The Silent Efficiency Killer - Making a Case for Automatic Tray Handling

By Ken Lento
I have spent many hours in many different sized optical laboratories, and as a result am truly convinced that there is a “silent efficiency killer” hurting their operations. Most people don’t recognize this killer, even though it’s operating right under their noses; it’s simply called manual tray handling.

This isn’t a joke or a trick answer. The “Silent Efficiency Killer” leaves his trademarks everywhere. For example, do you ever wonder why you have plenty of machines and human capacity, but yet the output is hard to predict? Do you work hard to get volume out the door by adding more people, changing machine layouts or processes but still don’t realize where the problem is? The “Silent Efficiency Killer” is manual tray handling, and it’s helped along the way by poor decision-making. For example, I have seen a lab add an extra generator to increase volume, only to realize that they cannot get enough trays to the machine to maximize the potential of the machine and gain the added efficiency.

Why is manual tray handling so bad for efficiency? When I ask manufacturing engineers why they are doing it this way, the response is often that this is the way that they have been doing it for years. They argue that conveyors and other solutions to move trays can break down and are costly to maintain. Conversely, there is a degree of unreliability and non-repeatability that is built into manual tray handling. In an optical lab where people are responsible for moving trays, they can forget, or lose trays by setting them in the wrong area, or drop them. It’s human behavior - walk slow, stop to talk to someone, stop to use the restroom and a whole host of other activities introduce variability into tray handling by interfering with or interrupting the movement of the trays through the facility. Sometimes, even if a good effort has been made to move the trays, they simply don’t have a direct and clear path through the lab. Have you ever taken a drawing of your facility and drawn a line to follow the path a tray takes? You might be surprised at the distance and extra travel that a tray takes. One lab owner hired a consultant and had this analysis performed and learned that a typical job tray traveled almost one mile within his own lab.

Once, while observing a second shift operation in a lab, I kept track of a single job tray to see who touched it, when it was left for chance, and when it was actually moved to an additional process. Between lens pick and blockers, the tray was moved manually. The tray sat unattended for almost ten minutes and trays coming into the station after this one were processed faster. Perhaps this was just an oversight, but nonetheless, the tray didn’t travel in a first in/first out flow scheme. After blocking, the tray was conveyed to a generator and processed in order. The travel time to the generator was 30 seconds, and after a 40 second process, the two lenses in the job tray went on to polishing. Problems continued with the job as more manual touches occurred, and at one point, the tray was never touched for 20 minutes. What I was observing were people deciding tray priority.

Slow handling and poor decision making negatively affected this customer’s order. I also checked to see if this was one event, or one of many. The production reports confirmed that there were customer orders that took one and a half to two times the processing time as others, and the delay was not due to breakage. In one study that I recently conducted, a tray-handling conveyor that feeds job trays from blocking to generating was turned off. This conveyor normally moves trays at 60 fpm (feet per minute), or about what a normal person walks when in a hurry. This conveyor is capable of moving 250 trays per hour at a steady rate. During conveyor downtime, workers were required to collect completed and blocked jobs and move them to the generator area. The observations were just what you would expect: about 50 percent of the required volume actually was achieved, or about 125 trays per hour. People forgot to make a run with the cart to pick up the trays, trays were stacked in a way that they could have easily fallen from the cart, trays were picked up on the cart, moved, but then not unloaded. At several points during the observation period, trays were not moving. If the conveyor would have been off or not present for a longer period of time, the problems would have gotten out of control.

I have observed situations where labs spend lots of money and go to great pains to alert workers of later and higher priority jobs. Some of these techniques include different colored trays, different colored Rx paper in the trays, colored stamps on the Rx paperwork, colored clips, balloons tied to the trays, dedicated people to walk trays through the system, and many more schemes of every variation, all to marginal effect. One lab purchased enough trays for their daily volume in seven different colors, one for each day of the week. The ideas are clever, but the cost and storage requirements of the extra trays are considerable. The concept of looking around the lab and seeing trays and knowing that you have work that is late and then providing a visual regarding what the priority tray is, is great, but there is no guarantee that the tray will move as one may wish.

When you discuss and/or try to convince someone that the cost of a conveyor for tray handling is better, more controlled and can automatically prioritize the work, the most common objection is cost. Some will argue that they cannot afford to be down for any length of time, so it won’t work.

