ã€China Aluminum Industry Network】 1) Fast forward and forward In the machining program, both G00 and G01 can define the linear motion of the tool, but their role is very different. Beginners are easy to confuse.
The feedrate of the work feed command (G01, G02, G03, etc.) is determined by the F command in the program; the feedrate of the fast feed command (G00 and part of the zero return command) is not specified in the machining program, but is set during the machine parameter setting. Saved as a machine parameter in the CNC system.
The work order instructions must not only ensure that the machining end point is accurate, but also ensure that the machining path and the feed speed are accurate, which depends on the microscopic interpolation calculation and dynamic control.
The purpose of fast-forwarding instructions is to minimize the idle travel time. In multi-axis linkage, the motion trajectory is unpredictable. Therefore, fast-forwarding instructions cannot be used for machining feeds.
2) Positioning Accuracy and Repeated Positioning Accuracy The machining center manufacturers often only give repeat positioning accuracy in the publicity material without giving the positioning accuracy index, which makes it easy for some users to misunderstand the repeat positioning accuracy as the main index for determining the part machining accuracy. In fact, high repeat positioning accuracy does not mean that the part machining accuracy is high. Positioning accuracy is the main indicator that determines the accuracy of part machining.
Repeated positioning accuracy reflects the ability of the machine to return to the same position multiple times. The measurement method is to fix a dial indicator, the head is pressed on the spindle, and the zero point of the dial indicator is calibrated. Move the spindle to any position and then return it to the calibration coordinate position just before reading the reading of the dial indicator. After many round-trip readings, the larger error is repeated positioning accuracy.
In accordance with the current level of CNC technology and the typical electromechanical processing center, the servo motor + rotary encoder + ball screw or rack and pinion repeat positioning error is generally not more than 2 pulse equivalent, far less than 0.01mm.
Positioning accuracy refers to the ability to accurately move a specified distance over the full stroke of the machine. The large stroke of the aluminum processing center can reach up to 7 meters, and laser interferometer is generally used for positioning accuracy measurement.
The positioning accuracy is mainly affected by the shape error of the guide rail, mechanical clearance, screw/rack error, machine deformation and electrical following error. The error data measured by the laser interferometer is input into the CNC system, and the positioning accuracy can be obtained with the error compensation function of the CNC system.
NSK manufacture a full range of deep groove ball bearings. These bearings are the most common type and are used in a wide variety of applications.
Single-Row Deep Groove Ball Bearings
Pressed Steel Cages
Single-row deep groove ball bearings are the most common type of rolling bearings. Their use is very widespread.
In addition to open type bearings, these bearings often have steel shields or rubber seals installed on one or both sides and are prelubricated with grease. Also, snap rings are sometimes used on the periphery. As to cages, pressed steel ones are the most common.
For big deep groove ball bearings, machined brass cages are used.
Machined cages are also used for high speed applications.
Extra Small Ball Bearings and Miniature Ball Bearings
Miniature and instrument ball bearings can be divided into two basic types, deep groove and angular contact. The first (deep groove) can be further divided into the following five classes depending on their design details:
Standard type
Flanged outer ring
Extended inner ring
Expanded type in which one ring has a radial thickness that is larger than normal compared with the bearing width.
Thin section type in which both rings are extra thin in the radial direction. They can also be classified as: open, shielded, or sealed.
Maximum-Type Ball Bearings
Maximum-Type ball Bearings contain a larger number of balls than normal deep groove ball bearings because of filling slots in the inner and outer rings. Because of their filling slots, they are not suitable for applications with high axial loads. types of bearings have boundary dimensions equal to those of single-row deep groove ball bearings of Series 6200 and 6300 respectively. Besides the open type, ZZ type shielded bearings are also available. When using these bearings, it is important for the filling slot in the outer ring to be outside of the loaded zone as much as possible. Their cages are pressed steel.
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Shijiazhuang Longshu Mechanical & Electrical Equipment Trading Co., Ltd. , https://www.lsjgbearing.com