DFU Preloaded Double Nut Ballscrew

Direction Change Control

Positioning error often becomes visible at the moment an axis reverses. Before the carriage moves in the opposite direction, internal clearance between the screw raceway, balls and nut may first need to be taken up.

 

The DFU addresses this condition with two nut bodies working on one screw shaft. Their relative setting applies an opposing axial force within the nut group, limiting the free movement that can occur during reversal.

 

This arrangement is useful for feed axes that repeatedly move forward, stop and return. It also provides a firmer axial connection than a comparable loose-clearance nut.

 

Driving the Machine Table

The flange is bolted to the moving table or nut housing. When the screw rotates, the complete nut group travels along the shaft while maintaining its established relationship between the two nut bodies.

 

The table still requires a separate linear guide. The guide controls the direction of movement and supports forces that act across or above the travel line. The DFU screw provides thrust along the axis but should not be used as the sole guiding component.

 

This page supplies the screw and twin-nut transmission assembly. It does not represent an enclosed actuator and does not automatically include rails, a carriage, motor, coupling or end-support seats.

 

Preload Limits

A tighter nut setting is not always better. Increasing preload can improve rigidity, but it also raises starting torque and running temperature. The correct level depends on the required positioning response, working load, speed and operating cycle.

 

The two nuts must remain in their matched working position. Loosening the connection between them or changing their relative angle can alter the preload. Removing a nut from the shaft also risks losing balls from the return circuit.

 

Product Information

Configuration Check	Confirmed Product Information
Series Identification	DFU
Transmission Form	Ball screw with twin nut group
Nut Attachment	Front mounting flange
Main Purpose	Reduced axial movement during direction reversal
Movement Produced	Nut travel along the screw axis
Force Transmission	Axial thrust
Guidance Requirement	Separate linear guide required
Nut Pair Condition	Supplied and installed as a matched assembly
Preload Selection	Chosen according to rigidity, torque and duty cycle
Shaft Preparation	Overall length and both ends made to drawing
Parts Not Automatically Included	Motor, coupling, guide rail and support units
Inquiry Information	Diameter, lead, stroke, shaft length, mounting position and end drawing

 

 

FAQ

Is the DFU supplied as a complete linear stage?

No. This page shows a ball screw shaft with a DFU double-nut assembly. It does not include a stage base, guide rail or moving table unless these parts are specifically included in the quotation.

Why does the DFU use two nuts?

The paired nuts allow axial preload to be applied in opposing directions. This improves rigidity and limits position loss when the axis changes direction.

Can the nut pair be separated during installation?

It should remain assembled on the screw shaft. Separating or independently rotating the nut bodies can disturb the preload and may allow balls to leave their circulation paths.

Does the ball screw replace a linear guide?

No. A separate guide system is required to control straightness and carry radial or moment loads.

What information is required for end machining?

Provide drawings for both shaft ends, including bearing seats, shoulders, threads, retaining features, coupling diameter and dimensional tolerances.

Can the assembly be produced for a custom machine?

We build to customer drawings under OEM/ODM, and accept orders as small as a single piece for standard sizes.

 

About Us

Lishui Guangyuan Industry & Trade Co Ltd supplies ball screws and related linear-motion components for machine tools and automated equipment. Screw length, shaft-end machining and support interfaces can be prepared from an approved installation drawing.

 

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