Fit & forget

Published:  06 May, 2015

Automated sawmills require reliable machinery to continue operating in difficult conditions, even when lubrication systems seem to be at odds with the constant accumulation of sawdust and woodchips. However, one of the major European sawmill businesses found a solution in the form of Tsubaki’s Lambda chain that has significantly cut maintenance costs and improved productivity. PWE reports.

The operating conditions in any sawmill are tough for moving machinery due to the large amounts of airborne dust from the cutting and shaping processes. Most sawmills employ a variety of conveyor systems to transfer timber between each processing station and these rely on chains to do most of the heavy lifting.

The cutting and shaping of the wood from rough-cut logs requires a multi-stage process, involving loads of up to 10 tonnes of timber that must be moved by the chain driven conveyors. The lubrication system in such situations is essential but in this particular site, the problem is exacerbated because the mill is exclusively cutting Spruce Sitka, a highly resinous variety of tree.

The maintenance engineers on site had continual problems with dust sticking to the greased chain and sprockets, which often caused clogging and subsequent derailment. The machines had to be regularly adjusted, dismantled and cleaned, which reduced valuable production time as well as increasing maintenance costs.

One of the first machines to benefit from the improved Tsubaki chain design was the chipper edging machine, which profiles the sides of 120 metres of board per minute. The previous conveyor chains used on the feeding ramp of the machine had an average service life of six months due to the amount of debris produced by the chipping process.

In contrast to the original arrangement, the Tsubaki Lambda chain uses oil impregnated bushings to allow the chain to effectively run dry, avoiding the problem of sawdust building up and clogging the links. Now, the system only needs to have a monthly visual check and the chain adjustment is only required once in every two years.

A separate transfer system handles the wood that is cut by the band saw and this requires the chains to be automatically tensioned as they operate in both forward and reverse directions. A standard chain would last between three and six months during which time the automatic tensioners would often fail or have to be padded out until the chain stretched enough to insert an extra link.

Installing the Tsubaki Lambda chain solved a number of problems; the very low elongation properties have enabled the installation of smaller automatic tensioners and this combination has resulted in over twelve months of trouble-free operation. The design of the chain pin and narrow side plates has also prevented the chain from rubbing against other components such as gearboxes.

Installing the Lambda chain also increased the effectiveness of the dust blower system that was designed to remove the debris from the conveyor system. The self lubricating properties of the Tsubaki chain have enabled the whole system to run problem free for over twelve months.

Following the initial success of the new chain installation on the chipper edging machine, the maintenance team also looked at improving the reliability of the largest chipping machine, which was used for squaring the edges of the rough-cut logs. It produced so much dust that the conveyor chains and sprockets often have to work through the mounds of debris, making normal lubrication impossible.

In this case, the Tsubaki application engineers suggested specialist duplex sprockets with extruder grooves, combined with a 1” Lambda chain. This combination ensured proper lubrication of the chain and also prevented sawdust becoming trapped in the teeth of the sprocket and causing a derailment.

The implementation of Tsubaki chains and sprockets has now significantly contributed towards the continuous improvement at the site in terms of reliability and productivity. Due to the success of the first application, Tsubaki's lube-free Lambda chain has now been fitted on machines throughout the plant.

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