How to reduce overtime in manufacturing ( Tried & Tested )
- April 25,2024
Category : Customer Problems
Dasarathi G V
Director in Leanworx
Dasarathi has extensive experience in CNC programming, tooling, and managing shop floors. His expertise extends to the architecture, testing, and support of CAD/CAM, DNC, and Industry 4.0 systems.
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Key Takeaways :
Focus on Overall Equipment Effectiveness (OEE): You need to increase your OEE from 40% to 60% to make up for the lost production time from eliminating a shift.
Tackle Downtime: There are two categories of downtime: low-hanging fruit (work ethic issues) and high-hanging fruit (management issues). Focus on eliminating low-hanging fruit first as it’s easier and faster.
Use a data-driven approach: Utilize reports to identify areas for improvement such as high setup times or long unload/load times.
Consider a partial night shift: If completely eliminating the night shift isn’t feasible, consider running a shorter night shift to capture some production time while reducing costs.
How do I work 2 shifts instead of 3, and do the same production ?
If you are working 3 shifts of 8 hours each and manage to produce the same parts in 2 shifts, the benefits are huge.
Advantages of reducing overtime in the manufacturing industry
- All your related costs are reduced by one-third.
- You cut your salary bill because you need fewer operators, supervisors, maintenance people.
- Your energy costs are 30% less because your machines are off in the night shift and so are most of your lights, you save on canteen facilities in the night shift, you save on transport costs in case you provide transport. That’s a huge saving in cost.
Is this really possible ?
Yes, absolutely ! In most shop floors involved in High-Mix Low-Volume (HMLV) manufacturing, OEE of 40 to 45 % is common. If your OEE is 45%, to stop working one shift, you need to increase the OEE to 60%.
Let’s say your theoretical maximum production capacity is 100 parts per hour, and your machines work 3 shifts of 8 hours each.
At an OEE of 40% you are producing 960 parts in 3 shifts. To produce the same parts in 2 shifts, your OEE needs to be 60%.
Assuming break time of 0.5 hrs. per shift, this is how we arrive at the numbers.
3 shifts: 22.5 hrs. x 0.4 x 100 = 900
2 shifts: 15 hrs. x 0.6 x 100 = 900
Improving the OEE by 20 % is not as difficult as it looks. Here is a plan of action:
How to improve OEE
Phase 1: Reduce the downtime (The A and P in OEE).
Phase 2: Reduce the rejections (the Q in OEE).
Divide the downtime into low hanging and high hanging fruit. The low hanging fruit is the downtime caused by work ethics issues: late starting and early stoppage in shifts, extended meal breaks, high downtime in night shifts.
The high hanging fruit is downtime caused by management issues: machine breakdowns, no raw material, power shutdown, high setup times, high inspection time, etc. All these are part of the Availability in OEE.
The total downtime typically is 30% low hanging fruit and 70% high hanging fruit.
Machine downtime – Low hanging fruit
The typical downtime due to this is 1 hour per shift. If the available time per shift is 7.5 hrs. which is 13 %.
It requires very little time to fix, and no additional investment in equipment.
The whole of this (100%) can get eliminated in just 2 weeks. This means 30% of your total downtime is eliminated.
Leanworx has a report showing late start and early stoppage in shifts, and hourly production report that shows low productivity hours.
Print these and put them up on the shop notice board every morning.
Machine downtime – High hanging fruit
What Is The Cause of Downtime In Manufacturing?
- High part unload-load time
- Machine breakdown
- No raw material
- High setup times
- High inspection time
High part unload and load time
The actual time to unload and load the part is more than the standard time that has been assigned. Eg. The standard time is 30 seconds, but the actual time taken varies between 1 and 2 minutes.
Cause: Poorly trained operator, long chip cleaning time, operator fatigue as the shift progresses because the part is heavy, etc.
Fixes: Operator training, providing mechanical aids (like a crane),.
Leanworx has a cycle details report that shows you the cycle time and downtime between cycles.
You can use these reports to check for high or erratic unload-load times and determine the cause by studying the process at the work spot.
Downtime due to high setup times
When there is a part setup change, the actual setup time is more than the standard time allotted.
Causes: Poorly trained operator, fixture maintenance issues, poor fixture design, etc.
Fixes: Operator training, better fixture design, auto work offset probe on CNCs, modular tooling, quick-change tooling.
Leanworx has reports that show setup times for each part change that can be used to determine long or erratic setup times. You can then analyze and fix the issue.
High downtime due to machine breakdown
Causes: Frequent breakdowns, long time to attend to a breakdown, long time to fix a breakdown.
Fixes: Leanworx has breakdown and preventive maintenance features that reduce downtime.
A lot of time is typically wasted in informing the maintenance department about a breakdown via the shop floor hierarchy chain – can even be half an hour or more.
This is eliminated by Leanworx’s automatic ticket creation and breakdown alert on mobile phones.
Breakdown frequency is reduced by Leanworx’s time-based preventive maintenance, usage-based preventive maintenance, and autonomous maintenance features.
Maintenance incidence reports and KPI trend reports (MTTR, MTTA, MTBF) help in improving maintenance systems in the long term.
How long will this take ?
Low hanging fruit: 2 weeks to get to zero.
High hanging fruit: gradual reduction, may take 3 to 6 months.
What if ?
What if my downtime due to work ethics is very high, because my operators sleep 3 hours every night ?
You can eliminate the night shift even faster. If your late start, early stoppage and extended break times add up to 1 hour each shift, this means your machines are only working 4 hours in the night shift.
If you eliminate 1 hour of low hanging fruit in the first and second shifts, and another 1 hour per shift of high hanging fruit, you can stop working night shifts. This can even happen in 2 months.
What if I’m not able to eliminate the night shift fully ?
Make the night shift a partial shift.
Example 1 (3 shifts): 6 AM – 2 PM, 2 PM – 10 PM, 10 PM – 3 AM.
Example 2. (2 shifts): 6 AM – 6 PM, 6 PM – 3 AM.
3 AM to 6 AM are typically the lowest productivity hours anyway.
To reduce downtime, you need to know the durations and reasons for downtime incidents.
Leanworx has a variety of dashboards and trend reports that show you downtime: downtime incidence details, Pareto charts, trends, etc. You can focus on key downtime reasons, eliminate them with improvement in systems, processes and training.
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