Large Crankshaft Grinding With CBN Wheels and In-Process Control
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Solution Overview
Problem
Large crankshafts for truck, ship, and stationary engines face challenges in grinding due to high material removal rates, distortion risks, and the need for frequent dressing of corundum grinding wheels, which increases production time and costs, while existing methods struggle to achieve high accuracy and long service life for grinding wheels.
Innovation Solution
The method employs CBN grinding wheels with CNC-controlled X, Z, and WK axes for precise interpolation and measurement, allowing for single-setup grinding of main and crank pin bearings, cylindrical end regions, and flanges, reducing dressing frequency and torsional issues through synchronized rotary drives and multiple steady rests, enabling high-accuracy and efficient machining without frequent wheel dressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If corundum grinding wheels are used for grinding large crankshafts, then the grinding process can be performed, but the grinding wheels require frequent dressing which increases production time and costs
Solution Approach 1:
The patent changes the material parameter of the grinding wheel from corundum to CBN (cubic boron nitride). This material parameter change enables the grinding wheel to maintain its cutting edge for much longer periods without dressing, directly resolving the contradiction between grinding efficiency and production time by eliminating the need for frequent dressing operations
2Productivity
If high material removal rates are used to grind large crankshafts, then grinding time is reduced, but the risk of crankshaft distortion increases
Solution Approach 1:
The patent changes the grinding wheel material parameter to CBN, which has superior mechanical properties including higher hardness and thermal stability. This enables maintaining high material removal rates while reducing crankshaft distortion through better heat management and more stable grinding forces, thus resolving the contradiction between productivity and manufacturing precision
3Manufacturing precision
If multiple process steps are used to grind large crankshafts, then each feature can be ground with appropriate wheels, but the number of dressing operations and setup time increases
Solution Approach 1:
The patent applies the universality principle by using a single CBN grinding wheel that can perform multiple grinding operations (rough grinding, finish grinding, and radius grinding) on different crankshaft features. The CBN wheel's durability and consistency allow it to maintain precision across all operations without requiring changes to wheel type or frequent dressing, resolving the contradiction between manufacturing precision and device complexity
4Duration of action of stationary object
If CBN grinding wheels are used instead of corundum wheels, then service life is extended and dressing frequency is reduced, but initial cost increases
Solution Approach 1:
The patent changes the material parameter from corundum to CBN, which has fundamentally different cost characteristics. While the initial cost per wheel is higher, the extended service life (by factors of 10-100 times) and elimination of dressing operations result in lower total cost per unit produced. This resolves the contradiction between duration of action and quantity of substance through a shift from short-term low-cost items to long-term high-value items
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for high-accuracy, efficient grinding of large crankshafts with extended grinding wheel service life, reduced production time, and minimized distortion, achieving precise cylindrical and convex surfaces without the need for frequent dressing, thus optimizing the machining process.
Implementation Method 1
at least all of the main bearings and crank pin bearings of the crankshaft are rough-ground and finish-ground with at least one first CBN grinding wheel
Data Source
AI summary
A grinding machine and a method for grinding large crankshafts are disclosed. During pre-grinding, steady-rest seats are ground, and a plurality of steady rests are placed against them. Synchronous electric drives drive the crankshaft at both ends. A desired shape is produced by interpolating motion of a first grinding disk about CNC-controlled X and Z axes and about a WK pivot axis. The grinding disk is a CBN grinding disk with a width less than the axial length of the main journals and crankpins of the crankshaft. Diameters are measured along the axial length of the main journals and/or crankpins by an in-process device. The drives for the X1, Z1, and WK axes are controlled in an interpolating manner on the basis of the measurements to achieve the desired shape.