Brick by Brick - Austral wins better Productivity

Austral Brick, one of Australia's leading brick & tile manufacturers, recently engaged the services of Action Bearings to overcome a continuing failure problem on a fully automated "De-Hacking" or brick stack & wrap machine.
The major causes of their problems were 2 ball screw transport axes mounted below the 2 main chain conveyor inputs which carry the end product into a robotic stacker. Continuous machine down time was being experienced by the company on their 3 year old "state of the art" machine in replacing these screws which were deteriorating because of environmental and misalignment issues. It was obvious on inspection by AB that not enough initial application had been given to two critical aspects of ball screw operational parameters at design stage.
The first of these was appropriate protection of the ball screws from the normal environmental hazards of a brick plant. Brick dust and other small particulates are constantly falling off the product during in plant processes with no other path to take in this case but directly onto the ball screws mounted below these two major conveyors. In no time at all this matter mixes into the lubricant and becomes a very effective lapping paste quickly deteriorating both the screw surface as well as the internals of the ball nut.
The secondary problem recognised by AB was the lack of any external support rails and guides to cope with any misalignment or deflection that might translate into the ball screws as a radial load. Ball screws are designed to handle axial or loads along the line of the screw and do not cope well with any radial or loads at a right angle from the screw. These loads would normally be handled by auxiliary linear rails or guides which were absent in this application.
As the loads being transported by these ball screws were extremely minimal in comparison to their maximum performance capacity , Action Bearings offered Austral Brick the option of a totally retro engineered system replacement which would seal off the ball screws from the harsh environment and include supporting rails to cope with all external deflective forces.
The decision in this instance was an evaluation of the cost of these two new systems and the benefits which they offered compared against the output losses incurred by continually interrupting machine productivity to replace ball screws and nuts in an extremely awkward location underneath the main body of the machine . In this case it wasn't a difficult decision for Austral to make as the new systems would offer uninterrupted service for many years by comparison and save the company man hours and machine down time losses that would more than compensate for the system costs.
Action Bearings designed the retro units using an Ironcad 3D package. All machining and assembly was then carried out in the company's workshop and installed at site by Bellato Engineering at Austral Bricks' main Sydney plant. Ball screws , linear rails and bearings were supplied by Thomson (USA) and the exercise exemplifies the value of retro engineering solutions providing major benefits where automated applications are experiencing repetitive failures.

Cutting Edge Retro-Design Saves Big Dollar Down-Time

Action Bearings recently played a major part in providing one of Australia's leading automobile manufacturers with enormous savings in production down-time costs.
The auto manufacturer had a production critical ball screw on its Robotic Weld Line where floor pan, roof and side panels are stitched. The function of the ballscrew is to lift these primary vehicle assemblies on a shuttle bar as they are moved through the robot cells. The original ballscrew, which came fitted to the imported assembly line, had operated without problems for in excess of 3 years. However serious problems developed for the company when an early failure of a replacement screw was then subsequently followed by the necessity to repeat that replacement a further 3 times over a 12 month period. Lost production caused by downtime on the line for these failures was estimated in excess of $1.5M

Fortunately Action Bearings had just run a front page in Manufacturers Monthly for THOMSON Ballscrews as the fourth replacement screw was giving evidence of imminent collapse . One of the company engineers noted the ad ,contacted AB and provided details of the application and its problems for assessment and comment.
Drawings highlighted a set up where the screw was supported at one end only . While a short travel length of around 700mm was required over a screw length of 1.3 metres, the load being lifted, including bodies and tooling was approximately 20 tonnes. The lift was achieved by connecting the ball nut to a racked con rod of 100 metres in length. The con rod activated several rack lifters supported by pneumatic assistance at critical points along the line. The flanged ball nut was connected to the con rod by a square steel tube which was supported on a single 65mm Linear guide rail . All in all a 20 tonne lift in 4 seconds on an 80mm diameter screw with peripheral assistance, for several hundred lifts a day , was a little different to the normally assessed applications.
As with all ballscrew and linear guide combinations the necessity for maintaining close tolerance alignment is critical. Descriptions of the catastrophic failure mode given verbally by the Auto maker definitely leaned towards a suggestion of an out of alignment situation . This however was not the answer that the company was looking for because they had been extremely meticulous to the point of engaging a laser alignment contactor, in setting up the 4th replacement installation.
AB considered that if any twist existed within the metal framework upon which the screw and guide rail were mounted then it would cause misalignment load hot spots in the body of the ball nut. These load hot spots squeeze the re-circulating steel balls through the heavier loaded areas between the nut body and the screw, spitting them out at very much higher than normal acceleration rates. These higher acceleration rates then create heavier impacting of the balls against the hollow tube type pick up fingers which these nuts were using. Constant higher level impacts will cause the pick up fingers to snap off resulting in catastrophic nut failures. AB then asked if the company had kept the failed screws for analysis purposes which they had wisely done , these were forwarded on for inspection. On receiving the failed nuts the first observations noted that the screws were in generally good condition along the surface length and that the nuts were jammed at the point of failure on the screw which supported the theory of pick up finger breakage . When disassembled the evidence was very clear that all but one of the 8 fingers in 2 nut bodies supplied had snapped off and the one that was left intact had a bullet like impregnation in its surface suggesting extremely heavy ball impacts. The screw surface was badly spalled at these points where the nuts had jammed because the balls could no longer re-circulate through the external hollow return tubes. All of this damage supported a misaligned set up which was accepted by the customer when shown the evidence and AB was requested to supply a re-design that would get the company back to acceptable performance levels from this production line.
It was obvious that any re-design should be mounted on an independent base which would guarantee in-built alignment. As hollow tube pick up fingers should be avoided where very heavy loads can develop it was decided to try and include a solid steel internal ball changeover mechanism which is a design available from Thomson IBL ( UK ).
As this was such a critical line for the auto maker they needed full design drawings before considering any radical changes. AB utilised the full 3D concept design capability of IRONCAD to present the company with a visual layout with detailed internal views as well as drawings which they then accepted as a better option.

The major design changes centred around building the system on an independent base plate and then providing non-drive end bearing support for the ball screw. Mounting of the connecting tube on 2 X 40mm Linear guides with solid lubricant wipers and using internal nut solid steel ball returns to avoid breakage. Last but not least changing the con rod connection to a swivel joint to avoid external load from shaft deflection moving into the assembly.
Having the design approved by the customer, AB then called on the expertise which exists within its own customer base to assist with manufacture , assembly and installation on site for the Auto maker.
The base plate was milled to a precision tolerance uniform thickness and then machined and drilled by Marand Engineering (Vic). Connector face plates and sides were drilled and machined by Enterprise Tooling (Vic) and Bellato Engineering (Vic) handled all assembly and on site installation at the plant which went very smoothly under Action Bearings supervision. The ballscrew was built by Thomson IBL (UK) and has performed reliably now for 2 years without problem.
This is a good example showing how retro engineering can provide cost effective solutions where a current application is having problems . Presentation of sound design combined with a skills base which produces quality output is an area where AB can see future opportunities to involve its own client base in solution as well as turnkey projects.