Driven by keen competition and demanding customers, and given that the cost of utilities and materials and labour are spiraling upwards, manufacturers are seduced with the idea of going home with the lights switched off, and leaving mechanical minions in the dark to crank out components.
Since modern technologies has made lights-out manufacturing possible also for small CNC shops, and the alluring promise of making parts overnight with little or no labor cost has led many to try out this new production method.
But, there are a number of issues that have to be considered before jumping on the bandwagon. Some important points are emphasized in this guide, and suggestions given to help develop a feasible, lights-out plan.
Although the entire purpose of lights out is to reduce labor costs, it is possible reduce other costs too.
To begin with, having long, overnight runs for the night-shift workers will give the shop’s machine more time to do short-run jobs during the day. These are jobs that requires monitoring because the parts are more complex, or changeovers on the line, or urgency in response to a customer’s needs.
Also, machine operators can more efficiently use their time in the day to set up the machines for overnight production while the machines are still running.
Finally, power companies often have a tariff for electricity used during the day, and another for the night. So, it could cost less to run machines for lights-out manufacturing.
Points to consider
Assuming that the components you want to produce is suitable for unattended operation, there are still some basic issues to take into account.
Reliability of equipment.
Because nobody will be at the shop to deal with machinery breakdowns, the equipment designated for lights-out production run must not fail. Can your machine tools, material handling equipment, chip management, coolant recycling system be operated with no downtime?
Is it stable and rigid? Can it operate continuously? Does it have enough spindle power? Is the number of tooling stations sufficient? Can the control system monitor processes and correct problems? If not Can it be communicated to someone? How does the machine compensate for heat? How does it avoid crashes?
Coolant and chip management.
If a high-pressure system is used to deliver the coolant, can the pressure be programmed to change throughout the machining cycle? Can the conveyor filter cutting fluid to prevent swarfs from contaminating the coolant? Metal filings can clog nozzles or cause pumps to break down. Can the chip conveyor satisfactorily handle the quantity and type of chips produced during a production run, or would the chips start to accumulate and create problems?
Material Handling Equipment.
If a bar feeder is used, can it hold enough barstock in its holding tray? Can it continuously feed barstock in tandem with the machine without crashing? If a family of parts is to be machined, can the feeder be controlled by the machine tool software to load a new type of barstock? Can the feeder handle continuous operation? After completing the machine cycle, is the part simply dropped into a bin, or unloaded by vacuum because its surface finish must be protected? Is a robotic arm required for unloading the machine tool?
This is crucial for lights-out manufacturing. If a machine breaks down when machine operators are present, schedules can be shifted or other machines used until help arrives. But if it stops working during a lights-out shift, time is wasted until someone arrives to fix the problem.
Reliable equipment and planned preventive maintenance will reduce problems, but the possibility of cutting tool breakage, machine failure, power outages remains. When any unexpected issues happens, a remote monitoring and control system is priceless. Many CNC machine controllers and peripherals are designed to send alert notifications (such as email, SMS, or SNMP) to devices (such as computers and mobile devices.) MTConnect is commonly used to retrieve information from numerically controlled machine tools. It is a protocol based on Internet standards to enable a central monitoring system to control machine tools and other shopfloor equipment.
Lights-out manufacturing need co-ordinated effort from every part of the company. It’s a cultural change for all, and change always carries the risk of making the situation worse. So it is essential to ensure that everyone in the company understands the plan and their roles and also what it means for the future.
What to Run
Not every process is suitable for lights-out manufacturing. Some complex pieces must be produced with operator intervention. As you evaluate applications for automation, it’s helpful to ask the following questions: • Which machine tools and fixturing can be automated? • Which machining processes are stable or controllable? • Which machine tools are devoted to specific parts? • Which parts share common machining processes? • Which machine tools are not fully utilized? • Which process can be speeded up with less manual intervention? • Which part does machinery operators have a sizeable influence on quality? • Which customers issue repeat orders?
Grinders, vertical and horizontal machining centers, multifunction lathes, and CNC turning centers are easier to adapt for lights-out manufacturing. To make sure that the system is accurate over the lights-out shift, use process control devices such as automatic gaging systems, probes mounted in the machine tool, or coordinate measuring machines.
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