THE VALUE OF BIANNUAL CORRUGATED ENGINEERING
AUDITS TO YOUR OPERATION
June 1, 2003
Editor’s note: Examples of engineering audit forms for corrugated operations
are included at the end of this article.
Today’s market and customer demands are experiencing
increasing levels of competition and a slack economy. Technology
has made our business more involved and quality standards have definitely
tightened. It is forcing us to look for techniques to improve our board
quality, productivity, and reduce maintenance, man-hours, operating and
overtime costs due to unscheduled downtime, waste levels.
I realize that this is a great deal to ask for in today’s environment
of minimal capital expenditures but it is possible through the effective
use of biannual corrugated engineering audits. Our equipment must be kept
in top condition, as most of performance containerboard produced today
is not as forgiving as what was produced a short decade ago. Corrugators
and flexos must run at higher speeds with fewer defects. It’s no
longer acceptable to have 1% to 2% defects. Automated setup equipment
requires fewer defects as most boxes are packed by high speed packing
machines. The target for 0 defects is now our goal. We are asked to deliver
“Just-in-time” and not within normal lead times. Production
levels must be high in order to stay cost competitive and we must adapt
to a constantly changing market place.
The basic philosophy of an audit is to get the primary components of
the corrugator back into O.E.M. (Original Equipment Manufacturer) condition.
O.E.M. condition is when the corrugator was newly installed. Request your
corrugator supplier(s) or supplier(s) for complete O.E.M. specifications
if they are not already in your position. I can help you acquire this
information when you supply the make, model, year of manufacture, and
serial number of each machine center.
After completing the audit and correcting all of the problem areas identified,
your equipment will run faster, smoother, and be more productive. You
will have less downtime due to breakdowns, less waste, less costly maintenance,
decreased energy costs, consistently improved box performance, and last
but not least, MORE PROFITS, while still remaining
“NOW DO I HAVE YOUR FULL ATTENTION?”
My Team’s Corrugated Mechanical Engineering Audit provides a full
physical examination of the mechanical condition of the following production
centers and their individual components:
- Hot Plates
- Double Backer
- Glue Machine (GM)
- GM Triple Deck Preheaters
- Bridge Guide
- Single Facer(s) (SF)
- SF Preheaters(s)
- SF Preconditioner(s)
- SF Inclined Conveyor
- Roll Stands
- Steam System
There are four basic phases of this evaluation which follow:
Phase One – Coordination Meeting
Before the audit begins, our team member will meet with the Plant’s
Management Team. This usually consists of the General Manager or Owner,
Plant Manager, Corrugator Supervisor or Superintendent, Maintenance Manager,
and Corrugator Scheduler. This meeting will set the priorities for auditing
the equipment, a tentative schedule for the audit, and coordinate the
resources required by our team from the plant. If any of the audit’s
downtime can be conducted in conjunction with scheduled Preventative Maintenance
(PM), that is fine as long as both teams are not working on the same component.
The time for each component is flexible and the longer we have the equipment,
the more thorough we can be with the planned mechanical checks. Days are
also flexible, but keep in mind, the day we check the glue machine, bridge
guides, preheater stack, and hot plates, the corrugator will obviously
not be producing board. The glue machine will have to be cleaned up and
cleared of all paper before the audit can start. An operator and plant
personnel must be available to start or jog the machine as required during
the audit for safety requirements.
Phase Two – Conducting the Audit
Safety is the first priority of our Team. During the audit we will need
the assistance of at least one maintenance person and others designated
by Plant Management who will be trained during your equipment evaluation.
A daily meeting with our assigned personnel will review our joint findings,
and the combined board effects/wastes caused by the mechanical/adhesive/heat
We will check the following:
- Rolls for wear
- Coating thickness, flute depth, parallelism, and operation of corrugated
- Steam vessels for proper temperature.
- Proper siphon operation/position.
- Steam supply/return legs and traps for proper operation
- Liner and medium for proper temperatures and side-to-side temperature
- Hot plates, glue machine, preheater stacks, bridge guides, single
facers, preheaters, preconditioners, roll stand, and splicers will all
be checked for proper level and alignment.
