Fareed Mohmed · Engineering
LM Rail and Block Selector
Load · Moment · Block · Life · Part Number
Describe the carriage: layout, mass, centre of gravity, drive and external force, acceleration, speed and stroke. The tool works out the load and moments on every block through the move, then picks the smallest HIWIN block that gives the static safety and rated life you ask for, with the model number, the rail length and the order code. Every calculation step is shown.
Load ratings (C, C0, MR, MP, MY) and the life and static-safety method are from the HIWIN Linear Guideways Technical Information catalogue G99TE23-2309. Series loaded: HG, EG, WE, MG, QH, QE, QW, CG, RG, CRG and QR. The MISUMI Economy series E-ELGH, E-ELGW, E-HLGH, E-HLGW, E-GMLG and E-GMLGW are added from the MISUMI Economy series 2025 catalogue (Malaysia), pp. 04-011 to 04-038. This sizes industrial machines only. Confirm the final choice, the preload and the rail length with HIWIN.
Start Here: The Selection Process
Ten steps from the carriage to the order code, in the order the tool works. Read this once, then use sections 01 to 03. Steps with a button link to where you enter or read that step. Step 9 is done outside the tool.
Describe the carriage
Before touching the tool, write down what the guideway carries.
- Number of rails and blocks on each rail, and their spacing (c across, d along)
- Moved mass: the load plus the carriage, plate and tooling
- Where the centre of gravity sits (x, y, z) measured from the block group
- Where the drive pulls (ballscrew or belt) and where any process force acts
Choose the mounting
The mounting decides which way gravity acts on the blocks.
- Rails on the floor: weight presses the blocks onto the rails (radial)
- Carriage hanging: weight pulls the blocks off the rails (reverse radial)
- Rails on a wall: weight acts sideways (lateral)
- Vertical travel: weight acts along the travel and gives a moment
Describe the motion
Acceleration, maximum speed, stroke and cycles per minute. The tool checks the load at every stage of the move: accelerating, constant speed and braking, out and back.
Set what the block must achieve
Three limits decide whether a block passes.
- Static safety: 1 to 3 for normal load, 3 to 5 with impacts or vibration
- Required life in km of travel
- Load factor fw, by speed: leave on Auto and the tool picks it from the maximum speed
Choose the series group
Merlin’s standard is the HG series, square block, tried first. The tool then tries the larger or special series. Pick the miniature group only for small, light carriages. Pick the MISUMI groups when you are buying from MISUMI.
Let the tool work out the load on each block
It treats the carriage as a rigid body, finds the load and moments on every block at every stage, then combines them into one equivalent load. The worst case sets the static check; the average sets the life.
See the loads in section 03 →Read the result
The tool picks the smallest block that passes both the static safety and the life check. Read the verdict, then the warnings under it. A pass with a warning still needs a decision from you.
See the result in section 03 →Compare the series
Section 03 shows the smallest block that passes from each series. Use it to compare a ball type and a roller type, or to see what MISUMI offers against HIWIN for the same job.
See which blocks pass in section 02 → Compare series in section 04 →Check what the tool does not
- Stiffness and deflection under load, which the tool does not calculate
- Preload: it raises rigidity and lowers life, and the life method here has no preload factor
- A brake on vertical or hanging carriages, because a guideway does not hold a load when power is lost
- Mounting surface flatness, lubrication and covers for the environment
Finalise and order
- Take the model number, rail length and order code from the result
- Rail length = stroke + block spacing + block length + 20 mm, rounded up to 10 mm; confirm standard lengths with the supplier
- Confirm the final choice, preload and rail length with the supplier’s catalogue
Six common mistakes
Brands that make this product
Filled gold: loaded in this tool and rated from the catalogue. Outlined gold: loaded for part numbers only, not strength-checked. Grey dashed: not loaded yet. Hover a brand for what is loaded. Only HIWIN and MISUMI are rated here; for another brand, take the loads from section 03 and check them against that brand’s own ratings.
HIWINrated
MISUMIrated
THKnot yet
NSKnot yet
IKOnot yet
PMInot yet
Bosch Rexrothnot yet
Schneebergernot yet
Rollonnot yet
Schaeffler INAnot yetTo use a brand that is not loaded, take the equivalent load and the moments on one block from section 03 to that brand’s catalogue and check its rated loads C and C0 and its moment ratings the same way: static safety, then life. The “Block to check” list in section 01 offers only the loaded blocks.
See every hardware and brand →Brand names and logos are trademarks of their owners and are shown only to identify catalogues.
Application
Choose from the lists, or pick "Type a value…" to enter your own number. All offsets are measured from the centre of the block group, on the face where the carriage sits on the blocks. The sketch shows your data.
Centre of gravity, drive and external force
Motion and life
Brands And Blocks That Pass
Your duty is checked against every block model loaded, from HIWIN and MISUMI, in both the regular and the miniature groups. A block is listed when it passes both checks: static safety against what you set, and rated life against the life you need. The cards show how many blocks of each series pass. Click a card to filter the table, or Select on a row to see the full working for that block in section 03. The block shape setting still applies.
Result
Load on each block through the move
Smallest Block From Each Series
Show every block in the catalogue data
Calculation Steps
Every step is worked with your numbers for the block shown in the result.
