Another Success Story

Stryker Reduces Errors with Predator Desktop

A Nice, Tidy Operation

Logo of PredatorNowadays, joint replacements are expected to meet greater demands and be in service longer than ever before. This means ever-increasing demand on design and production, ensuring maximum joint mobility; whilst minimising wear, through the use of materials such as ceramics, titanium and polyethylene.

Also, to meet the ever-widening range of issues, preferences, and patient demands, surgeons must have an equally wide range of choices and options so that the right joint is readily available whatever size the patient.

All this puts pressure on companies like Stryker Corporation, which specializes in manufacturing medical equipment. It has to deal with numerous design variations and batch changeovers daily, whilst maintaining traceability and effective production within the bounds of strict regulation.

Not easy by anyone’s standards; there are many opportunities for operator error, especially when changing one batch of components for another – which may look exactly the same, but embrace dimensional changes too small for most to see. Such errors prompted senior information technology analyst Walter Switzer of Stryker’s facility in Cork to seek a solution.

He found it in a bespoke DNC installation developed in conjunction with Predator Software Europe. The first two parts of the proposed three-part installation have been a huge success: the possibility of downloading the wrong file has been obliterated, and productivity significantly improved. In fact, the system now manages everything associated with making products on the machines and is currently being implemented across the American plants as a result.

Making Joints Better

The company, responsible for 25% of the world’s supply of inserts, wanted to be able to track and load CNC programs together with custom variables to individual CNC machines using Predator software and Bar Code Readers (BCRs). The purpose was to eliminate operator error in selecting and loading NC Code. The expandable solution was broken into two levels and implemented in two cells – the ‘Plastics cell’ and the ‘Titanium cell’.

Level one provided basic communications between machine tool and NC file database, using standard Predator hardware and software. This includes the complete and efficient sending of programs to and receiving of programs from CNC controls.

Level two added further functionality with the inclusion of standard and non-standard Predator objects – this facilitates the calling-up of CNC programs via bar-codes printed on the operators work instructions, and where applicable, allows subroutines and variables to be extracted from the given catalogue number. The use of BCRs to interrogate the part database and select programs thus eliminates the possibility of the operator calling incorrect programs and automatically engraves batch numbers on the components, taking care of traceability.

Safe And Secure

Predator configured two ‘live’ central servers in an air-conditioned Halon fire-protected secure room. One server addresses the Plastics cell while the other addresses the Titanium cell. Both could have been configured to work with one server but Stryker chose to have separate, independent systems. Should either fail, the entire system is backed up by the ‘host standby’ system that is always ready to go. This is ‘mission critical’ so if this goes down, the cell goes down.

There is also some backup hardware just in case – e.g. Predator ‘Flex2’ hubs and cabling. Each server is linked to a Flex2 hub via triple shielded cable capable of withstanding high magnetic fields and generally harsh environments.

From the hub there are either 8 or 16 outputs (16 in Stryker’s case), connecting to each of the BCRs situated along side each CNC machine making up the cell. The outputs from the BCRs are connected to the associated machine controllers via Predator’s ‘Grizzly adapters’, ensuring easy maintenance. Once wired up the BCRs are configured to send info back to the server. The system is expandable up to 256 machines per cell and unlimited cells.

Ease Of Use

In use the operator scans the catalogue part number; the operation sequence, which varies from job to job; the job lot ID for traceability; the quantity required; and finally his/her operator ID, again for traceability reasons. All the variables needed for this procedure are found on the job sheet issued to each operator and it’s as simple as selecting the code for ‘number – 12’ in the case of quantity 12.

From these, the system is able to load the specific job data, NC files, sub-routines and offsets into the controller. Knee cell manager Evan O’Mahony explains how the subroutines work. “We use the same program for a number of knee joint components – variations are dealt with by loading a small ‘7993’ program which then populates the main program with the various subroutines.”

At the same time the programs are loaded into the controller, an inspection guide sheet is generated and printed at a nearby PC for use by the operator. This includes drawings, dimensions, and all inspection parameters.

Subsequent ops requiring bar code scanning don’t require a new inspection guide sheet. Every scan made by the operator is recorded so if any operator tried to modify something he/she shouldn’t touch, it would be picked up at the job order/inspection point – deviations are recorded on the job sheet following final inspection. Any incorrectly input sequence is identified immediately and reported at the machine’s controller, so this really is a robust system.

It does not even require prove outs – all this has been taken care of before the code is even finalized on the server. Walter Switzer confirms its reliability, stating that Predator’s system was “the only system on site that came in at 100% reliable” when he did his stats.

Support team member Noel Kirby adds: “Previously programs were held in the machine tool controller and called up by the operator. If something were changed on the CNC, it would not necessarily get saved.” It’s now the responsibility of the support team member to ensure that qualified changes are made permanent at the server. Stem cell manager, Mathew Colley, points out that another advantage of the new system is that only one program is held on the controller at a time so there is no chance of running the wrong program whatsoever.

Walter Switzer says: “Apart from being reliable and robust, the Predator system has reduced set up time from around two hours to just 30 seconds in most cases, a highly significant point when you consider the nature of the work and the sheer number of batch changes required. At the moment, any edits needed are made on the source NC file; what we would like is to be able to control the editing so that it’s also traceable – by using Predator’s NC Code Editor, we should be able to do this in the future.”

Switzer concludes: “Phase three will include integrating the system into a Local Area Network. We’re working very well in tandem with the other companies in the group – when we move forward, all the companies move forward.”

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