FEATURE - In Part 2 of his article, the author reveals an improved process that allows this Hungarian company to replace machine parts with minimal production downtime.

By: Dénes Demeter

Originally published by Lean Enterprise Institute Hungary here

Maintenance and repairs are among the leading causes of downtime in production processes. In our client's company, which I wrote about in Part 1, machines could be idle for 15 to 20 minutes while replacing wear parts, even though the replacement itself took only 3 to 5 minutes (depending on size).

Observations

To understand what happened, we need to break down the problem into smaller, observable parts. So let's determine what this 15- to 20-minute period consists of.

During our observations, we discovered that the process could be divided into the following phases:

1. Detection - technician notification - technician arrival.

2. Remove the part - obtain the replacement part.

3. Replacing the part - installing - starting the machine.

In the first stage, we saw that the process begins when the machine reaches the maximum number of steps and stops. Moreover, about two hours before it stops, it indicates that it is approaching this point. We also learned that the policy prescribes replacement at this time, meaning that the part in question can be replaced between 30,000 and 33,000 steps. After reaching this last point, the machine stops producing.

After the machine stops, the operator notifies the technical team and, depending on their workload, the technician comes to fix the problem. By this time, the machine has stopped for 4-8 minutes.

Obviously, the biggest loss in this phase is due to waiting, because the technician is not there when the machine stops. This happens because the technicians do not get information in time.

In the second stage, we saw the technician remove the defective device, walk to the storage area for replacement parts and ideally find the part with the correct size. If not, they go to another station to cut the needed size. Walking and searching for parts after removal takes 2 minutes and cutting a new part takes another 5 minutes.

In this phase, losses are due to movement and waiting. The reason for movement was found in the third stage and for missing parts we saw that replenishment was always done internally, that is, when the machine was already out of operation.

In the third stage, the technician takes the obtained replacement part and the removed unit to his workstation, where he replaces the part using a special fixture, then returns it to the machine and reinstalls it. The process ends with the restart of the machine. The turnaround time at this stage is 1-2 minutes, while replacing the part takes 3-5 minutes.

Countermeasures

The guard loss observed in the first stage was eliminated in two steps.

First, at the beginning of each shift, a designated technician walked the entire fleet of machines to gather information about which machines needed to be replaced during the shift and schedule these replacements. In case of concurrent needs, they requested assistance to perform the replacements in parallel.

The second, currently used process is much more sophisticated. Today, all technicians have a PDA to schedule their tasks. The first signal, at 30,000 steps, is sent to the PDA of the technician in charge of the machine, with instructions to replace the part within 2 hours. This eliminates the time lost during the entire first stage.

To eliminate waiting times caused by internal restocking in the second stage, we introduced a kanban system for parts replenished externally, without machine downtime.

The displacement losses characteristic of the second and third stages were eliminated by placing the required fixture on a cart so that replacement of the part can be done right next to the machine, at the point of removal.

And where are the pre-cut replacement parts? In the drawers of the cart, where the kanban is located, so that all the necessary elements are at hand while replacing the parts.

RESULT

As a result, technicians receive timely information, allowing the process to be planned and executed before the machines stop. The cart allows replacements to be performed on-site, alongside machine units, so that the required replacement part is always available. Instead of the initial 15 minutes, replacement of wear parts now takes place with a maximum of 5 minutes of machine downtime.

It is important to emphasize that establishing the new process and necessary technical conditions is not the end. Initially, less than half of the replacements met the new time standard. For example, often technicians did not arrive on time despite the signal, or they brought the device to the cart - as they used to bring it to the technician's table - instead of the other way around. Therefore, engaging employees, ensuring understanding and developing skills are all fundamental actions. Implementing the new process and maintaining results was a challenge for leaders, but with the right goals and management routines, most replacements now meet the new turnaround time.

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