Appendix 1: Lead-time measurement information
A1.1 Lead-time data
In production there are different systems that contain production data. The systems in the table below are investigated. Only Data, Interactions and Fields related to the research are mentioned.
SAP
Data Production data for the whole production and finishing department. It contains products produced, ingredients, stock levels etcetera.
Interaction Is among other things used in production to notify if a lot is ready after a specific production section, used to make TO (Transport Orders) and used as input of the melting department.
Fields Times (start/finish), Quantities ready, Lots, Campaign numbers, Order numbers, Product Numbers, Process steps,
In theory all points in production should be traceable in SAP. PDB Production Data Base
Data Start data/time per shift of what orders are produced. Contains technical production data of the melting department and the finishing department. Interaction Not used in production. Only controlling program.
Fields Starting times of the sawing and sorting in the finishing department. The points 1,8 and a point between 8 and 9 is traceable.
MD Master Data
Data Certification information and specifications of the glass
Interaction The APS (….System) at the beginning of the melting department certifies the glass directly after it is produced.
Fields Item numbers, order numbers, campaign numbers and lot numbers Point 2 in production is traceable.
CT Certification Tool
Data Long lengths as well as finished products are certified after production. Contains certification data.
Interaction Production personnel certifies the products when these are packed. Fields Certification dates, production and finishing item numbers, order
numbers, campaign and lot numbers. The points 7 and 9 are traceable.
Table 4.3 Information systems and points to measure
• To estimate what is the most useful data, the structure of the product numbers is important. It starts with a glass type (for example 501) and is then divided in code numbers (length, diameter etcetera differ). Then it further falls apart in process orders for both the melting department and the finishing department.
At point 7 in figure 4.5, the process order number changed into another process order, namely that of the finishing department. In none of the systems described above the direct coupling between both order numbers can be traced.
• In the SAP system the procedure is to registrate a lot when it is ready after a specific production step. In practice, with this procedure are two problems:
o More lots can be registered at once, so the total number of glass tubes is more than in one specific lot. Only from the last lot the data is reliable in this case.
Code nr. 432211881841
o More lots are registered independent from each other but at the same time. So it is even not checkable at what time a specific lot was ready.
These points result in unreliable data about specific time information about lots. Together with the code number problem, the total lead-time is difficult to observe.
• The PDB data is reliable in the case that the program registers when orders are produced. Nevertheless there is no comparable data at the end of the production process.
• In the MD file the information seems to be reliable. The certificates are created directly after a lot is produced. The certificates are printed after a lot is packed into a box on a pallet and when this lot is ready for transport to the central stock. This happens after the vacuum ovens as well as after finishing the product.
• The certification tool is used to print certificates for the boxes at the moment a specific lot is ready for transport to the central stock. These certificates are used for both long lengths and finished products.
A1.2 Reliable measurement points
To decide what data to use for measuring, two preconditions are valid: • Measurement has to take place at lot-level
• There have to be a distinction between total lead-time and lead-time of long lengths
First there must be concluded that with the available information not all the points represented within figure 4.5 could be precisely measured. As a result, the research has concentrated at the points known for sure and makes estimations of the other points later.
Measuring ‘long length’ lead-time (2-7)
The most reliable data of the beginning of the process is found at point 2. The lots of glass are certified at point 2 by the APS (Advance Production system) after a whole lot is produced. So after point 2 each order is divided in lots and is traceable by Order number – Campaign number – Lot number These data can be found in de MASTERDATA (MD).
The second point measured (point 7, figure 4.5) is the moment the lot is ready for transport to the central stock. This information can be found in SAP. At the moment the glass is certified at the end of the process by using the certification tool, the lots are also confirmed as ready in SAP. So this SAP measure is to a large extent reliable. The certification information itself is not used because of the absence of a time indication here (only a date). The lots are also traceable by Order number – Campaign number – Lot number here.
Deviation: Some deviation in measuring between points 2 and 7 occurs. When we assume that point 2 is a fixed point in time, created automatically, the deviation could be explained by point 7. The confirmation in SAP is not directly given after a lot is packed into a box. This time differs per operator. The variation in time lies between 0 and approximately 45 minutes (the time it takes to fill another box). When taking total lead-time (2 till 7) into account, this fact is to neglect.
