April 2021 – Page 5 – CNC Machining & Turning, Milling, Metal parts

CNC computer gong processing method (Part 1)

General principles of tool path:

Roughing: under the maximum load of the machine tool, in most cases, the tool should be as large as possible, the feed should be as large as possible, and the feed should be as fast as possible. In the case of the same tool, the feed is inversely proportional to the feed. Generally, the load of the machine tool is not a problem. The principle of tool selection mainly depends on whether the two-dimensional angle and three-dimensional arc of the product are too small. After selecting the tool, the length of the tool will be determined. The principle is that the length of the tool is greater than the processing depth, and the interference of the chuck should be considered for large workpieces.

Light knife: the purpose of light knife is to meet the processing requirements of workpiece surface finish and appropriate allowance. Similarly, the light knife should be as large as possible and as fast as possible, because it takes a long time to finish the knife, and the most appropriate feed and feed should be used. Under the same feed, the larger the transverse feed, the faster it will be. The surface feed is related to the finish after machining, and the feed size is related to the surface shape of the surface. In the case of not damaging the surface, the minimum allowance, the maximum tool, the fastest speed and proper feed should be left.

Clamping method:

All clamps are long horizontally and short vertically.
Vise clamping: the clamping height should not be less than 10 mm, and the clamping height and processing height must be specified when processing the workpiece. The machining height should be about 5mm higher than the plane of the vise, so as to ensure the firmness and not damage the vise. The clamping height is also related to the size of the workpiece. The larger the workpiece is, the higher the clamping height will be.
Splint clamping: the splint is fixed on the worktable with a code, and the workpiece is locked on the splint with a screw. This kind of clamping is suitable for the workpiece with insufficient clamping height and large processing force. Generally, the effect is better for medium and large workpieces.
Clamping with iron Code: when the workpiece is large, the clamping height is not enough, and it is not allowed to lock the wire at the bottom, the clamping with iron code is used. This kind of clamping needs second clamping, first code the four corners and process other parts, then code the four sides and process the four corners. During the second clamping, do not let the workpiece loose, first code and then loosen. You can also code two sides first and process the other two sides.
Tool clamping: the clamping length shall not be less than 30mm when the diameter is more than 10mm; the clamping length shall not be less than 20mm when the diameter is less than 10mm. The clamping of the cutting tool should be firm, and the tool collision and direct insertion into the workpiece should be strictly prevented.

Classification and application scope of cutting tools:

(1) By material:

White steel knife: easy to wear, used for roughening copper and small steel.

Tungsten steel knife: used for angle cleaning (especially steel material) and light knife.

Alloy knife: similar to tungsten steel knife.

Purple knife; used for high speed cutting, not easy to wear.

(2) According to the cutter head:

Flat bottom knife: used for plane and straight side to clear plane angle.

Ball knife: used for all kinds of surface medium light and light knife.

Ox nose knife (one side, two sides and five sides): used for roughening steel (r0.8, r0.3, r0.5, r0.4).

Rough leather knife: used to cut rough, pay attention to the remaining method (0.3).

(3) By arbor:

Straight bar knife: straight bar knife is suitable for various occasions.

Inclined bar knife: but it is not suitable for straight face and face whose slope is less than the inclination of the bar.

(4) Blade points:

The more the number of blades, the better the effect, but the more the work, the more the speed and feed are adjusted, the more the number of blades and the longer the service life.

(5) The difference between ball knife and flying knife is as follows:

Ball knife: when concave ruler is smaller than ball ruler and plane ruler is smaller than ball R, the light can’t reach (clear the bottom angle).

Flying knife: the advantage is that it can clear the bottom corner. Comparison of the same parameters: v = R * ω, the speed is much faster (flying knife), the light is bright when the force is big, flying knife is mostly used for contour shape, sometimes flying knife doesn’t need middle light. The disadvantage is that the concave size and the plane ruler are less than the diameter of the flying knife.