How It Is Calculated
Load on each block
The carriage is treated as a rigid body on the blocks. For each stage of the move (accelerating, constant speed and braking, out and back) the tool adds the weight, the inertia force m·a at the gravity centre, the external force and the drive force that balances them. It takes the resulting force and moments about the centre of the block group, then shares them over the blocks in proportion to their position. This is HIWIN's method (catalogue Tables 1-3 and 1-4) in a general form: for four blocks it gives the HIWIN terms W/4, F·a/(2c), F·b/(2d) and F·k/(2d). Radial load N is positive when it presses the block onto the rail, negative when it pulls it off (reverse radial). Lateral load is Pt. With only one block along a rail, or one rail, the pitch, roll or yaw moment cannot be taken by a pair of blocks, so each block carries it as a moment and is checked against MP, MR or MY.
Equivalent load
HIWIN allows loads in several directions at once. For the HG, EG, WE, QH, QE, QW, CG, RG, CRG and QR series the equivalent load is Pe = P + Pt (radial or reverse radial plus lateral). For the MG series it is the larger of the two plus half of the smaller. The HIWIN catalogue gives no life formula for a moment on one block. For the blocks that carry a moment, this tool adds C0 × M/M0 to Pe, the way other linear guideway makers do. That is conservative, and it is flagged where it applies.
Static safety
fSL = C0 / P and fSM = M0 / M (Eq. 1.1), using the largest load seen anywhere in the move. HIWIN asks for 1.0 to 3.0 with normal load and 3.0 to 5.0 with impacts or vibration (Table 1-1). The tool uses the radial and lateral loads added together, which is on the safe side.
Rated life
Nominal life L = (fh · ft · C / (fw · Pm))³ × 50 km for ball types and L = (fh · ft · C / (fw · Pm))^(10/3) × 100 km for roller types (RG, CRG, QR) (Eq. 1.4 and 1.5). fh is 1 for a raceway hardness of HRC 58 to 62 and ft is 1 below 100 °C. The load factor fw is 1.0 to 1.2 up to 15 m/min, 1.2 to 1.5 up to 60 m/min, 1.5 to 2.0 up to 120 m/min and 2.0 to 3.5 above that (Table 1-2). Because the load changes through the move, the mean load Pm = (Σ Pn³ · Ln / L)^(1/3) is used (Table 1-5), with the distance Ln of each stage; roller types use the 10/3 power. The worst block sets the life. Service life in hours is Lh = L × 10³ / (Ve × 60) where Ve is the average speed in m/min (Eq. 1.6 and 1.7). The tool reproduces HIWIN's worked example, HGH30CA with P = 2.29 kN and fw = 2, as 30,258 km.
Choosing the block
The tool tries every block in the series group and block shape you pick, from the smallest dynamic rating upwards, and keeps those whose static safety and life both reach your limits. For the regular group the headline pick follows Merlin's rule: HG first, then the upper series (QH, CG, RG, QR, CRG, then the low-profile and wide-rail series). The miniature group uses the MG series only. The other series are listed in the table so you can compare sizes.
Rail length and order code
Rail length needed = stroke + block spacing + block length + 20 mm of margin, rounded up to the next 10 mm. HIWIN sells standard rail lengths and cuts special lengths on request, so confirm the length. The HG order code reads: model, number of blocks per rail, rail mounting R, rail length, preload (Z0, ZA, ZB), accuracy (C, H, P, SP, UP) and II for a matched pair of rails. For other series use the same pattern and take the preload and accuracy codes from the catalogue.
MISUMI Economy series
Pick the MISUMI groups under Series group. The tool reads C, C0, MA, MB and MC and the block height, width and length from the MISUMI Economy catalogue (miniature narrow short, standard and long blocks; miniature wide standard and long; low-profile E-ELGH and E-ELGW short and standard; E-HLGH and E-HLGW standard and long). The block mix is limited to what MISUMI prints. MISUMI gives no life formula for ball guides, so the HIWIN and ISO basis L = (C / (fw · P))³ × 50 km is used with MISUMI’s load factors (1.0 to 1.5, 1.5 to 2.0, 2.0 to 3.5). The rail uses MISUMI’s hole rule E = (L − (M − 1) × P) / 2, where P is 15 to 40 mm for miniature rails and 60 to 150 mm for the larger rails. Precision for the Economy series is a medium grade, with a height tolerance of ±0.1 mm and a pair variation of 0.02 mm on the medium and heavy load types. Masses are not used.
What is not covered
Stiffness and deflection under load, preload effect on life (higher preload raises rigidity and lowers life), friction force (about 0.004 for ball and 0.003 for roller types, small compared with the loads), lubrication interval, rail joints, mounting accuracy and the AG, PG, SE, E2, RC and stainless types. Only the models whose ratings were read are listed, and the miniature MG blocks of the -O type are loaded for size 5 only. The block length and height were read from the catalogue text and need a spot-check against the drawing before you design the mounting. The HIWIN catalogue gives each series' rail pitch and standard lengths, which this tool does not apply.
Source
HIWIN Linear Guideways Technical Information catalogue G99TE23-2309: selection method (pp. 1 to 9), series dimension tables with basic dynamic load rating C, basic static load rating C0 and static rated moments MR, MP and MY (HG, EG, WE, MG, QH, QE, QW, CG, RG, CRG, QR), and the model-number pages. Always check current figures with HIWIN.