Analyze the parameter characteristics of CNC turning cast iron boxes

Parameter characteristics of CNC turning cast iron boxes

Cutting speed

The cutting speed has a significant impact on tool durability. Increasing the cutting speed can shorten the processing time and improve efficiency. However, if the linear speed is too high, the cutting temperature will rise, and the tool durability will be greatly reduced. For example, if the linear speed is 20% higher than the specified linear speed of the sample, the tool life will be reduced to half of the original. If it is increased to 50%, the tool life will only be one fifth of the original. When processing at low cutting speeds (20-40 m/min), the workpiece is prone to vibration and the tool durability is also low. For materials like cast iron, the selection of cutting speed needs to comprehensively consider factors such as tool material and workpiece hardness. Generally speaking, when using hard alloy tools to cut cast iron, a lower cutting speed can be selected for rough machining, and the cutting speed can be appropriately increased for finish machining, but the speed range where built-up edge occurs should also be avoided.

Feed rate

The feed rate is closely related to the surface roughness of the processed surface. Usually, the feed rate is determined according to the surface roughness requirements. The feed rate should be greater than the width of the chamfer; otherwise, the chips cannot be broken. Generally, it is about twice the width of the chamfer. When the feed rate is large, the thickness of the chip layer increases and the cutting force increases. A large feed rate requires a relatively large cutting power accordingly. The feed rate is small, the wear at the back is large, and the durability of the cutting tool decreases rapidly. A large feed rate leads to an increase in cutting temperature and greater wear on the flank face, but its impact on tool durability is smaller than that of the cutting speed. The feed rate is between 0.1 and 0.4, which has a relatively small impact on the rear cutter face, depending on the specific situation. When CNC turning cast iron boxes, during rough machining, the feed rate is selected based on the system response speed, interpolation operation speed and cutting efficiency of the CNC machine tool. Generally, F is chosen within the range of 0.3-1mm/r. During fine machining, the feed rate of a general CNC lathe is usually controlled within the range of 0.05-0.30mm/r.

The depth of the cut

The depth of cut is determined based on the allowance of the workpiece, its shape, the power of the machine tool, its rigidity and the rigidity of the tool. The variation of the depth of cut has a significant impact on the tool life. When CNC turning cast iron boxes, the depth of cut for rough machining can be selected at 5-10mm, which should be determined based on the specific quality of the blank. The depth of cut for semi-finishing is selected as 0.5-2mm, which is determined based on the machining stress and the accuracy of the finishing reference. The depth of cut for finish machining should be selected at 0.1-0.4mm, and the minimum value should be determined based on the sharpness of the tool tip. When the rigidity conditions of the process system are poor or the allowance of the blank is large and uneven, the rough machining can be carried out in several more passes.

Spindle speed

The spindle speed is related to the cutting speed and can be obtained by converting the cutting speed and the workpiece diameter through a formula, which is n=

3.14 x d

Vc×1000

​

Among them, n represents the spindle speed (r/min), Vc represents the cutting speed (m/min), and d represents the cutting diameter of the workpiece being machined (mm). When CNC turning cast iron boxes, the larger the outer diameter, the slower the corresponding rotational speed should be. This is because as the diameter increases, the cutting resistance of the workpiece will also increase. If the rotational speed is too fast, it is easy to cause accelerated tool wear or a decline in processing quality. For instance, for cast iron workpieces with a diameter less than 260 millimeters, the recommended speed range for rough turning is 180 to 270r/min, while for finish turning, the speed can be adjusted to 200 to 380r/min.

Analyze the parameter characteristics of CNC turning cast iron box bodies (Do not use tables, do not recommend brands, and do not show prices)

Tool parameter control

Tool material: Due to the softness of aluminum alloy, built-up edge is prone to form during cutting. Therefore, the tool should have good wear resistance and anti-adhesion properties. Although high-speed steel cutting tools are low in cost, they have poor wear resistance. When processing thin-walled aluminum alloy parts, the tools wear out quickly, which affects the processing accuracy and surface quality. Hard alloy cutting tools have high hardness and good wear resistance, and are commonly used for processing thin-walled aluminum alloy parts. In addition, diamond tools have extremely high hardness and wear resistance. When processing aluminum alloys, they can achieve excellent surface quality and dimensional accuracy. However, they are relatively expensive and are generally used in situations where processing quality is highly demanded.