- All rolls for run out (Total Indicated Run out – TIR)
- All roll bearings for wear (Bearing Clearance – BC)
- All roll gaps for parallism
- Fingers/Clean-out clearance and performance
- Splicer operation
- Roll stand operation
- Adhesive performance – viscosity, pH, gel point, total oven-dry
percent solids, and WPA/WRA resins.
- Equipment upgrades
Phase Three – Out Brief
The detailed equipment system out brief with Plant Management will apply
suggested priorities on equipment adjustment, mechanical issues, repair,
modifications, or upgrades along with future equipment installations to
improve board quality, productivity, and plant profitability.
We also discuss specific serious mechanical issues:
Phase Four – Follow-Up
- How issues contribute to current plant problems.
- How corrective actions will eliminate plant issues.
- Equipment improvements and upgrades.
- Typical areas of improvement:
- Increase productivity
- Decrease waste
- Decrease downtime
- Decrease overtime
- Decrease energy costs
This visit enables the plant to ensure they have gotten the maximum benefit
from the mechanical audit.
- Review completed recommendations
- Determine if corrective actions have addressed plant issues
- Assess priorities and plant requirements
- Ensure plant can incorporate audit checks into their preventative
A possible schedule for a typical double wall plant would be as follows:
||Quick familiarization tour of the plant
1 Hour meeting to plan audit
||Initial survey of equipment/audit preparation
8 a.m. – 12 p.m. – Audit SF #1
1 p.m. – 5 p.m. – Audit SF #2
||8 a.m. – 11 a.m. – Review of findings and training videos
for maintenance/other assigned personnel.
12 p.m. – 5 p.m. – Glue machine/Bridge Guides/Preheaters
Stack/Hot plates/Double backer.
||8 a.m. – 12 p.m. – Audit SF #3
3 p.m. – 5 p.m. – Out brief with GM, PM, MM, Corrugator
Supervisor, other plant personnel as appropriate.
NOTE: In order to make this an on-going dynamic
exercise, you have to have the people who run the machine do this work
and be taught these vital techniques. After all, who knows more about
how this machine runs and its problems than the crews who run it day-after-day?
I firmly believe that after each day’s audit efforts we need to
come back to the classroom and discuss what we have found. It is pivotal
to the plant’s future that we discuss why certain components have
to be repaired or replaced as soon as possible. I think the most
important thing you have to do is start to integrate some of these checks
into your preventative maintenance program. Some of these critical checks
should be performed in every PM.
Maintenance certainly has to be fully involved during the corrugator
audit but the basic audit should be performed by the personnel that run
the machine. This not only gives them ownership in the equipment
that they run, but they will take better care of it to insure that it
runs better, consistently. Everyone wins!!
The second audit of your biannual audit should be conducted by
your operators and maintenance crews. You will find fewer areas that will
require repairs and adjustments with each audit performed. This net
result of your team’s efforts will significantly enhance
production efficiency; growing production records; improved combined board
quality and box performance; lower waste levels; an inability of your
competitors to compete against you, and most importantly growing market
share and profits.
We estimate an increased production level of 5 to 30+% and a waste savings
of 1 to 5+%, depending upon the corrugator’s condition. It is also
dependant upon how much you are willing to spend to bring the corrugator
back into O.E.M. condition.
Are you ready to make the biannual audit work for you?
Can you picture yourself as the leader of the pack?
Are you ready to get fully involved and make this simple process work
Once you decide to move forward, you will need the tools, training,
and engineering forms necessary to conduct the audit. I have attached
a list of tools required and some sample engineering audit forms to be
used as a guide to develop your own in-house forms.
We want to make sure that all the machine’s rolls are the correct
diameter, proper crown, roundness, level, and paralleled. We want to insure
all bearings have minimum clearances. Before going further, I would like
to explain the tools used in the audit along with the O.E.M.’s maximum
Easy Read Pi Tape
In this instance Pi stands for 3.14- the arc of a circle. It will accurately
measure the diameter of a roll to one thousandth of an inch (.0254mm).
These measurements are necessary for the kind of work we do with your
equipment. We use the Pi tape to evaluate proper roll diameter, roll wear,
and crown. Spec +/- .001” (.0254mm).
