Category Archive CNC Technology


Causes of over cutting of CNC machining parts

There are many reasons for workpiece overcutting in CNC processing. If the workpiece is overcutted, it will be processed after repair welding, or it will be directly invalidated. In particular, if the workpiece is overcutted during large mold processing, let’s share with you the work experience summarized in CNC processing

Hardware processing

If the workpiece overcut is programmed manually, it is caused by forgetting to take the tool radius into account in the programming. If it is software programming, it may be the selected tool alignment rather than tangency. These two programming methods will lead to the workpiece overcut.

  1. There is also a fault in tool selection for over cutting of machined parts. For example, a milling cutter with a diameter of 16mm is used in the program, but the result is a milling cutter with a diameter of 20mm. Although the difference between 4mm and 4mm is not big to the naked eye, all the machined parts will become smaller. This requires carefully checking whether the tool diameter is reasonable before machining, and don’t take chances.
  2. Another reason for workpiece overcutting is that the workpiece coordinate system input is wrong when zeroing. Be sure to remember to offset the radius value of a zero bar. The input error of tool compensation, tool length and tool radius compensation must be input correctly. If the input length of tool length is 0.5mm, the workpiece will be 0.5mm more. For large workpieces, they can’t be used directly. Whether the tool radius compensation is positive or negative should also be considered before tool compensation, Otherwise, it will also lead to over cutting of the workpiece.

The above are the reasons for overcutting of several common machining parts. Others, such as loose spindle and low precision of ball screw, will cause overcutting in the machining process. After overcutting, check the reasons in time to prevent similar situations from happening again.



How to improve surface finish in CNC machining

In terms of size, the parts meet the blueprint specifications, but the surface finish and overall appearance are not ideal? What should we do?

Consider the following options:

  1. Control chip: chip evacuation is the key factor to produce good surface finish. Control chip may be the first thing you should consider. If the produced chips come into contact with the workpiece during machining, or if you are re cutting the chips, it is likely to affect your surface finish in a negative way. Consider the possibility of changing the style of the chip breaker you are using to help disassemble the chip for better control.

Although using air and coolant is a good choice to control chip removal, pay attention to coolant. Avoid using coolant when cutting intermittently. Hot cracks on the cutting edge will occur Due to intermittent heating and rapid cooling of cutting edges And it can lead to premature blade failure, or at least start to affect your surface finish because of over stressed cutting edges and failure.

  1. Improve speed: This is especially true when using cemented carbide tools. Increasing the speed will ensure that the contact time between the material and the tool tip is shorter Therefore, the edge accumulation on the tool is reduced, which may lead to poor surface finish. Increasing the rake angle of the cutting tool also helps to reduce and control edge accumulation.
  2. Use the correct tip radius: a larger tip radius will be able to adapt to a faster speed. The insert can feed at about half of TNR per revolution and still produce good results. If you exceed this TNR to IPR ratio, the tool will create more “linear” surface finish than the glossy smooth surface you want. Therefore, the larger the TNR, the faster the feed speed it can accommodate and still produce the desired results. However, using a very large TNR can produce chatter – reduce cutting pressure – so be careful and consider the speed required to cut the material – use a TNR tool that meets your needs.

It is also worth mentioning that using a larger tip radius means that you must leave more material for completion. To ensure proper operation of the tool, you must set TNR equal to or greater than TNR in order to complete the removal of the tool.

When milling, try to use fillet or spherical end milling cutter instead of plane end milling cutter. Something with a rounded radius will give you a higher finish at sharp corners and will certainly help extend tool life.

  1. Try to insert the wiper: as far as possible. The wiper insert has a small flat area adjacent to the tip radius. When the tool is fed along the workpiece, this plane actually “wipes” the finish and helps eliminate the linear finish that may be encountered at a faster feed rate – this allows the use of a smaller TNR to help control chatter.
  2. Increase the lead angle of the tool. Higher lead angle and positive tilt blades produce better surface finish than tools with shallow cutting angles. For example, a face milling cutter with a 45 ° cutting angle will produce a better surface finish than a face milling cutter with a 90 ° cutting angle.
  3. Eliminate dwell and pause: every time the tool stops moving when it comes into contact with the surface of the part, it will leave traces. Change the process if necessary, but try to ensure that the tool never stops or hesitates during the cutting process.



Machining and milling technology of CNC parts

Let’s take a look at CNC machining and milling technology!

