2009:009
M A S T E R ' S T H E S I S
Measuring the Availability at the Sawmill and the Capacity at the Planing Mill
at SCA Timber Rundvik Sawmill
Svetlana Stolyarova
Luleå University of Technology Master Thesis, Continuation Courses
Wood Technology Department of Skellefteå Campus
Measuring the availability at the sawmill and the capacity at the planing mill at SCA Timber Rundvik sawmill
Svetlana Stolyarova
Master of Science Programme in Wood Technology
The Department of Wood Technology at Luleå University in Skellefteå
2008-04-15
Abstract
This master thesis was done at SCA Rundvik sawmill.
Rundvik sawmill belongs to SCA group. It is produced 231,000 m³ and with the share of developed timber is 61 %.
One of two goals with this master thesis is to measure the availability at the sawmill more detailed.
It means to start to count a stop as a downtime in the production after 10 seconds instead of 1 minute. And it is to make more stop codes over the sawline to show the sections where the stops appear often. It was not done any analyzes of the stops reasons or made any suggestions how to avoid them. The conclusion does not give any solutions how to increase the availability.
The measuring time was 127 hours and the availability gotten during the measuring is 65%.
Stops were started to be registered after 10 seconds since they occurred. The sorting of the stops were done. Stops from 10 seconds to 1 minute were sorted like short stops and gave about 2,3 hour per 1 productive week.
The distribution of the stops shows the area of the sawing house where the problems exist. These areas are the saw in feed, the sawline, the green sorting, the stick stacker, the chips and sawdust area. The share of the total stop time is viewed around these areas.
A brief analyze of the stick stacker area has been done.
For the sawline, the use of degree was measured - 76% - and zones (machines) were pointed out if they are in need of an improvement to increase the productivity.
The second goal of the work was to check the flow at the planning mill, at the specific section from the in feed to the planer. The assignment at the planer mill is to look at one special product that gives the lack of boards to the planer.
According to the data from SCA, the planer needs 200/3,7 ≈ 54 piece/minute in average.
The mean value (pieces/minute) that goes really through the planer is 23 pieces/minute.
Capacity losses and areas with problems in this section were estimated.
Preface
This master thesis was done from December 2007 to May 2008.
I want to say thanks to SCA Timber, Rundvik sawmill for the possibility to make my master thesis in the company.
I want to thank specially:
Sören Edmark (technical director) initiated to this master thesis.
Sten - Olov Andersson (sawmill manager) for his trust in this work.
Lars – Erik Jönsson (supervisor /production manager) for his support and trust in this work.
Peter Henriksson (supervisor /production manager) for his supervising and help.
Alf Eriksson (planing mill manager) for the help and support with data.
Kent Jonsson (production optimizer) for the help and support with the measuring equipment.
Micael Öhman (examiner/supervisor, LTU) for his support and help during the work for the master thesis.
Also I want to give big and great thanks to all operators, especially Johnny Grahn and Peter Eriksson, for the support during my master thesis work and thanks to the
maintenance staff for their help.
Svetlana Stolyarova Rundvik 2008-04-15
Index
Abstract I
Preface II
Index III
1. Introduction 1
1.1 Rundvik sawmill 1
1.2 Background to the master thesis 2
1.3 Mission 2
1.4 Goal 2
1.5 Delimitation 3
2. Presentation of the sawmill and the planing mill 4
2.1 Saw process 5
2.1.1 Saw in feed 5
2.1.2 Sawline 8
2.1.3 Green sorting 11
2.1.4 Pockets 13
2.1.5 Stick stacker 13
2.2 Planing process 14
2.2.1 Tilt area 14
2.2.2 Elevator area 14
2.2.3 Operator area 15
2.2.4 Area between the operator area and the planer 15 2.2.5 Briefly about the planer and what happens after the planer 16
3. Methods and materials 17
3.1 Sawmill 17
3.1.1 Measuring and calculating the availability for the saw house 17
3.1.2 Present situation at the sawmill 20
3.1.3 Use of degree for the sawline 20
3.1.4 Example of calculating the availability and the use of degree for
the saw house 21
3.2 Stick stacker 22
3.2.1 Measuring the use of degree of the stick stacker area 22
3.3 Planing mill 24
3.4 Easy calculating in excel 25
3.5 Measuring equipment 25
4. Theory 26
4.1 Value stream mapping 26
4.2 Some useful Lean thinking 27
4.3 Calculating the availability 29
4.4 Calculating the use of degree 30
4.5 The importance to have a short time until it start to register a stop 31
4.6 Statistical evaluation method 32
4.7 Bottleneck 33
4.8 Best practice 33
4.9 SMED (Single Minute Exchange of Die) 34
5. Results 35
5.1 Present situation availability for the sawmill 35
5.2 New measured availability 37
5.3 Use of degree for the sawline 43
5.4 Stick stacker 46
5.5 Planing mill 48
5.6 Calculating in excel for the first section of the planing mill 51
6. Discussions and conclusions 53
6.1 Availability in the saw house 53
6.1.1 Compare the present situation and the new measured
availability 53
6.1.2 New measured availability 53
6.2 Use of degree in the sawline 54
6.3 Stick stacker 55
6.4 First section in the planing mill 56
6.5 Use for the calculating in excel for the planing mill 57
6.6 Achievements of the project 57
7. Suggestions for the continues work 59
7.1 Sawmill 59
7.2 Planing mill 59
Reference 60
Appendix 62
Appendix 1. Layout Rundvik sawmill 63
Appendix 2. Data for the present situation at the sawmill 64
Appendix 3. Data for the stick stacker 66
Appendix 4. Data for the planing mill 67
Appendix 5. Layout Rundvik planing mill first section 69
1. Introduction
1.1 Rundvik sawmill
Rundvik sawmill is situated in a village called Rundvik near E4, between Umeå and Örnsköldsvik in Västerbotten.