Tray Handling Conveyor: What it Does

The main purpose behind installing a tray-handling conveyor is to improve efficiency by removing the variability and vagaries associated with manual tray handling. The goal is to make the job trays move consistently along a pre-determined path. You want to make sure that you have options within the system that will allow you to prioritize and re-route work. The system should be capable of moving material from point A to B in the fastest way possible, but it should also have a way to prioritize the late jobs or express jobs to the front of the system.

A controlled flow of trays gives you control. Once you have everything moving through the lab, as it is should, you can then focus on fine-tuning the machines and processes to get the highest yields possible.

The conveyor can also reduce the risk of breakage, or the risk of someone dropping a tray. It can obviously reduce the risk of losing a tray within the lab. One lab manager whom I spoke to told me that he remakes a large number of jobs annually simply because they cannot locate the job. He added that people will sometimes set a stack of jobs in the wrong area or department, either accidentally, or because they don’t fully understand the process. Thus, when the job is needed, it isn’t ready and must be re-started. Newer technologies are now in place to add RFID tags to trays. Combined with the right software package, this can eliminate the need for paper in the tray. Smart software and RFID systems can handle priority routing, provide visibility and tray locations in real time, and make the right prioritization decisions. There will no longer be a need to color code trays, attach special identifiers, or worry about where a tray is going.

Certainly, higher efficiency and the elimination of flow decisions made by individual workers results in peace of mind, and more; the result will be a 20 percent and higher increase in throughput efficiency, and possibly reduced labor costs.

Getting Started: Assemble the Right System

Once you decide to evaluate a tray handling system, there is no cost or risk associated with doing so. Suppliers of such systems will typically visit your facility, create a layout of the planned solution, and even test the solution for results before you make a purchase. It’s important to be certain that the equipment supplier specializes in conveyor systems and can not only create a drawing (a layout of the lab) with all the machines and work steps, but that they can also create a simulation of the flow. A simulation of the system can provide and predict what the lab will be able to produce. These numbers can then be compared to the current lab process. A simulation is also a great way to refine an existing system that was originally installed without making a simulation. A simulation is also a great way to create the best and efficient layout for an individual facility. During the design phase of one customer’s project, I recall we created a layout feeding three similar machines. After performing the simulation, we noticed that we were not getting the desired throughput from the system. So, we analyzed it again and determined that there were a few conveyors that needed to run at different speeds than all the rest in order to balance the process. After the changes in speeds, the desired numbers were achieved.

After a good, solid layout has been established and the simulation completed, you should have enough information about what you can do to the lab process. The tested layouts can also be created to show how to grow the facility in numbers through stepwise automation and adding on modules as volumes increase. This provides a plan and lets you know what to do when volumes reach higher levels. It can also predict when you will run out of space and be required to relocate, add-on, or move.

Justifying a Tray Conveyor System

There are many considerations involved when justifying a conveyor system. The first might be how to pay for it. You can outlay the capital and follow standard accounting practices to depreciate the investment and look for a payback over time. Another option is to borrow the funds and add the cost of the money to the purchase. You might consider a lease purchase, where you pay a monthly amount (with the added cost of the money). You can also work with the system supplier to spread the payments over a longer period of time, with no additional cash or cost of money.

The payback is going to come from efficiency gains, reduction in spoilage (maybe the reduction in lost trays), some breakage reduction from not dropping trays, and the reduction in personnel of persons who are required to manually move trays.

For example, in one conveyor layout, the conveyor is feeding trays from a manual finish blocking process to an automatic finish-edging machine. Prior to the conveyor, the machine was hand-loaded by a dedicated worker. The burdened rate for the technician was approximately $28K per year. There are two shifts, so the annual expenses were $56K. The conveyor system installed cost $30K, so the system has a 6-month payback, just on labor. This doesn’t include the efficiency gains by reducing inefficiency and the additional 20 percent output in production from the machine.

Finding and recognizing the “Silent Efficiency Killer” is the first step toward restoring efficiency in an optical lab. Recognizing that the payback from implementing a conveyorized handling system will be fairly quick will surprise many people for whom consideration of price is a hidden – and misleading – barrier. It’s important to invite a provider who specializes in tray handling solutions visit your facility and offer a few potential layouts. Test these layouts with a simulation to predict what the possibilities are for the new layout and with conveyor. If you are convinced the gain is significant, then determine how to pay for and justify the system. Look at all the options for the money, including spreading the payments over time with the supplier to avoid the cost of the money. Locate every justification element that you can find including efficiency, planning and cost avoidance of adding space, breakage due to handling and reduction in labor and time to manage the problems.


Labtalk June 2020