reliability & oee?

[bloch2006]

hi friends

what is the differnce betwee reliability and overall equipment effectiveness?

and how can i calculate it?

any articles will be gratefull?

best regards

 

[IRstuff]

Reliability is measured in a variety of ways:

mean time between failure (MTBF)

failure rate (1/MTBF) in failures per million hours

Availability = MTBF/(MTBF+mean downtime)



Effectiveness is usually a term relating to equipment performance, rather than reliability, per se., although reliability may be a component of effectiveness.


TTFN

 

[Veero]

It is possible to determine reliability from OEE data.

I am in the process of determining the Overall Equipment Effectiveness of 6 machines in our factory. I issue daily time recording sheets which is a simple table with time along the x axis and duties/operations along the y axis and at 15 minute intervals whoever is operating the machine at the time notes down what the machine is doing.

One of the critical aspects of measuring OEE is to ensure that the machinists are not under the impression they are being scrutinised under a "time and motion" style study. Creating this environment will help to gain more accurate data.

Each morning I gather in the orevious days' sheets and tot up the data. From this I look at 3 main factors:

- Overall shift time (ie the total theoretcial time the machines could be running)
- Overall availability (ie total shift time minus time taken performing setups, changeovers that kind of operation)
- Actual machining time (this is the total of attended and unattended operating time)

OEE is determined by multiplying 3 percentages, Availability x Productivity x Quality. This should give and overall %age.

Looking at the raw data it is possible to calculate averages for the mean time before failure (I am looking at machine stoppages) and mean time before restart (time taken to get the machines up and running again) which is not strictly MTBF and MTTR.

It is important to get across to the shop floor staff exactly why you are perfoming OEE measurements. Without proper instruction they could see it as I have said above as a "time and motion" study in which case the data will be well skewed, unless you can take data directly from the machine control panels.

Our new Mazak 5 axis machining centre runs on Windows XP and one of the built in programs monitors in real time exactly what the machine is doing so there is no need to record what the operator thinks we want.

I am perfoming OEE data collection as part of an excercise to identify and eliminate wastes. We are currently in the middle of perfoming a 5S audit and it will be interesting to see what effect the 5S has on our machines' OEE figures.

WHat industry are you in and what machines would you be examining OEE on?

(I have been a lurker on here for a while but this is my first post so please be gentle )

Thanks
Veero