Production
The production is nordic spruce. At Rundviks sawmill they produce 231,000 m³ timber of that it is 99,000 m³ further processed. Share of developed timber is 61 %.
Certification
Rundvik Sawmill is certified in accordance with ISO 9001:2000, 14001:2004 and FSC Chain of Custody (Forest Stewardship Council).
Site plan
Picture 1. Shows the site plan for Rundvik sawmill.
Employees
Today they are 78 employees and 26 contractors.
1.2 Background to the master thesis
At the sawmill the availability is measured in a rough way. In the future it is wanted to be more detailed. A more detailed measuring will give information to take the right decision to do some technical investments.
At the planer mill an investment will be made. It is needed to have data before to change the equipment and to see the effect of the investment. The assignment at the planer mill is to look at one special product that gives the lack of boards to the planer.
1.3 Mission
One of two missions with this master thesis is to make it more detailed about measuring the availability at the sawmill. It means to reduce time before man start to count the downtimes during the sawing process. And make more stop codes over the sawline so it will point out where the stops exist.
The second mission will be to look at the flow between the in feed at the planer mill to the planer (just a little section of the whole planing mill).
1.4 Goals For the sawline:
1. Measure the uptime and the downtime for the availability.
2. Make conclusions for the data according to the availability.
- Define how many short stops (from 10s to 1min) exist and summary value of them.
- Show stops distribution around the sections including what values short and long stops have for every section.
- Analyze the distribution of the stops around the areas in accordance to the sawing pattern.
- Show the distribution of the stops inside of the sawline.
3. Calculate the use of degree for the sawline.
4. Make conclusions for the old availability data.
- Show stops distribution around the sections including what values short and long stops have for every section.
- Compare this old data with the new results.
For the planing mill:
1. Find the mean value for the capacity (pieces/minute) on the section between the infeed (tilt) for boards at the planing mill to the planer.
2. Estimate capacity losses in this section.
1.5 Delimitation
At the sawmill, it is just to look from the area saw in feed to the area where the stick stacker is.
The conclusion will not give any solutions how to increase the availability. Any analyzes of stops reasons will be not done or made any suggestions to avoid them.
It will just be to look for the zone between the in feed (tilt) for boards at the planing mill to the planer.
The conclusion will not give any cost estimate.
Status report during the work will only be oral at the leading board meetings.
The study excludes to look at the quality and mechanics damage of the planks and sideboards.
2. Presentation of the sawmill and the planing mill
Rundviks sawmill belongs to SCA Timber together with seven more sawmills. The raw material that is transported to Rundviks sawmill will pass some stations at the sawmill area before it goes to the customer.
The stations that they will pass are log sorting, saw house, drying kilns, grading plant and the planing mill.
At the log sorting the logs are divided into classes according the top diameter and length. The sorting consists of 64 bins.
The sorting at this station is made by an impartial organisation called VMF.
At the saw house area there are many sections where barks, planks, boards, chips and sawdust are produced.
The bark, chips and the sawdust are the rest products. And the plank and board are the main products.
The bark is taken away at the saw in feed area. The sawline cuts out the planks and boards and also gives the material for the rest products like chips and sawdust.
At the green sorting they make the first adjustments for the planks and boards and sort them in different pockets. The sorting is according to the quality, length and dimensions.
Finally at the saw house it is the stick stacker section where they make the packages for the drying kilns.
The drying process takes a lot of time. It takes between 2 to 20 days. The difference in time depends on which dimension and the moisture content that are needed to be achieved.
The boards of the same dimension and moisture content are collected together in the same kiln.
After drying the planks and the boards go either to the grading plant or the planing mill.
At the grading plant they grade every plank and board piece by piece. When the grading is finished, packages are made to be delivered to the customers.
At the planing mill the planks and boards are planned and then graded and made package for delivering to the customers.
The process that is observed in this project consists of the saw house and the part before the planer in the planing mill.
2.1 Saw process
This part is included in this project and it will be more described what happens in each section at the saw house.
The sections are:
Saw in feed
Sawline
Green sorting planks and boards
Pockets
Stick stacker 2.1.1 Saw in feed
The first step is to get the log from the log truck, see picture 2.
Picture 2. Shows a timber truck and the beginning of the saw in feed.
After that the logs are divided one by one in a step feeder. After the step feeder it goes on a longitudinal conveyor through a scanner.
When the scanner has given the information of the shape of the log, it is decided in which way the log should turn when it comes to the log turner, see picture 3.
Picture 3. Shows the log turner.
After the turner the log goes on a longitudinal conveyor through the debarking machine, see picture 4.
Picture 4. Shows the debarking machine.
The debarking machine is cleaning the logs from the bark. After the debarking machine the logs go on a cross way conveyor to the butt reducer, see picture 5.
