Tool selection and quality control of CNC lathe
Tool selection method
Because CNC lathe processing is a high-precision job, and its processing procedures are concentrated and the number of parts clamping is small, so higher requirements are put forward for the CNC tools used. The following Dongguan Tongli Metal Products Co., Ltd. will do it for you Introduction.
When choosing tools for CNC machine tools, the following issues should be considered:
① The type, specification and accuracy grade of CNC tools should be able to meet the requirements of CNC lathe processing.
②High precision. In order to meet the requirements of high precision and automatic tool change of CNC lathe processing, the tool must have high precision.
③High reliability. To ensure that no accidental damage and potential defects of the tool will affect the smooth progress of the processing during CNC machining, the tool and the accessories combined with it must have good reliability and strong adaptability. Precision metal processing
④High durability. The tools processed by CNC lathes, whether in roughing or finishing, should have higher durability than those used in ordinary machine tools, so as to minimize the number of times of changing or grinding tools and tool set, thereby improving the processing of CNC machine tools Efficiency and guarantee processing quality.
⑤Good chip breaking and chip removal performance. In CNC lathe processing, chip breaking and chip removal are not handled manually like ordinary machine tools. Chips are easy to wrap around the tool and workpiece, which will damage the tool and scratch the machined surface of the workpiece, and even cause injury and equipment accidents. , Which affects the processing quality and the safe operation of the machine tool, so the tool is required to have better chip breaking and chip removal performance.
Application of frequency converter
When the CNC lathe is started, the current of the motor will be 5-6 times higher than the rated value, which will not only affect the service life of the motor but also consume more power. The system will have a certain margin in motor selection during the design. The speed of the motor is fixed, but in actual use, it sometimes runs at a lower or higher speed, so it is very necessary to carry out frequency conversion transformation. The frequency converter can realize the soft start of the motor, achieve the purpose of energy-saving and speed regulation by changing the input voltage frequency of the equipment, and can provide the equipment with protection functions such as overcurrent, overvoltage, and overload. country
Quality Control
If the ordinary lathes used and the long-used lathes are not modified, and only a new CNC lathe is purchased, it will increase the equipment cost of many manufacturers. Therefore, it is the only way for manufacturers to carry out numerical control transformation on ordinary lathes and long-used lathes.
Because the numerical control transformation is more complicated and messy for the transformation manufacturers, how to control the quality of the transformed numerical control machine tools is a problem that we have always needed to discuss. Here is how to carry out the quality control of the transformed numerical control lathes.
The CNC transformation of ordinary lathes is divided into new machine transformation and old machine transformation. The new machine transformation is when the user purchases an ordinary lathe or an ordinary light machine (referring to a lathe with only a headbox and longitudinal and transverse guides), and the transformation manufacturer performs numerical control according to its requirements Transformation. Old machine transformation means that the user refurbishes the used ordinary lathe or numerical control lathe and carries out numerical control transformation. Among them, old machine transformation includes overhaul lathe transformation and user old machine parts transformation. Here is a brief talk about the quality control method, focusing on the control points and inspection process of the transformation of CNC lathes in mechanical aspects.
Both the new machine transformation and the old machine overhaul lathe transformation must undergo the same transformation as follows
① Replace the X-axis and Z-axis screw rods, bearings, and motors.
②Add electric tool post and spindle encoder.
③Increase the drive device of the axial motor, limit the overtravel travel switch, install the frequency converter (customer needs), and the electrical parts required for processing and safety.
④Scraping of the supporting surfaces of the two ends of the X-axis and Z-axis screws, the matching of the ball screw bracket and the saddle, and the matching of the bed and the saddle rail pair.
⑤Add protective facilities as needed, such as protective covers for all-direction screw rods, safety protective doors, and protective devices for travel switches.
The difference between new machine transformation and old machine overhaul lathe transformation
①The main shaft and tailstock of the new machine have not been modified, and the main shaft and tailstock do not need to be modified.
②The old machine overhaul lathe has worn out the guide rail after long time use. In order to ensure that it can be used for a long time without deformation after overhaul, it must go through a quenching process and then grind the guide rail. After grinding the guide rail, the hardness of the guide rail must be ≥HRC47.
③The old machine overhaul lathe should modify and adjust the main shaft and tailstock parts according to customer needs.
Accuracy inspection of new machine transformation and overhaul machine tool transformation is an important item of inspection
Accuracy inspection implements JB/T8324.1-1996 "Accuracy of Simple CNC Horizontal Lathe".
