Choosing the right Ball Screw in 10 steps

How to choose the right High-Precision Ball Screw

Selecting the right Ball Screw requires a systematic approach. Depending on the application—whether precise positioning or pure load transport—the requirements for accuracy, preload, design, and lubrication can vary greatly. This guide walks you through the key criteria step by step, helping you find a Ball Screw that fits your application both technically and economically.

Step 1: Define the application: Positioning vs. Transport

When choosing a Ball Screw, the type of task is the key factor. For positioning tasks (precise movement to a target, often over short distances), preloaded Screws are typically used—they have no axial play and offer high precision. For transport tasks (moving larger loads over longer distances), Screws with some axial clearance are usually sufficient, as they have less friction and wear. As a rule of thumb: use preloaded Screws for positioning applications, and Screws with axial clearance for transport systems.

Step 2: Determine the required accuracy class

The accuracy of a Ball Screw is specified in classes C1 through C7 (C1 = highest precision). Typical applications dictate these classes: high-precision CNC or measuring machines require classes in the C1–C3 range, while simpler applications can work with C5–C7. Keep in mind, however, that higher accuracy usually means longer machining times and sometimes shorter maximum Screw lengths. Positioning Ball Screws are available in classes C1 to C7, but when choosing the class, you should also consider the maximum manufacturable length of the Screw (very high classes are often limited to shorter Screws).

Step 3: Choose preload or clearance

Preload means the balls in the nut are slightly compressed—this eliminates play and increases rigidity but requires more driving force. Axial clearance, on the other hand, results in less friction and can offer longer service life under high loads. As mentioned above, preloaded Ball Screws are often used for positioning tasks, while Ball Screws with clearance are common in transport applications.

Note: Preload improves precision and rigidity, while clearance saves power and generally wears more slowly.

Step 4: Nut design and circulation type

There are different nut designs and circulation types you can choose to suit the application. Essentially, we distinguish:

1. Nut design: Single-Flange Nut (with a mounting flange for the customer’s system), Double-Flange Nut (a flange nut with an additional Cylindrical Single Nut for preload or as a safety nut), or Cylindrical Single Nut (no flanges, very compact). Single-Flange Nuts are easy to install, while Double-Flange Nuts offer higher safety against breakage due to wear or help reduce backlash (when preloaded).
2. Circulation type: Internal Circulation (balls circulate internally within the nut housing), Tube/End Plug Circulation (balls are recirculated through an external tube). The Tube Circulation offers great flexibility—it can be adapted to the shaft diameter, lead, and number of ball circuits, and can reach DN values of up to around 100,000.
3. End-Plug Diversion Circulation (e.g., FEEG, FDEG): extremely compact and quiet. It reduces nut volume by 18–30%, supports high rotational speeds, and achieves impressive DN values—up to approximately 180,000—while maintaining very low running noise. Example: a compact electronics testing machine might use an end-cap Ball Screw for high speed and minimal space requirements, while a heavy-duty machine would more likely use a robust single-flange or double-nut design with tube circulation.

Step 5: Consider installation space and compactness

Check the available space: some Ball Screw types are designed to be especially small and lightweight. As mentioned above, end plug diversion circulation systems are up to 30% more compact than conventional nuts, making them ideal for applications with very limited space (small XY tables, measuring devices, etc.). Weight also matters: thinner screw diameters and aluminum supports can reduce overall weight.

Also, pay attention to the limit DN value: depending on the design, values up to 100,000–180,000 are possible, indicating the maximum allowable combined speed × diameter. If space is extremely limited, a compact design is worthwhile—but this may mean sacrificing maximum rigidity.

Step 6: Consider material and environmental conditions

Choose the material and protective measures according to the environment. Standard Ball Screws are made from hardened steel (e.g., 42CrMo4, 50CrMo4, CF-53) and hardened bearing steels (e.g., 100Cr6, 15CrNi6). For special requirements, Ball Screws are also available in stainless steel (for example, for corrosive environments). Keep temperature effects in mind: high heat can affect expansion and the lubrication film, while cold temperatures can thicken lubricants.

Step 7: Dynamics: DN value, rotational speed, and lead

For fast movements, the DN value (speed × diameter) is crucial—it indicates the maximum allowable rotational speed. Modern high-speed models reach DN values up to 180,000, while heavy-load Screws reach up to 150,000. Choose a Ball Screw with a sufficient limit DN value for your planned speed.

The thread lead also plays an important role: Coarse leads (e.g., 10–20 mm) provide a large stroke per revolution but less force, and allow for higher feed rates. Fine leads (1–5 mm) deliver more force in a compact space but operate at slower speeds. (Our partner can manufacture Ball Screws with leads from 1 to 80 mm—allowing you to select the optimal lead depending on your required travel and driving force.)

Step 8: Load capacity: rated load and rigidity

Compare the dynamic and static rated loads of the Ball Screws with your requirements. These values indicate the axial force the system can withstand for a given service life or under extreme conditions. Also important is the axial rigidity (K-factor), which determines how much the clearance changes under load. For very high loads, there are special heavy load designs (e.g., the “FEKS” series), where the ball groove shape is optimized to achieve maximum load capacity. These designs use modified contact angles and adapted ball diameters to maximize heavy load capacity. It’s best to compare the tables in the catalog for “dynamic rated load C_dyn” and “allowable axial load”—higher values mean greater load capacity.

Step 9: Plan screw length and shaft ends

Make sure the Ball Screw has the required length. Our partner manufactures single screws up to 12,000 mm long, and even up to 22,000 mm when joined. For extreme lengths, pay attention to support bearings (mid-span supports) and bending considerations. Also, plan the shaft ends carefully: at least one end must have a full thread to allow the nut to be screwed on. The shaft diameter in the fully threaded section must be smaller than the core diameter of the ball groove; otherwise, the nut won’t fit. If you need a drive or connection at one end (e.g., keyway, internal thread), the remaining threads can be consolidated inside a shaft sleeve.

Example: for a long travel, you might choose an 8-meter Ball Screw with tube circulation and add a sleeve component at one end to provide enough space for the threads.

Step 10: Lubrication concept and maintenance

Precision Ball Screws require regular lubrication. Check whether the system includes oil holes (central lubrication) or grease fittings for grease guns—many models come standard with oil holes (marked as “lubrication holes”). Some nuts also offer double dust seals to keep out contaminants. Determine how often re-lubrication is needed and whether you want a lubricant reservoir or automatic supply (grease gun). A well-planned lubrication concept significantly extends the Ball Screw’s service life.

Summary

Clarify step by step what the Ball Screw will be used for and the resulting requirements. Choose accuracy, preload, design type, lead, length, and lubrication accordingly, and compare the data (rated load, rigidity, DN value) in the catalog. This way, you’ll find a Ball Screw that’s optimal for your application. Good examples in the catalog (e.g., tube or end plug circulation, heavy load types) can serve as a guide if they match requirements similar to yours.