Picture 5. Shows the butt reducer.
After the butt reducer logs go on a longitudinal conveyor to a cross way conveyor and finally to the step feeder that puts them to the sawline.
This step is necessary to get a round shape of the butt end of the logs. If this is not taken away, it can cause a problem for the optimizing the saw process. The problem can be that the turner will not turn as much as it is needed. If it has happened it is expected that the yield out of the log perhaps will be lower than a predicted value.
2.1.2 Sawline
The sawline is a full automatically optimizing profiler sawline from Ari, see picture 6.
In the line it is optimizing the sideboards individually for each boards and it is also a curve sawing line.
Picture 6. Shows a sawline from Ari.
In the picture 7, 8 and 9 there is the function of the machines at the sawline. The beginning of the saw process is started in the picture 7 to the left end then it moves to the right through the picture 8 and 9. So the finally step in the sawline will be the circle saw that cut out the centre
planks/boards.
First four steps in the sawline, see picture 7:
1. The first step is the 2-D scanner (Stockmätning/mätram). The scanner gives the
information for every saw machine in the sawline. This information makes every log to be optimized through the saw process.
2. Second step is the turner (Rundvridning). The turner make the log turn to the optimized position.
3. Third step is the precilog measuring (Precilogmätning). This measuring is done if the log should move cross way. The log moves depending on the optimizing from the scanner and the precilog measuring equipment.
4. Fourth step is a conveyor. This conveyor can move a little bit crossway (left or right) at the same time it puts the log in the longitudinal direction.
Picture 7. Shows the first four steps in the sawline.
Next four steps in the sawline (the steps after picture 7), see picture 8:
5. Fifth step is the first cutting. This machine cuts out two plane surfaces on the log and turns in to a block with two plane surfaces.
6. Sixth step is measuring (Blekesmätning) for optimizing the profile cutting in step seven.
7. Seventh step is a cutter that cuts out a profile of a board on the block.
8. Eighth step is a circle saw that cuts out the first pair of sideboards.
Picture 8. Shows next four steps in the sawline.
Last six steps in the sawline, see picture 9:
Make a notice in the picture 9, it just shows 5 steps. There is one more machine after step twelve, so step thirteen does not exist in picture 9.
9. Ninth step is measuring (Blekesmätning) for optimizing the profile cutting in step ten.
10. Tenth step is cutting out the final profile from the block.
11. Eleventh step is a block turner.
12. Twelfth step is to cut away the last existing round surface on the block.
13. Thirteenth step is to cut out sideboards.
14. Fourteenth step is to divide the finally block into centre boards/planks.
Picture 9. Shows the finally five steps in the sawline.
After this procedure the centreboards/planks and sideboards are divided into two flows. The centre boards/planks go to the green sorting for planks. The sideboards move to the green sorting for sideboards.
2.1.3 Green sorting
Green sorting centreboards/planks:
Green sorting for planks just go on a crossway conveyor, see picture 10 to the pockets, see picture 11. Some sorting can be done when it is different dimensions of the centre planks. Then they go on the upper cross way conveyor, see in picture 10. There is possible to sort the planks so the planks of same dimension fall in the same pocket, see picture 11.
Picture 10. Shows the cross way conveyor for the planks just after the sawline.
Picture 11. Shows the planks falling into a pocket.
Green sorting sideboards:
Green sorting for boards goes on a crossway conveyor, see picture 12 to the pockets. The sorting to the pockets is according of dimension, quality and length. This process is done with scanning measuring equipment for grading boards. The dimension, length and amount of wane of the board can be measured with the equipment. Just before the pockets it is a trimmer which is cutting the boards to the right length according to some parameters that is set in the measuring equipment.
Picture 12. Shows the green sorting for the sideboards.
2.1.4 Pockets
Depending on the quality, dimension and length the boards are sorted in one of the 25 pockets see picture 13. The planks side consists of 6 pockets and the sorting is based on the dimensions.
Pockets make the storage after the green sorting. When a pocket is full it can be opened and pieces/package drives to the stick stacker.
Picture 13. Shows the pockets.
2.1.5 Stick stacker
The last step is the stick stacker area.
When a pocket at the sorting area is full the operator automatically or manually empties the pocket.
The planks and boards from each pocket are put together to a package ready for the drying kiln.
These packages consist of the same dimension of boards or planks.
To make the packages it is also necessary to have a flow of sticks.
The main purpose of the sticks is to make a gap between every layer of boards or planks in the packages. These gaps help the drying process.
The planks and boards go on the crossway conveyors from the pockets to the package making.
The flow is stopped periodically to make a gap between every layer so a package can be made.
It also puts the boards piece by piece so they can go in longitudinal way. When the boards go in the longitudinal way, they are separated to opposite directions. So every first board goes more to the right and the every second board is moved to the opposite left direction. That makes the packages wider and is necessary for the further process at the sawmill.
Picture 14 is a view of the finished package with visible gaps that the sticks make.
Picture 14. Shows a final package from the stick stacker section.
2.2 Planing process
This part is included in this project. Further it will be more described what happens in each zone in the section before the planer in the planing mill. What happens after the planer will be
overviewed briefly.
The zones of the studied section are:
Tilt area
Elevator area
Operator area
Area between operator area and the planer 2.2.1 Tilt area
This area consists of the intake for packages, the tilt and two cross way conveyors after the tilt, see picture 15.
