool machine manufacturers, and its demand has increased significantly in 2017, which shows that both CNC processors and CNC tool machine manufacturers have increasingly keen demand for CNC cutting vibration monitoring scheme.

PETALING JAYA: Low-profile Datuk Gan Kim Huat is consolidating his businesses in two listed companies, SKP Resources Bhd and Tecnic Group Bhd, in a move that will pave the way for the establishment of a major plastic parts manufacturer.
Yesterday, the share prices of SKP and Tecnic climbed to all-time highs of 71 sen and RM5.08, respectively, before both stocks were suspended, "pending a material announcement".
It is learnt that the merger and acquisition exercise could involve cash and the issuance of new SKP shares.
Gan and his family own about 67% in SKP and 69% in Tecnic, formerly known as STS Tecnic Bhd.
"It's a move that the Gan family has been looking at for some time to create an entity with economies of scale. A merger can be synergistic for the two companies, which can lead to accretive earnings going forward," said a source.
SKP, which has been on expansion mode over the past few years, is in the business of manufacturing plastic parts and components, contract manufacturing, precision mould making, the sub-assembly of electronic and electrical equipment and other secondary processes.
For the financial year ended March 31, 2013 (FY13), British electrical appliance brand Dyson contributed 55% to SKP's total sales.
According to SKP's website, its other clients include Hewlett-Packard, Sharp, Flextronics and Pioneer.
Tecnic, meanwhile, is involved in plastic moulding design and fabrication, plastic injection and blow moulding for the automotive, electrical and electronic sectors as well as industrial consumable products. It counts Valeo, Sharp, Panasonic, Denso, Suzuki, Proton and Perodua as its clients.
SKP and Tecnic had cash and cash equivalents of RM19.4mil and RM25.7mil, respectively, as at June 30. However, SKP has seen a higher trading volume in recent months, while Tecnic is a relatively tightly held stock.
In an earlier note, RHB Research said SKP could achieve a two-year earnings compounded annual growth rate of 57.9% on the back of a 75% expansion in capacity to cater to increasing orders from Dyson.
SKP has a new plant in Senai, Johor, which is slated for completion next month and achieve full-scale operations by FY17, Kenanga Research said in a separate report.
The research house noted that SKP's stronger order-book, underpinned by orders from Dyson to manufacture two new product lines for vacuum cleaners and fans, will provide earnings visibility for the next few years.
"The new products are next-generation appliances that will be able to fetch higher margins and contribute to the group's earnings. We understand that a major part of the group's new plant will cater to the production of the two new products," it added.
SKP jumped 10.5 sen to 71 sen, with 38.37 million shares being traded.
Tecnic rose 31 sen, or 6.5%, to RM5.08, with 219,500 shares changing hands.