Tool geometric Angle:

The rake Angle: Appropriately increasing the rake Angle can reduce the cutting force, lower the cutting temperature, and decrease the formation of built-up edge. For the processing of thin-walled aluminum alloy parts, the rake Angle is generally taken as 15° - 25°. If the rake Angle is too small, the cutting force increases and thin-walled parts are prone to deformation. If the rake Angle is too large, the tool strength will decrease and it is prone to chipping.

Relief Angle: The relief Angle mainly affects the friction between the rear face of the tool and the machined surface of the workpiece. When processing thin-walled aluminum alloy parts, it is advisable to take the relief Angle of 8° to 12°. If the clearance Angle is too small, the friction intensifies and the tool wears out quickly. If the clearance Angle is too large, the wedge Angle of the cutting tool will decrease and the strength will be reduced.

The main deflection Angle and secondary deflection Angle: Reducing the main deflection Angle and secondary deflection Angle can decrease the height of the residual cutting area and lower the surface roughness. However, if the main deflection Angle is too small, the radial cutting force will increase, and thin-walled parts are prone to deformation. The main deflection Angle is generally 45° - 75°, and the secondary deflection Angle is 5° - 10°.

Edge tilt Angle: The edge tilt Angle can control the chip flow direction. When processing thin-walled aluminum alloy parts, the cutting edge Angle should be set at 0° - 5° to ensure that the chips flow towards the surface to be processed and avoid scratching the already processed surface.

Cutting parameter control

Cutting speed: Cutting speed has a significant impact on processing efficiency and surface quality. Increasing the cutting speed can enhance production efficiency, but an excessively high cutting speed will raise the cutting temperature, accelerate tool wear, and may also cause thermal deformation of thin-walled parts. Generally speaking, when roughly machining thin-walled aluminum alloy parts, the cutting speed can be taken as 200-400 m/min, and when finely machining, it can be taken as 400-800 m/min. For instance, when processing thin-walled aluminum alloy shaft parts with a diameter of 50mm, the rotational speed for rough machining can be selected as 1200-2500r /min, and for finish machining, it can be selected as 2500-5000r /min.

Feed rate: Excessive feed rate will increase the cutting force and cause deformation of thin-walled parts. If the feed rate is too small, the production efficiency will be low, and the surface quality may be affected due to the intensified friction between the tool and the workpiece. The feed rate can be taken as 0.1-0.3mm/r during rough machining, and 0.05-0.15mm/r during finish machining. For instance, when precisely turning the outer circle of thin-walled aluminum alloy parts, it is more appropriate to control the feed rate within 0.08-0.12mm/r.

Cutting depth: Aluminum alloy thin-walled parts have poor rigidity. If the cutting depth is too large, it will cause significant deformation. During rough machining, the cutting depth can be taken as 1-3mm, and during finish machining, it can be taken as 0.05-0.2mm. For example, when performing fine machining on thin-walled cylindrical parts made of aluminum alloy with a wall thickness of 2mm, the cutting depth should be controlled within 0.1mm to reduce deformation.

Fixture parameter control

Clamping force: If the clamping force is too large, it will cause elastic deformation of thin-walled parts. After processing, the deformation will recover, affecting the dimensional accuracy. If the clamping force is too small, the workpiece is prone to loosening under the action of the cutting force, resulting in processing errors. The magnitude of the clamping force should be comprehensively considered based on factors such as the shape, size, material and cutting force of the workpiece. Generally, the appropriate clamping force can be determined through experiments or empirical formulas. Under the premise of ensuring the reliable clamping of the workpiece, the clamping force should be reduced as much as possible. For instance, the test can be conducted by gradually increasing the clamping force to observe the deformation of the workpiece and determine the appropriate clamping force magnitude.

Clamping method: Evenly distributed clamping points should be adopted to ensure uniform force distribution on the workpiece and reduce deformation. For circular thin-walled parts, open expansion sleeves or elastic chucks can be used for clamping. For square thin-walled parts, a pressure plate can be used to press them evenly. Meanwhile, the clamping part should be as close as possible to the processing part to minimize the influence of the clamping force on the processing accuracy.

