Robust, wear-optimised guide systems in EME Parker linear actuators

Profile

• What was needed: Linear bearing systems from igus
• Requirements: Linear actuators in conventional systems often have problems such as carrying dead mass with the slider, an unfavourable lever ratio between support and load arm, they require lubrication and cleaning as well as regular maintenance
• Industry: Manufacture of machine parts
• Success for the customer: igus guide systems are the ideal alternative for Parker EME: e.g.  they are extremely robust, have optimum coefficients of wear and friction, and require no lubrication

drylin R linear plain bearings run extremely reliably even in very dirty environments.

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► drylin W linear guide sample box
► drylin R shaft guide sample box

Problem

Linear actuators with conventional guide systems can cause a variety of problems in a design, for example they often introduce a large moving dead mass at the slider. In addition, there is an unfavourable lever ratio between the support arm and the load arm in the case of internal guides, as it is located far away from the load. The speed is limited (especially with recirculating roller guides) and the acceleration is restricted. Skate wheel guides in particular give way quickly under high moment loads - they are very susceptible because roller axes can be bent or misaligned. Not to mention the lubrication that is usually necessary with these machine elements, which attracts dirt and where discharged grease or oil can contaminate the overall system. They must be installed in a protected manner or provided with a bellows as a cover. The regular maintenance required - mostly cleaning and relubrication - makes them additionally expensive. Last but not least, the multi-part overall system means high assembly costs. Christoph Lindemann, product manager for mechanical components and systems at Parker EME in Offenburg, is also aware of the risks and side effects in practice: "Our linear actuators to date are mainly equipped with skate wheel guides. For clearance-free adjustment, the skate wheels are attached to the slider with screws and eccentric bushes - a so-called "cantilevered attachment" is created. If the skate wheels are already working close to their maximum load capacity during normal operation, a collision, for example, can easily lead to the misalignment or even bending of these fastenings. Guides that are overloaded even for a short time can thus cause severe permanent damage to the entire system. The ratio of harmful to typical exposure is in the range of 3:1 and 5:1."

Solution

The drylin WQ guide systems from igus, which Parker EME  installs in its linear actuator "LCB", are different. Here, this ratio ranges between about 100:1 and 500:1. These figures show the extreme robustness of the guides. After all, the glider transmits the forces directly to the guideways. There is no possibility of adjustment; the danger of bending is practically excluded. 
The sliding elements are made of high-performance polymers. For most applications, the use of the material iglidiur J is recommended due to its wear and friction properties. Basically, the drylin linear bearing systems are designed for dry operation. Contamination by grease or oil is now a thing of the past. Ambient dust or abrasion during machining are not bound to the bearing position. drylin guides are divided into two main groups with different geometries: profile rail and shaft guides.
In the drylin T system, the carriages run on a T-rail made of hard-anodised aluminium. All connection dimensions are the same dimensions as most commercially available recirculating ball guide systems. A miniature version can be accommodated even in the smallest installation spaces. Extremely flat "N" variants are available in four sizes from 17 to 80 mm rail width. The slides are movable in C-profiles made of anodised aluminium.
drylin R linear plain bearings, on the other hand, which correspond to the size of ball bushings, use round shafts as counter partners. Thereby different shaft materials are used. Thus, hard-coated aluminium shafts guarantee low wear and low coefficient of friction. The drylin W linear guides used by Parker EME combine two round shafts, rectangular guides and the support profile for the linear actuator in one profile made of hard-anodised aluminium. They allow the greatest freedom of design through various shaft diameters, profile widths, carriage lengths and geometries.

In order to obtain a homogeneous product, Parker EME uses the positive specifications of the igus guides in its linear actuator "LCB" for the first time.

In addition, igus offers a comprehensive product range, which also includes the simplest guides for pneumatic cylinders.