After the equipment is qualified and in mass production,
all optimized parameter setting should be documented in standard operating
procedure (SOP). Production should
follow the same setting to reduce variation in the process output. There must be performance monitoring of the
equipment and total preventive maintenance (TPM) system set up. A good
metrics to use for monitoring the performance of manufacturing equipment would
be overall equipment efficiency, OEE, developed by Seichi Nakajima in 1960s. OEE
address equipment losses due to plan and unplan shutdown, production
adjustment, idling, speed, quality defect and reprocessing : -
Metrics
|
Calculated
based on
|
Availability
|
uptime
and downtime
|
Performance
|
total
output, operating machine speed and time
|
Quality
|
Yield
rate
|
OEE
% = Availability X Performance X
Quality
|
From the above table, in order to calculate OEE,
manufacturers need to setup proper data collection infrastructure which should be
included in the planning phase of equipment setup per my previous article. OEE ought
to be reviewed by management on regular basis.
There should be a management goal or target set for OEE metrics and
investigation must be conducted if OEE does not meet the target. The better the equipment efficiency, the higher the OEE value.
In order to optimize OEE, it is utmost important that the
equipment is well maintained base on total preventive maintenance (TPM) system. Total preventive maintenance concept was also
founded by Seichi Nakajima. TPM is aim
to achieve Zero Defects, Zero Breakdown and Zero accidents in all functional
areas of the organization by involving all levels of people in organization to
promote self-maintenance. The table
below shows the eight pillar use in TPM.
TPM
Pillars
|
Elements
|
Autonomous Maintenance
|
Person
who is using the machine such as operator own equipment daily maintenance
through step by step approach that include inspection and cleaning. This will free up the time of maintenance
team to focus on specialize maintenance and improvement work.
|
Focused Improvement
|
Small
group of dedicated equipment specialist to conduct complicated PM work. They should review and analyze the OEE data
to find incremental improvement opportunity for equipment towards Zero
Defects, Zero Breakdown and Zero accidents
|
Planned Maintenance
|
1. Maintenance planning
should take into consideration of available resources and number of equipment
need PM.
2. Determine the
preventive maintenance interval from daily, weekly, monthly, quarterly to
yearly and what are the PM activities should be carried out. PM interval could also base on production
volume.
3. There should be
auto trigger system before PM due date to the management and equipment owner
4. Ensure the planned
maintenance is feasible to be carried out by the maintenance team
|
Quality management
|
Equipment
has the capability to have auto warning such as andon light if there is
error. All warning must investigated,
documented with action plan. A study
must be conducted on how to prevent any error.
|
Early/Development management
|
Established
proper documentation which include lesson learned on the current equipment
from qualification to sustaining phase. Apply the lesson learned in the
future new equipment.
|
Education and Training
|
Person
who conducts preventive maintenance must be trained and certified. For complicated equipment, the training and
certification should be done by equipment supplier.
|
Safety Health Environment
|
Sustain
a safe and healthy accident free working environment
|
Administrative & office TPM
|
Reiterate
the TPM principles beyond
manufacturing equipment in the production floor
|
The recommended activities for preventive maintenance
are:
- Preventive maintenance activities generally consist of inspecting the equipment parts for wear and tear, replace short usage life part before they worn out, cleaning, lubrication for moving parts.
- All preventive maintenance action must be recorded. This encompass parts that was replaced.
- Document PM Activities in checklist format to ensure all PM are carried per PM checklist and according schedule date.
- After a major preventive maintenance work, actual production parts must be verified before handover for mass production. This is known as 1st piece verification done after major PM.
In order to prevent downtime due to unavailability of
equipment spare parts, the PM team
must setup a spare part management system and keep stock for frequent replaced
parts.
Automated manufacturing is mostly suitable for high
volume low mix type of manufacturer due relatively longer model conversion time
compare to manual/semi auto line.
Complicated equipment which need expert maintenance |
Manufacturer had perceived that automation will bring cost
competiveness into their product, which in actual fact there are also hidden
cost in maintenance of the equipment. There
are many Japanese/Korean/China multinational
brand suppliers (LCD, battery cells and semiconductor) invested millions USD to purchase a fully automated
manufacturing line, however there are
only a handful who had qualification, monitoring and maintenance system to
match the investment made in equipment acquisition. Automation can produce consistent good or bad
parts, therefore a lot of planning by expert must be done to ensure only
consistent good parts being manufactured and maintained.