Grow in the dark: CMM Inspection

Even low-volume operations producing many different parts can benefit from lights-out production.

As in the book “The Elves and the Shoemaker,” the idea of arriving to work in the morning to find a day’s worth of production already completed sounds too good to be true for many job shops. However, with advances in automation technology, the “fairy tale” of lights-out manufacturing has become a reality, or at least a possibility, for many shops that might not have previously considered it. By studying and understanding specific characteristics of manufacturing processes, automation can be applied to achieve lights-out production even for companies producing small volumes of many different parts. Most stable machining processes can be automated, as can part loading/unloading and other processes.

Courtesy of Genesis

This lights-out manufacturing installation operates for up to 4 hours with no operator intervention. It includes a material handling robot (pictured).

Depending upon the processes being automated, the benefits of automation will vary among companies. It is worth evaluating the potential return on investment (ROI) of a project early on to better understand how to implement automation to achieve the best bang for the buck. Often, the scale of an automation project is proportional to the scale of the company and its production volumes. With an in-depth analysis of production processes and goals, an automated concept can be tailored for an application whether the company is large or small.

For example, even the simplest robotic load/unload project will often increase the utilization of existing capital equipment from 60 to around 90 percent. With automatic bulk feeding and a part logistics strategy, that simple system can be enhanced to achieve an unattended multishift operation, essentially pushing the utilization of process equipment beyond what had been regarded as maximum capacity in a single shift.

The benefits of increasing the amount of product coming from a single machine in a given time frame are obvious—more parts in less time for less cost. If automation enables one machine to achieve the throughput of many, the benefits grow beyond the variables considered with a typical ROI calculation.

An automated approach could require less capital equipment and lower operating costs, enabling a company to bid more aggressively with better margins. With existing programs, adding automation could enable equipment to be reapplied to other products or to be setup to exclusively run specific products, eliminating time-consuming changeover. Again, the result is greater profit.

In general, the two largest gains of implementing lights-out production are greater production efficiency and lower labor costs. Added bonuses include predictable production capacity and the ability to adjust production rates without having to modify employee work schedules.

Lights-Out Considerations

Determining whether lights-out production is appropriate begins with an evaluation of the manufacturing process. An automation project can make all the financial sense in the world, but will not succeed if it requires an unsustainable support effort. An evaluation should determine the following.

Is the process stable in that it does not require continuous dimensional “tweaking,” fault recovery, manual tool changes and manual tool offsets?

How often does the process need to be adjusted, manually restarted, cleaned or measured?

Can anyone perform the work now or does it require a specific person?

Sometimes, as in the case of periodic in-process gaging or tool offsets, these issues can be addressed with new equipment; however, if, for example, a CNC turning process is not dimensionally capable, simply adding a robot to it will only exaggerate that problem by removing the person who could solve the recurring problem.

Once a shop determines automation can be successfully applied, it should step back and consider the bigger picture.

• What should the production flow look like?

• How much floor space is available?

• Are parts processed in batches?

• If so, what is the batch size?

• What are the cycle times for each part?

• How many part models does the system need to be capable of handling, and how often will changeover occur?

• What does the incoming and outgoing packaging look like?

These questions differ for every company, but they all require the same type of answer. The goal of the exercise is to fully understand how parts are to arrive and exit the process equipment in the most efficient manner.

Case 1: Gear Making

Consider the example of a gear making division of a large company that makes earth-moving equipment. The gear division makes drivetrain components and wanted to automate a CNC turning operation that took the part from a forging to the final OD/ID prior to gear cutting.

Its product mix is steady and includes 12 models with changeover every three shifts. Cycle times are in the 2-minute range, and frequent tool offsets are required due to tool wear.

An ROI study was performed, and it was determined that adding automation to the lathes would be financially beneficial, assuming a two-shift operation. The turning process was known to be stable because the product was a mature design and had been produced for years using CNC lathes with manual load/unload.

The specifications for the automated system included the following:

• Unattended operation of the two lathes for up to 2 hours

• 100 percent part inspection

• Automatic tool offsets

• Internal six-piece bank for work-in-process (WIP) between lathe operations

• Access to the lathes without stopping the automation

• Automated loading of parts from incoming bulk-loading tubs