The crankshaft is the center of the internal combustion engine and the core of the engine. If the function cannot be performed correctly, the horsepower of the engine cannot be used normally. The relative angle of the crankshaft must be accurate. Otherwise, the exact ignition timing and valve timing will not work exactly in succession. If you have problems with this sequence, imagine the result is an explosion.
Crankshafts are one of the most difficult workpieces to machine. It is very asymmetric, elongated, elongated, the materials used are also very poorly processed, but the quality is very strict and the manufacturing requirements are very high. By using the 3D software platform that is widely used today, the design accuracy of the crankshaft can be significantly improved by continuously improving the 3D stereoscopic shape, and as a result, to improve the performance. The foundation is laid.
Keywords: crankshaft, UG, 3D modeling, automatic programming, CNC machining
Crankshaft CNC machining requirements
The crankshaft, eccentric shaft, eccentric sleeve, etc. are eccentric rotating parts. The main contours, including the ends of the main journal and bearing journal, are machined on a lathe. The general features of machining technology are:
When machining a rotor journal, the shaft must be adjusted to match the center of rotation of the lathe spindle. Therefore, the most important process requirement in mass production must be the use of reasonable fixtures and tightening methods to ensure eccentricity accuracy.
The second is to use the center hole and the eccentric center holes at both ends as the processing standard.
Currently, various processing methods and processing methods can be selected according to the accuracy requirements of the crankshaft itself, the batch size and the specific requirements of the existing processing equipment level. For example, the main journal can use traditional lathe technology and advanced machining techniques such as lathes and high speed milling to improve machining efficiency and machining quality.
Comprehensive design concept
The parametric design is used for 3D modeling of the crankshaft, allowing you to adjust the local structure and dimensions of the crankshaft at any time. Engineers can use the eigenvalues, arrays, and other feature editing features provided by UG to make a parametric design of the crankshaft based on the features. The general idea of using the UG modeling module for 3D modeling of crankshafts can be summarized as follows:
- a) Draw reasonable curve interfaces and curve notches and cross sections using sketch size and geometric constraints. The entire solid model of the crank curve is then obtained by stretch modeling and material removal operations.
- b) Repeat the feature operation to copy another crank entity. Do not use geometry conversion instructions.
- c) Complete basic entities such as bolster bearings, keyways, grooves and screws using the basic voxel features provided by UG.
- d) Perform a Boolean sum on all the above entities to get a 3D solid model of the crankshaft entities.
- e) Improve the crankshaft by chamfering, rounding and drilling the center hole on the end face of the crankshaft.
- f) Based on the above modeling, a multi-turn crankshaft entity is constructed by making a crankshaft copy operation and partial modification.
Crankshaft 3D modeling
A diagram of the crankshaft is shown in Figure 1. Analysis of the drawings reveals that most crankshafts are symmetrical, providing great convenience for modeling. With UG’s mirroring capabilities, you can significantly reduce your 3D modeling workload.
The main modeling process involves the following steps:
- a) Draw a sector contour in the sketch (see Figure 2), then use the stretch feature of the UG modeling module to generate the sketch and generate solid sectors.
- b) Boss function of UG modeling module (shown in Figure 4).
- c) Use the UG mirroring feature to mirror the entities generated in steps a) and b).
- d) Use the UG modeling module to generate the rightmost truncated cone and use the same method to generate the rightmost truncated cone.
- e) Generate a cone and use the boss function to generate a cylinder for the threaded part.
- f) Steps to create release grooves and threads,
- g) Perform detailed processing such as fillets and chamfers to complete the modeling.
Crankshaft CNC simulation
The NC simulation crankshaft includes the following steps:
- A. Create a program (see Figure 12).
- B. Creation Tools: Crankshaft machining requires four tools: roughing, finishing, pulling, and threading.
- Figure 13 shows the process of creating a tool.
- C. Create geometry: Set blanks, such as blank size, blank installation location, etc.
- D. Drawing operation: Select the cutting type and set the cutting parameters.
- E. After completing the above settings, you can generate an NC toolpath and run a dynamic simulation.
- F. Check and analyze the tool path. If there are any errors, you can edit the toolpath. After confirmation, you can enter the post-processing stage to generate CNC machined NC code.
- G. Some of the generated NC code is shown below (roughing and finishing code is listed due to space limitations).
a) Wrapping:
N0010 G94 G90 G20
N0020 G50 X0.0 Z0.0
: 0030 T00 H00 M06
N0040 G94 G00 X15.5 Z3.9747
N0050 G97 S0 M03
N0060 G95 G01 Z2.7747 F.3
N0070 Z-.2253 F.5
N0080 X16. Z-76.5
N0090 X16.8485 Z-75.6515 F1.
N0100 G94 G00 X17.
N0110 Z3.9747
N0120 X15.5
N0130 G95 G01 Z2.7747 F.3
N0140 Z-75.4456
N0150 X15.5959 Z-76.5
N0160 X 16.
N0170 X16.8485 Z-75.6515 F1.
N0180 G94 G00 Z4.1832
N0190 X15.
N0200 G95 G01 Z2.9832 F.3
N0210 Z-.0168
N0220 X15.5 Z-75.4456
N0230 X16.3485 Z-74.597 F1.
N0240 G94 G00 X16.5
N0250 Z4.1832
N0260 X 15.
N0270 G95 G01 Z2.9832 F.3
N0280 Z-69.9456
N0290 X15.5 Z-75.4456
N0300 X16.3485 Z-74.597 F1.
N0310 G94 G00 Z4.2
N0320 X14.5
N0330 G95 G01 Z3. F.3
N0340 Z0.0
N0350 X15. Z-69.9456
N0360 X15.8485 Z-69.097 F1.
N0370 G94 G00 X16.
N0380 Z4.2
N0390 X14.5
N0400 G95 G01 Z3. F.3
N0410 Z-64.4456
N0420 X15. Z-69.9456
N0430 X15.8485 Z-69.097 F1.
N0440 G94 G00 Z4.2
N0450 X 14.
N0460 G95 G01 Z3. F.3
N0470 Z0.0
N0480 X14.5 Z-64.4456
N0490 X15.3485 Z-63.597 F1.
N0500 G94 G00 X15.5
N0510 Z4.2
N0520 X14.
N0530 G95 G01 Z3. F.3
N0540 Z-58.9456
N0550 X14.5 Z-64.4456
N0560 X15.3485 Z-63.597 F1.
N0570 G94 G00 Z4.2
N0580 X13.5
N0590 G95 G01 Z3. F.3
N0600 Z0.0
N0610 X14. Z-58.9456
N0620 X14.8485 Z-58.097 F1.
N0630 G94 G00 X15.
N0640 Z4.2
N0650 X13.5
N0660 G95 G01 Z3. F.3
N0670 Z-53.4456
N0680 X14. Z-58.9456
N0690 X14.8485 Z-58.097 F1.
N0700 G94 G00 Z4.2
N0710 X13.