No More Seizing / Jamming

On Jul 26, 2013

Good combination: iglidur Q2 heavy-duty bearings and hard chrome shafts

Bearings are subject to a lot of wear, particularly in high-load oscillating applications in construction , agricultural machinery etc. The series of tests by igus which confirms a very low wear rate for the iglidur Q2 plain bearings in combination with hard chrome-plated shafts from Ovako comes at just the right time.

Plastic plain bearings from igus are made of special, self-lubricating plastics. They are suitable for high bearing forces and are thus amongst the most important lubricant- and maintenance-free plain bearings. iglidur polymer plain bearings from igus have been firmly established in heavy-duty applications for a long time, for example their properties can be exploited in construction and agricultural machinery in particular – because the heavy-duty material iglidur Q2 stands out through its extremely high mechanical strength.

Brass with initial lubrication — Fig. 1: During the test “brass with initial lubrication” the shafts show heavy signs of wear. The test had to be abandoned due to seizure after 150,000 cycles. (Source: igus GmbH)

And in contrast to metallic bearings, bearing systems with iglidur bearings cannot seize/jam due to “cold welding” the two surfaces get joined at high loads. In addition, the material permits favourably priced bearing solutions when compared with bearings made of conventional materials. The material can cope with a static load of up to 120 MPa and is especially suitable for heavy-duty pivoting applications such as those found in all hydraulic connections.

The advantages of igus polymer plain bearings are:

• Maintenance-free dry running
Corrosion-resistant
High mechanical strength
Vibration-dampening
Insensitive to dust and dirt
Compensate tilting and sagging

Proof in tests
At igus, wear tests are continually performed on polymer bearings and shafts with a wide range of different materials, because the use of a suitable shaft is decisive for a good wear resistance since it creates the right tribo – connection.

Good results were achieved with hard chrome-plated Cromax shafts from the steel manufacturer Ovako. The tests were carried out with 30 MPa. The bearings tested had a diameter of 20 mm and a length of 20 mm. This resulted in a force of 12,000 N, which corresponds to 1.2 tonnes or the weight of a small car. The pivoting/oscillating angle was 60 degrees, and 30 movements per minute were achieved in the test.

Fig. 2: There was hardly any bearing wear during the test with the material iglidur Q2 in connection with the Cromax shafts from Ovalo. The shafts revealed no wear after 200,000 cycles. (Source: igus GmbH)

Initial lubricated brass bearings served as reference objects. It was noticed that the metallic bearing under similar conditions was seen to elongate/flow (See pic.) i.e. became wider in the contact area to the shaft. This reaction was not seen in the test with the iglidur Q2 bearing.

There was no measurable wear whatsoever on the shafts from the tribological pairing with iglidur Q2, however. It is particularly pleasing that it makes no significant difference to the wear whether a hardened chrome-plated base material (Cromax 482IH) or a non-hardened chrome-plated base material (Cromax 280X) is used in combination with the iglidur polymer plain bearings. This combination allows very efficient and low-cost bushing/bolt connections to be implemented.

Dry, not lubricated
A further cost aspect in heavy-duty applications is lubrication. The mechanical working required for the fitting of a lubricating nipple and regular maintenance both result in significant expenditure. Applications with iglidur bearings work dry. If no lubrication is carried out, the corrosion protection it provides for the shaft ceases to apply. Cromax shafts are a good solution from this point of view, too, since they are corrosion-resistant thanks to the hard-chrome layer.

Technology in detail

Heavy-duty material iglidur Q2
Due to the great response, the standard range of the lubricant-free heavy-duty material iglidur Q2, which was introduced in 2011, was expanded comprehensively in 2012. Now, iglidur Q2 bearings with and without collar are now available for all standard shaft diameters up to 75 mm. The focus is particularly on the material when heavy-duty applications need to be solved. This material stands out especially on account of its extremely high mechanical strength – it can cope with static loads of up to 120 MPa – and is particularly suitable for heavy-duty slewing applications such as those which can be found in all hydraulic connections.

Because the material is:

Lubricant and maintenance-free
Wear-resistant and sturdy under high loads
Sturdy in terms of dirt and dust
And has a good price/performance ratio.

Its areas of application are mainly agricultural engineering, commercial vehicles, construction machinery, jig construction or in general mechanical engineering applications.

The terms “igus, chainflex, readycable, easychain, e-chain, e-chainsystems, energy chain, energy chain system, flizz, readychain, triflex, twisterchain, invis, drylin, iglidur, igubal, xiros, xirodur, plastics for longer life, manus, vector” are legally protected trademarks in the Federal Republic of Germany and, where applicable, in some foreign countries.

Authors: Uwe Sund, Branch Manager Agricultural Engineering, igus GmbH and Gerhard Frei, authorised signatory of Ovako GmbH in Germany, by courtesy of KE Next

For more inforamtion
Web: www.igus.in

Igus (India) Pvt. Ltd.