Clearance- reduced pre-loaded lead screw nuts

Product range

Maximum positioning accuracy

Part No.	Thread	d1	d2	d3	d4	d5	b1	b2	Max. axial load [N]
DST-JFRM-PL-0001-DS8X2	DS8x2	8	20	38.1	28.2	5.2	41-46	4.8	40
DST-JFRM-PL-0001-DS8X8	DS8x8	8	20	38.1	28.2	5.2	41-46	4.8	40
DST-JFRM-PL-0001-DS8X10	DS8x10	8	20	38.1	28.2	5.2	41-46	4.8	35

▲ Permanently minimal axial clearance for high positioning accuracy
▼ More cost-effective compared to the ZB lead screw nut due to fewer components and injection moulding manufacturing process
■  Reduced axial clearance due to spring preload on the lead screw nut
●  No grease or oil in the lead screw drive

The dimensions of the new dryspin® pre-load lead screw nut at a glance

Further important information:

What should you do in the event of unwanted axial clearance?

Pre-load lead screw nut with dryspin® thread

Axial clearance - what exactly is it? How is it defined and what needs to be considered?
The question of clearance is often asked in the case of plastic lead screw nuts. This describes the lost motion, i.e. the "dead travel" on the lead screw. Or in other words the gap between the thread flanks of the lead screw and the lead screw nut. The term clearance is often used in general. In this context, the correct technical term is axial clearance. It outlines the movement of the lead screw nut in the axial direction without movement of the lead screw. Lead screw drives require a minimum clearance to maintain their function. If the axial clearance is too small, the torque required to move the lead screw nut also increases.

What I have to bear in mind:
In addition to the axial clearance caused by the manufacturing tolerances, the application-specific influences must also be taken into account. In addition to thermal and hygroscopic environmental influences, the minimum clearance to be considered in the application must also take into account the friction heat generated by the application. This plays a decisive role in connection with the expansion behaviour of the polymer material used. This means that the axial clearance in the system can change with temperature fluctuations.

How can I reduce the axial clearance?
In addition to the right choice of material, a preloading mechanism has proven to be an effective measure to reduce unwanted clearance. For our dryspin® high helix threads and trapezoidal threads there are four versions with pretension: Zero-Backlash, Preload, Low-Clearance and AB lead screw nut.The working principle of the pre-load lead screw nut
PL lead screw nuts reduce the axial clearance in a lead screw drive by preloading two lead screw parts with a compression spring. The spring pushes the two halves of the lead screw nuts apart axially in the direction of the lead screw flanks. As long as the axial load in the lead screw drive is lower than the spring pre-load, the entire lead screw drive has a minimised backlash. This also permanently reduces clearance caused by wear.

Potential application in medical technology
Lubrication-free operation and high precision are very important, especially in medical technology. Due to the low-clearance and cost-effective function of the PL lead screw nut, numerous advantages can be achieved for both horizontal and vertical movements:

• Clean operation due to lubrication-free and maintenance-free properties
• Minimum axial backlash without readjustment
• Precise positioning and infeed movements
• Smoother operation and fewer vibrations thanks to the combination of the dryspin® thread profile and the pretension of the lead screw nut

The price and technology advantages can be combined optimally in both pipette head adjustments and sample collection. For applications with high loads, high temperatures or in heavily polluted environments, a standard lead screw nut should always be used. The reason for this is that all four principles are cancelled out by high loads. For this reason, the maximum static axial loads are specified separately for each lead screw nut model.