About CNC Turniing

ken.tang@chengcg.com

Tool path used in five axis CNC machining center

Although there is no clear requirement for the tool magazine selection of five axis CNC machining center, we always choose a better tool magazine when we choose the tool magazine of five axis CNC machining center. This is the choice based on the characteristics of five axis CNC machining center. The workpieces processed by five axis CNC machining center are generally very complex, and the requirements for accuracy are very high. The selection of tool magazine and tool directly affects the machining efficiency and the quality of workpieces processed by five axis CNC machining center, so the selection of tool magazine of five axis CNC machining center can not be ignored.

When selecting tool magazine for 5-axis CNC machining center, we need to choose better tool magazine and more precise tool. A good magazine is based on its type and brand. For example, for a five axis vmc850 CNC machining center, we can choose the hat type tool magazine and arm type tool magazine, so we’d better choose arm type tool magazine.

Five axis CNC machining center can make large vertical CNC machining center, can also be small vertical CNC machining center, but these two kinds of CNC machining center’s tool magazine only has the hat type and the knife arm type choice, generally five axis CNC machining center we can’t see the hat type tool magazine, few people will use the hat type tool magazine on the five axis CNC machining center. The type of tool magazine of five axis high-speed CNC machining center is different from that of ordinary CNC machining center. The tool magazine used in high-speed CNC machining center is arm type and synchronous type. Generally, synchronous type tool magazine is better and tool changing speed is faster. The same is true for drilling and tapping centers. There is no big difference between the two types of tool magazine. The tool changing speed of the flying saucer type tool magazine is faster than that of the clamping arm type tool magazine. Generally, the capacity of the tool magazine is larger than that of the clamping arm type tool magazine, which can meet the needs of most customers.

About CNC Turniing

ken.tang @ chengcg.com

Loss of the electrode cutting nozzle in NC plasma cutting machine

Operators of CNC plasma cutting machine are clear, if CNC plasma cutting machine nozzle appears damaged, it is easy to lead to no arc in the plasma processing process, to prevent this situation, in the use of CNC plasma cutting machine electrode cutting nozzle, how to use the electrode cutting nozzle more flexible.

Causes and solutions of electrode cutting nozzle loss in CNC plasma cutting machine

In the process of NC plasma cutting machine, under normal conditions, the service life of a set of electrode cutting nozzle is about 3-4 hours. In order to reduce the cost of consumables, many users buy electrode cutting nozzle with low price and poor quality. This method will only aggravate the loss of cutting nozzle, and it is easier to burn the cutting gun, which will bring some uncertain safety hazards, so we do not recommend this How to do it. In order to reduce the loss of electrode cutting nozzle, we summarized the following solutions in the long-term after-sales work with customers

Method 1: remove the oxide from the air or oxygen nozzle

When air or oxygen plasma is used in the nozzle, oxide will accumulate in the nozzle, which will affect the air flow and increase the service life of consuming parts. Wipe the inside of nozzle with clean flannelette to eliminate oxide.

Second, reflect on the air flow and cooling methods every day

One of the most rare reasons for cutting torch damage is the short cooling flow. The air flow, air pressure or cooling liquid required for cutting torch are often reflected. If the air flow is insufficient or leakage is found, the machine should be shut down immediately to clean up the problem.

The third method is to inject hardened water into the cutting torch

Hard water will precipitate metal impurities on the nozzle ring, which will affect the air flow, reduce the quality of the cutting torch and prolong the service life of the parts.

Method 4: ensure the correct pressure and activity of plasma

It is very important to correct the pressure and movement of plasma to counteract the service life of consumable parts. If the air pressure is too high, the life of the electrode will be greatly increased; if the air pressure is too low, the life of the nozzle will be affected.

