Adjustable Damping for Vertical Lathe Ram Stiffness
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Solution Overview
Problem
Vertical lathes with narrow rams at long extensions suffer from inadequate dynamic stiffness, particularly at specific frequencies related to structural natural frequencies, limiting their cutting capability.
Innovation Solution
An adjustable damping arrangement using springs to suspend a damper mass within the ram and compressible rubber rings allows for selective adjustment of dynamic stiffness by tuning the damper mass to resonate at the ram's natural frequency, enhancing damping and stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the ram extension is increased to reach tall parts, then the reach is improved, but the dynamic stiffness deteriorates
Solution Approach 1:
The patent applies a tuned mass damper system that utilizes mechanical vibration principles. A damper mass is suspended within the ram by springs and connected through tie rods, creating a vibrational system tuned to the ram's natural frequency. This resonant vibration system absorbs harmful vibrational energy, thereby improving dynamic stiffness without requiring changes to the ram extension length.
Solution Approach 2:
The patent employs adjustable damping elements (rubber rings) that can be selectively compressed to modify the dynamic characteristics of the system. By changing the compression state of these damping elements, the natural frequency and damping ratio of the ram-damper system can be adjusted to optimize dynamic stiffness across different operating conditions and extension lengths.
2Strength
If damping elements are added to increase damping, then the dynamic stiffness is improved, but the device complexity increases
Solution Approach 1:
The damper assembly is nested within the hollow interior of the ram structure. The damper mass, springs, tie rods, and damping elements are all contained within the existing ram volume, utilizing the available space efficiently. This nested arrangement adds the necessary damping functionality without requiring external additions that would increase overall structural complexity.
Solution Approach 2:
The damper mass serves multiple functions: it provides the inertial element for vibration damping, acts as a counterbalance to reduce dynamic loads, and its suspension system contributes to the overall structural stiffness. The rubber damping elements simultaneously provide vibration isolation and adjustable tuning capability, making the system multi-functional and reducing the need for separate components.
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 solution increases the cutting capacity of vertical lathes by effectively absorbing vibrational energy, thereby improving dynamic stiffness and reducing the minimum stiffness to match or exceed other frequencies, thus enhancing machining performance.
Implementation Method 1
springs to suspend a damper mass
Implementation Method 2
tuning the damper mass to resonate at the ram's natural frequency
Implementation Method 3
absorbing vibrational energy
Implementation Method 4
compressible rubber rings allows for selective adjustment of dynamic stiffness
Data Source
AI summary
A damper assembly for use with a non-rotating tool holder includes a hollow ram for supporting a non-rotating tool and a damper assembly mounted in the hollow ram for absorbing vibrations of the ram. The damper assembly includes a front plate and a rear plate, an upper tie rod and a lower tie rod extending between the front plate and the rear plate, and a damper mass mounted between the front plate and the rear plate. Ring dampers are mounted between the damper mass and the front and rear plates, and suspension springs are mounted between the upper tie rod and the lower tie rod. The suspension springs carry the weight of the damper mass so that the ring dampers do not have to carry the weight of the damper mass, and the damper mass is free to respond to vibrations in the ram.