UNISIG’s Approach to Automating Surgical Instrument Manufacturing

As surgical instrument manufacturers pursue greater throughput while facing increased labor costs, automating the medical instrument manufacturing process has become a necessity. However, integrating automation into the gundrilling process for drilling deep holes in extremely precise surgical instruments in lights-out operation is a major engineering challenge requiring more than simply pairing a robot with a deep-hole drilling machine.

The right machine, tools and process must all come together to create small holes with extreme precision in difficult-to-machine materials such as titanium and surgical stainless steel. More importantly, the entire system must flow from a unified concept where the whole is greater than the sum of its parts.

To meet these challenges, UNISIG developed its UNE6-2i-750-CR twin-spindle gundrilling machine. The UNE6-2i is capable of gundrilling hole diameters ranging from 0.8 – 6 mm in part lengths measuring up to 30 inches with depth-to-diameter ratios from 20:1 to more than 100:1. The machine has a maximum combined drilling speed of 28,000 rpm and a 3,000 psi (207) bar programmable flow-based coolant system with dedicated pumps for each spindle to ensure precise temperature control.

Automating hundreds of cycles of precision manufacturing, however, is not possible unless the overall operation is considered from the outset. Surgical instrument manufacturing is a sequential process: parts must be loaded into the machine in a particular way for specific operations that happen in a specific order.

Workpiece length, shape and configuration determine where it is gripped by the robot when loaded into a machine, moved from spindle to spindle for drilling, residual cutting fluid removed, and returned to the pallet. Where a part is gripped impacts where it is clamped for drilling to ensure accuracy. Every variable along the process chain must be considered and accounted for, and the calculus is detailed and complicated.

Then there are unique customer needs and requirements. The equipment and process must accommodate a variety of part families and hundreds of parts to increase runtime and efficiency. Operators must be able to change over part types and programming without calling in an automation specialist, and the entire process must be controlled from a central interface. Add to the mix that everything must be packaged in as small a footprint as possible, and the scope of the engineering challenge comes into focus.

UNISIG’s approach to solving these problems, however, results in targeted automation that enhances the existing benefits of gundrilling, ensuring a solid foundation for reliable process-wide automation.

At its core, the automated UNE6-2i is a purpose-built machine with automation embedded in its design, not added as an afterthought. Flexibility and adaptability are maximized by a harmonious, interdependent mechanical, software and operational planning scheme.

To meet size constraints, a 6-axis robot was embedded in the machine with a pallet system on the backside of the machine, allowing easy operator access from the front to setup the machine without compromising ergonomics. The configuration enables quick setup changes between prototype and proving operations and full production runs.

The robot automatically repositions the workpiece from the front of the first spindle into the rear of the second spindle without operator input. The process of drilling a part from both ends in a single-piece flow is unique to UNISIG. Workpieces with enlarged features on one side are loaded from the rear of the collet, solving a common problem in gundrilling medical surgical instruments with full automation.

Control of the UNE6-2i and a computer are consolidated into the Human Machine Interface (HMI), a menu-driven touch screen system for easy, intuitive operation. Training and operator engagement with the system is significantly reduced due to user-friendly UNISIG controller menus and prompts.

UNISIG’s comprehensive and integrated approach to automating medical part manufacturing is a vison that sets it apart in the industry. It’s more than drilling the impossible hole. It’s a commitment to understanding and to the research that drives continuous improvement and innovation for automated part production at its full potential.



Stress Relief For Your Rifle Barrels (and your operations)

Stress relieving, when it follows the button-style barrel rifling process, is a critical firearm manufacturing operation. Button rifling draws a tungsten-carbide cold-forming tool through a drilled and reamed barrel blank. The button compresses and moves the barrel wall material to create rifling grooves in the barrel bore without actually cutting the metal. As such, button rifling requires application of considerable force and induces stress in the barrel walls.

Stress relieving processes will vary based on many factors, but in general it involves heating a rifled barrel to a high constant temperature that is below the alloy steel barrel’s critical temperature (usually ~1300˚ F). (Higher temperatures change the composition/grain structure of the metal and are considered heat treating.)

In the stress relief process, the barrels are loaded into a vertical rack in an industrial furnace. After the furnace reaches about 200˚F, the furnace chamber atmosphere is replaced by nitrogen from a nitrogen gas generator. The temperature in the furnace is gradually raised to around 1050˚F and held there for an hour. After that, the furnace stops firing and the chamber temperature decreases slowly and steadily, still with a nitrogen gas atmosphere.

The entire stress-relieving cycle encompasses about 16 hours, and it is important that the cooling process occurs in the nitrogen atmosphere because rapid cooling can result in excessive humidity and condensation on the barrels, causing surface oxidation. When the barrels reach a safe handling temperature, they are removed from the furnace and treated with a rust inhibitor.

Two furnace types – sealed vacuum furnaces and non-sealed furnaces – are available for the stress relief process. A non-sealed furnace displaces air from the furnace chamber during purging and consumes a continuous flow of nitrogen while operating. A vacuum furnace, in contrast, draws the air out of the chamber and then purges it with nitrogen.

The vacuum sealed furnace conserves nitrogen because it doesn’t require continuous purging. The maintained steady-state environment of the sealed furnace enables better control of variables that affect barrel quality and cycle time, and maintenance of consistent temperature during stress relieving in a sealed furnace enables the barrels to be heated and cooled off faster.

A non-sealed furnace will typically cost from about $50,000 to $100,00, while a vacuum furnace may exceed $500,000. Either type of furnace requires a nitrogen source and other ancillary equipment, as well as barrel racks, a rust inhibitor dip tank and other ancillary equipment.

In most cases, it is preferable for a barrel maker to work with an established heat treating provider than to perform stress relieving in-house, especially when initially setting up the operation. Partnering with a heat-treating specialist that uses sealed vacuum furnaces for stress relieving will make expert advice and process guidance immediately available and provide access to high-capacity furnaces as a barrel maker’s markets expand. While stress relieving operations with an unsealed furnace may be a lower-cost option, expanding output and maintaining process consistency can pose problems.

A barrel’s finish will affect its performance as well as its looks. Before stress relieving it is important to remove oils left by prior machining operations. Temperatures of the stress relief process can bake any contaminants on to inner and outer surfaces of a barrel, as well as onto the furnace chamber. Stress relief process capacity is also a consideration, and care should be taken to not overload the furnace. Excessive mass can stall the recommended heat cycle.

The goal of stress relieving in barrel production is producing consistently high quality barrels in a reasonable amount of time with no rejects due to process inconsistencies. Barrel makers that want to deliver best in class products are well-served by seeking out and utilizing experienced, established heat-treating specialists to handle stress relief services in a reliable and economical way.



Counter Rotation Maximizes Deep Hole Concentricity

In a routine drilling operation on a milling machine or drill press, a drill’s cutting edges rotate against a stationary workpiece. The opposite is true in holemaking on a turning machine where a stationary drill advances into a rotating workpiece. Either of these drilling methods produce sufficient reliability and hole quality for a wide range of applications. However, other tactics are necessary to produce more exacting tolerances and larger depth-to-diameter ratios.

Drill and workpiece rotation has a major influence on a hole’s concentricity – a key measure of drilling accuracy. When the drill alone rotates in a horizontal setup common for deep hole drilling, accuracy will vary as gravity acts on the drilling tool. A rotating drill can produce sufficient concentricity in relatively shallow holes, but performance will suffer as holes become deeper and less forgiving tolerance wise.

On the other hand, because the direction of gravitational forces relative to the workpiece constantly changes when the drill is stationary and the workpiece rotates, that arrangement can produce holes approximately twice as concentric as the rotating drill approach. While shops can perform rotating-workpiece deep hole drilling on a turning machine, a dedicated deep hole drilling machine using what’s known as counter-rotation will net much better results.

Benefits of counter-rotation

A drilling setup that involves both the drill and workpiece rotating in opposite directions will balance out drilling forces, which are never static in a constant net direction. The balanced forces keep the drill from drifting for a much more concentric hole. With the right equipment and setup, counter-rotation is possible for smaller gundrilled holes as well as larger holes drilled with BTA tooling.

In counter-rotation testing, UNISIG drilled a ¼”-dia. hole in a 30″-long, ¾”-dia. OD, 4140HT steel workpiece. This 120:1 depth-to-diameter application is one typically found in the production of power transmission shafts or aerospace linkages.

Drill drift at the 30″ hole depth was measured via ultrasound. With a rotating drill and stationary workpiece, drill drift was 0.026″; a stationary drill and rotating workpiece exhibited 0.015″ drift; and when both the drill and the workpiece were rotating, drill drift was only 0.009″. It should be noted that results will vary due to many factors, including material, depth-to-diameter ratio and the specific tooling involved.

Dedicated deep hole drilling machines

Even with careful application of drill and workpiece counter-rotation techniques, typical machining centers – if equipped for counter rotation – usually do not have the alignment capabilities needed to consistently produce high-quality holes of 20:1 or greater depth-to-diameter ratio. Superior alignment is critical in maintaining concentricity.

In dedicated deep-hole drilling equipment, the machine base, rotating bearing groups and spindles as well as tool and workpiece supports are all designed with alignment as a first priority. Deep-hole drilling machines also emphasize control of other machining and environmental factors such as consistent temperature maintenance.

Some machines not originally engineered for counter-rotation operation can be retrofitted with a secondary counter-rotating group, but the alignment processes needed to make the arrangement work will be challenging and expensive. Additionally, a machine originally designed to employ counter-rotation will be manageable for nearly any operator. Dedicated deep hole drilling machines, for instance, include operator interfaces that provide detailed process information and maximize control over drilling parameters to enable accurate, efficient and repeatable production.

Basic application guidelines

Every deep-hole drilling application is essentially unique. However, general application guidance for counter-rotating operations includes allowing one-third of the total drilling speed to come from workpiece rotation and two-thirds from the drill. Operating parameters can then be adjusted to maximize drilling speeds and accuracy.