Picture 15. Shows the tilt area.
2.2.2 Elevator area
Elevator is viewed on the picture 16. The elevator function is to divide the boards piece by piece to the cross way conveyor before the feeder to the operator area.
Picture 16. Shows a common elevator.
2.2.3 Operator area
The operator area consists of the few small cross way belt conveyors and separators. See picture 17.
This area makes big gaps between the boards, so the operator can check piece by piece.
Picture17. Shows the operator area.
2.2.4 Area between the operator area and the planer
In this area it is just crossways conveyors until the feeder to the planer, see picture 18.
Picture 18. Shows the area just before the planer.
2.2.5 Briefly about the planer and what happens after the planer Feeder fills a planer to make the surfaces of the boards smooth.
After the planer a sorting machine locates – “Wood Eye”. There the boards are sorted according to quality and “Wood Eye” sends information about the locations of defects to a marking machine.
All the boards go through the marking device that marks them based on the information from
“Wood Eye”. The marking is done with an invisible ink.
Then it is located a scanner device which recognizes the marks on the boards and sends
information to a separator. The separator turns some boards to the second floor conveyors if it is necessary.
The boards with satisfied quality and length continue to follow first floor conveyors to the package assembling section.
Before this section the label machine and trimmer exist. Labels are tagged only to boards for USA market.
The finished packages follow on rolls-conveyors to the package packing section.
The boards with defects move on conveyors of second floor to “OPTICUT 350”- cutting device.
Defects are cut depending on marks of the invisible ink and the length module.
The boards passing “OPTICUT 350” have usually two groups of quality: “A” and “B”.
The boards and the wastes after cutting go the same conveyor to the waste pusher first and then to the pushers that separate boards according to their quality.
The boards of quality “B” turn to another conveyors and then to the package assembling sections.
Boards of quality “A” move to the last pusher and are separated there in accordance to their lengths to the different package assembling sections. Before the packaging boards are tagged with labels if they keep going to USA market.
All finished packages go to the package packing section.
3. Methods and materials
A computer will be used for putting together all data.
A software excel and a usual calculator will be used for calculating.
For measuring the availability and use of the degree, the mobile measuring equipment will be used.( Description of the mobile measuring equipment is done further on, see chapter 3.5 )
3.1 Sawmill
3.1.1 Measuring and calculating the availability for the saw house
Calculating the availability is like a share of the real production time and the planned production time.
time 100 production Planned
time)) stop Unplanned time
up (Set - time production (Planned
(%)
ty Availabili
Planned production time Planned stop time Set up time
Unplanned stop time
= Total available time - Planned stop time.
= Planned break time + Maintenance time.
= Time for pattern changing.
= Stops that appear during planned production time.
Measuring point is between the 2D-scanner and the log turner in the sawline, see layout (Layout Rundvik sawmill) in appendix 1 or between steps 1 and 2 in the picture 7. This point was chosen for the measuring point to check the presence of logs flow in the beginning of sawline to keep production in this section during planned time.
Sawing patterns will be noticed during the measuring period to look if some correlation between availability of sawline and a saw pattern exist. Because of short time of
measuring it is impossible to make reliable analysis of availability in accordance to every saw pattern. Like it was observed the most repeated patterns consist of from 3 to 10 boards as a total amount out from one log. That is why all sawing patterns will be divided in two groups in accordance to amount of the boards. First group will include all sawing pattern that give 1-5 boards, second group includes sawing pattern that give more than 5 boards. So, the conclusion of stops distribution around the areas will be done for two groups of sawing patterns.
Stop in the flow will be recognized like a downtime after 10 seconds. Downtimes are sorted in different groups (short and long) in accordance to their lengths and these are:
Stops between 10 second to 60 seconds.
Stops sorting in two groups is good to define the amount of chronic stops (Definition for chronic stops is done in chapter 4.5) Besides, to define summary value of short stops (from 10s to 1min) is a requirement from a company side.
The stop codes have different colours in the layout, which you see in appendix 1. For making it easy between the operator and the master theses worker, it was suggested to colour codes on a paper.
The sawline is divided into small zones adapted to the layout of the line, see appendix 1. These zones will also be used to look for the use of degree.
Stop codes for the availability are (see layout in appendix 1):
Planned stops:
1. Planned stops. Include breaks, night stops and planned maintenance.
Unplanned stops:
2. Saw in feed and debarking area. It includes everything before the first conveyor in the sawline: debarking machine and every handling for the bark after the debarking.
3. Chips and sawdust area. Includes conveyors handling chips and sawdust.
4. Green sorting planks area. Includes the sideway conveyors for the planks after the lengthway conveyors of the sawline and the pockets of the green sorting.
5. Green sorting boards area. Includes the sideway conveyors for the boards after the lengthway conveyors of the sawline and the pockets of the green sorting.