The fifth method is to adopt reasonable cutting distance

According to the requirements of the application specification, the reasonable cutting distance should be adopted. The cutting distance is the interval between the cutting nozzle and the surface of the workpiece. When piercing, the interval of twice the normal cutting distance or the maximum height that can be transferred by plasma arc should be adopted as far as possible.

Method 6: do not overload the nozzle

Overloading the nozzle (i.e. exceeding the task current of the nozzle) will quickly damage the nozzle. The current intensity should be 95% of the task current of the nozzle. For example, the current intensity of 100A nozzle should be set to 95A. Method 7: the perforation thickness should be within the allowable range of the machine parts. The cutting machine can not pierce the steel plate beyond the task thickness. The usual perforation thickness is 1 / 2 of the normal cutting thickness.

Method eight, adhere to the dry and clean plasma gas

Plasma system needs dry and clean plasma gas to be able to work normally. Dirty gas is usually the result of gas compression, it will prolong the service life of consuming parts, forming abnormal damage.

Method 9, prevent the extension of the plasma arc. If the plasma arc can only contact the surface of the workpiece by extending, this kind of extension and extension will occur at the beginning and end of the cutting, which will cause abnormal damage to the nozzle. If we adopt the right edge terminal technique and choose the appropriate “arc breaking” signal time, this result can be prevented.

Method 10, cutting should start from the edge, as far as possible from the edge of the beginning of cutting, rather than perforation cutting. Using the edge as the starting point will extend the service life of the workpiece. The correct way is to align the nozzle with the edge of the workpiece indirectly and then start the plasma arc.

Therefore, in the purchase of CNC plasma cutting machine, we should pay attention to whether the cutting gun and electrode cutting nozzle match. In addition, the appropriate cutting thickness of nozzles with different apertures is also different. Therefore, before the cutting task of CNC plasma cutting machine, the electrode cutting nozzle with cutting ability and plate to be cut should be selected.

About CNC Turniing

ken.tang @ chengcg.com

Significance of dividing CNC machining into stages

Experienced CNC processing masters all know that CNC processing needs to be carried out in stages, so what is the significance of doing so? The main points are as follows:

(1) Rational use of CNC processing equipment

With large rough machining allowance and large cutting amount, the machine tool with high power, good rigidity, high efficiency and low precision can be used. High precision machine tool is used because of small cutting force and small damage to machine tool. This gives full play to the respective characteristics of the equipment, which can not only improve productivity, but also extend the use of precision equipment.

(2) It is convenient to find the defects of CNC blank in time

All kinds of defects (such as porosity, sand inclusion and insufficient allowance) of the blank can be found after rough machining, which is convenient for timely repair or scrapping, so as to avoid unnecessary waste caused by continuous machining.

(3) Easy to arrange heat treatment process

After rough machining, stress relief heat treatment is usually arranged to eliminate internal stress. Before finishing, quenching and other final heat treatment should be arranged. The deformation caused by heat treatment can be eliminated by finishing.

(4) Guarantee CNC machining quality

In the rough machining of CNC parts, the metal layer cut out is thicker, the cutting force and tightening force are larger, and the cutting temperature is also higher, which will cause greater deformation. According to the processing stage, the machining error caused by rough machining can be corrected by semi finish machining and finish machining, so as to ensure the machining quality of parts.

About CNC Turniing

ken.tang @ chengcg.com

CNC machining center spindle fault

The spindle is the power auxiliary device of CNC machining center. The spindle drives the workpiece to rotate to process the workpiece of the rotating body. Spindle is an important guarantee for high-speed and high-precision machining of CNC machining center, so the maintenance methods and skills of spindle fault are the basic knowledge that operators and maintenance personnel of CNC machining center must master. In the operation of CNC machining center, the spindle will inevitably have some faults. What is the specific reason?

Different types of CNC machining centers adopt different types of spindles. According to the different transmission systems, the spindle system can be divided into the main transmission spindle with variable speed gear, the main transmission spindle with belt transmission, the dual motor drive spindle and the motor spindle integrated spindle. No matter what type of spindle application, the common faults in use are as follows:

Overload.

