What are the Causes of downtime in manufacturing ?
- July 13, 2024
Category : Downtime tracking software
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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Causes of downtime in manufacturing
The causes of downtime in manufacturing can be divided into Low hanging fruit and High hanging fruit.
- Low hanging fruit is caused by work ethics issues. It can be fixed easily, in a short time, with little or no investment.
- High hanging fruit is caused by systems (i.e., management) issues that reduce the availability of the machine.
- The typical ratio of causes of machine downtime is: 30% due to low hanging fruit, 70% due to high hanging fruit.
The OEE in discrete manufacturing is typically very low, 40-50% in HMLV (high mix low volume) production, and 60-70% in mass production.
It should ideally be 20-25% more than this. What does 40% OEE in HMLV mean in terms of production and profitability ?
- Your ROI is reduced by 60 %.
- You are producing 40 parts per shift when you could be producing 60 to 70.
- Your CapEx (Capital expenditure) on machines is much higher than it should be.
- Your running cost is much higher than it can be.
- Your prices are much higher than they can be, in a competitive market.
What is the cause of machine downtime?
Process problems:
These are downtimes that are a necessary part of the process but can be reduced. E.g., Setup time, first-part inspection time, tool adjustment and change time (in case there is a tool breakage), etc.
Machine Breakdowns:
Breakdowns due to avoidable reasons, which can be fixed by simple and cheap preventive maintenance.
The problem is that there are numerous manufacturing downtime reasons, and you have no idea of them unless you are standing on the shop floor all the time.
The problem worsens as the number of machines in the plant increases. Numerous such small leakages add up to a big chunk of idle time every shift, and NOBODY notices.
These become accepted practice, part of the system, absorbed into the culture of the shop, and everybody just says “Oh, that’s how we work here.”
Act now !
No raw material
There is no raw material available from the upstream process because that machine is underproducing or has a breakdown. Else there is no raw material from an external vendor.
Work ethics problems :
Operators coming late at the beginning of shift, taking more time than allotted for tea, lunch, dinner, etc. This can easily add up to 1 hour per 8-hours shift, or 12 % of the available time.
Delay in attending to machine breakdowns:
When there is a machine breakdown, the operator goes in search of the supervisor or maintenance person to report the issue. This takes 10 to 15 minutes. This is the ‘time to report’. Maintenance personnel arrive at the machine after a further delay. This could be because they do not take the issue seriously, or they are attending to problems on other machines.
Unplanned downtime in manufacturing
Unplanned downtime is very expensive because it has a cascading effect on other downstream processes. In a part with multiple processes, each process is the raw material for the next process.
If an upstream machine is not producing to schedule, all downstream processes are starved of raw material.
Unplanned downtime examples
Some causes of unplanned downtimes are:
- Machine breakdown
- No raw material
- Power shutdown
- Tool breakage
- Abnormally long setup change time
- Operator starts production late at beginning of shift
- Operator stops production early at end of shift
- Extended break times
Average cost of downtime in manufacturing
The average cost of downtime in manufacturing is easy to calculate. You need to know the machine hour rate.
This is the amount of money that the machine can earn in an hour, or conversely, the amount of money that you lose in an hour if it is idle.
Cost of downtime = Machine hour rate of a machine x Downtime duration.
E.g., if the machine hour rate is Rs. 500 and the downtime duration in a day is 6 hours,
Cost of downtime = 500 x 6 = Rs. 3000.
To determine the average cost of downtime for a whole cell or shop, add the individual cost for each machine and divide the sum by the number of machines.
Cost of unplanned downtime in manufacturing
Unplanned downtime reduces predictability. E.g, in mass production, if you have to deliver 1000 nos. of a part every day, unplanned downtimes will disrupt the production.
To compensate for this, maybe you need to have a finished goods inventory of 1 day.
This means you have a constant stock of 100 parts on which you have spent on the raw material and processing, but are never going to recover the cost and are paying constant interest.
Inventory is inversely proportional to Predictability. Lower the predictability, higher the inventory. And inventory is Money.
If you can process and deliver 1000 parts every day without fail, with 100% predictability, then you do not need finished goods inventory.
