Rotating Headstocks - LBU 5000

Automotive Engine Cylinder Head NDT

Large Bench Unit (LBU) - 5000A

A multinational company with divisions in the UK required a MPI solution to increase the efficiency of their engine inspections, specifically the non-destructive testing of large engine cylinder heads using MPI.

Engine cylinder heads inherently feature complex geometry but are also relatively heavy, the heaviest in this range nearing 100kg in weight. Without a suitable solution inspection of these components would be extremely time consuming at best.

With this in mind Johnson & Allen proposed an LBU 5000 design MPI bench unit with rotating headstocks.

Rotating Headstocks

One key feature on this LBU was rotating headstocks which were designed to allow unlimited 360 degree rotation in both directions. For increased safety a safe start button mechanism was included so that the headstocks could only be operated with a 2 hand start, meaning that there was minimal chance for operators to have the hands near the component when moving.

A bespoke jig to hold and clamp the components when rotating was designed to accept the range of components this unit was intended for. However these could in theory be temporarily swapped out for a different jig if new components required inspecting.

Manual Current Control System - 'Pot' control

This LBU was designed to for using AC waveforms only with no HWDC or FWDC capability as this was not required.

The LBU was designed around Manual Current Control System (sometimes called ‘pot’ control) where the current is infinitely varied with thyristors using a dial on the front facia. Manual Current Control is Johnson & Allen’s entry level operating system for MPI Bench Units and is well suited to units which only feature single waveform output.

Operators can select Current Flow (CF) or Coil modes using the relevant buttons which engage contact change overs inside the unit between the headstocks and the coil carriage.

For ease of operation a push-button AC decaying demagnetization feature was also included so operators could demagnetize their components after inspection with a single button press.

Ink Application & Traversable Coil Carriage

LBU MPI Bench Units feature a 50 Litre ink hopper fitted with a mesh macro filter with re-circulation pump as standard. This allows bulk magnetic ink to be applied via an inking hose with lance nozzle which drenches the component.

The coil mounted on the LBU can be traversed and locked along the bed bars and energization can be performed by either foot pedal or using a button mounted on the coil itself.

A coil mounted inking bar or ink curtain was installed on the coil so that components could be drenched by just moving the coil over the component without the need for the hose and again controlled by a button on the coil.

Blackout Booth - Cantilever UV Hood Design

As previously mentioned in this case study, the cylinder heads are too heavy for a manual loading so a crane hoist system is used to load them safely. Johnson & Allen manufacture a number of different Blackout Booth designs and for this unit the customer had a preference for a Cantilever UV Hood design, where the canopy’s frame hinges backwards to allow component loading - And is then closed with the curtains being drawn at the front by the operator to darken the headstock area fully for inspection.

For ergonomic considerations the opening and closing of the hood was pneumatically driven, which allowed opening and closing of the hood via buttons on the bench unit itself.

Designed and built in Sheffield, UK

Like all Johnson & Allen MPI Bench Units this one was designed and manufactured by our skilled and friendly team in Sheffield, UK.

Johnson & Allen specialise in both standard and bespoke NDT equipment, so if your organisation has similar requirements Johnson & Allen is on hand to help. Don't settle for second best because of manufacture inflexibility.

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