Guides are absolutely indispensable elements in the world of hydraulics and pneumatics. They are installed in the rods and pistons of hydraulic and pneumatic cylinders, in order to allow a good guiding between the piston and the cylinder liner or between the rod and the cylinder head. The use of guides avoids damage caused by contact between metal surfaces.
In addition, the guides must allow a smooth, straight movement with the least possible friction in order to minimize energy losses as much as possible due to friction. For this reason, you must select the correct material for the guides. In this article we aim to make your decision a little easier.
Index
Materials for guides in hydraulic or pneumatic cylinders
The main materials for guides in hydraulic or pneumatic cylinders are:
- PTFE loaded with carbon.
- PTFE loaded with bronze.
- Resin with fabric.
- Thermoplastics, The most important of these are polyamides and acetal resins.
The first thing to keep in mind when selecting the most appropriate material for the guide is that friction between parts or moving parts of a mechanism is a matter of two. That is to say, you must take into account between which materials the friction is going to occur: the guide itself and the contact surface on the cylinder, usually a metal.
We will choose the PTFE + Carbon when the contact is made with a non-ferrous metal (aluminum, copper, brass alloys, lead, nickel), or in contact with plastic materials, which is becoming more and more common in the world of pneumatics. The PTFE + Carbon guide material is particularly suitable for pneumatic applications or in poor lubrication conditions, as the air in the pneumatic system often contains moisture. In this case, the contact between bronze, water and other metals can lead to corrosion.
On the other hand, the material for guides PTFE + Bronze is indicated when the contact surface is of ferrous metal (irons, cast irons and steels) and preferably with oils or lubricating fluids. This usually occurs in hydraulic cylinders.
Another reason for using PTFE-based guides is high temperatures. Although you must take into account that, although its temperature limit is higher than the rest of the guide materials, its mechanical resistance decreases with temperature.
The guides prepared in fabric-reinforced resin, and also the thermoplastics are indicated for those cylinders that work with high compression loads on the guide itself. In these cases, these materials resist wear much better than PTFE guides.
Available sizes of guides on hydraulic or pneumatic cylinders
The bronze or graphite loaded PTFE guides are usually supplied in the form of an open ring, i.e. with a cut-out for easy installation in the cylinder. These guides are preformed to better adapt to the required dimension.
There are also guide tapes or bands which are supplied in rolls of varying lengths, in sections and widths to cover any application. This allows the installer to cut the required length on each cylinder.
In the case of resin guides reinforced with fabric, they are usually supplied either in the form of a formed ring or in spiral form. The latter are available in both metric and inch dimensions.
In addition, in our production workshop we can manufacture rings made of guide in both PTFE with fillers and Thermoplastics, We are able to manufacture slides in rectangular sections or special shapes, such as T-sections, L-sections or special shapes according to drawings. We are able to manufacture guides in a very short time up to 600 mm diameter, depending on the availability of raw material in our facilities.
Wrong selection of guide material in hydraulic or pneumatic cylinders is one of the main causes of premature cylinder failures.
Do not hesitate to contact us at your needs.