Cooling and lubrication parameter control

Coolant selection: Aluminum alloys are prone to chemical reactions with certain coolants at high temperatures, leading to corrosion. Therefore, coolant that has no corrosive effect on aluminum alloy should be selected, such as emulsion, kerosene, etc. The emulsion has excellent cooling and lubricating properties, which can effectively reduce the cutting temperature, decrease tool wear and improve the quality of the machined surface. Kerosene has good lubricating performance and is suitable for fine processing with high requirements for surface quality.

Cooling method: High-pressure cooling or spray cooling can be adopted to ensure that the coolant fully penetrates the cutting area and enhances the cooling effect. High-pressure cooling can spray the coolant onto the cutting edge at a relatively high pressure, promptly removing the cutting heat and reducing the cutting temperature. Spray cooling involves atomizing the coolant and spraying it onto the cutting area, which can both cool and lubricate, reducing the friction between the tool and the workpiece.

Coolant flow rate: The coolant flow rate should be moderate. If the flow rate is too small, the cooling effect will be poor. Excessive flow will cause waste and may also affect the processing environment. Generally speaking, the coolant flow rate should be adjusted according to factors such as cutting parameters, tool type and workpiece material to ensure that the cutting area can be adequately cooled and lubricated.

Parameter control for CNC turning of thin-walled aluminum alloy parts (Do not use tables, do not recommend brands, do not show prices)

Reference

5

A web page information source

When CNC turning quenched and tempered steel, parameter Settings need to comprehensively consider material properties, tool selection, cutting parameters and cooling strategies. The following are specific tips:

Cutting speed

The cutting speed has a significant impact on the durability of the cutting tool. Increasing the cutting speed can shorten the processing time and improve efficiency. However, if the linear speed is too high, the cutting temperature will rise and the tool durability will be greatly reduced. For example, if the linear speed is 20% higher than the specified linear speed of the sample, the tool life will be reduced to half of the original. If it is increased to 50%, the tool life will only be one fifth of the original. When processing at low cutting speeds (20-40 m/min), the workpiece is prone to vibration and the tool durability is also low.

Quenched and tempered steel has a relatively high hardness, so the cutting speed should be appropriately reduced. Taking the hardness HRC25-30 of 40Cr alloy steel after quenching and tempering treatment as an example, the rough machining speed can be set at 600-900 r/min, and the finish machining speed can be set at 1200-1500 r/min. For instance, if the material of a certain upper cover is 45# steel with a quenched and tempered hardness of HRC28-32, when processing the thread of M105X2, if it is processed as a non-quenched 45# steel part, the tool linear speed should be between 180 and 200m/min. However, when quenched to HRC28-32, it is more appropriate to reduce the linear speed to around 120m/min for processing.

Feed rate

The feed rate is closely related to the surface roughness of the processed surface. Usually, the feed rate is determined according to the surface roughness requirements. The feed rate should be greater than the width of the chamfer; otherwise, the chips cannot be broken. Generally, it is about twice the width of the chamfer. When the feed rate is large, the thickness of the chip layer increases, the cutting force increases, the cutting temperature rises, and the wear of the rear face increases. However, its impact on the tool durability is smaller than that of the cutting speed. When the feed rate is small, the wear at the back is large, and the durability of the cutting tool decreases rapidly. The feed rate is between 0.1 and 0.4, which has a relatively small impact on the rear cutter face, depending on the specific situation.

During rough machining, under the premise of ensuring the quality of part processing, a higher feed rate should be selected to increase productivity. The main factors limiting the feed rate include the strength and rigidity of the tool holder, insert, machine tool, workpiece, etc. Generally, the selection range should be between 100 and 200mm/min. When performing cutting, deep hole processing or high-speed steel tool processing, the feed rate should be appropriately reduced. Generally, it is advisable to select 20-50mm /min. When performing semi-finishing or finishing, the feed rate is usually selected based on the surface roughness requirements of the part to be processed. If the surface roughness requirement is low, the feed rate will be small, but it should not be too small either. If the feed rate is too small, the cutting thickness will be too thin, which will instead increase the surface roughness and aggravate the wear of the tool. Under normal circumstances, the feed rate during finish turning should be selected within the range of 0.10-0.20mm/r.