Fault causes: excessive cutting amount, frequent forward and reverse rotation, spindle motor fault, spindle drive device fault.

The spindle does not rotate

Fault causes: spindle drive failure, CNC device can not output speed signal, spindle motor failure, spindle drive failure, drive belt fracture.

The spindle speed deviates from the command value

Fault causes: motor overload, CNC system output spindle speed command output problem, speed measuring device failure or speed feedback signal disconnection.

Abnormal noise and vibration of spindle

Cause of failure: it usually occurs in the process of deceleration, and there is something wrong with the spindle drive device, such as the regeneration circuit fault in AC drive.

Computer gong processing to prevent collision

Under the condition of such high speed and structure, once the operator has no time to press the emergency stop button due to programming and operation errors, the tool has collided with the workpiece. In order to prevent machine tool and personal troubles, the following methods can be adopted in programming and operation (take FANUC system as an example).

The origin of the workpiece coordinate system set by the programmer should be outside the workpiece blank, at least on the workpiece surface.

Under normal conditions, the origin of workpiece coordinate system can be set anywhere, as long as the origin has a certain connection with the origin of machine coordinate system. But in practice, if the command value is zero or close to zero, the tool will point to zero or close to zero. In milling, the cutter will run to the table or fixture base surface; in turning, it will run to the chuck base surface. In this way, the tool will penetrate the workpiece and point directly at the reference plane. At this moment, if you want to move quickly, you will have trouble.

FANUC system generally set: when the decimal point is omitted, it is the minimum input unit, generally μ M. When the decimal point is omitted, the input value will be reduced to one thousandth. At this moment, the input value will be close to zero. Perhaps, due to other factors, the tool should be separated from the workpiece, but the practice is not separated from the workpiece and into the workpiece. In this case, the zero point of the workpiece coordinate system should be set outside the workpiece or on the base surface of the worktable (or fixture), and the result will be different.

Programmers and operators should be more careful about decimal points when writing programs.

FANUC system is the minimum setting unit when the decimal point is omitted, while most domestic systems and some European and American systems are mm when the decimal point is omitted, which is the input method of calculator. If you are used to calculator input method, there will be problems in FANUC system. Many programmers and operators may use both systems. In order to prevent the scale from getting smaller due to decimal point, decimal point should be added to the input program of calculator. But it’s not because of the habit of doing something like this.

In order to make the decimal point eye-catching, the isolated decimal point is usually written as “. 0” in programming. Of course, when the system is executed, the zero after the decimal point of the value is ignored.

When adjusting the workpiece coordinate system, the operator should set the reference point beyond the physical (geometric) length of all tools, at least on the tool position of the longest tool.

For the workpiece coordinate system on the workpiece installation drawing, the operator obtains it by setting the machine coordinate system offset on the CNC machining center. In other words, the operator sets a reference point on the CNC machining center, finds the scale between the reference point and the zero point of the workpiece coordinate system set by the programmer, and sets this scale as the workpiece coordinate system offset.

On the lathe, the datum point can be set on the base of turret rotation, the datum tool tip or other directions. If there is no additional movement, the zero of the programmer’s instruction is the zero position of the tool rest (CNC machining center) moving to the offset. At this moment, if the datum point is set at the base of turret rotation, the turret must collide with the workpiece. In order to avoid collision, the datum point of CNC machining center should not only be set outside the tool holder, but also outside all tools. In this way, even if the tool is installed on the tool holder, the datum point will not collide with the workpiece.

In CNC machining center, the datum points of X and Y axes are on the axis line of spindle. However, the reference point of the z-axis can be set at the spindle end or at a point other than the spindle end. If it is at the spindle end, when the command is zero, the spindle end will reach the zero position specified in the coordinate system. At this moment, the end key of the spindle end will collide with the workpiece: if the spindle is equipped with a tool again, it will collide with the workpiece. To ensure that there is no collision, the reference point on the z-axis should be set beyond all tool lengths. Even if no other motion is attached, the reference point will not hit the workpiece.

