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Structual Parts
Structual parts, such as beds, columns, cross bars and bodies are the main components of a machine. They usually meet even the task of guiding process units such as headstocks, supports, carriages, etc. Structual parts can be a single-and multi-part, usually are manufacturing and transportation the limiting factors.
Structual parts accept the process forces and pass them mostly in a foundation. Larger parts (usually beds) are often not intrinsically stiff, but need a stable foundation to achieve the desired operating results. These structual parts are connected with high-precision alignment elements to the foundation.
Structual parts are made from the following materials:
Steel (welded)
Steel casting (GS)
Grey cast iron (GG)
Nodular cast iron (GGG)
Polymer concrete
Aluminium
Carbon fiber-reinforced plastic
The selection of the optimum material according to the following criteria:
Strength (plastic deformation, fracture)
Weight (mass distribution, static and dynamic behavior)
Modulus of elasticity (static and dynamic behavior)
Damping (Dynamic Behavior)
Residual stresses, creep (long-term accuracy)
Thermal expansion / capacity (thermal behavior)
Single / Series Production (model costs)
Costs (raw materials, manufacturing)
Constructive design options
Resource availability
New designs of high-quality structual parts are often calculated using the finite element method and optimized.
Guideways
Guideways are important components the force flow of a machine and often an integral part of structual parts. They are responsible for the performance and the accuracy of the machine and must meet the following requirements:
Low friction
Stick-Slip-Free
Little or no wear
Seizure resistance
Backlash free
High stiffness
Good damping characteristics
High accuracies
High travel speeds
Low heat generation
Shared lubrication options
Easy installation and commissioning
Maintenance free
Hydrostatic guideways at a cross rail
The guiding principles are divided into:
hydrodynamic,
hydrostatic,
aerostatic,
electromagnetic and
roller bearing guideways
Hydrodynamic connecting rod bearing scraped
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Source: Werkzeugmaschinen Konstruktion und Berechnung Bd. 2, 8. Auflage, Manfred Weck, Christian Brecher, Springer-Verlag 2006