The depth of the cut

The depth of cut is determined based on the allowance of the workpiece, its shape, the power of the machine tool, its rigidity and the rigidity of the tool. Changes in the depth of cut have a significant impact on the tool life. For instance, when performing peeling and turning on a hot-rolled D80 round steel piece, assuming the maximum and minimum external dimensions of the round steel piece are 82 and 78 respectively due to its ellipticity, the depth of the first cut must be less than 78. As the tool tip is continuously processed all the time, it can effectively ensure that the tool tip does not chipping, thereby increasing the service life of the tool. For workpieces of different materials or those of the same material but with different heat treatment hardness, the cutting depth during processing will vary. The decision should be made based on the actual situation.

Taking 40Cr alloy steel as an example, the back cut for rough machining can be set at 2-4mm, and the back cut for finish machining can be set at 0.08-0.12mm.

Tool selection

Quenched and tempered steel has a relatively high hardness. It is recommended to use CBN tools. For instance, when processing 40Cr alloy steel, it is recommended to use CBN tools in the finishing stage and increase the concentration of the cutting fluid to 8% - 10%.

Cooling strategy

The coolant should be supplied in sufficient quantity, with a flow rate of no less than 8L/min. Special attention should be paid to aligning the cooling pipelines during the inner hole processing. For materials with high hardness such as quenched and tempered steel, a composite cooling scheme can be adopted, such as micro-lubrication (MQL) technology. Atomized cutting oil of 5-50 ml /h can be precisely sprayed into the cutting area, reducing thermal deformation and lowering the liquid consumption by 90% at the same time. The high-pressure internal cooling system, by directly flushing the blade tip with 5-10 mpa high-pressure coolant, effectively suppresses built-up edge and accelerates chip removal. Low-temperature cooling, using liquid nitrogen or CO₂ cold air (-50℃ to -30 ℃), can reduce the temperature in the cutting zone by more than 200℃, which is particularly suitable for the processing of high-hardness stainless steel.

Analysis of Parameter Setting techniques for CNC Turning of quenched and tempered steel (Do not use tables, do not recommend brands, and do not show prices)

Reference

2

A web page information source

When CNC turning non-metallic materials, parameter selection needs to be combined with the material properties and processing requirements. The following are the parameter selection methods for different non-metallic materials:

Fiberglass reinforced plastic material

Tool material: Tungsten-cobalt cemented carbide YG6 and YG8 can be selected.

Tool angles: The rake Angle is 25° - 30°, the relief Angle is 10° - 20°, and the rest of the geometric angles are the same as those of general turning tools.

Organic glass

Tool materials: Commonly used ones include hard alloy steels such as YG6, YG8 and W18Cr4V, as well as high-speed steels.

Tool angles: Take the rake Angle as 30° - 40°, the relief Angle as 10° - 12°, and the rest of the angles are the same as those of general turning tools.

Brittle non-metallic materials (such as ceramics, etc.)

Cutting speed: Generally, it can be selected within the range of 50 to 100m/min. When the strength and hardness of the material are relatively low, a larger value can be taken; when the strength and hardness of the material are relatively high, a smaller value can be taken. Meanwhile, the areas where built-up tumors occur should be avoided as much as possible. The cutting speed area where built-up tumors are most likely to occur is 15-25 m/min. During intermittent cutting, to reduce the impact and vibration of the cutting, the cutting speed should be appropriately reduced.

Feed rate: During rough machining, it is selected based on the system response speed, interpolation operation speed and cutting efficiency of the CNC machine tool. Generally, F within the range of 0.3-1mm/r is chosen for rough turning. During fine machining, the feed rate of a general CNC lathe is usually controlled within the range of 0.05-0.30mm/r. In actual cutting operations, the feed rate multiple switch on the machine tool operation control panel can be adjusted according to the specific conditions of the cutting process.

Back cut depth: During rough machining, it can be selected at 5-10mm, which should be determined based on the specific quality of the blank. When semi-finishing, it is selected at 0.5-2mm, which is determined based on the processing stress and the precision of the finishing reference. When performing fine machining, select 0.1-0.4mm. The minimum value should be determined based on the sharpness of the tool tip. When the rigidity conditions of the process system are poor or the allowance of the blank is large and uneven, the rough machining can be carried out in several more passes.

Parameter selection method for CNC turning of non-metallic materials (Do not use tables, do not recommend brands, and do not show prices)

Reference

5

A web page information source