For several years now, manufacturers and machine shops have lamented the shortage of skilled employees. The general opinion from business leaders is that this trend is only going to continue.
One of the surest ways to overcome these challenges is by automating machining processes. Automating can seem like a daunting task to those who have not been exposed to automated machining processes, but it’s much simpler than it appears. Knowing where to start and having a basic roadmap is usually all it takes for a creative machinist or engineer to begin automating.
It is important to remember that there are degrees of automation from very advanced to very simple, but the goal is always the same — to reduce human intervention.
For shops that have never automated machining processes the best place to start is with turning operations, which are less complex and require fewer inputs than most milling operations. Turning operations will usually have fewer tools, a single work offset and CNC turning centers usually come from the factory with the necessary options.
If you have a machine tool with a control that has been manufactured in the last decade there are only a few things that you need to do to begin automating your turning processes.
Cost-effective automation
Automating the turning process requires having a reliable method of delivering stock to the spindle. It is common to see a turning center feeding a piece of bar through the spindle and cutting off the finished part. This is commonly referred to as “bar work,” which is the most common way to automate a turning process. Bar feeders are used to feed the bar stock through the spindle so the lathe can run in a continuous loop. Bar feeders are relatively inexpensive and very flexible, and that makes them a good investment for the shop that wants to automate.
In lieu of a bar feeder, a shop can use a bar puller. They are simple devices that mount in the turret and grasp the stock while the turret pulls the stock forward for the next part. It’s a poor man’s bar feeder. Both methods are effective and easy ways to introduce automation to a shop.
Doing bar work will require a cut-off operation in the turning process. A parts catcher for the machine is a valuable option to add for this kind of work. The catcher is actuated when it’s time to cut the part off, and, once complete, the part is ejected outside of the machine. While not absolutely necessary, a parts catcher is a clean and safe way to get finished parts out of the machine.
When bar work is not possible, then the workpiece has to be loaded another way. This is where robots and gantry loaders are utilized. Machines with robots and gantries are complex and not very flexible. They are also expensive and the integration of the loading device and the turning process can be complex. Therefore, robots and gantries may be out of reach for some shops, forcing them to load parts manually.
Loading parts manually does not qualify as “fully automated,” but may be necessary for a shop that is implementing the steps to reach full automation. Implementing some of the tools mentioned below will lay the foundation for implementing advanced part loading later.
Tool monitoring
Automating a turning process is going to require some kind of tool life monitoring. It is critical that the machine can be signaled to stop when a tool reaches the end of its life. Breaking a tool while running unattended can be catastrophic.
Tool monitoring in the most basic form utilizes timers or part counts to signal the machine to cease operation when the allowable limits have been reached. More complex processes will utilize tool probes to measure the tool and monitor wear. The most sophisticated machines will monitor power consumption to detect worn tools. While complex tool monitoring systems have many benefits, the onboard timers and part counters are sufficient to create a stable automated process.
Have the next tool ready on the turret
Not only is it necessary to employ some sort of tool life monitoring, it is important to “tool-up” the machine in a manner that promotes the goal of reduced intervention. Once a tool has timed out, having a second or third just like it in the turret allows the tool management system to retrieve the redundant tools so the machine doesn’t stop.
The biggest drawback to redundant tools is not having enough open spaces on the turret. This can be overcome with some creativity. Utilizing form tools that make multiple features or replacing standard turning tools with groove-turn tools. In other cases, it might be necessary to use a standard tool in an unorthodox manner, like chamfering with a threading tool or turning an outside diameter with a boring bar. Getting the maximum number of tools in the turret is the goal. The more tools there are in the turret, the less a machinist has to intervene in the process.
Probing for accuracy and long tool life
Part probes are not necessary for automation but they certainly make life a lot better. Having a probe on board allows the machine to measure critical dimensions. When the dimensions deviate from the specification the machine can automatically adjust offsets to correct the condition.
Data from the probe can also be used in conjunction with tool life management to trigger actions that prevent scrap and damage. Probes can also be used to evaluate other conditions, such as the diameter of the raw material to ensure the correct work piece is loaded into the machine. Integrating a part probe into an automation project is one of the best ways to build a stable and repeatable turning process.
Building reliable, repeatable automation
These are foundational steps that a shop can begin doing to automate, and most of these can be done with minimal investment. Again, the goal is to identify and automate process steps that require a person to interact with the machine. By methodically identifying and automating these activities, shops will build repeatable turning processes that can be left to run unattended, and, ultimately, generate increased profits by reducing costs. Automated turning processes are a force multiplier allowing shops to produce more work without increasing headcount.
Related Glossary Terms
- boring
boring
Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.
- boring bar
boring bar
Essentially a cantilever beam that holds one or more cutting tools in position during a boring operation. Can be held stationary and moved axially while the workpiece revolves around it, or revolved and moved axially while the workpiece is held stationary, or a combination of these actions. Installed on milling, drilling and boring machines, as well as lathes and machining centers.
- centers
centers
Cone-shaped pins that support a workpiece by one or two ends during machining. The centers fit into holes drilled in the workpiece ends. Centers that turn with the workpiece are called “live” centers; those that do not are called “dead” centers.
- chamfering
chamfering
Machining a bevel on a workpiece or tool; improves a tool’s entrance into the cut.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- feed
feed
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- lathe
lathe
Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- threading
threading
Process of both external (e.g., thread milling) and internal (e.g., tapping, thread milling) cutting, turning and rolling of threads into particular material. Standardized specifications are available to determine the desired results of the threading process. Numerous thread-series designations are written for specific applications. Threading often is performed on a lathe. Specifications such as thread height are critical in determining the strength of the threads. The material used is taken into consideration in determining the expected results of any particular application for that threaded piece. In external threading, a calculated depth is required as well as a particular angle to the cut. To perform internal threading, the exact diameter to bore the hole is critical before threading. The threads are distinguished from one another by the amount of tolerance and/or allowance that is specified. See turning.
- turning
turning
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.