Magnetic Base and Dial Indicator
This 100 lb. pull magnetic base has an adjustable gooseneck that is more
versatile than the standard model. This may sound like overkill, but when
you have four to five layers of paint to penetrate, the magnet will support
a 10” to 12” (25.4 cm to 30.48 cm) extension rod necessary
to reach difficult places. You will need it for a firm hold while making
measurements. A dial indicator is used to measure the roundness of the
roll. We call this Total Indicated Run-Out (T.I.R.). (See TAPPI’s
TIP 0304-56 – T.I.R. and its impact on combined board quality.)
We also use this instrument to measure the bearing clearance (B.C.) of
each roll. (See TAPPI’s TIP 0304-47 – Bearing clearance
checks and their impact)
Generally T.I.R.’s maximum allowable specs on rolls are as follows:
- Cold rolls - .005” (.127mm)
- Applicator and meter rolls – replace at .004” (.100mm)
- Hot rolls - .005” (.127mm)
- Preheater, Preconditioner drums - .010” (.254mm)
- Corrugator rolls (must be out of the machine in most cases) and pressure
rolls – 002” (.0508mm)
- Note: Heated rolls should be checked when at temperature.
Generally the maximum allowable spec on a roll’s bearing clearance
is as follows:
- Cold rolls - .005” (.127mm)
- Applicator and meter rolls -.002” (.0508mm)
- Hot rolls, drums - .010” (.254mm)
- Note: Heated rolls should be checked when at temperature.
Corrugator Roll Depth Gauge
This instrument is used, once zeroed, using the appropriate gauge blocks
for the corrugator roll’s flute, to measure chordal flute depth (measured
from the tips of two adjacent flutes to the base of the flute). This check
should be accomplished cold for safety reasons. Maximum acceptable wear
which will permit reconditioning are as follows: .003” (.076mm) initial
coating – maximum wear is .002” (.051mm), .006” (.152mm)
initial coating – maximum wear is .003” (.076mm).
Note: Rolls should be checked monthly after 60,000,000 lineal feet
(18,288,000m) have been run to check for roll wear. (See TAPPI TIP 0304-73
Checking chrome thickness on corrugator rolls)
Note: Worn rolls increase take-up factor and consumes more medium.
Corrugated Roll Biddle Chrome or Tungston Carbide Thickness Gauge
This simple instrument utilizes a highly sensitive spring and magnet to
check coating thicknesses down to as low as .0001” (.0025mm). This
check should be accomplished cold for safety reasons. Rolls should be
checked monthly after 60,000,000 lineal feet (18,288,000m) have been run
to check for roll wear. See maximum wear limits listed above in the “Corrugated
Roll Depth Gauge” write-up. (See TAPPI TIP 0304-73 Checking
chrome thickness on corrugated rolls)
Corrugator Roll Parallelism Check with NCR (National Cash Register)
This procedure is used to check the parallel of corrugator rolls when
they are at operating temperature (Safety procedures must be taken to
avoid burns). When the NCR strips are fed through the corrugator rolls,
the flute tips leave their impressions on the NCR paper where contact
occurs. (See TAPPI TIP 0304-62 Checking the parallel of corrugator
rolls with “NCR”)
Note: Misaligned rolls can result in medium fracture, leaning flutes,
hi-lows, and reduced combined board caliper, roll life.
Machinist Level and 100’ (30.48m) Steel Tape
These easy to use instruments once calibrated are utilized to measure
the components of the corrugator for proper level and alignment. Specification
maximum is +/- .006”/foot (+/- .152mm/. 3048m).
Example: A 98” (245 cm) wide corrugator’s spec is +/- .049”/8.17
feet (+/- 245cm/. 3048m) for level and for proper alignment +/- 1/8”
or .125” (+/- 3.175mm). (See TAPPI article “The Machinist
Level” by John R. Troyke, and “The Importance of
Keeping your Corrugator Leveled and Aligned” by Richard J.
Note: Out of level or missalignent corrugator components can cause twist
warp, flip up or down warp, loose edge bond, misalignment waste, and
abnormal bearing wear.