  1. Feed line of precision CNC machining and milling plane parts: when milling plane mechanical parts, the side edge of end mill is usually selected for cutting. In order to reduce the tool receiving trace and ensure the appearance quality of parts, the cutting in and cutting out procedures of tools are carefully designed.
  2. In the machining process, when milling the surface, the cutting in and cutting out points of the cutter and milling cutter should cut in and cut out the surface of the part along the extension line of the part summary curve, rather than directly cutting in the part along the normal direction, so as to avoid scratches on the machined surface and ensure the general lubrication of the part.
  3. In the process of precision CNC machining and milling, if the inner generalization curve allows extension, it should be cut in and out along the tangent direction. If the inner generalization curve does not allow extension, the tool can only cut in and out along the normal direction of the inner generalization curve, and the cutting in and cutting out points are selected at the intersection of two or more elements of the generalization of mechanical parts. When a few internal elements are tangent without intersection, in order to avoid leaving a notch at the general corner when the tool compensation is cancelled, the cutting point of the tool should be far away from the corner.

The above is about the skills in the process of precision CNC machining and milling. For the machining of simple and complex precision parts, the CNC milling technology will be different, which can be based on the appropriate machining line.



Precision parameter control of CNC machining

In the machining industry, the accuracy parameters of CNC machining are mainly the level that the specific geometric parameters (specification, shape and position) of CNC parts are consistent with the ideal geometric parameters. Learn the following parameters in detail:

In the process of machining mechanical parts and small batch parts, CNC machining accuracy usually includes three level parameters: specification accuracy, shape accuracy and position accuracy.

  1. Appearance specification parameters of CNC processing

The specific specification of the surface itself or the middle of the surface after machining of CNC parts is consistent with the middle of the ideal part specification. The ideal part processing specification refers to the median value of the specification indicated on the part drawing.

  1. Shape accuracy parameters of CNC machining

The specific shape of the machined surface of CNC parts is consistent with the ideal part surface shape. The ideal part surface shape refers to the definite surface geometry shape.

  1. Precision parameters of machining parts of CNC parts

After machining, the specific parts of each surface of CNC parts are consistent with the parts between the surfaces of ideal parts. The position between the surfaces of ideal parts refers to the certain position between the surfaces.

The above is the accuracy parameter control of CNC machining. For different shapes, shapes, simplicity and complexity, it is necessary to select appropriate machining process parameters to improve CNC machining efficiency and ensure the machining accuracy of parts.



Four key points of CNC precision machining

In order to ensure the quality of precision CNC processing products, the following four key points should be followed in precision CNC processing:

  1. Datum first: that is, the datum plane shall be processed first. In the machining process of precision parts, the appearance as the positioning datum shall be processed first, so as to provide a precision datum for the processing of subsequent processes as soon as possible, so as to reduce the processing error.
  2. Division of processing technology: for the drawing size with high quality requirements for precision machining, multiple processing process routes shall be made, which can generally be divided into three stages: rough machining, semi finishing machining and finishing machining. Mainly to ensure the machining quality of mechanical parts; Conducive to the scientific application of equipment; Facilitate the arrangement of heat treatment process; And facilitate the discovery of blank defects.
  3. Face first and then hole: for precision CNC processing, for parts such as box, support and connecting rod, the plane shall be processed first and then the hole shall be processed. In this way, the plane can locate and process the hole, ensure the position accuracy of the plane and the hole, and bring convenience to the hole processing on the plane and ensure the processing quality.
  4. Finish grinding: the finishing of main surfaces, such as grinding, honing, finish grinding, rolling, etc., should be placed at the end of the process route. The general principle of formulating the process route of precision CNC machining and the formulation of the process specification of precision parts can be roughly divided into two links. The first is to draw up the process route of machining mechanical parts, and then determine the process size, equipment and process equipment, cutting specifications and man hour quota of each process.

The above is a personal understanding of the four key points that need to be followed in precision CNC processing.



CNC machining surface treatment process!

