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Laser alignment and soft foot

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Laser alignment of power transmission drives can be a maintenance necessity for viable plant operation.

Misaligned drive components cause the motor to draw more amps, which can be substantial when considering multiple drives across a site. By decreasing the misalignment, one can realise substantial savings through drive efficiency as well as reduced power consumption.

Power savings are however, a secondary benefit of accurate alignment with the primary benefit being the extended operating life of the machinery. Bearings and power transmission drive components such as gearboxes, electric motors, pumps, couplings, V-belts, pulleys, industrial brakes, chain and sprockets will operate more effectively with a reduction in noise emission, vibration and operating temperatures, extending the lifetime of the particular drive component.

Accurate laser alignment will also extend the MTBF, reducing costly downtime, which in turn reduces maintenance costs. Traditional alignment methods do not always produce the accuracy required by today’s precision machinery. An alternative is to use dial indicators, which offer a higher degree of accuracy but also pose difficulties.

A laser shaft alignment tool facilitates quicker and more accurate laser alignment than traditional methods. However, operating laser equipment requires certain alignment processes to be adhered to, and various influencing factors to be considered.

Soft foot is one important influencing factor that may be overlooked when trying to achieve accurate laser alignment. Soft foot is a term used to describe distortion present under a machine, caused by a warped machine base or when one or more feet of the machine differ in height.

If soft foot is not eliminated or reduced to an acceptable level, it can create stress on bearings, significantly reduce the life of the machine and also considerably lengthen the laser alignment process, causing inconsistencies with results.

Soft foot should be checked via a deflection method at each foot and shimmed accordingly. Two conditions of soft foot may be diagnosed: parallel soft foot and angular soft foot.

Parallel soft foot is where one or more mounting points, or feet are too short, or one base plate-mounting pad is not level with the other three. Parallel soft foot is also caused when shims under one of the feet are the wrong height. This is corrected by placing a shim under one of the shorter feet.
Angular soft foot is where the bottom of one mounting point or foot is not parallel with the base and is only partly in contact with the mounting base. This should be measured with a feeler gauge, and built up with the appropriate thickness shims, taking care to only fill the gap as required.

Often, both parallel and angular soft foot conditions are present under the same foot. Attention should be given to define the type of soft foot condition present, prior to shimming accordingly. Soft foot can also be induced during the alignment process, or during previous alignment. A common mistake can be to place a shim of incorrect thickness under a foot, inadvertently creating a difference in height. It is therefore, important to check all shims prior to alignment and even during the alignment process.

Shims, an important part of the laser alignment process are supplied by CBC in varying thicknesses in stainless steel shim and plastic shim materials as well as shim kits and sheets. Slotted shims are considered to be the most appropriate and user-friendly for alignment of rotating machinery. Shims can also be manufactured in specific designs, thicknesses and materials for specialised applications.

CBC’s specialised technicians not only provide on-site laser alignment services, but also offer on-site and off-site training in laser alignment. 

CBC Australia also supplies the industry leading Pruftechnic laser alignment equipment, which includes Rotalign and Optalign models. The Pruftechnic Rotalign is one of the most user-friendly laser aligners for machinery alignment including shaft alignment, coupling alignment, straightness, flatness, bore alignment and live trend.

CBC also supplies a wide variety of laser alignment brands including Damalini, Easy Laser, FAG Inline Laser and Fixturlaser.

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