LM Stroke Model ST
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Ball Ball cage Fig.1 Structure of LM Stroke Model ST Structure and Features Model ST has a ball cage and balls both incorporated into a precision-ground cylindrical nut as shown in Fig.1. The balls are arranged in zigzags so as to evenly receive a load. The ball cage is a drilled cage made of a light alloy with high rigidity, and is capable of high-speed motion. A thrust ring and a snap ring are installed on both sides of the inner surface of the nut to prevent the ball cage from overshooting. This structure allows rotational motion, reciprocal motion and complex motion with a small friction coefcient. Model ST has a stroke length up to twice the range within which the ball cage can travel. Since high accuracy can be obtained at a low price, this model is used in a broad array of applications such as press die setting, ink roll unit of printing machine, workpiece chuck unit of punching press, press feeder, work head of electric discharge machine, wound roll corrector, spinning and weaving machine, distortion measuring equipment, spindle of optical measuring instrument, and photocopiers.

ST Minimal Friction Coefcient The balls and the ball raceway are in point contact, which causes the smallest rolling loss, and the balls are individually retained in the ball cage. This allows the LM stroke to perform rolling motion at a minimal friction coefcient (=0.0006 to 0.0012). Compact Design Since it consists only of a thin nut and balls, the outer diameter of the bearing is minimized and a light, space-saving, compact design is achieved. High Accuracy at a Low Price A highly accurate slide unit can be produced at a low price. Types and Features Specication TableA Model ST is a...

Rated Load and Nominal Life Load Rating The basic load ratings for model ST are indicated in the respective specication tables. Nominal Life The nominal life of model ST is obtained using the following equation. :Nominal life (rotating 106 times) (The total number of revolutions that 90% of a group of identical LM strokes independently operating under the same conditions can achieve without showing aking) : Basic dynamic load rating (N) : Calculated radial load (N) : Hardness factor (see Fig.2 on A ) : Temperature factor (see Fig.3 on A ) : Contact factor (see Table1 on A ) : Load factor...

ST Calculating the Service Life Time When the nominal life (L) has been obtained, if the number of revolutions per minute and the number of reciprocations per minute are constant, the service life time is obtained using the following equation. For Rotating Motion or Complex Motion 6 : Service life time (h) : Revolutions per minute (min 1) : Number of reciprocations per minute (min 1) : Stroke length (mm) : Pitch circle diameter (mm) (dm 1.15 dr) : Ball inscribed bore diameter (mm) : Factor for cage material (=0.7)

Tolerance Value in Rotation and Reciprocating Speed The permissible speed limit of model ST is obtained using the following equation. For the DN value above, the following value applies as a standard value. For oil lubrication DN=600000 For grease lubrication DN=300000 However, the following points must be taken into account. n 5000 ℓS•n1 50000 To maximize the load capacity of model ST, the hardness of the raceways needs to be between 58 to 64 HRC. If the hardness is lower than this range, the basic dynamic load rating and the basic static load rating decrease. Therefore, it is necessary to...

ST fC: Contact Factor When multiple nuts of model ST are used in close contact with each other, their linear motion is affected by moments and mounting accuracy, making it difcult to achieve uniform load distribution. In such applications, multiply the basic load rating (C) and (C0) by the corresponding contact factor in Table1. Note) If uneven load distribution is expected in a large machine, take into account the respective contact factor indicated in table 1. Number of nuts in close contact with each other fW: Load Factor Table2 Load Factor (fw) Vibrations/ impact Faint Table of...

Accuracy Standards The tolerance value in inscribed bore diameter (dr), nut outer diameter (D) and nut length (L) is indicated in the corresponding specification table. The end of the nut may be deformed due to tension of the snap ring. Therefore, when measuring the nut outer diameter, it is necessary to calculate the measurement range using the following equation, and obtain the average diameter value within the range. The tolerance value in the nut outer diameter is equal to the calculated average value of the maximum diameter and the minimum diameter obtained through two-point...

ST ST Shaft With the ST shaft, used in model ST, balls roll directly on the shaft surface. Therefore, it is necessary to pay much attention to the hardness, surface roughness and dimensional accuracy when manufacturing it. Since the hardness of the ST shaft has especially large impact on the service life, use much care in selecting a material and heat treatment method. THK also manufactures high-quality ST shafts. Contact us for details. Hardness We recommend surface hardness of 58 HRC ( 653 HV) or higher. The depth of the hardened layer is determined by the shaft diameter; we recommend...

Model ST (For light load) Maximum stroke Inscribed bore diameter Outer diameter

Model ST-B (For medium load) Unit: mm Basic dynamic load rating Basic static load rating

Model ST (For light load) Maximum stroke Inscribed bore diameter dr

Model ST-B (For medium load) Unit: mm Basic dynamic load rating Basic static load rating

Model STUU (For light load) Maximum stroke Inscribed bore diameter Outer diameter

Model STUUB (For medium load) Basic dynamic load rating Basic static load rating

Model STUU (For light load) Maximum stroke Inscribed bore diameter Outer diameter

Model STUUB (For medium load) Unit: mm Basic dynamic load rating Basic static load rating