310 TECHNICAL INFORMATION t Clearance and preload of MISUMI Linear Guides are controlled with minute ball size adjustments. t Increased rigidity and reduced elastic deformation will result by preloading (negative clearance). t Generally, selecting some preloads would cause favorable effects on accuracy and life of Linear Guides. t MISUMI-manufactured Blocks and rails guarantee their own radial clearances (preload) and accuracies as sets of blocks and rails. Be sure to use the blocks and rails in sets. 2Allowable Load t Basic Dynamic Load Rating (C) Basic dynamic load rating is defined as: a load applied in a constant direction and ran under equal condition on a group of linear guide specimen where 90% of specimen will reach 50x103m without experiencing any damages due to rolling fatigues. t #BTJD 4UBUJD -PBE 3BUJOH $P Basic static load rating is defined as: a load applied on non-moving linear guides where a sum of rolling element plastic deformation amount and rolling surface plastic deformation amount becomes equal to 0.0001 times that of the diameter of the rolling element (balls). t "MMPXBCMF 4UBUJD .PNFOU .A, MB, MC) Allowable static moment is a critical static moment load defined by permanent deformation value similar to basic static load rating Co. t 4UBUJD 4BGFUZ 'BDUPS Gs) Basic Static Load Rating Co, in the static state or in low speed, is divided by Static Safety Factor fs in Table - 2 depending on operating conditions. Allowable Load (N) ≤ Co/fs Allowable Moment (N ∙ m) ≤ (MA, MB, MC)/fs fs: Static Safety Factor Co: Basic Static Load Rating (N) MA, MB, MC: Allowable Static Moment (N ∙ m) Condition of Use Lower Limits of fs For normal operating condition 1~2 When smooth running performance is required 2~4 When vibrations and impacts exist 3~5 2Selection of Radial Clearance (Preload) Type Preload Size (Height H Dimension) Radial Clearance (μm) Miniature Existing Products Light Preload 6~20 -3~0 Slight Clearance 0~+15 Medium/ Heavy Load Existing Products Normal Clearance 24 -4~+2 28 -5~+2 33 -6~+3 Interchangeable, Light Preload 24, 28 -4~0 30, 36, 40, 42 -5~0 *42 -7~0 Cost Efficient Products Normal Clearance 24 -4~+4 28, 30 -5~+5 33, 36, 40 -6~+6 45 -7~+7 * marked size is for Super Heavy / Extra Super Heavy Load. 2Friction Force (Required Thrust Force) Linear Guide friction force (required thrust) varies depending on load, speed and lubricant property. Especially when moment load is applied, Preload Type friction force increases. Although seal resistance varies according to seal lip press-fit allowance and lubrication conditions, it is not proportionate to load and keeps a constant value. Friction force is obtained by the following formula. F= μ t W+f F : Friction (N) μ : Dynamic Friction Coefficient W: Applied Load f : Seal Resistance (2N ~ 5N) Type Dynamic Friction Coefficient (μ) Miniature Linear Guides 0.004~0.006 Linear Guides for Medium Load 0.002~0.003 MC MA MB MA MB MC Pitch Direction Yaw Direction Roll Direction Table-1. Dynamic Friction Coefficient Table-2. Static Safety Factor (fs Lower Limit) Linear Guide Preload and Allowable Load
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