Lead screws. MODENGY dry solid-film coatings technology is a modern alternative for greases

Lead screws are one of the most common tools used to transform rotating mechanical motion into progressive one.

Fig.1. Lead screw of the thermal power station locking valve covered with MODENGY coating

Modern materials and coatings enable to use these parts in a various equipment such as for semiconductors production, in medicine appliances, fast prototyping machines, in the units of the pipeline fitting, in the doors opening systems at the railway transport, in motor-car lifters, etc.

Ability to operate without need in periodical maintenance is one of the advantages of using lead screws.

Since at producing most of the drive nuts polymer materials with the lubricating substances integrated into them are used, use of oils and greases in the screw mechanism units can be excluded.

However, in cases when a lubricating material is not used at all, service lifetime and load-carrying capacity of the parts reduce.

The most effective solution at producing lead screws is applying anti-friction solid-film coating. The best products to protect drive mechanisms are MODENGY coatings based on solid lubricating materials such as polytetrafluorethylene (PTFE), molybdenum disulfide, graphite, tungsten disulfide, etc.

Fig.2. Screw-nut gearing

Composition of these coatings includes additives that help enhance adhesion of the materials to the basis improving its wear resistance, and to enlarge service temperatures range.

A layer of about 25 µm thickness provides the parts with a package of advantages including friction and wear reduction, corrosion protection.

Coating applying is done on the stage of producing the lead screws. The end users rarely use solid lubricating materials by themselves without necessity to strictly observe applying technology, thorough control over coating thickness, and other quality parameters.

Prior applying the coating, the lead screws are prepared in a special way to achieve the optimal surface features, are thoroughly cleaned and degreased. MODENGY Special Cleaner-Acticator is used for finishing treatment of the surface.

After that all parts of the components on which the coating is supposed to get are covered with a masking tape, paper.

MODENGY solid-film product is applied in several layers by using spraying equipment up to getting the required thickness. Spraying can be done manually by using MODENGY M1-250 professional spraying gun, or at the automated equipment. Some kinds of the coating are available in the aerosol cans as well.

Depending on the coating mark, there are different polymerization modes such as at heating in a kiln or at room temperature.

As a result, a wear-resistant lubricating coating is formed on the lead screws surface that significantly extends service lifetime of the parts, and have a number of advantages over greases and oils.

MODENGY coatings demonstrate low friction coefficient (from 0.03) at slow sliding, and high contact pressures.

Unlike conventional lubricating materials, anti-friction coatings can be effectively used under severe conditions, and in environments with high dust content.

Dust, dirt, and abrasive particles significantly cut down service lifetime of a drive nut. From this point of view, use of MODENGY solid-film coatings is considered a preferential solution, since a dry layer attracts and holds no solid particles unlike greases with their sticky texture.

One more important advantage of the anti-friction solid-film coatings in comparison with the other lubricating materials is stable operating within a wide conditions range. For instance, their friction coefficient remains constant despite axial load value.

Fig.3. Lead screws of the pipeline valves

MODENGY coatings have good resistance to alkalis, acids, solvents, and other aggressive substances, negative environmental conditions such as salt water, road chemical reactants, and ultraviolet radiation.

The solid-film coating retain their operability within a wide temperature range. The service temperature upper limit of one of the MODENGY coatings line product makes + 860 °C, and the bottom limit reaches - 210 °С.

The anti-friction coatings are able to eliminate a strange noise and vibration at mechanisms running.

Here is an example. The lead screws of the office equipment such as copying machines is exposed to toner particles contained in the air. It is necessary to provide trouble-free operating of the equipment during a long while after it is turned on without any stops for their maintenance. To solve this task the solid lubricating materials fit exclusively.

Implement of the screw pairs covered with anti-friction solid-film coating is perspective at the enterprises of the chemical industry as well as at productions of the high-quality fibrous materials.

In the unit of forming glass canvas, the screw conjugations with a liquid lubricant can be used. The typical issue of these connections is that the liquid lubricant gets onto the products what causes appearing the defective finished items.

The following points can be referred to the issues of the given screw conjugation as well:

• The liquid conventional lubricant lose its anti-frictional properties under conditions of alkali media
• Increased wear of the parts at the start-stop moments
• High load on the first turn leads to reduction of the screw conjugation load-carrying capacity, and enhanced wear

These drawbacks reduce reliability of the screw pair, and increase probability of failure. Solution of the given issues is implementation of the solid lubrication technology at production.

Fig. 4. Lead screws covered with MODENGY 1014 anti-friction solid-film coating

Use of MODENGY solid-film coatings also helps to create the equipment for fast prototyping that requires no maintenance

The solid lubrication technology is implemented into medicine, semiconductors production, and other fields where high requirements are demanded regarding pureness.

One of such applications is machine for collecting DNA samples where use of the liquid lubricants can cause problems with contaminating the samples.

MODENGY 1001 anti-friction solid-film coating is applied at the gas supply facilities for the handwheel of gate valve rods of various diameters.

Fig. 5. Anti-friction solid-film coating MODENGY 1001

"The following advantages have been revealed during their application:

• Ability to prevent jamming, loads reduction
• Good adhesion to metals
• It is not subjected to running off at higher temperatures
• Convenient applying onto a treated surface
• High resistance of the coating to scuffing"

Use of the lead screws treated with the MODENGY solid-film coating enables to achieve the best operational properties including reliability, service lifetime, corrosion resistance, lifting capacity, rate.

Numerous high requirements towards lead screws were satisfied by using solid-film coatings. The application fields of the given products keep enlarging as the more and more number of the equipment producers make sure in their advantages.