When should you use a bronze lead screw nut?

Lead screw manufacturers offer nuts in a variety of materials,including various plastic and bronze grades.While plastics have attracted much attention for their versatility and wide range of applications,bronze screw nuts are particularly suited for applications with high loads or extremely high(or low)temperatures.Plastic nuts have dozens of formulations,ranging from materials such as acetal,PEEK and nylon to certain manufacturing-specific materials.

 

Customized lead screws made from plastic

Bronze nuts are usually made from bearing grade bronze.

When bronze lead screw nuts are the best choice?

In lead screw components,nuts play an important role in ensuring several features(including load capacity).Bronze has a significant advantage over plastic.This is because bronze can withstand higher loads,including thrust loads,and has better impact and impact load resistance than most plastics.However,lead screw nuts made of bronze generally have a higher coefficient of friction than those made of plastic,so they generate more heat and may not be suitable for high-load and high-duty ratio applications.

 lead screw made from bronze

Lead screw nuts made of bronze are more suitable for higher loads and extremely high and low temperatures.Bronze nuts are also better suited to corrosive and high(or low)temperatures than plastic versions.Bronze nuts paired with stainless steel screws provide excellent corrosion resistance to most liquid contaminants,a combination commonly used in food and beverage applications.Bronze nuts also have a wider operating temperature range than most plastic versions.

Can you use the PV coefficient to select bronze lead screw nuts?

Because sliding bearings rely on sliding friction rather than rolling friction like ball bearing and roller bearing,the standard L10 bearing life equation is not applicable to sliding bearings.Instead,the suitability of a sliding bearing for a particular application is usually assessed by the bearings PV(pressure x velocity)value.But the PV equation was developed for plastic materials whose wear characteristics do not depend on lubrication.

However,any metal-to-metal sliding or rolling contact,such as a bronze nut on a steel or stainless lead screw shaft,requires lubrication.The type and amount of lubrication will affect the coefficient of friction between the nut and the lead crews,thus,for lead screw assemblies using bronze nuts,the PV value is only useful as an indicator of whether the nut is suitable for a particular application.

To solve this problem,some manufacturers have conducted empirical tests to create modified PV charts for bronze nuts.These modified diagrams include a third parameter that describes the operating frequency and lubrication conditions of the screw assembly.

To solve the role of lubrication and duty cycle in the wear of bronze lead screw nuts,some manufacturers have developed modified PV charts for bronze nuts.In block A,it can run continuously.Zone B allows limited operation with continuous lubrication.Zone C only allows intermittent operation,even under continuous lubrication.

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