6. Stick stacker area. Includes the conveyors from under the pockets to the forklift truck.
Unplanned stop codes for the sawline (see layout in appendix 1):
7. Log conveyor + Scanner.
8. Log turner.
9. Centring machine KSI-7 + conveyor between KSI-7 and SKR-700.
10. Plane reducer SKR-700.
11. Conveyor between SKR-700 and SBF-2.
12. Profile cutter SBF-2.
13. Sideboards cutter SBS-2.
14. Sideboards conveyors (chain conveyors + band conveyors).
15. Conveyor between SBS-2 and BBF-4.
16. Profile cutter BBF-4 + conveyor between BBF-4 and BV-1.
17. Block turner BV-1.
18. Conveyor with holder between BV-1and BKR-700.
19. Wane cutter BKR-700 + conveyor between BKR-700 and DS-72.
20. Sideboards cutter DS-72.
21. Conveyor between DS-72 and DS-72+1.
22. Planks cutter DS-72+1.
23. Band conveyors after DS-72+1.
24. Stop for pattern changing. Includes time from a stop beginning to a moment of the planned stable flow (that means that flow goes with planned speed and dimensions of the sawn products are correct).
3.1.2 Present situation at the sawmill
Old data for the year 2007 is viewed in the appendix 2. The data gives the present situation for the availability. The calculation is made like it is explained in the chapter 3.1.1.
A difference between the old and new data is that the stops were registered like downtimes during 2007 only if they were longer than 1 minute.
The definition for long and short stops was also done in 2007.
Short stops are between 1 to 15 minutes.
Long stops are longer than 15 minutes.
3.1.3 Use of degree for the sawline
The use of degree for the sawline will be defined like:
time 100 operative Available
time processed (%) Real
degree of
Use
Available operative time Real processed time Downtime
= Real processed time + Downtime in the saw section.
= Time when a flow of logs exists in the sawline.
= Stops are caused by disruptions occurred in saw section (stops that have stop codes numbers 7-25).
Important: Stops will be not calculated like a downtime for the sawline if they are caused by disruptions and stops in other sections. So, the stops, defined by stop codes numbers from 1 to 6, will be not counted like downtime for sawline.
The use of degree for the sawline will be calculated like this:
Take the data from the measuring the availability.
The downtime for the saw in feed-, green sorting (plank and board area)-, stick stacker and the chips and sawdust area will now be excluded from the data.
Left is the time for the sawline that includes: real processed time and available operative time.
Sawing patterns will be noticed to look if some correlation between use of degree for the sawline and a saw pattern exist. Like in case of availability analysis, all sawing patterns will be divided in two groups. First group includes all patterns that give less than 5, or 5 pieces out from one log. Second group includes all patterns that give more than 5 pieces out from one log.
3.1.4 Example of calculating the availability and the use of degree for the saw house Take up an example of calculating the availability and the use of degree for the saw house.
Conditions during 1 week:
Planned production time to 112h = (112*60) = 6720 minutes.
Stop in Saw in feed and debarking area with 400 minutes.
Stop in Sawline with 1000 minutes.
Stop in Chips and sawdust area with 100 minutes.
Stop in Green sorting planks area with 115 minutes.
Stop in Green sorting board’s area with 400 minutes.
Stop in Stick stacker area with 250 minutes
The availability of the saw house:
100 66,3%
6720
250 400 115 100 1000 400
6720
The use of degree of the sawline is:
Planned production time to 112h = (112*60) = 6720 minutes.
Time for the stops excluding the sawline is (400+100+115+400+250) = 1265 minutes.
The time that it should be a flow in the sawline is (6720-1265) = 5455 minutes.
Downtime in sawline was 1000 minutes, includes all types of stops.
So that gives:
Real processed time = 5455-1000 = 4455 minutes.
Available operative time = (4455+1000) = 5455 minutes = Planned time – stops from exterior sources = (6720-1265) = 5455 minutes.
Use of degree of the sawline is:
% 7 , 81 5455 100
4455
The availability will be 66,7 % and the use of degree will be 81,7 %.
3.2 Stick stacker
3.2.1 Measuring the use of degree of the stick stacker area The measuring equipments in this area are:
A stopwatch
A note book
The measuring point is chosen at the separator because boards and planks are coming piece by piece there, see picture 19.
Picture 19. Shows the measuring point at the stick stacker area.
Calculating the use of degree at the stick stacker area:
time 100 operative Available
time processed (%) Real
degree of
Use
Real processed time Available operative time Downtime
= Time, when a flow exists in the measuring point in the stick stacker area.
= Real processed time + Downtime at the stick stacker area.
= Stops are caused at the stick stacker area.
Measuring point at the stick stacker
Stop codes for the stick stacker area:
Stops are caused by disruptions in the other sections and will be excluded from downtime of the stick stacker area:
1. Lack of boards means that it is impossible to drive the stick stacker because of lack of planks and boards in the pockets.
2. Truck causes a stop when it does not take away the package in time.
.
Stops are caused by disruptions in the stick stacker area. They will be included in downtime of the stick stacker area to calculate the use of degree for this area:
3. Boards area stops are caused by disruptions inside the stick stacker area.
4. Dimension marking is the stop where the paper marking is put on the package that shows dimensions of boards for every package.
5. Sticks area stop includes stops in the board flow because of the problems in the sticks area. Sticks area starts from the truck puts sticks to the incoming conveyor until sticks are laid on a package.
3.3 Planing mill
At the planing mill, it is just to look at one section. This section is from the in feed (tilt) for boards to the planer, see layout on appendix 5.
The given data from SCA are:
The dimension to look at is 21*95 mm and the length of each board is 3,7 meters.
Planer capacity is 200 meter/minute (maximum capacity is 350 meter/minutes).
