Automation solutions for high-mix manufacturing

A high-mix plant produces many different parts, each of which has different processes and a total overhaul to automate processes is expensive, which makes the planning process for manufacturers very important.
By Manan Banerjee, Cross Company May 4, 2018

Courtesy: Cross CompanyThe competitive landscape presents a constant pressure to lower prices and run more efficiently. When dealing with a single product being made in manufacturing, it is not difficult to identify process improvements that increase efficiency. If several different products are being produced, an improvement to just one production process is unlikely to have a significant impact on return on investment (ROI).

A high-mix plant produces many different parts, each of which has different processes such as computer numerical control (CNC) machining, stamping/forming, visual inspection, and picture documentation. All of them require some human involvement (loading/unloading parts, placing parts in packaging, taking and saving pictures, etc). A total overhaul to automate processes is expensive (not to mention daunting) and low or unpredictable volumes for any individual part makes the per-unit cost of such a large capital investment difficult to justify.

Shown are some examples of typical high-mix processes and the challenges of adding automation to them:

Process Human Involvement High-Mix Challenges
CNC machining of different parts of varying lot size. Fixturing and removing each part from machine vise(s). Part geometries require wide array of gripping mechanisms and varying locations for placement in vise.
Visual inspection of parts and assemblies. Products require pictures taken from various angles and saving as records. Many configurations of camera locations are difficult to make consistent. Creating fixtures for each part type can be expensive and ineffective if the part undergoes design changes. Saving and labeling pictures manually can be time-consuming.
Packaging several sizes of parts into boxes. Pick up part, place in bins or boxes as required. Optimal packing configurations may be drastically different depending on the part and package sizes.

At the foundation of any high-mix operation is the concept of changeover time. Any endeavor to automate must take into account the non-value-add time associated with changeovers, or eliminate them entirely. With this in mind, here are three paths possible to automate in a high-mix environment.

Traditional (fixed) automation benefits

There are nearly endless options available for traditional fixed automation, including industrial robots, gantry-style cartesian robots, conveyors, or even a turnkey machine designed by an integrator. The main takeaway for this category of solutions is that they are typically going to be fixed to one or a handful of products in the mix.

On the positive side, the "tailored" nature of this category of solutions means they tend to be very efficient for the processes on which they are deployed. If cycle times have to be much lower than 2 seconds, then traditional automation may be the simplest path to improving a process. However, in a high-mix environment, fixed automation generally means a decision between a lower capital investment that only touches a few of the products or a much higher investment for a system that can handle all of a company’s products.

Traditional systems tend to be designed for throughput, not rapid flexibility, so tooling changeovers can take considerable time, especially when safety protocols require physical separation from human traffic. The total cost of ownership (TCO), when considering the safety equipment, floor space, and setup needed for traditional safety methods, tends to be high. In any case, this lengthens the ROI period longer in a high-mix environment, particularly if volumes are relatively low.

Courtesy: Bob Vavra, CFE MediaRobots-as-a-platform (RaaP)

The available RaaP solutions can be as varied as a company’s product lineup, but one thing they have in common is using the robot as part of a system designed to be quickly redeployed as needed. Rather than the traditional deployment paradigm of coupling a robot to one specific process, RaaP enables the robot to go wherever production demands on any given day. The ideal solution in a high-mix environment should have the ability to be quickly deployed from application to application with as little changeover time as possible. This minimizes the non-value-add changeover time that can make traditional automation prohibitively expensive.

For a high-mix scenario with a lot of manual involvement, it may be more beneficial to look at collaborative robot solutions either by themselves or as part of a platform. Both of these platforms can be placed exactly where they are needed to expand existing capacity while allowing quick changeovers, increasing ROI and shortening the payback period on the investment.

High-mix production environments can be difficult to improve upon. The ideal improvement will touch several production lines, but the investment required to accommodate several processes can be expensive enough to significantly decrease ROI. Traditional automation is certainly an effective solution in high-volume or rapid cycle-time production.

Manan Banerjee, MBA, is a robotics technical specialist at Cross Company. This article originally appeared on Cross Company’s Robotics and Machine Automation blog. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com.