Measuring total lead-time (2-9)
For measuring the total lead-time point 2 is still the same (MD). The point at the end of the production process (point 9) is registered by use of the certification tool. By using this tool, the process orders out of the melting department as well as the finishing process orders can be linked by campaign and lot numbers. Nevertheless it is not possible to link the different order numbers directly.
Deviation: The deviation in measuring takes place here at point 9. All the days the products are registered as to be ready ends at 0.00 because no time is registered. So there is a variation with a maximum of one day in the total lead-time.
Measuring stock time (7-8)
To analyze the stock time between the points 7 and 8, the starting of the finishing department has to be measured. This is possible by using PDB. At order number level is registered at what time (per shift1) production is started. As known from the coupling problematic, it is not possible to trace
1
production lots or orders at this point. So stock time has to defined in another way. First measuring the finishing lead-time itself (8-9, see below) using large quantities of orders so a good average of the products originate.
So stock time is measured as: [7-8] = [LT 2-9] – [LT 8-9] – [LT 2-7]
Deviation: The deviation occurs here is a combination of the [LT 2-9], [LT 2-7] and [LT 8-9] variations.
Measuring finishing lead-time (8-9)
The lead-time between the points 8 and 9 is measured by using PDB and SAP information. PDB registers the start time of the sawing and the start time of the sorting at shift level. So this information is set together. By using the process order numbers of the finishing department a SAP query is build to determine the end of the sorting. Sorting is the last step in the finishing department. The order quantities are calculated backwards to lot quantities known from the production department. So it is possible to combine average values from the production department with that of the finishing department at a lot level.
Deviation: The registration in SAP (point 9), is here too, to a large extent reliable. The starting point (point 8) can differ several hours from reality. The starting points of orders are registered per shift, not the real start time of the order that is made.
The information above results in the following points to measure. Point in the process Measuring tool
2 • MASTERDATA – certifications from APS. 7 • SAP – Ready for transport notifications. 8 • PDB – Start times sawing per shift.
• PDB – Start times sorting per shift.
9 • Certification tool – Date finished products are certificated. • SAP – Ready for transport notifications of finished
Appendix 2: Production process
As showed in the basic structure above, the production process of quartz glass consist out of four general steps. There are some more activities within and out of these steps, which are not in the scope of this project. So the activities the project concentrates at, are the following:
1. Melting / Sawing the glass
• At the beginning of this process a constant stream of sand is created without all useless gasses between the granules. The sand is melted in an isolated oven by use of electricity. • Than the glass created must be shaped in a right form by use of a hole with a thorn that has a
ring formed opening. The glass tube is pulled out of the oven and is broken at the right length. • The glass tubes are rolling out of the oven over a conveyer belt where they cool down.
• Process operators pack the tubes into cassettes for further operations. The glass tubes are packed into cassettes for further operations. Each cassette contains one
lot of a specific order. With each cassette a lot traveller contains all information about that lot, and has to be enclosed.
Grondstof voorbereiden kwarts 1. bunkeren SQ-ovens 2. smelten / vormgeven SQ-ovens 3. afkoelen lange lengtes SQ-ovens 4. sorteren / inpakken SQ-ovens 5. in-line inspectie SQ-ovens gereedmelding trekken kwarts week prod.plan trek./zuren/uitst week prod.plan trek./zuren/uitst SAP Verzenden order A Zuren en uitstoken kwarts Nabewerken kwarts 2. Acid Washing
Goal: Cleaning the glass
• Placing the cassette in the input of the acid washing department. The lot traveler is placed at a board till the cassette is cleaned.
• Now the machine takes over the work and the containers with the quartz glass are hoisted into the acid washing department. First the glass is soured, then cleaned and finally dried.
Between this production section and the next. The glass has to be prepared for stoking. It must be loaded from the cassettes into special wagons made from sulphite.
3. Stoking the glass
Goal: Reduce the water percentage in the quartz glass.
• Two wagons with quartz glass are placed into the oven at the same time. The stoke time of the glass depends on the glass quality.
• After stoking, the glass is packed of the wagons, sorted and packed into external or internal boxes. The packed products are being audited and are prepared for transport. Both are shipped to the central stock.
4. Finishing
Goal: Sawing and shaping the glass to customer specifications.
In the finishing department there are several activities to be announced: • Sawing
The quartz glass is sawed in different sizes by use of automatic as well as hand handled sawing machines.