CNC computer gong processing for the knife

In the case of the same tool, the feed is inversely proportional to the feed. In general, the load of the machine tool is not a problem. The principle of tool selection mainly depends on whether the two-dimensional angle and three-dimensional arc of the product are too small. After the tool is selected, the tool length will be determined. The principle is that the tool length is greater than the processing depth, and whether the chuck can be removed for large parts.

The purpose of light knife: to meet the workpiece processing requirements: finish, flying die allowance, copper male spark position, etc., at the same time, as large as possible, as fast as possible, because the precision knife takes a long time, with the most appropriate feed and feed, in the same feed, the larger the transverse feed, the faster. The surface feed is related to the finish after processing, and the feed size is related to the surface shape In the case of no damage to the surface, the minimum allowance should be left, the maximum knife should be used, the fastest Belt should be rotated, and the proper feeding should be carried out.

Clamping method:

All clamps are long horizontally and short vertically;
Vise clamping: the clamping height should not be less than 10 mm. When processing the workpiece, the clamping height and processing height must be specified. The processing height should be about 5 mm higher than the vise plane, so as to ensure the firmness and not damage the vise. This kind of clamping belongs to general clamping, and the clamping height is also related to the size of the workpiece. The larger the workpiece is, the higher the clamping height will be;
Splint clamping: the splint is fixed on the worktable with the code, and the workpiece is locked on the splint with the screw. This kind of clamping is suitable for the workpiece with insufficient clamping height and large processing force, generally medium and large workpieces, and the effect is very good.
When the workpiece is large, the clamping height is not enough, and it is not allowed to lock the thread at the bottom, it should be clamped with code iron. This kind of clamping needs to be clamped twice

a. First code the four corners, process the other parts, and then code the four sides and process the four corners. The principle is that during the second clamping, be very careful not to let the workpiece loose, code before loosening,

b. Also has first code two sides, processes other two sides

CNC computer gong processing

In the process of computer gong processing, the operator shall not leave the machine tool without authorization, and shall keep a high degree of concentration and observe the running state of the machine tool.
In case of abnormal phenomenon or accident, the program operation shall be terminated immediately, the power supply shall be cut off and the instructor shall be informed in time, and other operations shall not be carried out;
It is strictly forbidden to tap the control panel and touch screen. It is strictly forbidden to knock the worktable, dividing head, fixture and guide rail;
It is strictly forbidden to open the control cabinet of the numerical control system to watch and touch without permission;
Computer gong processing operators are not allowed to change the internal parameters of the machine tool at will. Interns are not allowed to call or modify other programs that are not compiled by themselves;
On the control microcomputer of machine tool, no other operation is allowed except program operation, transmission and program copy;
CNC milling machine belongs to large precision equipment. Except for the tooling and workpieces placed on the worktable, it is strictly forbidden to stack any tools, clamps, blades, measuring tools, workpieces and other debris on the computer gong processing machine;
It is forbidden to touch the blade tip and scrap iron with hands. Scrap iron must be cleaned with iron hook or brush;
It is forbidden to touch the rotating spindle, workpiece or other moving parts by hand or in any other way;
It is forbidden to measure the workpiece and change the speed manually in the process of processing. It is also forbidden to wipe the workpiece with cotton yarn and clean the machine tool;
Trial operation is forbidden;
When using the hand wheel or fast moving mode to move the position of each axis, make sure to see the “and -” signs in each direction of X, y and Z axes before moving. When moving, slowly turn the hand wheel to observe the correct direction of the machine before speeding up the movement.

CNC processing hand proofing

CNC hand proofing, so hand production in the new product development, product shape in the process of scrutiny is indispensable.

