How machinery and equipment manufacturers efficiently implement special requirements for ball and planetary screw assemblies
In robotics, medical technology, semiconductor manufacturing, machine tools and intralogistics – the need for specific screw drives is growing. In some instances, the focus is on dynamics, compactness or safety, while in others it is on corrosion protection, temperature management or vacuum suitability.
The common denominator with all these applications is that they need to be realized faster and more economically despite increasing requirements. Read this blog post to find out how to:
Tip: You can find an overview of the main types of screw drives – from ball assemblies and planetary screws assemblies to complete drive units with nut housings and pillow block units – on our screw drives product page.
There are many reasons why so many application-specific screw drives are needed:
The challenge:
Once it is determined that the application requires a ball or planetary screw assembly not available in the standard catalog, the engineering and manufacturing costs increase significantly. Special designs are not only costly, but also rarely tried and tested in practice.
The solution:
Bosch Rexroth offers you the possibility to order custom-made screw drives made from tried-and-tested standard and add-on components, which are machined directly in the factory according to customer requirements.
The result:
Machinery and equipment manufacturers receive practical solutions more quickly with a predictable cost – including CAD data and comprehensive documentation.
The Rexroth offering includes coatings, special lengths and machining according to customer specifications, combined screws and special nuts, all the way through to pre-assembled units for heavy-duty applications.
Typical screw modifications: Special lengths, extensions, special machining and nuts. (Image: Bosch Rexroth)
In the case of screw drives operating under special conditions of use, the surface finish is a critical factor for precision and service life. Moisture, aggressive media, or vacuum conditions not only affect the material – they also change friction and wear. Optical reflections can also pose a challenge in certain applications.
Typical examples of coated and corrosion-resistant solutions include screws and nuts coated with thin-layer hard chrome, stainless steel versions for hygiene-critical areas such as food production, and matt black or matt silver chrome-plated surfaces for semiconductor production or the optical industry.
Corrosion-resistant finishes: Thin-film hard-chrome plated in black and matte silver, as well as a stainless steel version. (Image: Bosch Rexroth)
In many applications, the screw has long since become more than a transmission element. It also takes on additional functions such as:
An example from machine tool construction are temperature-controllable screws. In these, targeted cooling using deep-hole bores and hose lines enables thermal influences to be controlled – and process stability increased without additional installation space. In the patented screw temperature control system from Bosch Rexroth, the cooling medium is introduced via a stationary rotary feed-through at the end of the screw and guided longitudinally through the screw. This results in up to 75% higher part precision from the first workpiece.
Screw with hollow-drilled shaft and rotary lead-through for optimum temperature control. (Image: Bosch Rexroth)
The machining of screw ends is also frequently desired. This usually involves:
Various machining options at the spindle end (from left): External splining with internal thread, internal splining with external thread, and internal keyway. (Image: Bosch Rexroth)
Combined screws have two sections, each with a right-hand and left-hand thread, if necessary, also with different leads. This allows opposing movements in opening, closing, and clamping mechanisms to be achieved with just one drive. Typical examples of applications include gripping car tires in the automotive industry or lateral fork adjustment in AMR (autonomous mobile robots) for handling different pallet types in intralogistics.
Combined screw with opposing threads, bolting, and connecting bolt. (Image: Bosch Rexroth)
The potential for adaptation offered by screw nuts is often underestimated.
Targeted modifications allow functions to be integrated into the screw drive which would otherwise require additional components and would increase the solution costs unnecessarily. These include:
Arrestor nuts are essential in safety-critical applications for vertically operated ball screw assemblies. Whether as an integrated solution or as an attachment, they prevent the screw drive nut and the elements attached to it from suddenly falling off uncontrollably. They are used, for example, in medical technology, where they act as a safety mechanism to keep the CT scanner securely in place above the patient.
Arrestor nuts (integrated and external) for protection against falling loads and special nuts with external toothing. (Image: Bosch Rexroth)
For high temperatures, in highly dynamic components, or even in a vacuum, we have developed special deflectors that are used, for example, in the semiconductor industry or in glass production.
