A manufacturer of PET (polyethylene terephthalate) bottles frequently had to replace the linear guides on its blow moulding machines. However, after switching to NSK’s RA series roller guides, there have been no failures for over a year, producing annual cost savings in maintenance, spare parts and downtime of €60,000.
Dissatisfied with the number of linear guide failures on its blow moulding machines, the manufacturer invited NSK to investigate several faulty guides. Expert analysis identified the cause to be end cap damage, which was occurring due to the combination of short stroke movements, short cycle times, frequent start-stop operation and increased displacement force during start-up.
Given this application profile and the damage that was taking place, NSK recommended that the plastics processor installed RA series roller guides. These guides offer, among other things, very high load-carrying capacity and motion accuracy, extreme rigidity, smooth running, and long service life under conditions of short cycle rates and high loads.
A principal design feature of the RA series are its spacers, which perform a restraining function between each of the rollers. These spacers reduce roller skew and ensure smooth running, as well as lower displacement force during start-up.
The user followed the recommendation and, on a trial basis, equipped one of its blow moulding machines with NSK RA series roller guides. This machine ran for more than a year without any problems or breakdowns, reducing production downtime costs to zero. NSK’s cost savings analysis showed that the retrofit of this one machine alone resulted in a saving of €59,500.
In the light of this outcome, the PET bottle manufacturer had no hesitation in upgrading its other blow moulding machines.