The transmission case is an important part of the mechanical transmission roller, and its processing quality will directly affect the use of the roller's transmission system. The transmission case material used in high-end Dain products is HT200. The transmission has the characteristics of small size, simple structure, convenient use and reliable action. It has been widely used in the LSS series vibratory rollers produced by our company. In the past, box processing was done on gantry planers, boring machines and drilling machines to process flat surfaces, bearing retaining holes and connecting holes. The production efficiency was low and the processing quality was difficult to guarantee. In order to solve the above problems, High-end Dain introduced Ethernet manufactured by Daewoo Company of South Korea. ACE HM800 horizontal machining center is used for box processing and has achieved good application results.

Part process analysis and process arrangement

Box workpieces have the following characteristics: First, there are many processing contents, which require frequent replacement of machine tools and cutting tools; Second, the processing accuracy requirements are high, and it is difficult to guarantee the processing quality using ordinary machine tools. Moreover, due to the long process flow and high turnover times, the production efficiency It is difficult to improve; third, the shape is complex, and most of them are thin-walled shells. The workpiece has poor stiffness and is difficult to assemble. A CNC machining center is used for box processing, relying on the machining center's own precision, high processing efficiency, good rigidity and automatic tool change. As long as the process flow is well formulated and reasonable special fixtures and tools are designed, the above problems can be completely solved. Since the equipment has a double workbench, we will complete the processing of various processing elements on the B and C surfaces of the workpiece on the 01 workbench (processing process 1), and place the remaining processing elements on the G, H and gear side sides on 02 Completed on the workbench (processing process 2), according to the above process arrangement, design the corresponding special fixture.

Blank preparation

The preparation process before the machining center of the workpiece is completed by other equipment, such as the rough machining of the G and H sides of the part, which are processed on ordinary machine tools. This firstly reduces the thermal deformation caused by large margin machining; secondly, in order to The machining center provides the necessary positioning benchmark; third, it improves processing efficiency. After both sides are planed, place the workpiece flat on the bench with G surface as the benchmark (consistent with the benchmark when processing in the machining center), and the benchworker marks out the finishing lines on surfaces B and C and the K and H (both sides) surfaces of the box. The central datum line is used for calibration of the machining center.

Process 1: Design and use of fixtures and processing process

Process and fixture structure and use

1. As mentioned above, the processing process of step 1 mainly includes fine milling of B and C surfaces, and drilling of the 6-φ18 hole (F) on C surface. In order to improve the processing quality and efficiency, a special fixture is designed based on the processing characteristics of this process. The fixture consists of a pressure plate 1, an elastic positioning pin 2, a positioning pin 3, an elastic positioning pin 4, an adjustment bolt 5 and a base plate 6. When in use, the D surface of the workpiece is placed flat on a plane composed of four height-adjustable positioning pins 3. There are two elastic positioning pins 2 and 4 on the fixture to cooperate with the D and E holes on the workpiece, forming a typical two-sided structure on one side. Pin positioning, positioning pins 2 and 4 are designed to be elastic. This is because the reference hole of the workpiece is a rough reference, and its casting aperture is irregular. Since the positioning pins are elastic, even if the aperture changes, the surface of the workpiece G can still be flat at 4 On a plane composed of two positioning pins, the workpiece can be quickly initially positioned. This clamp adopts a hole system combination clamp, which can be quickly assembled and adjusted. It has high positioning accuracy, firm and reliable tightening, and is suitable for the production of small batches and multiple varieties.

1. Pressure plate 2. Elastic positioning pin 3. Positioning pin 4. Elastic positioning pin 5. Adjustment bolt 6. Bottom plate Figure 2 Special fixture for process 1

Programming

The machining center is equipped with an automatic tool changer, which can automatically complete milling, drilling, boring, reaming, tapping and other processes in one clamping of the workpiece. It has the characteristics of high productivity and quality stability. In order to give full play to the high efficiency and multi-functional characteristics of the machining center, attention should be paid to the division of processes and the rationality of the process methods in the design of the machining program, which is directly related to the use efficiency, machining accuracy, number of tools and economy of the machining center. , try to achieve centralized processes, the shortest process route, and the minimum machine tool pause time and auxiliary time. When designing the program, one tool change should be regarded as a working step, and the processing content and dimensional requirements to be ensured should be noted. Add the M01 command between work steps and use it in conjunction with the OPTION-AL STOP switch on the machine tool. The machine tool will stop running after changing the tool. The accuracy of the tool change can be checked to fully verify the program. During batch processing, only Turn off the OPTIONAL STOP switch and the program will still execute continuous operation mode. When rough milling the plane, the machining allowance is large and the workpiece will undergo large thermal deformation. Rough and fine milling should be separated to allow the parts to be fully cooled. When designing the drilling program, the hole processing accuracy requirements should be considered. For hole processing with average accuracy requirements, it is not necessary to use a center drill to pre-drill. Since tapping is required after drilling, the position of each hole can be programmed into a subprogram and called into the main program using the M98 command, which can be easily reused and reduce coordinate errors during programming.