Total deflection enables high load capacities by using the full nut length, quiet running, and particularly uniform torque curve.
Metal deflectors for applications in demanding environmental conditions, such as high temperatures and vacuum. (Image: Bosch Rexroth)
As well as the structural design itself, assembly is another often underestimated factor in the development of cost-effective custom solutions.
Large screw drives for heavy-duty applications – for example in servo presses for sheet metal forming – place high demands on assembly and handling. In addition to the heavy weight of the individual components, they are also difficult to handle. For example, a 53 kg flange bearing for a 75x20-sized planetary screw assembly must be heated before being mounted, and then the slotted nut must be tightened with the correct torque. Pre-assembled screw drives with end bearings shift this work to the manufacturer. This means:
Complete solution with a pre-assembled end bearing for heavy-duty applications, such as in servo presses. (Image: Bosch Rexroth)
| Requirement | Typical solutions | Benefits |
|---|---|---|
| Corrosion, hygiene, optics | Coatings, stainless steel | Safe processes, longer service life |
| Precision, temperature | Temperature-controlled screws | More stable processes, higher precision |
| Integration, movement | Special geometries, combined threads | More compact and efficient structural design |
| Safety, function | Special nuts, arrestor nuts | Greater operational safety |
| Assembly, time | Pre-assembled end bearings and assemblies | Less work, lower error rate |
In addition to technology and function, there is one factor that is becoming increasingly decisive: time. Whether coated, modified, or with ready-mounted bearings – every customized screw drive needs to be designed, manufactured, and supplied as quickly as possible.
Digital tools such as the Linear Motion Technology Selector help to quickly find a robust solution – without getting lost in variants. They enable rapid pre-selection of suitable standard solutions and provide technical data and CAD models as the basis for customer-specific drawings and modifications.
From here, it requires only a few clicks to send the modification request to the Rexroth Engineering Team, which implements the customer-specific adaptations in dialog with you. This results in a perfectly adapted screw drive based on tried-and-tested standard components – in proven Rexroth quality and including project documentation with instructions, 3D CAD data, and calculation information.
Use the Linear Motion Technology Selector to find the right screw drive and submit your modification request directly to the Rexroth Engineering Team.
Author: Rainer Sauer
Position: Product Manager Screw Drives
When is a customer-specific screw drive worthwhile?
A standard screw drive reaches its limits when there are special requirements in terms of the environment, precision, safety, installation space, or integration. Typical examples are aggressive media, high thermal loads, vacuum, special connection geometries, or applications where safety is critical. In such cases, many requirements can be met economically by means of modified standard components.
What coatings are available for ball and planetary screw assemblies?
Depending on the application, thin-layer hard chrome and stainless steel are used. They improve corrosion protection, wear behavior, hygiene, or optical properties – for example for the food and packaging industry, medical technology, or semiconductor production.
What end machining options are available for screw drives?
Depending on the drive concept and installation situation, screw drives with different end machining can be ordered. These include, for example, internal and external toothing, drive journals, power take-off shafts, hardened bearing seats, slots, or special lengths. Such machining facilitates integration into motors, bearings, and machine structures.
What special screw drive nuts are available?
Screw nuts can be adapted to different functional and safety requirements. Typical examples include nuts with external teeth for pinion drives, specific fastener and lubrication options, and arrestor nuts for protection against falling loads in vertical applications. In addition, special deflection systems ensure smooth running and a uniform torque curve for high precision requirements or sensitive processes.
How quickly can customer-specific screw drives be configured?
Digital engineering tools such as the Linear Motion Technology Selector and the Configurator speed up the selection and preliminary design process. Customer-specific modifications based on standardized components can be implemented significantly faster than with complete special designs.
Why are screw drives temperature controlled?
Temperature-controlled screw drives minimize the impact of thermal effects on precision. Integrated cooling channels help to compensate for temperature differences and improve process stability – especially in machine tools or high-precision machining processes.
What are combined screws?
Combined screws have several threaded sections with different directions of rotation or leads. This allows opposing or synchronized movements to be realized with only one drive, for example, for mechanisms for clamping, gripping, or opening and closing.