In the field of precision CNC machining, surface treatment technology is needed for machined parts with high requirements for strength and toughness. Let’s take a look at the surface treatment process of CNC machining:

  1. In the hardware mold industry, the process polishing technology of mold accessories processed by CNC is a very important link, and it is also an important process in the process of workpiece processing. The machining surface treatment process of precision mechanical parts is very important in the machining process. It is worth reminding that the mold surface polishing treatment of precision parts is not only affected by the process and polishing equipment, but also affected by the specularity of part materials. This has not been paid enough attention in the current machining, which also shows that, The polishing process itself is affected by the material.
  2. Precision CNC machining. At present, the machining technology to improve the surface performance of precision parts is constantly innovated and upgraded, but the most widely used in precision CNC parts machining are mainly hardening film deposition, nitriding and carburizing technology. Because nitriding technology can obtain a high level of surface properties, and the process of nitriding technology is very consistent with the quenching process of steel in precision parts.
  3. Details of surface treatment. The nitriding temperature is very low, so there is no need for fierce cooling process after nitriding technology treatment, so the deformation of precision machined parts will be very small. Therefore, nitriding technology is also one of the early technologies used to strengthen surface properties in the processing of precision mechanical parts, and it is also widely used at present.

The above is about the surface treatment process of CNC machining.



Steps of CNC precision machining

What is the order of CNC machining? For precision part processing, it must be based on the structure of the part, the condition of the blank, and the requirements of positioning and clamping. The key point is that the rigidity of the workpiece will not be damaged. There are the following points:

1、 The familiar understanding of precision parts processing technology can be divided into several points:

  1. How to handle the previous process will not affect the positioning and clamping of the next process. The middle cross section has a general fine part processing process.
  2. First stop the adding process of the inner cavity, and then stop the shape processing process.
  3. It is better to use the same positioning and clamping method or the same tool to stop the process, so as to reduce the number of repeated positioning, tool change and the number of moving pressing plates. Dongguan machining factory method.
  4. In multiple processes stopped in the same device, the process of damaging the workpiece stiffness shall be arranged first.

2、 The precision machining process of all parts can be completed by using the same tool sequence. Using other tools can successfully complete other parts. This can reduce the number of tool changes, shorten the dead time and reduce unnecessary positioning errors.

3、 Sorting method of processing parts: for parts with a large amount of processing content, according to their structural characteristics, the processing parts can be partially red, such as internal shape, shape, surface or plane. Common machining plane, locating surface and post machining hole; First deal with simple geometry, and then deal with complex geometry; Firstly, the parts with low precision shall be processed, and the parts with high precision shall be processed.

The above is the steps of precision CNC machining.



Reasons affecting CNC machining accuracy

In the field of machining industry, what are the reasons for the influence of CNC machining accuracy? Let’s look at the following reasons:

  1. The first is the error of position influence: it usually refers to the change or deviation degree of the mutual position of the actual surface, axis or symmetrical surface of the machined part relative to its ideal position, such as perpendicularity, position, symmetry, etc.
  2. Machine tool error: the self error of the machine tool usually refers to the dead angle error. The main causes of position error are the machining error caused by the gap and elastic deformation caused by the transmission in the machining process of machine tool parts, and the position error caused by the friction force that the tool head needs to overcome in the machining process. In the open-loop system, the position accuracy is greatly affected, while in the closed-loop servo system, the position accuracy mainly depends on the displacement detection.
  3. Geometric error: machining accuracy error caused by geometric error of CNC machining. In the process of CNC machining, due to the influence of external factors such as external force and heat generated in machining, the geometric accuracy of machine tool is affected, and the geometric deformation of parts processed on machine tool will lead to geometric error. According to the research, there are two main reasons for the geometric error of NC machine tools: internal factors and external factors. The internal factors causing the geometric error of the machine tool refer to the geometric error caused by the factors of the machine tool itself, such as the levelness of the machine tool workbench, the levelness and straightness of the machine tool guide rail, the geometric accuracy of the machine tool and fixture, etc. External factors mainly refer to the geometric errors caused by the influence of external environment and thermal deformation in the machining process. For example, the geometric error caused by the thermal expansion and deformation of tools or parts in the cutting process will affect the machining accuracy of machine tools and parts.
  4. Cumulative error: from the long-term data analysis and actual operation of part processing, it can be seen that the machining accuracy error caused by the positioning of CNC machining machine tool. The positioning of machine tool has a great influence on the machining accuracy of NC machine tool. In terms of structure, the machining error of NC machine tool is mainly caused by positioning accuracy, and the feed system of machine tool is the main link affecting positioning accuracy. The feed system of NC machine tool is usually composed of mechanical transmission system and electrical control system. In the structural design, the positioning accuracy is related to the mechanical transmission system. In the closed-loop system, the CNC machine tool can usually prevent the position deviation of the main components in the feed system (such as ball screw and other components) through the positioning detection device. However, for the open-loop system, due to many influencing factors and complex conditions, it is impossible to carry out positioning monitoring, so the machining accuracy of NC machine tool is greatly affected.

