- AGR Automation was tasked with the development of an automated system to manufacture electrode guide wires for pacemakers that would offer comparable precision to a manual process but with a significantly higher throughput
- Allen-Bradley GuardLogix Programmable Automation Controller
- Allen-Bradley Kinetix Servo Solution
- Allen-Bradley PanelView HMI
- Extremely tight tolerances
- Excellent repeatability
- Integration of robot solution working with servo solution
- A SIL 3 to IEC 62061 safety system
- Small machine footprint
Automated fabrication cell matches human precision and delivers significantly higher yield
Rockwell Automation OEM Partner, AGR Automation, has recently developed a pacemaker electrode wire-guide fabrication machine for a customer that offers comparable precision to the manual process it replaces, but with a significantly higher throughput – thanks to the deployment of an Allen-Bradley® Kinetix® servo solution.
AGR Automation offers a complete in house mechanical, electrical and software design capability, including advanced robotics and industrial vision to develop automation and motion solutions designed to meet the increasing demands of optimised production.
Its services, which work to the highest standards through ISO9001 and GAMP, encompass the development of all manner of automated systems. These include high-speed linear, rotary and flexible conveyor assembly systems, vibratory bowls and vibratory tracks, cannula insertion systems, centrifugal feed systems, robotic assembly and handling systems, multi-lane feed systems, hoppers and elevators.
Pacemakers have revolutionised the lives of many people. Since their original development the technology inside them has significantly improved, in terms of size, power and capability. Their method of operation though has remained relatively unchanged and they still require the implantation of pacing leads via an artery in the groin or armpit.
During the implant process the pacing wires are fed to the heart and electrodes are put into the heart muscles. Once the electrodes have been established the guide wires are then withdrawn leaving just the pacing wires behind.
Like the pacemaker itself, these pacing wire assemblies have to be fabricated to extreme exacting standards and this precision manufacturing must also encompass the ancillary components that are used to implant the wires, even though they are eventually disposed of.
In many instances, such as this one, the wire assemblies are fabricated by hand in multiple stages and using multiple personnel. After final assembly the manual process continues with QA inspection by another group of operators. However, manual labour is not as fast as an automated solution and there is nowhere near the same levels of repeatability, even for what is essentially a highly repetitive operation.
There is also a lot of product differentiation. Wires can be different lengths and can have different forms on the end depending on the insertion method and location. They can also be straight or curved, with the curved wires using a sleeve to keep them straight, until the sleeve is retracted and the wire’s natural curve takes the implant around corners.
AGR Automation was asked by the customer to automate this whole process into one system, requiring accurate assembly of the units to the correct length (±0.5 mm), and handling all the product variations (plastic handles, aluminium handles, wire forms and different lengths) via a user-inputted recipe number.
According to Derek Beattie, Electrical Design Manager at AGR Automation: “Our new machine can assemble 33 different variants of guide wires, primarily straight ones, but with different ends, diameters, lengths and end forms.”
In operation the guide wire ‘blanks’ are fed into the machine six at a time on a pallet secured to a pneumatic gantry, which is indexed and mapped using laser sensor. A servo walking-beam conveyor is then used to transport pallets between machine stations. On the input side the plastic components – finger tab and inserts – are fed by bowl feeders before being picked and visually inspected by robots. Depending on pass/fail criteria these are then placed into the assembly position or rejected.
With an Allen-Bradley GuardLogix® programmable automation controller (PAC) at its heart, connected to the various stages using Allen-Bradley POINT Guard I/O™, the machine’s first operation is to cut the guide wire length. This operation is defined by the desired final product format and is selected via a ‘recipe’ on a 15” Allen-Bradley PanelView™ HMI. The length of the cut is defined and controlled using two Allen-Bradley Kinetix 350 servo drives and Allen-Bradley TLY servo motors, to accurately the position camera systems for precise length measurement and the type verification of wires.
The next station is the assembly station. As soon as machine detects a good product, robots preload the assembly stations. The machine has been designed in such a way that the overall cycle time is not affected by the robot’s traversing, as the robots are looking ahead to the next product. When the sixth wire has been processed the robot is already looking at the first product on the next pallet. There are no pauses.
A kink is put into each wire to match up with the type of insert required. The insert is then applied using an interference fit. This process is handled by two robots. The plastic inserts, which are the handle or hand grip of the device, comprise two plastic parts that latch together. These are loaded into a pneumatic rotary cylinder and the robots then feed these onto the kinked end of the 0.3 mm wire, with the kink locking the wire into the insert. There are two nests on the rotary cylinder, one is for building the other is for preloading ready for next assembly operation.
The next station is the test station, used for all batches. In the test station, the wire assemblies are gripped at each end and a displacement sensor measures how far the parts can move. This station also checks for all components being present. 15N destructive pull tests are also undertaken on the first product of every batch and then every 1,000 after that. In this test, a Kinetix servo motor is used to pull the wire against a fixed load cell. The final operation is the unload cycle, which is achieved using a choice of three servo-controlled belts – good, reject or QA.
AGR also defines the motion and control parameters for products that deploy an aluminium handle. These products are similar to the plastic-handled models, with eight or nine variants, but it only requires one robot to operate as the handles are single pieces.
Communication between the GuardLogix Programmable Automation Controller, the Kinetix 350 servo drives, the TLY servo motors and the POINT Guard I/O is via EtherNet/IP™ using a Stratix 5000™ managed switch.
One of the primary advantages of using this servo-based approach is the larger throughput, with minimum batch quantities in the thousands being manufactured far quicker than a manual process.
Repeatability and historic data capture are also enhanced as the process manufacturing recipe can be entered via the HMI. This data comprises all of the important information such as the batch number, the length the components required, etc. This can then all be logged for traceability purposes.
Beattie concludes: “It is a relatively simple machine in operation, but it has a lot of complexity. With two six-axis robots, four vision systems, six servos axes and safety devices controlled by the GuardLogix safety system, there is a lot going on and hence a lot to control. However, with the GuardLogix PAC, we can achieve extremely tight tolerances and excellent repeatability, which is vital for medical industry components.”
The inclusion of GuardLogix also allows the machine to have zoned control in a single programming environment with information-rich diagnostics – previously this would have required a separate safety controller, software and training and the information would have had to be programmed – this is not now required with significant savings in engineering effort. The machine’s footprint is also very small, meaning that is also has less of an impact on valuable factory real estate, which can be especially restrictive and at a very high premium in cleanroom environments.
The results mentioned above are specific to this customer's use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers.