For deep-hole drilling, part-handling might be the most visible automation element, but it’s not necessarily the most impactful. Often, it’s internal process automation that yields the most significant results even with a manually loaded drilling machine.


Deep-Hole Drilling Automation Is More Than Part Load/Unload


For deep-hole drilling, part-handling might be the most visible automation element, but it’s not necessarily the most impactful. Often, it’s internal process automation that yields the most significant results even with a manually loaded drilling machine.

When it comes to automating deep-hole drilling, there are challenges unique to the process itself. These include fixturing complexities — where maintaining alignment requires elements such as guide bushings and tool supports not present in a conventional lathe or milling machine — and part attributes such as length and weight.

Long parts mean a long drilling cycle time, and maintaining production rates often requires multi-spindle, deep-hole drilling systems. Unfortunately, stopping a two- or four-spindle machine means two or four spindles sit idle until the parts are loaded and unloaded. So, in these instances, the more parts in the machine at one time, the more automation can actually inhibit cycle time while the machine is running.

Solving this problem in multi-spindle machines requires internal automation to achieve the objectives of lean manufacturing and one-piece flow. In-machine loaders singulate processes so that even within a small four-piece batch you maintain one-piece flow. The operator or automation device puts in a part and takes a part out, and the machine does a bit of maneuvering inside to sequence those four parts in such a way as to minimize spindle downtime while maintaining upstream and downstream processes for one-piece flow. For instance, parts could be loaded onto a smart conveyor, indexed, and lifted into chucks for the drilling cycle before robotic unloading on the out-feed side so that there are no bottlenecks to a steady production flow.

Tool life management is another form of internal automation. Getting feedback to the machine enables the deep-hole drilling process to adapt or halt, if necessary, before tools and parts are damaged.

Tool life management is built into a machine’s control, and the machine senses torque thrust and coolant. Chip condition is usually the first indicator of wear, which would otherwise require an operator present to detect, so the machine actually monitors the process and can predict tools starting to wear and identify when they need to be changed. A tool life management system also can count distances drilled and the number of cycles, then prompt  a tool change at the appropriate time.

That kind of in-machine automation smooths the path for external automation. As the process builds, highly standardized options for robot-ready machines such as an automatic door, workpiece-present sensors and programmable workpiece fixturing makes it easier to add a robot at a later date. These robot-ready machines also create efficiencies before they’re fully automated. Even with manual loading, the automatic doors and programmable clamping make the process more efficient.

In UNISIG’s experience, an embedded reamer tool changer enables manufacturers to manage significant throughput increases, even with an operator. With this technology, operators can maintain the pace of production loading the machine, while eliminating the task of inserting reaming tools for each cycle. This allows the operator to redirect efforts towards tasks such as additional quality checks and off-machine setups.

Across every industry, manufacturers are working to meet growing customer demand in a globally competitive market.


Deep-Hole Drilling and Automation Make for Productive Work Cells

Across every industry, manufacturers are working to meet growing customer demand in a globally competitive market.

Despite a widening skills gap, by organizing advanced technology into highly optimized work cells, manufacturers are maximizing productivity through automation.

Specialized equipment, like a deep-hole drilling system, often is challenging to integrate, which quickly can create production schedule bottlenecks. To eliminate the risk, shops that perform deep-hole drilling should seek out OEMs that understand the needs of high-production manufacturers and have the capabilities to bring technology into the factories and work cells of the future.

Deep-hole drilling systems, which can produce holes that exceed a 20-1 depth-to-diameter ratio, are a unique class of manufacturing equipment because of the focused tasks they conduct. An increasing number of machining centers boast deep-hole drilling capabilities, but these machines simply cannot operate at needed speeds, particularly for parts that require exceptionally high accuracy. Manufacturers that must perform deep-hole drilling capable of rapid production and high throughput should instead select machines designed for the task.

Automating Holemaking

These shops increasingly opt for deep-hole drilling systems that also work with automation. In a typical deep-hole drilling work cell configuration, such as one for producing rifle receivers or automotive shafts, the equipment can use automation to time its cycle completion to mesh with other production processes. For straightforward automation, conveyors and pick-and-place robots move and position parts for deep-hole drilling with exacting repeatability and accuracy while automatic toolchangers, doors and inspection stations keep parts moving swiftly into, out of and around the cell.

Because deep-hole drilling tends to apply to long, cylindrically shaped parts, workpiece configuration eases or complicates some aspects of automating load-in and load-out cycles tied to drilling operations. Workholding axes, for example, can provide automatic part gripping with pneumatic or hydraulic chucks operated through advanced controls for deep-hole drilling systems. In this configuration, machines can pick up a part, drill it and set it back down on a conveyor or part collection area. In deep-hole drilling systems themselves, specialized designs also offer automatic chucking, while robot-tending systems can add further flexibility with end-of-arm tooling, workholding and measuring systems.

As the automation configuration grows more complicated, however, manufacturers require an OEM that can act as a collaborative partner to find available solutions or engineer individualized products for unique applications or production lines. Shops that depend on deep-hole drilling as part of a high-production environment should seek a partner that has a demonstrated record of working directly with manufacturers to modernize processes and create robust automated work cells.

Gundrilling Application

UNISIG, for instance, worked with a manufacturer of rifle barrel receivers to help it accommodate growing demand and relieve production bottlenecks. The manufacturer’s older gundrilling machines were replaced by a multiple-spindle machine, the UNI25HD. It had the power and controls necessary to apply indexable gundrilling tools, significantly improving feed rates.

To enable fast one-piece-flow manufacturing, UNISIG integrated the system via automation for in-feed, pick-and-place, conveyor loading and automatic clamping, which fed two lathes that turned the parts. The result was an effective work cell that produced more than 100 parts an hour, a dramatic financial and process improvement.

The viability of automated deep-hole drilling production can depend on tool life and part length. At extreme depths, for example, some parts require more than one set of inserts to produce a completed hole, and the high level of hardness of some workpiece materials causes rapid tool wear. To overcome this challenge, UNISIG programs its machines to detect wear and predict when a tool will reach its breaking point, allowing operators to prevent a failure that could stop the line.

For further process efficiency, deep-hole drilling machines should have either a CNC or programmable logic controller. Both can integrate with other control systems and interface with a controller in the work cell. Systems such as a fully automated barrel cell are capable of unmanned, lights-out production with efficient programming.

Deep-hole drilling equipment’s application-specific configurations suit the production of parts that necessitate techniques and processes that go beyond the easy capabilities of general-purpose equipment. In years past, many manufacturers thought of this kind of specialized equipment as old-fashioned and a drag on production. But with the right equipment—and a partner with the right engineering and applications expertise—deep-hole drilling in work cells can keep up with the productive factory environment that manufacturers need to succeed.

The future of the auto industry is interesting but uncertain. No one knows how quickly electric vehicles are going to replace gasoline- and diesel-powered vehicles, how completely it will happen


Deep Hole Drilling Aids Change in Auto Manufacturing

The future of the auto industry is interesting but uncertain. No one knows how quickly electric vehicles are going to replace gasoline- and diesel-powered vehicles, how completely it will happen, and when it will occur in passenger cars as opposed to SUVs and heavy trucks. However, we do know that fuel economy standards continue to progress and drive vehicle design toward smaller displacement, higher-technology engines.

Off-center automated drilling machineAs a result, technology that was developed years ago for high-performance vehicles is now becoming mainstream. For example, sodium filled valves, which formerly were used in only extremely high-performance engines to manage heat in the valve train, are becoming more common. The same goes with hollow camshafts, which reduce energy-consuming rotational inertia and provide opportunities for engine management.

Within vehicle drivetrains, today’s automatic transmissions now have as many as eight or even 10 speeds instead of five or six. This wide selection of gear ratios enables smaller displacement engines to provide better fuel economy and deliver higher performance.

These kinds of technological upgrades for higher performance and economy are not new, but previously were considered too costly for general use. Now, advanced manufacturing and materials technology make common application of these upgrades viable.

Enabling Cost-Effective Production

Deep hole drilling is one advanced manufacturing technology that allows for the cost-effective production of key features of those performance-boosting parts. Sodium-filled valves, for example, have holes drilled the length of the valve stem in which liquid sodium circulates and draws heat from the valve head. Precise deep hole drilling methods enable hollow and more energy-efficient camshafts to be manufactured. Complex multi-speed transmissions feature shafts with multiple off-center holes of varying depths for lubrication or hydraulic sequencing. The holes in the shafts are too deep to produce effectively on machining centers, so deep hole drilling machines are critical in those instances.

Balancing Volume Output with Flexibility

Other manufacturing challenges in automotive production can also benefit from today’s advanced machine tool technology. For decades, the automotive industry focused nearly exclusively on volume production. The emphasis was on making as many parts at the lowest cost possible. Flexibility was merely a minor consideration.

Market changes have made balancing volume output with flexibility a major issue. If volume drops on a vehicle program, there remains a need to produce the vehicle cost-effectively. Expanded product mixes created to meet customer desires for different powertrains and other options demand high efficiency regardless of volume.

Consequently, flexibility and spindle utilization have become the main drivers of deep hole drilling machine design. Instead of having a gang of four spindles pounding out parts, a two-spindle machine with a rotary table and X-Y positioning system can provide extremely high spindle utilization along with flexibility. Technology such as automated setup through servo motion to reduce changeover time is also considered in the early concept development of the machines. These systems allow manufacturers to plan and implement small, agile cells to replace large, old-school, high-volume systems.

Benefits of Machine and Fixture Design

A recent customer experienced significant benefits with UNISIG’s machine and fixture design. Previously, the customer was processing a challenging family of parts on a system that involved nearly 20 fixtures. Each part required multiple holes with varying depths and diameters. A bulky, dedicated machine created an unnecessary expense and bottleneck in their production.
UNISIG provided a machine that allowed the company to manage deep hole drilling of these parts with just two pallet-changeout type fixtures, and requiring only the selection of a new part program. By eliminating fixturing, setup, and programming time, the company experiences significant savings every time the machine runs.

Lighter Yet Stronger

In addition to production benefits, a future opportunity for automotive manufacturers that involves deep hole drilling technology is in making vehicle parts lighter yet still maintaining or even increasing their stiffness and strength. Deep hole drilling can produce thin-wall parts such as axles and power transmission shafts, for example, that provide significantly higher mechanical integrity and better improved energy economy.

For instance, drilling a 20-mm axial hole through a heavy 30-mm diameter shaft makes the shaft much lighter while maintaining its stiffness. This lighter shaft has less rotational inertia which, in turn, reduces energy consumption. Designers continually search for such small gains in efficiency and will seek ways to enhance lightness and stiffness throughout the automobile.

As machine tool manufacturers, our job is to listen to our customers, understand what they need, and develop those needs into a solution that is viable from a cost and reliability standpoint. With ongoing advancements in engineering technology, machine manufacturing, and service, what might have been very expensive to do only three or four years ago is now viable. Concepts that once seemed a bit far-fetched are now quite common.

Because of that, we design our machines to provide both flexibility and utilization that will enable our customers to successfully face the expected—but not yet fully known—major changes in the automotive manufacturing industry.

UNISIG's production cell integrates our UNE 2-spindle gundrilling machine and UNR 2-spindle reaming machine with robotic automation. The cell leads into our R-2A rifling machine for steady, repeatable rifle barrel blank manufacturing at high production.


Rifle Barrel Manufacturing Cell with Automation | Video

UNISIG’s production cell integrates our UNE 2-spindle gundrilling machine and UNR 2-spindle reaming machine with robotic automation. The cell leads into our R-2A rifling machine for steady, repeatable rifle barrel blank manufacturing at high production.

The cell includes automated tool handling and machine guarding. Effortless production is furthered with racking systems, inspection, and oil blowoff capabilities.

Continue reading“Rifle Barrel Manufacturing Cell with Automation | Video”

Picture yourself facing knee surgery, under the care of a skilled orthopedic surgeon. Precision instruments, state-of-the-art monitoring equipment, and decades of experience


How to Drill Straighter: Concentricity in Deep Hole Drilling

Picture yourself facing knee surgery, under the care of a skilled orthopedic surgeon. Precision instruments, state-of-the-art monitoring equipment, and decades of experience are on hand, as they conduct a procedure that will ideally lead to more days on the court. The surgical team works patiently and carefully towards a successful outcome, relying on tools to guide their movements with exact precision, placing instruments exactly where they need to be in the body, and not even a half millimeter off. For deep holes in components to be accurate – including surgical tooling – they need to uphold tight concentricity tolerances, and in gundrilling, this happens best with counter-rotation. For a manufacturer, this is vitally important. For an end user, or in this case a patient facing surgery, it can make all the difference.

These precision parts are one of several applications that have deep holes, where concentricity is critical to the function of the part. Concentricity tolerances are achieved when the hole follows the desired axis of the part, eliminating drift from the point of entrance to the exit. In a round part with on-center drilling, this is easily illustrated; some applications may include deep holes which are off-center, or in non-round parts, but still have tight concentricity requirements.

Low concentricity in some applications can result in parts with weak sidewalls, mismatched holes, or even scrapped parts. In other cases, manufacturers may decline production of these components, because of perceived impossibility or unproductiveness. With the addition of a counter-rotating process on deep hole drilling equipment, critical concentricity tolerances can become both achievable and economical.

How Counter-Rotation Improves Concentricity

Drilling a deep hole is commonly achieved by rotating the cutting surface of a tool against the metal of a workpiece with two opposing spindles in a horizontal setup. Typically, this consists of a stationary workpiece and rotating tool, but can also be configured with a rotating workpiece and stationary tool, or a third option, with a counter-rotating tool and workpiece.

Common machining centers use a rotating cutting tool, such as a mill, and a fixtured, stationary workpiece. A lathe, alternatively, rotates a workpiece and cuts with a stationary tool. Much of the time, setups such as these are enough to achieve the goals and tolerances of a majority metal cutting tasks, but are limited when it comes to more extreme tolerances and depth-to-diameter ratios.

A tool-rotate configuration is the least accurate when it comes to concentricity. In this setup, gravity is believed to act on the base and shank of the tool, not the drilling tip, and along with the rotation of the tool. Because of the relative position of the tool and gravity to the workpiece, this configuration produces the poorest results. This tool-rotate process is common for shallower holes on a machining center, but as holes become deeper, and tolerances become tighter, this no longer works as a solution.

Workpiece-rotate-only setups produce holes that are approximately twice as concentric as tool-rotate. A rotating workpiece changes the relative force of gravity compared to the workpiece position, negating some of the effects on the finished hole. A rotating workpiece can be done on a lathe with limited capability, but is ideally performed on a dedicated deep hole drilling machine.

deep hole drilling diagramCounter rotating tool and workpiece improve significantly upon both of these, as the forces are never static – changing relative gravity and orientation will provide drilling conditions without a single constant net direction that the tool will follow. In this setup, the tool is restricted from drifting, and will produce a much more concentric finished hole.

Counter-rotation is easily achievable with the right equipment and setup, whether it is for smaller gundrilled holes, or larger, longer BTA drilled components.

Deep holes are typically classified as anything with a depth-to-diameter (D:d) ratio of approximately 10:1 or greater, and can even reach extreme ratios of 100:1. As deep holes approach ratios of 20:1 or greater, drilling with specialty tooling on dedicated equipment is optimal. Modern deep hole drilling machines are designed to maximize the potential of tools such as gundrill and BTA processes.

deep hole diagram

The Data

To represent the impact of counter rotation, a test was performed on a 4140HT workpiece, 30 inches in length, ¾” outer diameter and a ¼” drilled hole. The depth to diameter (D:d) of this test is 120:1. This part is easily representative of a power transmission shaft or aerospace linkage.

Drilling these test workpieces produced the following results (measured using ultrasound):

  • Rotating Tool, Stationary Work: 0.026 inch drift at 30 inches of drill length
  • Stationary Tool, Rotating Work: 0.015 inch drift at 30 inches of drill length
  • Rotating Tool, Counter Rotate Work: 0.009 inch drift at 30 inches of drill length
    *results may vary based on material, depth-diameter ratio, tooling, etc.

Drilling holes with a 40:1 or less depth-diameter ratio can be done with limited drift using standard drilling practices. Beyond 40:1, counter-rotation really begins to deliver benefits with minimal drift.

Total Drift Comparison, Drilling Methods

  • Rotating Tool - Stationary Workpiece
  • Stationary Tool - Rotating Workpiece
  • Counter-Rotating Tool and Workpiece

Getting Started with Counter-Rotating Deep Hole Drilling

Typical machining centers are often not capable of deep holes greater than a 20:1 D:d ratio, and are not configured for counter-rotation. Rather, dedicated deep hole drilling machines are a superior consideration because they are designed specifically to manage accurate counter-rotation in gundrilling and BTA processes.

Deep hole drilling machines that enable successful counter-rotation include the right components, machined and assembled to maintain superior alignment. These range from the machine base, to rotating bearing groups and spindles, to tool and workpiece support – all of which uphold alignment and work as a system. This allows the machine to maintain accuracy while moving, and hold concentricity tolerances throughout the depth of the hole.

rotating deep hole drilling workpieceFor deep hole machine builders, alignment considerations begin with the machine base. Each component is designed with alignment as a priority,as well as machining and environmental factors like temperature and gravity. Counter rotation may be possible on machines retrofitted with a second rotating group, but will often need to undergo an alignment improvement process which creates additional challenges. Equipment designed with this purpose will have the right combination of benefits to make concentricity tolerances manageable for nearly any operator.

On a counter-rotating drilling machine, a good operator interface will provide a full picture of process information, as well as allow control over process parameters, for fine-tuning and process repetition. Manufacturers can optimize their counter rotation application, and proceed into highly accurate and efficient production.

A general starting point for counter rotation is to allow one third of the total speed to come from the workpiece, and two thirds of the speed to come from the tool. This is a typically recommended starting point for counter-rotating drilling with confidence. Operators can adjust for their specific application, and work with industry partners for recommended parameters to meet deep hole drilling goals.

Productivity Considerations

The addition of counter-rotation in a deep hole drilling process gives operators an additional factor to optimize for both specification and production requirements. The ability to hold improved concentricity tolerances with counter-rotation allows feeds to be run at optimal rates, as well as extends tool life. Manufacturers can reliably produce more parts per hour, with fewer tool changes and improved tool consumption.

For applications where concentricity is indeed critical, the productivity benefits are significant, and easily justify the added capability. Counter-rotation consistently produces a more concentric drilled hole, typically with higher surface cutting speeds, offering clear benefits to manufacturers in both accuracy and efficiency.

Manufacturers can increase capability, improve hole tolerances, and optimize productivity, ultimately cutting costs and providing a competitive manufacturing advantage. With the right resources, drilling deep holes with extreme concentricity is economical, repeatable, and commercially viable.