A GUIDE TO UNATTENDED OR "LIGHTS OUT" CNC MACHINING

The Need for It

Almost everyone will agree that automation is a very important factor in today's economy. Companies who depend on CNC machines to generate their revenue are hearing the words "Unattended Machining" and "Lights Out Machining" used more and more lately.

The Benefits of It

The implication is that this technology can provide lower costs of production by allowing automation to replace manual labor. By minimizing the labor cost for each part made, manufacturers can compete with the low costs encountered from foreign manufacturers, as well as gain a larger market share among domestic competition. At the minimum, automation is necessary just to stay in business.

Not surprising then, the words "Unattended" and "Lights Out" are being used more in advertisements to describe the benefits of all kinds of items from CNC machines, bar feeders, robots, probes, software programs, etc.

Anyone who is serious about achieving Unattended or Lights Out machining on CNC machines must address all of the following items:

CNC Machine must be equipped as follows

• Raw stock input - Requires a bar feeder or robot input integrated to work with the CNC machine.
• High Pressure Coolant - To adequately clear the chips away from the cutting edge.
• Redundant Tooling - Substitute tools to automatically replace worn or broken tools and allow the machining process to continue.
• Full Time Tool Monitoring - To control the machining process by maximizing tool life, calling up redundant tooling and preventing crashes.
• Fire Suppressant System - To stop any fire inside the machine when ever a spark or excessive heat from the machining process could start a fire.

Trying to run without high-pressure coolant is very risky. It has been demonstrated that proper chip control is vital to Unattended machining. Fire suppressant - yes, you can run without it - is also highly risky, but in another way: it may not have anything to do with the number of parts you get per shift, just whether you have a machine or building left after the fire.

Full time tool monitoring, of all the elements involved in the Lights Out machining process, is the least understood. Many so-called Lights Out or Unattended processes are limping along at a snail's pace to avoid machine crashes, and are using various types of probes to measure and verify tool existence and condition. This indulgence of these inefficient methods is justified by the fact that they at least get to run Unattended, even though at a slow pace.

A result of being the least understood item in equipping a machining process for Lights Out operation is the tendency to shop for the lowest cost possible when purchasing tool monitoring. Since the choice and utilization of the tool monitor has the potential to affect the output, and thus the revenue generated from the Lights Out operation, more than any of the other essential items, the features/ benefits should be the guide, not the original purchase price.

Predominately, CNC machines are operated at 50% - 60% of their original run-off accepted cycle times once they are producing parts in production. Then, when launching into Unattended operation, the tendency is to slow the process even further with the idea that this will enable stable, uneventful, continuous operation and at least reduce the operator attention.

The minimum benefit would be provided by broken tool detection such as probes, whiskers, or lasers in the $2,000+ price range. The payback is the cost savings from stopping the process or calling up redundant tooling in the event a tool does break.

The next benefit level is provided by the vast majority of computer-based tool monitors. These monitors typically range in price from as little as $4,000 to $30,000+, depending on the process, number of tools and points being monitored. The payback is the cost savings from being able to catch worn tools as well as broken and missing tools. No need to slow the CNC cycle time, and the payback comes primarily from reduced labor cost and tooling costs.

Finally, the maximum benefit level is provided by computer-based tool monitors that provide Live Process Visibility as well as Process Protection.

These monitors typically range in price from $16,000 to $30,000, depending on the process, number of tools and points being monitored. The payback from these units can be enormous when the Live Process Visibility is utilized to maximize the throughput by reducing the cycle times and catching tools in the worn condition, thus producing the maximum number of good parts.

For more information, visit atam.com