The accuracy and quality control of the new lathe transformation is as follows
① Shovel inspection. The transformation of the new lathe includes the matching and scraping of the supporting surfaces of the X-axis and Z-axis screw rods, the matching and scraping of the ball screw bracket and the saddle, and the bed and the saddle rail pair. The main shaft and tailstock of the lathe are not removed. The inspection method is as follows: paint with the mating surface, combine the mating surfaces, and rub against each other, then check the number of scraping points on the scraping surface, and check the degree of bonding with a feeler gauge at the joint.
② Inspection of the parallelism of the screw rod and the guide rail: When assembling the screw rod, the parallelism between the screw rod and the guide rail must be ≤ 0.02mm.
③In the G1 item of the accuracy test, the straightness of the guide rail in the vertical plane (only convex) should be guaranteed by the ordinary lathe manufacturer, not as a key inspection item.
④The accuracy of the main shaft parts G4, G5, and G6 in the accuracy inspection should also be guaranteed by the ordinary lathe manufacturer and not as a key inspection item.
⑤The heights of the two centers of the head and tailstock of item G11 are guaranteed by ordinary lathe manufacturers and are not considered as key items for quality control of the transformation manufacturers.
Accuracy inspection of user overhaul lathe transformation
Since the guide rail has been ground and the reference level has changed, all items in the accuracy test must be inspected and strictly controlled to ensure the performance after the transformation.
Other important quality control points for overhaul lathe transformation and new machine transformation
1. Corrosion inspection: each horizontal and vertical guide rail surface, main shaft, main shaft flange, and hollow sleeve of the tailstock.
2. Anti-rust measures must be taken on all exposed non-painted surfaces. For example, after cleaning, use lubricating grease for anti-rust inspection: the scraping surface, screw rod, and bearing must be cleaned before assembly, and no red lead powder, Iron shavings, and other dirty materials; there is no dust or dirt inside the electric box and inside the protective cover.
3. Leakage inspection: The main shaft bearings and gears of the overhaul lathe must be kept lubricated. The axial screw and bearings of the overhaul lathe and the new lathe must be lubricated, and there must be a cooling device, and the above lubrication and cooling of the joints, there must be no leakage in oil and water tanks.
4. Machine tool noise, temperature rise, speed, dry running test:
①The main shaft runs continuously for 4 minutes at various speeds, and the maximum speed running time is not less than 2 hours. The dry-running time of the whole machine is ≥16h, and the cyclic turning of arcs, threads, outer circles, end faces, etc. are simulated dry running tests.
②After the spindle bearing temperature is stable, measure the bearing temperature and temperature rise. Rolling bearings: temperature ≤70℃, temperature rise ≤40℃; sliding bearing: temperature ≤60℃, temperature rise ≤30℃.
③The noise pressure level of the machine tool is less than or equal to 83dB(A) under dry running conditions, and whether the machine tool has abnormal screaming or impact noise. The feed movement in each axis direction should be smooth, without obvious vibration, chatter, and crawling.
④The continuous dry-running test of the machine tool has no failure, reliable and stable operation within the specified continuous dry-running time.
5. Transformation of user replacement parts (including maintenance of machine tool parts): As there are many transformation projects for lathe replacement parts, mainly the replacement of spindle bearings, axial screws, axial motors, axial bearings, and systems.
①Replace the spindle bearing: Since the replacement of the spindle bearing is to ensure the accuracy of the outer circle and end face, it is necessary to check the spindle noise first after the bearing is replaced. The noise level of the whole machine should not exceed 83dB (A), And then inspect the processing accuracy and inspect the surface roughness of the processed workpiece.
②Replace the axial screw rod inspection: check the position accuracy of all directions to ensure that within the specified range, the treadmill runs to achieve the axial operation without abnormal impact and noise. Replacement of the axial motor: As other items have not been modified, the inspection only checks the noise of the running machine, and there is no abnormal impact sound and noise in the axial operation. Check the axial reverse clearance to prevent the reverse difference caused by the assembly from not meeting the requirements during assembly.
③ Replacing the axial bearing: In the case of replacing the axial bearing, it is necessary to ensure that the axial reverse difference meets the requirements, and check for abnormal noise.
④Replacement system inspection: In the case of replacing the system, only check the system function, check whether the system has alarms, and check whether the test thread is normal (for the lathe with encoder).
Luoyang Yujie Industry &Trade Co.Ltd located in Luoyang City, one of the main heavy industrial bases in China. We specialize in the production of bearing, nonstandard machinery parts, and CNC machine tools. If you have any interests, feel free to contact us and we warmly welcome customers and friends visit us
Luoyang Yujie Industry & Trade Co., Ltd.
Tel: +86-379-80865527
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ADD: Jianxi Industrial Park, Luoyang City, Henan, China
https://www.yogiemachinery.com/products
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