Check the structure design: because it can be assembled, CNC hand board, so it can directly reflect whether the structure is appropriate, installation will not trouble. It is convenient to find out the problem immediately.

To prevent the risk of directly opening the mold: because the cost of mold manufacturing is usually very high, the relatively large mold is probably several hundred thousand, some even several million, if in the process of opening the mold, it is found that the structure is not appropriate or other problems, its loss can be imagined.

Professional CNC hand proofing, CNC hand manufacturers_ Solve the problem of hand model for you

It requires a high degree of mechanical operation, manual carving and design ability for designers. For example, in the design of action tooth box, it is necessary to design toys with walking, running or flying effects according to the requirements of customers, which emphasizes the design ability.

The simulation driver board pays attention to the craftsmanship and the sense of the line of the photo, and is very familiar with the plastic and hardware mold, focusing on the manual carving and mold knowledge; The design of plaster and oil clay hand board by CNC hand board can be called handicraft sculpture independently. There are many hand board creation rooms. The next section will talk about it in detail. It takes a lot of interest and long working experience to do well in the front three kinds of hand boards, and many great masters have got through.

Most parts can reach ± 0. 01mm。 But there are some special problems. For example, when machining POM material with lathe, it can only reach ± 0.05mm. If the product is 1m long, the material is acrylic, no matter how precise the CNC machining machine is, the professional CNC hand proofing will expand, shrink and absorb water with the change of temperature. In that case, the tolerance may be about 1mm. What are the conditions of quotation? Accurate quotation is based on the drawings (can see the size, appearance and structure), materials, post-processing and other specific requirements to measure the price and delivery time.

Computer gong boring type processing

1、 Processing type:

Hole processing:
Drilling: before drilling on the machining center, the center drill must be used for positioning, and then the drill bit 0.5 ~ 2mm smaller than the drawing size shall be used for drilling, and finally the appropriate drill bit shall be used for finishing.
Reaming processing: when reaming the workpiece, it is also necessary to use the center drill to locate, then drill with a drill 0.5 ~ 0.3mm smaller than the drawing size, and finally ream with a reamer. When reaming, pay attention to control the spindle speed within 70 ~ 180rpm / min.
Boring: to boring the workpiece, first use the center drill to locate, then use the drill 1 ~ 2mm smaller than the drawing size to drill, then use the rough boring cutter (or milling cutter) to process to the left side of 0.3mm machining allowance, finally use the pre adjusted size of the fine boring cutter for fine boring, and the last fine boring allowance shall not be less than 0.1mm.
Direct numerical control (DNC) operation:
Before DNC NC machining, the workpiece should be clamped, the zero position should be set, and the parameters should be set.
Open the processing program to transfer data in the computer for checking, then let the computer enter DNC state, and input the file name of the correct processing program.
Press the tape key and the program start key on the machine tool, and the machine controller will flash LSK.
Press enter on the computer to process DNC data.

2、 Contents and scope of workers’ self inspection:

Before processing, the processor must see clearly the contents of the process card, know clearly the parts to be processed, the shape, the dimensions of the drawing and the processing contents of the next process.
Before the workpiece is clamped, the blank size should be measured to see if it meets the requirements of the drawing. When the workpiece is clamped, it must be carefully checked whether its placement is consistent with the programming operation instruction.
After rough machining, self inspection should be carried out in time to adjust the data with errors in time. The main content of self inspection is the position and size of the processing part.

(1) Whether the workpiece is loose or not;

(2) . whether the workpiece is correctly divided into parts;

(3) Whether the dimension from the processing part to the datum edge (datum point) meets the drawing requirements;

(4) The position and size of processing parts. After checking the position and size, measure the rough machined shape ruler (except arc).

Finish machining can only be carried out after rough machining and self checking. After finishing, the workers should carry out self inspection on the shape and size of the processing parts: check the basic length and width of the processing parts on the vertical plane; measure the base point size marked on the drawing for the processing parts on the inclined plane.