The above explanation is the reason why Dongguan CNC machining accuracy is affected. I hope it will be helpful to you after reading it.

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How to correct with cutting fluid in CNC machining

There are two kinds of cutting fluids for CNC machining of product parts: Oil-based cutting fluid and water-based cutting fluid. Precision parts processing is a kind of accessories widely used in automobile, communication, medical treatment, clocks, mobile phones, computers and other industries. Different from ordinary parts, precision parts are more precise and more suitable for some industries with high requirements for precision. Micropore processing less than 2 nm is called micropore. The pore size of some catalysts is usually described. Micropore processing is difficult, especially for micropores with a diameter of less than 1mm. However, many mechanical products have this microporous structure. CNC machining feed machining route refers to the turning tool from the tool setting point (or the fixed origin of the machine tool) starts to move until it returns to this point and ends the processing program, including the cutting path and non cutting empty stroke paths such as tool cut in and cut out. The cutting fluid used for CNC processing of product parts can be divided into cutting oil, emulsion, semi synthetic fluid and synthetic fluid, cutting oil, emulsion (sometimes referred to as soapy water) and synthetic fluid (commonly known as environment-friendly fluid), synthetic fluid may be commonly used, but little is known about how to select cutting fluid in the machining process. Let’s look at the advantages and disadvantages of each cutting fluid.

  1. Cutting oil for CNC machining of product parts. Very high physical lubrication B is suitable for low speed, less cutting allowance C surface finish and provides excellent service.
  2. CNC processing emulsion is used for product parts: advantages: multi metals have good safety and good lubricity. The advantages of this method are: good rust prevention, easy sewage treatment, disadvantages: increase the dosage; emulsify the sewage oil at the same time. The odor is not well controlled. The equipment is very dirty. The stability of hard water is very poor. The filtration is poor and the mixing is poor
  3. Semi synthetic liquid is used for CNC processing of product parts: advantages

1。 Cooling effect is better than emulsification effect.

2。 Better rust prevention

3。 Cleaner than emulsion.

4。 Better filtration performance

5。 More suitable for hard water and dirty oil. More suitable for hard water and dirty oil. The antibacterial effect is better than emulsion. Disadvantages:

1。 Blisters easily in soft water.

2。 Oil resistance is worse than synthetic liquid.

3。 At high concentrations, there may be a tendency to skin allergy

4。 Synthetic fluid used in CNC processing of product parts: advantages:

1。 Very clean.

2。 It doesn’t smell.

3。 Senior operator acceptance

4。 Low consumption (12-20 weeks)

5。 Excellent cooling performance. Figure 6. Completely refuse to spill oil. Low bubble 8. Long service life. Very good filtration / rapid sedimentation performance, disadvantages:

1。 Low physical lubrication

2。 Sewage treatment is difficult. A sticky residue, especially in hard water. Incompatible with emulsion. React with polycarbonate. It may damage the paint surface of the machine. Through the description of the cutting fluid used for CNC machining of the above various product parts, we can better understand them and be more clear about what kind of cutting fluid to choose.



What tools are used for CNC processing aluminum

In the machining process of mechanical parts, the appropriate selection of cutting tools can be directly related to production efficiency and ultra-high machining cost! Therefore, it is also a skill in the machining industry to choose what materials to process and what tools to use. Let’s take a look at what kind of cutting tools are used for metal and aluminum processing?

Aluminum, also known as aluminum alloy in the machining industry, is one of the most common and important metal materials. In the mechanical equipment manufacturing industry, almost 60% of the mechanical equipment spare parts are processed with aluminum, especially in lithium battery equipment, laser equipment, non-standard automation equipment, optical industry and electronic technology. More than 80% of the spare parts of this equipment are replaced with aluminum. In machining aluminum is also the most contact!

For aluminum processing, many people may say that it is OK to use ordinary white steel tools. It is also applicable if the cost is not high, which is really good. However, our production efficiency can’t be improved. It’s easy to wear when processing with white steel tools, and the tools will often break, especially small ones. This is not cost-effective. The tool we want to say is not two edge or four edge. It is a three edge tool. Aluminum cutting has unique advantages. Compared with ordinary tools, it continuously improves the working efficiency, is not easy to wear and break, and the dimensional accuracy control is also guaranteed. In the machining industry, it is called aluminum special tool, which is the best choice for aluminum processing!

The above is a brief description of what kind of cutting tools are used for machining aluminum. Thank you for your attention!