Plastic instead of recirculating balls - Linear guides for mechanical deburring

Profile

• What was needed: plastic plain bearing
• Requirements: Heavy mechanical load, strong vibrations, lots of dust
• Industry: Mechanical engineering
• Success for the customer: A low-wear product with good sliding properties

When deburring metal parts by machine, high demands are placed on the drives and, above all, on the guide elements of the milling motors. High rigidity is required and the guidance must be designed for high feed speeds. In theory, these are ideal operating conditions for recirculating ball bearing guides - if it weren't for the high levels of dirt and dust. A machine manufacturer therefore decided in favour of plastic plain bearings, with success.

Automatic edge milling machine for charge air coolers.

The two main axes for the milling process are equipped with linear recirculating ball guides. This also seems to be the right choice for the high speeds involved. However, the vertical guides for the two milling motors and the sawing unit, which also perform the infeed stroke of around 25 mm, are a different matter. These guides are subject to heavy loads, as they have to absorb the forces that occur during milling and counteract them accordingly. In addition, the fast-running motors generate extreme vibrations. Finally, there is a high load from aluminium chips and dust at this point, in the immediate vicinity of the machining process.

All these factors tend to speak against recirculating ball bearing guides. For this reason, the designers at the engineering office looked for an alternative solution. They decided in favour of the drylin® T-plastic plain bearing from igus®. In this bearing, a carriage with sliding elements made of the abrasion-resistant high-performance polymer "iglidur® J" moves in a guide profile made of hard-anodised aluminium. This is a perfect sliding pairing, as it is around three times more abrasion-resistant than sliding partners made of steel.

Good sliding properties
Thanks to its excellent sliding properties, the system also runs quietly. It is also insensitive to corrosion and dirt. The so-called "dry operation" is decisive for this specification. As the drylin® T bearings do not require lubrication, the sliding elements act as wipers and simply push chips and dust away from the glide bar. The fact that such good sliding properties are nevertheless achieved is due to the high-performance polymer iglidur® J. The lubricants are permanently "built in" to this highly abrasion-resistant material developed by igus®. The linear guide drylin® T is used successfully today, particularly in dirty environments. In woodworking machines, for example, in paper and textile processing and in packaging machines. The linear guide also holds up in environments where water, alkalis or acids attack most ball guide systems.

No signs of wear
This is not a matter of course because the machine is subject to heavy loads. The guide units have to complete around 300,000 strokes a year - with vibrations, heavy mechanical loads and in an environment that is contaminated with aluminium chips and dust. A little wear would be understandable, but the drylin®guidance units are still running without bearing clearance even after three years and 900,000 strokes.