Bearing life extended from two weeks to one year

An abrasives manufacturer was spending approximately GBP 6,000 to maintain a ball rail system per annum - using a V-guide system replacement costs to date are now just GBP 600.

The ball rail system Hermes Abrasives specified for its purpose-built abrasive belt joining machine may have met all the loading requirements but that didn't stop it failing, sometimes as frequently as once a fortnight.

Associated costs were substantial.

Replacing this single element accounted for 8% of the company's overall annual maintenance budget, added to which was the cost of downtime for every failure.

This was compounded by the need to hold a stock of bearings in anticipation of a problem.

The solution came on the recommendation of a Hermes engineer who had previous experience of Hepco's linear slides using the proven V guide principal.

With Hepco's GV3 system installed, replacement costs have been cut by a massive 90% and the company is enjoying significant gains in productivity.

The UK arm of Hermes Abrasives, based in Colchester, is part of an international operation that is now the world's third largest manufacturer of abrasive products.

The 56,000ft2 UK factory is responsible for converting the abrasive medium into the finished product, 60% of which is returned to its German parent for sale to OEMs.

The product range is extensive, from sanding products used in the car refinishing trade to 1600mm wide continuous abrasive belts used in the automated finishing of steel and wood.

Ellesco's Sandingmaster and Grindingmaster machines are typical recipients of these products and it is on the in-feed of the machine designed to produce a perfect join in the abrasive belts that the Hepco GV3 system is used.

Pre-cut lengths of abrasive paper are manually loaded into a fixture and then automatically fed into the machine by two Hepco GV3 linear slides.

The machine is designed to produce a perfect overlap joint in the belt with no imperfections that can be transferred to the work piece during machining.

As Works Director John Tilbrook confirms,"Cutting the abrasive material is easy, the skill is in the way it is joined." Aluminium oxide, silicon carbide and ceramics are typical abrasives that coat the variety of substrates used for making belts.

A particularly aggressive coating is Hermes patented Hermasit that relies on abrasive spheres to produce a consistently high quality finish.

All these abrasives produce dust that can cause catastrophic mechanical failure.

Particle size ranges from 16 grit - the most aggressive - to 2,500 grit which resembles flour.

The finest can be the most damaging of all as it forms an abrasive paste when mixed with lubricant.

For this reason Hermes prefers systems that will operate dry, a known quality of the Hepco's GV3 system that ensures smooth and almost frictionless movement even without lubrication.

"It only took the minute piece of grit to get into the old recirculating linear system for the problems to start," John Tilbrook explains.

"Basically it ground the system from the inside out and the bearing broke down in next to no time." Initially Hermes thought the failure was a loading problem and tried to rectify it by firstly siting a bearing at either end of the rail and then by doubling the bearings to four.

This presented alignment problems which actually increased the loading on the bearings and reduced the mean time between failures.

Mounting the bearings on rubber feet helped with this issue but the frequent failures continued.

John Tilbrook continues, "We were missing the point that the ball rail system simply wasn't up to the job." One of the key features of the GV3 replacement is its V profile.

This ensures that any grit effectively falls off its surface whereas the trough profile of the ball rail system acts as a receptacle, effectively trapping any airborne particulate.

Another important GV3 benefit is the combination of concentric and eccentric bearings that allow easy adjustment to compensate for wear; no recirculating system offers this sophistication.

Hepco's cap seals also extends the working life of Hermes' GV3 installation by physically preventing the ingress of dust.

Thanks to these features the original Hepco bearings have only just needed to be renewed after a working life of nearly a year.

"We were spending approximately GBP 6,000 to maintain the ball rail system per annum - with Hepco our replacement costs to date are just GBP 600" concludes John Tilbrook.

"The GV3 system has been a highly cost-effective solution for us.".

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