What does MTR Stand For?
MTR stands for Mean Time to Repair.
In automated processing and packaging lines, Mean Time to Repair is the average time it takes to repair a machine once it malfunctions. It’s used to calculate how much buffering is required upstream or downstream. If your line’s longest MTR is 3 minutes, then you need at 3 minutes of accumulation.
Wait, but doesn’t that mean I will only be able to buffer against half the downtimes? If you have an even distribution of downtime durations, then yes, you’d only buffer against half the downtimes. What we see in reality is that most packaging machinery has a high number of very short downtimes (under 3 minutes) and a small number of very long downtimes (10-60 minutes). Here’s some representative (but fabricated) sample data to illustrate this point.
The MTR on this machine is 3.76 minutes. A 3 minute buffer would cover 92% of all downtimes on this machine. What would be the machine and facilities cost of capturing that last 8%?
How do I reduce MTR?
MTR is made up of three components: Knowing, Finding, and Fixing. You must reduce one of these three to reduce MTR.
Knowing: The time it takes for anyone to realize the machine has malfunctioned and requires human intervention. The ways to reduce this component are by adding alerts (light stacks, alarms) or operators to continually watch the equipment.
Finding: The time it takes for someone to find out what the problem is. This step can be reduced by programming helpful error messages into the machine’s HMI that tell you exactly where the problem is. Modern photocopiers do this by telling you where the likely jam points are. When training operators, make sure they know what the most common malfunction reasons are so they can check those areas first.
Fixing:: The time it takes to actually fix this problem. Reducing this step is the hardest and most difficult to change once a machine is installed. Hopefully this has been thought about and discussed during the design phase of the equipment. Machines that are easy to repair must start and stop gracefully, have disconnects easily within reach, accessible doors and guarding, and easily explained repair instructions.
In many cases, the first two steps take far longer than the third so there is a lot of room for improvement. Reducing MTR helps keep your line running efficiently and allow you to tolerate more frequent hiccups in production.
Tags: accumulation table, buffer, conveyor, line analysis, mtr