It is important to check the flow of pieces/minute for the feeder that feeds the planer. According to the data from SCA, the planer needs 200/3,7 ≈ 54 piece/minute in average.
First, capacity of every area inside of the chosen section will be calculated in relation to real speeds of conveyors and existing gaps. Areas, where the capacity (pieces/minute) will be counted for, are presented in the layout in the appendix 5:
1. Tilt area.
2. Elevator area.
3. Operator area.
4. Feeder to the planer.
Second, it is to measure real capacity (pieces/minute through the planer) for the whole chosen section and estimate losses. Capacity losses are related to downtime at the measuring point.
Measuring point is chosen at one-piece separator at the operator area.
All stop codes are done in relation to studied areas and are divided in two groups.
First group includes stops that are caused by disruptions in the section that was studied.
Tilt
Stick area
Elevator
Elevator conveyor (conveyor following the elevator)
Operator area
Operator conveyor(conveyors between operator area and the feeder)
Feeder
Second group includes stops are caused by disruptions occurred in rest of the planing mill.
Planer
Wood Eye
Sorting area
Cutter
Package area
Other (stops such ventilation and electricity problems in the planing mill)
3.4 An easy calculating in the excel
An easy flow calculating will be made in the excel program just to visualize the flow in the first section in the planing mill.
According to the given initial condition for the planer (see chapter 3.4), speeds, required to the tilt area, the elevator, conveyors, can be calculated.
For making this flow calculation, followed devices will be used:
A computer and the excel program.
A measuring tape to get gaps in average between boards on the conveyors.
A measuring device for speed of the conveyors.
3.5 Measuring equipment
Given mobile measuring equipment is used to register and collect data from the sawing process.
It is also able to monitor data and analyze data in GantBrowser software.
The measuring equipment consists of:
Hardware:
Inductive sensor.
Computer/Server
Monitor.
Cable
Software:
GantBrowser.
Sensor: Feeds the server with a flow at some measuring point.
Signals from sensor go through the cable to the server.
Server: Stores the data for the measuring and handle software GantBrowser.
Monitor: Makes it possible to visualize the data.
Cable: Makes the connection between the sensor and the server.
GantBrowser: Makes the data to be analyzed and view the graphical presentation of stops and flow continuously together with a time scale. It also represents the list of stop codes that is used to notice the reasons of the stops.
From this mobile equipment it is possible to get an excel-file with collecting data.
4. Theory
4.1 Value stream mapping
According to (Sayer at al 2007 e), the value stream is the flow of materials and information through a process to deliver a product or service to a customer.
Value Stream Map is a graphical representation of how all the steps in any process line up to produce a product or service, and of the flow of information that triggers the process into action.
Based on (Sayer at al 2007 a), Value Stream Maps are often hand drawn plots that describe a process from input of raw materials through to delivery of goods or services to the customer.
The indentified customer at the end of a Value Stream Map may not be just the end customer who buys the finished product or service, but the customer may be another business or some other function within the same organization.
First, the current state of Value Stream Map is constructed – the way things are now.
The process steps are timed and divided to value-added and non-value added.
Second, the ideal Value Stream Map is constructed – the ideal process, where all steps are value–
added steps.
Next, improvement to refine the current state is conducted and Value Stream Map is updated to visualise the changes to the process. The improvement should constantly move the process in the direction of the ideal state.
Value Stream Map of the sawing process will be done from saw in feed like input to stick stacker as output of products. The layout of the sawline will be used for Value Stream Map graphical presentation (see Layout Rundvik sawmill in appendix 1) . Every section or machine of this layout represents a separate step of the process. And every section is used to be value-added step when the production flow exists through this section. If it is no flow through the chosen section, that means that during this downtime, no value is added to the process.
4.2 Some useful Lean thinking
This chapter is a presentation of some thoughtful words which Lean thinking production is based on.
Kaizen:
“Kaizen” is an improvement.
Dennis (2007 a), says that “kaizen” is a small incremental improvement. “Kaizen” activity should involve everyone regardless of position.
According to (Sayer et al 2007 e), “kaizen” is incremental continuous improvement that increases the effectiveness of an activity to produce more value with less waste.
Gemba:
“Gemba” is there the product has there operation to become the finally product.
According to (Dennis 2007 a) “gemba” is the real place or a specific place. Usually it means the shop floor and other areas where work is done.
Based on (Imai 1997 a), Japanese word “gemba” is meaning “real place” – now is adapted in management terminology to mean the “workplace” – or that place where value is added. In manufacturing, it usually refers to the shop floor.
In accordance to (Sayer et al 2007 e) “gemba” is place where the action occurs.
Go to gemba:
This usually means go to the shop floor.
Imai (1997 a) says that “go to gemba” is the first principle of gemba kaizen. This is a reminder that whenever an abnormality occurs, or whenever a manager wishes to know the current state of operations, he or she should “go to gemba” right away, since “gemba” is a source of all
information.
GTS:
According to (Dennis 2007 a) GTS is Grasp The Situation; the heart of PDCA cycle.
Muda:
“Muda” means waste.
According to (Imai 1997 a) the Japanese word “muda” is meaning “waste” which when applied to management of the workplace, refers to a wide range of non-value-adding activities. In gemba there are only two types of activities: value adding and non-value adding activities.
