Ball Screw Support Structure Analysis
Ball Screw Support Block is the key hub of the transmission system, responsible for fixing the screw, transmitting driving force and bearing load. Its structural design needs to take into account the rigidity, precision and installation space, the following from the core components, types of features and design points to start explaining:
I. Functional analysis of core components
1. Bearing components: the determining factor of performance fixed end (axial positioning side)
Angular contact ball bearings (contact angle 30°/45°) are mostly used, which can withstand both axial and radial forces. Preload adjustment eliminates clearance and increases rigidity. For example, P4 grade bearings are used in high-precision scenarios, with double bearings mounted back-to-back to increase tilting resistance.
Supporting end (free side)
Usually deep groove ball bearings or cylindrical roller bearings are used, which only bear radial loads and allow a slight axial displacement of the screw to compensate for thermal expansion. High-speed conditions can be upgraded to ceramic bearings to reduce centrifugal force and heat generation.
2. Support base body: Load bearing and mounting base
Material technology
The main body is made of 45# steel (tempered) or aluminum alloy (lightweight), the surface is precision ground with flatness ≤ 0.005mm to ensure the installation accuracy.
Structure form angle type (square):
Such as BK/BF, FK/FF type, right-angle mounting surface rigidity, easy to bolt, suitable for most mechanical scenes. Round type: e.g. EK/EF type, radially compact, suitable for direct embedding of the shaft end into the equipment housing (e.g. robot joints).
3. Auxiliary Components: Sealing System for Long-term Stable Operation
The combination of labyrinth seal and rubber dust ring blocks the intrusion of dust and cutting fluid, and the combination of lithium soap-based grease extends the life of the bearings to more than 2,000 hours.
Adjustment components
Lock nut (fine thread + stop washer) ensures that the bearing is tightened with the shoulder of the screw, and the adjusting ring is used for fine adjustment of axial preload (e.g. double bearing spacer thickness adjustment).
Structure type and characteristics
1. Standard type distinction EK/EK type (convex)
Fixed side (EK) with flange, double-row angular contact ball bearing preload, high rigidity and precision, suitable for automated production line horizontal mounting; support side (EF) for the round shaft hole, deep groove ball bearings, for light load equipment.
Type BK/BF (square)
Fixed side (BK) right-angle mounting surface, single-row angular contact ball bearings, high load carrying capacity, suitable for machine tools and other heavy-duty scenarios; support side (BF) through-hole structure, insertion type mounting, used for heavy machinery.
FK/FF type (flat square) FK (fixed side): thickness 30% thinner than BK type, single row angular contact ball bearing, suitable for narrow space (such as compact machine tools, medical equipment), through the thickening of the side plate or rib plate to compensate for the rigidity of the FF (support side): paired with the FK, deep groove ball bearing support, flat and lightweight structure, suitable for high-speed reciprocating motion (such as lithium battery equipment handling mechanism), but the upper limit of load is lower (≤ 0.5mm). The upper load limit is low (≤5kN).
Key design and installation points
1. bearing preload strategy preload can eliminate clearance and enhance axial rigidity (usually enhance 40-60%), preload force formula for \(F_p = k \cdot C_a\) (k take 0.02-0.05). Double bearing fixed side recommended "back-to-back" mounting (wide side of the outer ring opposite) to enhance bi-directional load capacity.
2. Space and rigidity balance of conventional scenarios give priority to BK/BF square seat (rigidity), space constraints choose FK/FF flat type, need to pay attention to make up for the loss of rigidity through structural strengthening. When installing, it is necessary to ensure that the perpendicularity between the support base and the axis of the screw is ≤0.01mm, so as to avoid abnormal wear and tear of the bearings due to skewing.
3. Lubrication and Maintenance Regularly check the status of grease, replenish the lubricant every 500 hours in high-speed scenario, and replace the lithium grease every year in low-speed and heavy-duty scenario, so as to ensure that the bearings are in good lubrication status.