For this to happen, machines never break down (because you have great preventive maintenance), operators are never absent (or you have standby roving operators), etc.
If your machines sometimes break down or other things happen that can cause a delay of 24 hours, then you need to have a finished goods inventory of 1000 parts.
The cost of holding finished goods is more than the cost of holding raw material, because the cost is now (raw material cost + processing cost & profit margin).
You have a constant stock of 100 parts on which you have spent on the raw material and processing, but are never going to recover the cost and are paying constant interest.
Unplanned downtime example, with a simple fix
In a shop with VMCs where our Leanworx is used as the downtime tracking system, the reports showed that operators spent up to 15 minutes every shift ‘searching for tools’.
The VMCs had a machine hour rate of Rs. 1000. It turned out that each bay had one set of Allen keys, and when an operator required a key he went around all machines searching for it. If the keys were already in use on a machine, he had to wait till they were free.
That’s a loss of 3 % of the available time, or Rs. 19,000 per VMC per month. The simple solution ? The firm just gave each operator a set of Allen keys costing Rs. 200, and saved Rs. 19,000 a month.
Planned downtime in manufacturing
When there is a planned downtime, production does not get disrupted because the downtime is scheduled in advance. It is scheduled during the weekly off or planned shutdown days during holiday breaks or at the end of the year.
Examples:
1. All machines are idle for 10 minutes at the start of the first shift for autonomous maintenance.
2. Preventive maintenance is done on weekly off days.
3. Minor preventive maintenance is done in non-working shifts.
4. Major preventive maintenance or overhaul is done in the last week of December with the whole plant shut down.
The aim must be to always replace unplanned downtimes with planned downtimes. E.g., if you improve preventive maintenance, breakdowns are reduced and unplanned maintenance reduces.
Manufacturing downtime reasons - the low and high hanging fruit
In most shop floors, idle time on machines can be up to 40 %, and people think this is normal.
Basically, these firms have bought a bunch of elephants to do their work, and the elephants are sleeping 40 % of the time.
The problem is that even when they’re sleeping, the elephants have to be fed and their mahouts have to be paid their salaries.
Wastes can be low hanging or high hanging fruit, and fortunately, the low hanging fruit are very easy to pluck.
Low hanging fruit (can be fixed very quickly) - Work ethics problems
Operators come late at the beginning of shifts, taking more time than allotted for tea, lunch, dinner, etc.This can easily add up to 12 % of the available time.
When there is a technical clarification or a machine breakdown, the operator goes in search of the supervisor or maintenance person to report the issue.
The latter come when they are free, 10 or 15 minutes later.
High hanging fruit (can be fixed in the medium term) - System and process problems
- High setup time
- High inspection time
- Machine breakdown
- No raw material
- Power shutdown
How does a machine monitoring system help in reducing the cost of unplanned downtime in manufacturing ?
To be able to reduce downtimes, you need to know the durations and causes of machine downtime, analyze them, and take action to fix them.
You cannot take action unless you have accurate and instant data on these.This cannot be done using the old manual and paper-based data collection system.
Such a system gives you inaccurate data because it is dependent on people’s memory and honesty. It also does not give you instant data to take action in case there is a situation that requires immediate attention.
Only an Industry 4.0 based machine downtime tracking software can give you accurate and instant data.
Leanworx is one such system that tracks machines in your shop floor 24/7 electronically, remotely.
Sitting at your desktop, from home, or wherever you are in the world, you can get reports on production quantity, idle times, part quality, OEE, rework, breakdowns, manufacturing downtime reasons,and other key statistics.
You can get alerts on your mobile phone on any abnormal situations – machine breakdown, production below target, rejections above limit, etc. In the shop with the Allen key issue mentioned above, the idle time was 28 %, and they reduced it by half in the first month of installing Leanworx.
The system also speeds up your Lean and TPM implementation, and OEE improvement. You can get accurate and immediate reports on your PC or mobile phone, wherever you are in the world. You are informed of potential problems before they occur, so you can prevent them, instead of doing post mortems after they occur.
Increase your profits automatically. Use Leanworx to get accurate and instant data 24/7.