According to (Sayer et al 2007 e) “muda” is any activity that consumes resources, but creates no value. “Muda” is categorized in two forms: “Type-1 muda” is necessary for the process, but non- value-added; “type-2 muda” is both unnecessary and non-value-added.
Genchi genbutsu:
Based on (Dennis 2007 a) “genchi genbutsu” is translated like go and see; go to the real place and see what is actually happening.
According to (Sayer et al 2007 d and e) “genchi genbutsu” means “go and see”.
It is also written that one of the fundamentals of the Toyota way is called “genchi genbutsu”. In short, this means “go to the actual scene (genchi) and confirm the actual happenings or things (genbutsu)”.
The power of “genchi genbutsu” is in the firsthand knowledge that you gain. It’s one thing to look at a report, see a bunch of numbers, and draw conclusions. It’s totally different experience to go to an area and see what the numbers mean.
Such methods like “Genchi genbutsu”, GTS and “Go to Gemba” will be used during this project in the way to observe the process and the reasons of downtime directly in the shop floor.
Unplanned downtimes can be characterised like muda or non-value-adding activities.
4.3 Calculating the availability
According to (TPM for Supervisors 1992 a) the availability is defined like this:
100
loadingtime downtime -
time loading y
Availabilt
In this case, loading time is the daily (or, monthly) time available for operation minus all forms of scheduled stops – breaks in the production schedule, stops or routine maintenance, morning meeting, and so on.
Downtime is the total time taken for unscheduled stops such as breakdowns, retooling and adjustment.
Loading time minus downtime yields the operating time.
Finally (TPM for Supervisors 1992 a) say that the availability tells us what percentage of the time equipment is actually running when we need it.
In this project the availability will be calculated in the way as described in chapter 3.2.1. and that is like this:
100
time production Planned
time)) stop Unplanned time
up (Set - time production (Planned
(%)
ty Availabili
Planned production time Planned stop time Set up time
Unplanned stop time
= Total available time - Planned stop time.
= Planned break time + Maintenance time.
= Time for pattern changing.
= Stops that appear during planned production time.
Availability is one component to Overall Equipment Effectiveness (OEE) calculating.
The other parts are Performance and Quality.
According to (OEE for Operators 1999) OEE traditionally consists of Six Major Losses, and these are briefly described like this:
Availability:
Downtime losses
Failures
Setup time
Performance:
Speed losses
Minor stops
Reduced operating speed
Quality:
Defect losses
Scrap and rework
Startup loss
OEE will be calculated like this:
OEE = Availability x Performance x Quality x 100 (%) Example of OEE calculating:
0,66 x 0,80 x 0,85 x 100 = 44,9 %
4.4 Calculating the use of degree
According to (Ljungberg 2000 a) the definition for real use of degree is the quota between real process time and available operating time.
time operating Available
time processed degree Real
of use
Real
Ljungberg (2000 a) says that the use of degree is measuring losses from small stops and idle running.
Real use of degree means how big share of the available operating time is used.
In this project the use of degree will be defined like this:
100
) sections) other
all for time Stop time stop (Planned -
time running (Total
section measured
in time degree Flow
of Use
Flow time in measured section:
This means when a flow occurs where the measuring point exists.
Total running time:
There is all time for the measuring period.
Planned stop time:
This is a stop that is planned, for example breaks and maintenance work.
Stop time for all other sections:
There are stops that occur in other sections and these stops time should not influence on the measured section.
4.5 The importance to have a short time until it start to register a stop
During working with measuring it is important to have a short time until starting to registry the stop time. Why it is important is that a production line can consist of many short stops. These stops are called chronic stops, and they occur very frequently and have a short stop time.
It also exist stops called a sporadic stops. A sporadic stop is very difficult to predict when it will be happened, but it occurs not so often.
According (Nord et al 1997) a sporadic stop is very obvious and very often really easy to repair.
Most of time it is just to put the machine back to the current existing state. This stop occurs not so often and is haphazard and leads to long stops.
The chronic stop is often shorter, but happens all the time. These stops are often hidden and are difficult to find. To estimate the chronic stop take a deep analyze to find the cause of these stops.
Graphical plot of chronic and sporadic stops, see picture 20.
Picture 20. Shows a picture for chronic and sporadic looses, before and after improvement.
Here come some examples of both types of looses.
Sporadic looses
Broken axle.
Broken gear wheel in a gearbox.
Chronic looses
Put away sawdust/chips that interrupt the process.
Turn boards.
Sticks that go wrong at stick stacker section.
A photocell need to be cleaned.
Stop intensity
Time Sporadic
looses Chronic
looses
Sporadic looses
Before improvement After improvement
Improvement occur
Chronic looses
4.6 Statistical evaluation method
Pareto diagram shows a collected data in a very visible way. The biggest stop caused for the process points out easily in a vertical staple diagram. Usually man looks for some of the biggest staples to the left in the diagram, which will usually have a very big effect on the process.
It is also possible to have the staple in horizontal position. When the staples are in a horizontal position so is the biggest stop cause highest up in the diagram.
According to (Dennis 2007 a) it is said that pareto diagram is a problem solving tool comprising a bar chart showing possible contributing factors in decreasing order.
According to (Sayer et al 2007 c and e) the pareto chart is explained like as a bar chart where the categories are presented in descending order of frequency. The pareto principle states 80
percentage of the data will fall in 20 percentage of the categories.