When the power of the machine tool permits, all screw holes are rigidly tapped to improve processing efficiency. When precision boring, since single-edged boring tools are generally used, several issues should be paid attention to when programming: First, when manually installing the tool at the spindle position, you should first use the M19 command to pass the spindle, and then let the tool tip face inward. (i.e. facing away from the operator) for installation; secondly, when programming using the G76 command, the corresponding Q value should be set. After boring is completed, the spindle will move in the opposite direction of the tool tip to position the value (Q) value and retract the tool. This can prevent the tool from scratching the surface of the hole. Since the coaxial precision of the symmetrical holes in this workpiece is relatively high, when precision boring, the holes on both sides should be bored without turning the head. If the diameters of the holes on both sides are the same, you can use one tool to process the holes on both sides in the form of straight boring. If the diameters of the holes on both sides are different, you can boring the hole with the larger diameter first when compiling the processing program, and then change the tool (symmetrical (Precision boring tool for small holes), the worktable does not change positions, and the X and Y coordinates of the large hole are used. By setting the appropriate Z coordinate, the boring tool extends straight from one end of the large hole to complete the small hole on the other side. Boring. In this way, since the same plane coordinate system and the same spindle coordinate are used, the error in the rotation of the U-turn processing table is eliminated. Therefore, high coaxial processing accuracy can be ensured. There is a premise for using this method: the distance between the two holes cannot be too large, otherwise the tool bar will be too long, causing vibration during processing and affecting the processing accuracy. The general design principle of the machining program is: follow the principle of gradually increasing from rough to fine, first perform rough machining and heavy cutting, remove most of the machining allowance on the blank, and then arrange some parts with low calorific value and low processing requirements, so that the parts can be Allow sufficient time for cooling before finishing and then finishing. The processing sequence of the workpiece is: rough milling of each plane - drilling - tapping - rough boring - fine milling - fine boring.

Cutting amount selection

When roughing, select a larger cutting depth and a higher feed rate as much as possible, subject to the rigidity of the process system and the power of the machine tool. The generally selected cutting depth is 5~6mm, the spindle speed S is 200~300r/min, the spindle moving speed F is 300mm/min when rough milling the plane, and the spindle moving speed F is 200mm/min when rough boring; during finishing, in order To obtain better geometric accuracy and surface roughness, the cutting depth can be smaller, generally 0.3~0.5mm, the spindle speed S is 300~450r/min, the spindle movement speed F for fine milling plane is 220mm/min, and the precision boring process The spindle moving speed when drilling is 100~150mm/min; the spindle moving speed when drilling is 300mm/min; the spindle moving speed when tapping is the main spindle speed multiplied by the pitch. This value cannot have a decimal point.

Tool selection

Face milling cutters and boring tools use machine-clamped indexable tools, and the blade material is carbide or coated blades. Internally cooled carbide integral tools are used for drilling and tapping. When using the non-turning head method to process symmetrical holes on both sides, due to the long tool shank, the long tool shank can be combined according to the modular tool holder and tool holder system according to different needs; at the same time, in order to reduce the vibration during cutting, a heavy metal vibration-damping tool should be used Rod or damping tool holder. All cutting tools in the machining center shall use international standard cutting tools as much as possible. Tool specifications, special tool codes and the content to be processed by the tool should be recorded in a list for use when compiling. At the same time, all tools used in the tool magazine must be tested using a tool setter, and the data must be entered into the tool compensation value in OFFSET. From a cost-effective perspective, due to the large blank margin and low machining accuracy requirements during rough machining, domestic tools should be used as much as possible, such as rough milling cutters and rough boring tools. In order to improve the cutting efficiency and obtain better surface processing quality during finishing, the brands of cutting tools can be selected from well-known brands such as ISCAR, Kennametal, Walter, Konami, and Sandvik.

in conclusion

Using a machining center to process the box body, after mass production, the processing time of each workpiece is about 2 hours, which is only 1/6 of the previous processing time, and the processing efficiency is greatly improved. In addition, due to the guarantee of the accuracy of the machine tool itself, the tool joint marks are completely eliminated, and the coaxiality between the bearing blocks is also effectively guaranteed, thereby significantly improving the processing quality of the transmission box. The fixture design is simple and Practical, easy to use, and achieved good application results.