Stainless Steel Feeler Gauges 1’ (2.54cm) Long .003” to
.040” (.076mm to 1.016mm)
Utilized to check meter, applicator, rider roll gaps +/- .001” (+/-
.025mm) side-to-side measurements and for single facer applicator roll
pan dam wear – “C” Flute = .0015” (.038mm); “B”
Flute = .001” (.025mm), and “E/F/G/N/O/Z” Flutes = 0”
Steel Scoring Rule or Straight Edge 18” (45.72cm) Long
Utilized to check the level of the double backer’s hot plates for
proper level. The hot plates must be maintained so that the leading edge
of any plate is slightly lower than the trailing edge of the preceding
plate. We utilize a step down spec of .003” to .005” (.076
to .127cm) when measured hot. (See TAPPI TIP 0304-66 The impact of
double backer hot plate level on board quality and how to measure it)
Note: This test must be accomplished at normal operating temperature
thus protective gloves must be used.
Infrared Pyrometer with Laser Sighting
Utilized to conduct temperature audits on all of the corrugator’s
steam heated vessels. The pyrometer is a very valuable and safe tool to
use in conjunction with an inexpensive primer gray spray paint.
This paint is used to dull a heated surface to insure accurate measurements
on top, and the very bottom of all steam heated rolls and hot plates.
We are targeting an idle temperature of not less than 350ºF (177ºC).
If the temperature variation top to bottom is high you may have a siphon
placement or steam balance issue which will have to be addressed. (See
TAPPI TIP 0304-66 Conducting a corrugator temperature audit)
Note: Set the pyrometer’s emissivity (reflective index) to .95
prior to use for accurate results.
The pyrometer is also used to check the “side-to-side” temperature
variation on the liners, single face web (open face), and medium at a
point just after leaving the preheaters, pressure rolls, preconditioners,
and hot plates. The maximum allowable side-to-side temperature variation
on liner, medium, single face web, and combined board is 6ºF (3ºC)
when measured at a constant line speed. The measurement is taken at about
the same distance from the heated vessel and inward at about 1 foot (.3m)
in on each side of the sheet to insure measurement accuracy.
Note: If the “side-to-side” temperature variation exceeds
6ºF (3ºc) on “A/B/C/D/K” flutes or 3ºF (1ºc)
on all micro flutes, you may have a level, alignment, or liner/medium
winding issue. This may cause twist warp, flip up or down warp, loose
edge bond, low ECT performance, waste, and reduced production speeds.
(See attached sample “side-to-side” liner, single face web
temperature audit form.)
I would like to address the matter of ordering rolls. We’ve touched
on this subject earlier. It is important to set up an audit check on all
incoming rolls to protect yourself. Make sure the diameter and crowns
are correct and that there is no more than .0005” T.I.R. in the
applicator and meter rolls. This can be accomplished by building a set
of roll support stands for use in T.I.R. measurements. (Detailed drawings
and parts are available if requested.) Tell your supplier that you are
going to check everything he sends you and that the rolls will
be returned if they don’t meet your T.I.R. spec of .0005”
(.0127mm) at their cost. Supply the QEM with your specs. Do not install
an out of spec roll! Causes more harm than good!
Finally, you are ready to accomplish the actual audit. Plan on spending
at least four hours on each machine center unless you divide into two
or more audit teams with the appropriate training and tools. Supply the
auditors with the machine specs so that they can determine immediately
how close the rolls are to specification. I suggest that you computerize
the machine specifications and audit results on an Excel spreadsheet to
compare the current audit with the past audit to track component wear
and failure rates. This simple procedure will help you establish “Predictive
Maintenance Failure Points” thus significantly reducing unplanned
Do you want to become the best in your business by achieving consistent
gains year after year in productivity, efficiency, box performance, waste
reduction, customer satisfaction, and market share?
All it will take from you to make this happen is having the initiative
and the staying power to complete two audits per year thus keeping your
corrugator in OEM condition! Know what you want to accomplish and keep
this goal firmly in sight.
I hope this paper gives you a clear picture of what we
accomplish during an audit. Please call if you need help or ask questions.
Contact the author by email at firstname.lastname@example.org.
Examples of engineering audit forms for corrugated operations.