Assembly Automation – Can we use a Robot for this Application?

Manufacturing assembly automation systems have traditionally been envisioned as custom machines, designed & built for a specific purpose and a specific product or product family. As such, this hasn't changed and still remains the intent but with the advent of increasingly easier to program and relatively lower cost general purpose robots, the line has been blurred and an interesting conversation is being frequently heard. Namely the question, “Can we use a robot for this application?” is asked and in many cases a robot can be custom tooled and integrated to provide the intended assembly automation system. But, is this the right approach?

Maybe! ... but what are we trying to accomplish? Use a robot? or build an automated assembly system to increase productivity in our specific application?

Simple enough question, so let's try to answer it.

The question is certainly timely as we see a continuous flow of many new robot announcements and a large number of robot suppliers are busy developing new features and specific applications while solving existing manufacturing automation challenges and even imagining some problems that are to be solved by robots! .... starting with the robot as the basis of the solution. The relative programming flexibility, “off-the shelf” availability and a fast growing ecosystems of peripheral devices and tooling available all beckon while manufacturing management weighs automation options and strategies with the pressure to reduce labor costs, solve labor availability challenges, create shorter production lead times and address many other productivity factors overhanging and all this often points to assembly automation to strategically provide the next leg up in competitiveness. With this backdrop, the word “robot” is starting to be synonymous with “automation” as far as many in manufacturing are concerned.

Taking a step back, automation in manufacturing is nothing new and indeed, has always been a key competitive driver and advantage going back 100+ years so it should not come as a surprise that all new developments in automation, whether the PLC some 50 years ago or today's robots, that appear to have “come of age”, will be widely accepted and reach some deployment equilibrium in wider manufacturing and assembly operations. With a by now well understood architecture, reliable motors and feedback along with a long history of success in the automotive industry for one, robots are being deployed in many new manufacturing applications with varying degrees of success, while many new use cases are proving to be profitable and paradigm shifting. Not only eliminating direct labor but also eliminating indirect labor and lead times associated with the previously manual processes.

However, it may be worth taking the time to fundamentally review what recommendations we might give to our manufacturing management when asked to provide input on automation options and strategies going forward and answering the question, “Can we use a robot for this application?”.

Assuming we have some history and experience with automation, that automation in our plant has probably been created by our own engineers or perhaps one of our competitors but for the most part, from within our industry or someone who has worked in our industry and understands the fundamental economic drivers. The extent to which the robots evolved and developed from any industry, that would for the most part be the automotive or the electronics assembly industries and that's important! Those are not necessarily our industries nor reflective of our specific business model or production needs.

At the root, a robot is basically a general purpose, multi-axis, motion system which in the most familiar embodiment resembles a human arm with multiple “elbows” or joints and capable of carrying some payload at the end. A platform for the EOAT as it were.

As such, a robot is very flexible, within its operating parameters, and can be used in many applications where mimicking the human arm motions may be important. Valuable applications have been executed in contour following processes while carrying a tool such as a grinder, a weld head or any tool that needs to follow a path while in contact with the work and my have been previously manually performed. If our product family has a low volume high mix configuration, that much the better, as unique programs can be easily run for even lot size one requirements. Add in the ability to “reach into” areas where conventional automation structures would be challenged and the multi degrees of freedom and a robot is ideal for many applications and for the most part, those have already been identified over the last several decades while simultaneously today, those applications may be more readily accessible through improved ease of programming and ease of tooling change-overs as is common with all types of automation.

On the other hand, since a robot arm is fundamentally a cantilever structure, it has to be articulated with a limited, finite load at the end of the arm and at relatively slow speeds since all the loads, direct, moment and acceleration, are brought back to ground through a single joint at the base. This leads to the programmed paths and positions to be carefully considered as relatively fast, point to point, “line of sight”, movements can easily exceed load limits at any of the sequential arm joints. (Incremental increases in payload or speed requirements require a much larger increase in the robot size/structure to maintain rigidity and accuracy.) Add this to the fact that the “return trip” of any robot motion is a “dead head”, and it quickly becomes apparent that given the many advantages of a robot, it's overall efficiency is best optimized for a defined narrow band of applications, unless of course there's some other imperative to use it in a particular design or some other strategic objective such as introducing robots to the plant.

Most important, the "general purpose" attribute of the robot inherently means that it's full capabilities will seldom be used in any particular application and reminds one of the old adage "jack of all trades, master of none."

These and other limitations are non-existent for a custom designed, application specific system as they all remain within the designer's control.

In summary, we might say that when asked the question, “Can we use a robot for this application?”, we can answer it by first ignoring it and initially sketching out our required tool or product path through the range of assembly/process steps to achieve our inputs-outputs, speeds and cycle times while optimizing footprint, serviceability and continuous “forward” motion of the product. Then we can ask the question, “which of the steps can be performed by a robot without presenting an undue burden to any of the other criteria”. We will often find that a robot DOES offer many advantages for some operations but more often than not, we will also find that the robot presents additional constraints, (Technical, Footprint, Overall Costs), that we can best solve by not introducing them in the first place by not using a robot for that particular application and concluding that a custom designed system will lead to higher overall productivity gains through automation ... which is after all the goal.

“Can we use a robot for this application?” the answer often is YES!

But! .... Why? or What is the compelling reason to do so as compared to a simpler, custom designed, application specific alternative?

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