• Cleaning / Drying
After the sawing the glass is cleaned with water and after that dried in special cases by use of warm air.
• Scratching
The glass is scratched instead of sawed. After this activity, there is the possibility to remove the sharp ends of the little glass tubes with a burner.
• Sorting
After drying the glass tubes are sorted and packed for shipping.
Trekken kwarts week prod.plantrek./zuren/uitst
2. zuren kwarts 3. uitstoken? gereedmelding zuren kwarts SAP 7. nabewerken? 4.
uitstoken kwarts gereedmelding
uitstoken kwarts SAP
Appendix 3: Total score of brainstorm session
Feasibility Costs Quality Lead-time reduction
2. Buffer between the VAC-ovens and the finishing department 3.71 3.86 3.29 4.57
1. FIFO way of working after VAC-ovens 4.14 3.71 3.29 3.86
3. Other way of planning personnel for the VAC-ovens and finishing department 4.29 3.57 3.29 3.71
4. Cooling room after the VAC-ovens 4.14 2.14 3.57 3.86
5. Optimize the fan in the VAC-ovens. 4.14 3.86 2.86 3.14
6. Make the planning of the melting ovens subordinate of that of the VAC-ovens 2.86 3.00 3.00 3.86
7. Offer less glass qualities to the customer 3.00 3.29 3.57 3.14
8. Extra dry capacity in the acid washing department 3.14 2.00 3.14 4.00
9. Longer cool times in the VAC-ovens 4.17 3.29 3.00 2.86
10. Make structural combinations of stoking qualities 3.00 3.14 3.86 2.86
11. Change the composition of the charges 4.13 2.00 3.14 2.86
FACTOR 15 25 20 40
Rating the solutions
Appendix 4: Global capacity check acid washing department 2006
In this appendix the capacity of the acid washing department over the year 2006 is checked. The capacity the installation has is represented in figure 1.
The bottleneck in the installation is the drying compartment. Here are two tanks that can be used simultaneously and so the capacity of both tanks is important. The calculation is based on an availability of 24 hours a day and 7 days per week. Further 1 hour of revision a day is incorporated and an availability of 85%.
Capacity acid washing (in minutes)
Drying tank 1 10080
Drying tank 2 10080
Revision time 420
Capacity 19740
Capacity with 85% availibility 16779
Figure 1: Capacity of the acid washing department
Further the times the different types of glass must be soured and dried are required for the capacity calculation. These are represented in figure 2.
Glass type Time Hoist time Information
300 35 9 321 55 9 304 35 9 308 55 9 361 55 18 2 times 370 70 9 409 35 9 500 55 18 2 times
Figure 2: Program times of glass types for souring
For the further calculations historical information about 2006 is used. For every week is known how many lots per week are produced from each type of glass. The total number of lots is calculated for every fifth week in the year 2006 (week 1, 5, 10 etcetera). This is represented in figure 3 on the next page.
Now the capacity check could be applied. The lots of the different glass types are multiplied by their program times. When add all the lots and all the program times, the total minutes of capacity required could be calculated. The result is represented in figure 4.
Week number Required capacity in
minutes Sufficient? Week 1 15380 YES Week 5 7234 YES Week 10 12818 YES Week 15 11578 YES Week 20 8507 YES Week 25 10968 YES Week 30 10658 YES Week 35 9067 YES Week 40 7991 YES Week 45 10523 YES Week 50 10328 YES
Glass type wk 1 wk 5 wk 10 wk 15 wk 20 wk 25 wk 30 wk 35 wk 40 wk 45 wk 50 300 192 116 187 50 86 225 72 23 40 44 46 321 0 0 0 0 0 0 0 0 0 0 0 304 15 0 0 0 0 0 0 0 62 46 46 308 4 7 1 16 3 3 18 17 0 19 18 361 52 14 62 93 41 7 73 78 35 59 60 370 14 0 0 0 10 0 10 10 12 0 0 409 22 15 0 14 17 0 0 6 0 17 17 500 2 0 0 13 0 5 3 3 0 4 0
Total number of lots: 301 152 250 186 157 240 176 137 149 189 187
Appendix 5: Oven plans Week plan 1
Lots KG Quantity Code number
Week plan 2
Lots KG Code number Finshing code number Finishing type
Week plan 3
Lots KG Quantity Code number
Week plan 4
Lots Quantity KG Code number
