In order to stay competitive in today’s medical device marketplace, it is imperative that companies continually invest in the latest technologies to ensure that they produce the highest quality metal tubing products, while also reducing costs. To meet these demands, full-service contract manufacturing operations must also be vertically integrated to handle complex medical device tubing projects.
For example, most handheld surgical instruments incorporate a formed metal tube as the structural shaft. This metal shaft lends rigidity and serves as a conduit for an actuating rod or wires between the handle and the end effectors of the device. These are often high-volume, single-use disposable instruments. To reduce tube manufacturing costs on such parts requires sophisticated equipment with laser-cutting technology, coupled with efficient production processes and automated work cells.
Two Precision Technologies in One Advanced Machine
Advanced machining equipment, such as a Citizen L2000 Swiss style CNC machining center with an integrated 400 W laser cutter, for example, is essential for addressing the requirements of today’s complex medical tubing. This system combines two technologies: Swiss-turn machining and laser cutting. The combination of a Swiss-style 7-axis CNC lathe and a fiber laser opens up a whole new world of possibilities in flexible manufacturing applications.
This innovative system is particularly useful for fabricated tube production. It can laser cut features (such as slots or holes) and machine features (such as differing outside diameters) simultaneously, reducing setup time, secondary processing, and handling costs. Swiss-turn machining can hold extremely tight tolerances, which is great for components made from either thick- or thin-walled tubes.
Combining both functions in a single unit allows for greater flexibility than separate systems. Design engineers easily recognize that this CNC/laser combination requires only a simple programming change, instead of employing several machines that require costly tooling and setup conversions.
Because of the increasing complexity of tubing, tubing production has gravitated from traditional metal stamping in power presses to CNC equipment and laser cutting machines over the past few years. To create features in tubing, traditional metal stamping might involve a rolled tube technology approach. Using this method, coil stock is fed into a 220-tn stamping press, and the piercings and slots are stamped through by the stamping tool punches — in the early progression in the flat blank stage. As the material is fed through the stamping die, it is rolled up into a tube during the remaining few progressions in the tool. It is then butt-fit together with a seam or is passed onto another machine for the seam to be welded. This process requires costly tooling and so it is now reserved for only the highest volume applications.
The majority of tubing projects, however, can benefit from the new CNC lathe/laser-cutting equipment. Unlike traditional metal stamping, the new equipment uses long-length, drawn metal tubing with automatic feeding, cut-off, and part ejection. Not only can features such as holes and slots be fabricated here, but any machining, such as grooves or ODs, can take place simultaneously. The inherent reduction in setup and cycle times results in significant cost savings.
Robots and Automation
The features needed for medical device tubing are often detailed and thus highly labor intensive. For such tubing components, it is essential that OEMs look for a manufacturer that uses flexible laser cutting systems. Automated work cells designed to cut features and holes into stainless steel tubing while inspecting in-line can improve quality and reduce overall manufacturing costs.
Such innovative systems incorporate automated power checks, laser crosshair alignment, and vision calibration. A complete work cell might feature a robotic arm sandwiched between two identical 4-axis laser cutters. When the system is running, the robot simultaneously loads and unloads parts, alternating between the two laser-cutting machines.
At MICRO, for example, a system is in place that requires an operator only for placing two tray-like totes (with unprocessed tubes) in front of the robotic arm — one tote for each laser-cutting machine. After completing that simple task, the operator can walk away and tend to other machines on the shop floor — the robot does the rest. The system is designed to run unattended for approximately five hours. Thus, an operator only has to load the system once or twice during a shift.
The unique feature of a setup that integrates two laser-cutting machines (programmed identically) is that the two machines can cut all the features of the tube and inspect them in the process. An intricate vision system incorporated into each machine, with two cameras in each, inspects the features as they are being cut and relays statistical process control information to a monitor and computer. If a hole or slot is out of specification, the robotic arm automatically drops the tube into a reject bin. And, of course, the good parts that meet all specifications are dropped into an accepted bin.
It is quite mesmerizing to watch the robotic arm pick and place the parts into position in each machine as the laser gets set to begin cutting on the leading end of the tube. An advantage of this system is that it does not require orientation of preformed tubes when they loaded, because the two cameras work in unison to ensure orientation of the tube prior to the start of the cutting process. The two cameras are then utilized post-cutting to inspect critical features.
By incorporating a robotic arm with two laser-cutting machines, the system virtually takes operator labor — including handling, processing, and inspection — out of the process. Removing these manual processes translates directly into reduced manufacturing costs.
Automated Work Cells
Free-standing automated work cells for pad printing and inspection are another advancement that has reduced the cost of manufacturing complex medical tubing products. By pad printing a part name on two sides of the tube and simultaneously inspecting the part in the process, this methodology combines several steps, thus further reducing labor costs. It removes the excessive handling by operators individually loading and unloading tubes and then moving the racks of parts between machines and departments.
A sophisticated vision system is incorporated into the work cell system, with cameras at several locations in the pad printing process — for in-process inspection and for final inspection. These cameras also serve to eliminate the need to orient formed tubes entering the work cell.
The part-loading area is positioned at the back side of the work cell. Three tube-loading racks are stationed there for the robotic arm to pick up the tubes to be processed. The system is designed to run unattended for approximately four hours.
As each individual tube is being picked out of the rack by the robot, a camera with sensors verifies the length of the tube. It also checks and adjusts the orientation of the tube as the robotic arm loads the tube into the pad printing unit. The printer then places the company’s part name on two opposite sides of the tube. After printing, the robot hands the tube to another vision inspection unit with two cameras. One camera checks the location and print quality of the two imprints. The other camera checks critical formed features on the tube. At this point in the process, a tube can be rejected for printing issues and placed in a reject bin. If the printing on the part is good, the tube passes through a heat unit, which cures the ink permanently.
Finally, the robotic arm places the tube into an inspection station to check for straightness. If the tube passes this last inspection criterion, the robotic arm automatically unloads the tube onto a moving conveyor belt. The finished product is then loaded into totes at the end of the belt — ready for shipment to the customer.
Staying competitive in today’s medical device marketplace means that companies must find ways to reduce costs and create efficiencies, while also producing high-quality devices and parts, including metal tubing components. To do this, manufacturing operations must be vertically integrated, with robots and automated work cells in place.
This article was written by Steve Santoro, Executive Vice President for MICRO, Somerset, NJ. For more information, visit here.