Such counter-rotation techniques provide a way to achieve accuracy and production requirements in deep-hole drilling and are especially effective when drilling holes of 40:1 depth to diameter ratios or more. Counter-rotation generates higher levels of concentricity that enable use of optimal feed rates while also extending tool life. The result is production of more parts per hour with fewer tool changes.



Make Better Molds – Mill Better, Drill Faster

Mold making isn’t easy. There are many intricate challenges that include: highly complex geometry with 2D and 3D features, managing a wide range of part sizes, and short lead times on small quantities and new designs with no room for error. Compounding these challenges is the pressure to keep up with the rapid pace of demand and technology.

But there’s a way to overcome those obstacles: Do better work with technology designed specifically for complex mold making.

Our USC-M series Milling and Drilling Centers allow you to drill faster and mill better with a single machine and fewer setups. These Milling and Drilling Centers meet the challenges of milling and gundrilling all types of metals with either a single universal combination spindle or dedicated milling and drilling spindles. Utilizing high performance spindles that provide exceptional rigidity and power transmission, these machines deliver high-torque milling capability for aggressive metal removal and shorter cycle times. Additionally, 5-axis positioning enables mold manufacturers to tackle complex geometries with exacting precision in a single setup.

Many manufacturers claim to provide milling and drilling in a single machine, but the truth is those hybrid machines neither mill nor drill well enough to make a significant difference in either operation. In effect, one process is an afterthought of the other. Our USC-M series, however, was designed from the beginning to be a single machine with superior milling and drilling performance and accuracy. State-of-the-art milling technology is embedded into a machine that has the power, thrust, speed and process monitoring competitors thought would be difficult to attain, or simply not possible.

In addition to superior quality and accuracy, the pay-off for single setup milling and drilling is efficiency and an improved bottom line. Mold makers cut delivery times to their customers with faster setups and production along with reduced overall labor costs. Once they move away from mold making operations with two machines, most of our customers find they can’t afford to manufacture without a USC-M-series Milling and Drilling Center.

The benefits of milling better and drilling faster with USC-M series machines do not stop at the spindle. There are intangible benefits as well. UNISIG USC-M series Milling and Drilling Centers allow mold manufacturers to approach their work differently and explore different approaches to mold making. With the entire manufacturing process streamlined, customers find their engineers and design teams enjoy more freedom and flexibility with the expanded capabilities. Finishing and assembly are faster because the design is more efficient, and manufacturers can do things effortlessly that were a struggle previously.

Ultimately, it’s about setting the bar high and keeping it there. UNISIG sets a standard looked up to by the competition. It’s a state-of-the-art mindset that takes mold finishing to a new level with a machine that allows you to mill better and drill faster.



Effective Medical Instrument Gundrilling

Most conventional machine tool OEMs can help medical manufacturers produce highly complex and precise components such as surgical implants and tools. However, only an experienced and capable gundrilling machine OEM with a deep understanding of the challenges of stringent medical part drilling requirements can supply a truly effective solution.

For today’s medical parts, UNISIG makes impossible holes possible with reliable, highly productive and automated gundrilling processes. Such solutions allow medical manufacturers to overcome the challenges of medical parts and meet demands for higher volumes and cost reductions, while they also improve part quality and ease the pressures of labor issues where there’s either not enough of it or it costs more.

Our combination of integrated solutions and technical expertise cures your medical gundrilling headaches and allows you to produce very difficult holes, especially when dealing with:

  • Small holes with extreme depth-to-diameter ratios and tight tolerances
  • Difficult materials such as stainless steel, Inconel® and titanium
  • Thin-walled parts
  • Irregular OD parts that require multi-step operations

Not just any gundrilling system provider can drill the impossible hole. It takes a commitment to research, continuous improvement and collaboration. In fact, having an OEM to collaborate with you to solve complex problems can give you the confidence to incorporate gundrilling into your medical part production and use it to its full potential.

Once up and running, your in-house gundrilling capabilities will eliminate the hassles and extended lead times associated with outsourcing this work. Plus, when paired with Swiss-style turning machine cells often used in medical part production, in-house gundrilling will help improve throughput.

Overcoming the challenges of gundrilling medical parts is only half the battle. The other half requires continuous, reliable precision for thousands upon thousands of parts – and for the entire life of your gundrilling machine. At UNISIG, we consistently achieve those tight tolerances with our UNE6 series machines engineered with the utmost precision in mind, our specialized workholding for medical instruments and intelligent machine controls.

Well-targeted automation solutions can further enhance the benefits of gundrilling, especially in terms of process consistency and stability while also increasing the output of existing workforces. For many medical shops, automation is a game changer – and can provide the means for survival against the competition as well as a sustainable path to growth and profitability.

UNISIG’s automation-ready gundrilling machine design ensures a solid foundation for reliable, process-wide automation. Additionally, flexible workholding configurations such as our lantern chuck and other peripheral components make robotic integration even easier for medical gundrilling applications.

While automation helps ease labor issues, today’s medical part manufacturers still face numerous challenges, from stiff competition and constantly increasing production demands to cost control. However, drilling deep holes in tough medical components is one industry challenge that is forever improved thanks to UNISIG, a company that makes drilling the impossible holes possible.