How Imai (Imai 1997 a) explain the pareto chart is: it is a graphical tool for ranking causes from the most significant to the least significant. It is based on the Pareto principle, first defined by J.M. Juran. This 80:20 principle suggests that 80 percentage of effect com from 20 percentage of the possible causes.
The pareto diagram is very often useful in the PDCA –circle to give the priority to stop causes in a process.
In this project the pareto diagram/chart will be vertical staples, see pictures 21 for example.
Example on a pareto diagram
0%
5%
10%
15%
20%
25%
stop cause 11 stop cause 7
stop cause 12 stop cause 10
stop cause 6 stop cause 13
stop cause 4 stop cause 9
stop cause 8 stop cause 2
stop cause 5 stop cause 1
stop cause 3 Causes
Percent
Picture 21. Shows a pareto diagram in percentage share.
4.7 Bottleneck
A bottleneck in a line is the machine or operation that has the slowest processing. According to that you can say that this is machine or operation that makes less pieces/minutes in the whole line/process.
According to (Sayer et al 2007 b) the definition is: The bottleneck process is the process with the longest cycle time. In continue (Sayer et al 2007 e) it is explained a bottleneck like this: A process that constricts or limits the flow of overall process.
According to (Bicheno 2004) bottlenecks govern both throughput and inventory in a system. A plant’s output is the same as the bottleneck’s output and inventory should only be let into a factory at a rate that bottleneck is capable to handling.
It is the bottleneck that should govern flow.
4.8 Best practice
Best practice is an improvement technique that goes in relation of what have been occurred really.
Take a sawline as a process line. The measured goal for the sawline is, for example, the
availability. And this number is following up every week. After this measuring is done for some weeks, it is possible to see a best practice. The week that had the highest result for the availability is the best practice.
With this result man knows what is possible to reach against the best practice; it means to make everybody to be better in their work.
According to (Ilsley 2000) the biggest benefit with best practice is that all of the common workers should be better and catch up to the best performers at the shop.
Best practice improvement tools are always in change because a new situation can occur, and it means the process line can be rebuilt in some way. If it happens it must be observed over the goal of the best practice that was done. The improvement tool can be changed or it is possible to continue with it, so even this improvement tool is always under constant improvement.
Best practice method can be applied to analyse the work at the stick stacker section.
4.9 SMED (Single Minute Exchange of Die)
Single minute exchange of die is a method to improve the set up time. One example of meaning can be improved the changing of equipment in the saw machines when changing from one to another sawing pattern occurs.
According to (Santos et al 2006 a) this improvement method developed by Shigeo Shingo in Japan between 1950 to the 1980s.
With this methodology, it is possible to achieve good result without costly investments, which makes implementation an many factories an easy decision to make.
So what is a set up process? Definition according (Santos et al 2006 a) is a setup process
corresponds to the time required to go from the end of the last good part from one batch to when the first good part of the following batch is produced.
When a setup process occurs, it exists of two types of operations and they are external and internal setup.
According (Santos et al 2006 a) it is described this operation like this:
Operation that can be carried out with the machine running and producing parts for the previous lot. Shingo called these types of activities external setup.
Operations that required the machine to be idle while they were performed, Shingo denoted those operations as internal setup.
According to (Santos et al 2006 a) SMED – method consists of four steps, and they are:
1. Preliminary stage. That means to study the current process for setup.
2. Stage 1. Separating internal and external setup.
3. Stage 2. Converting internal setup to external setup.
4. Stage 3. Streamlining all aspects of the setup process.
A good thinking example from (Santos et al 2006 a) about SMED is:
“For instance, when you are replacing the tires on your personal vehicle, what does it matter if it takes an hour to change all four tires? However, in car racing (Formula 1 or NASCAR), losing 15 seconds may have very catastrophic consequences for the driver’s success.”
Finally about SMED, it improves the availability and quality rate. According to (Santos et al 2006 a) they say SMED implementation improves the availability rate as well as the quality rate because SMED reduces all the setup process time.
5. Results
5.1 Present availability for the sawmill
During the weeks 1- 4 in the year of 2007, the dividing of stops is viewed on the figure 1.
Downtime was registered like a short stop from 1 to 15 minutes, and the stops longer than 15 minutes were sorted as the long stops. These four weeks represent January of 2007, the most problematic month of saw production because of low temperatures.
Figure 1. Shows the availability, share of the total stop time around stop causes in the saw house and the share between long and short stops for each stop cause during the weeks 1- 4 of 2007.
Results of the availability measure that was done during the weeks 1 – 48 of 2007, are shown on the figure 2. Downtime was registered like a short stop from 1 to 15 minutes, the stops longer than 15 minutes were sorted as the long stops.
Figure 2. Shows the availability, share of the total stop time around stop causes in the saw house and the share between long and short stops for each stop cause during the weeks 1- 48 of 2007.
These two diagrams look the same but both of them are represented that the availability and distribution of the stops are obviously constant during the whole year of 2007. The results during January and the rest of the year 2007 are similar and do not depend much on the weather
conditions.
5.2 New measured availability
The figure 3 gives the common picture for the weeks 4-6 of measuring in the beginning of 2008.
Figure 3. Shows the availability, share of the total stop time around stop causes in the saw house and the share between long and short stops for each stop cause during the weeks 4 – 6 of 2008. It also represents the use of degree for the sawline.
