A. polyethene and polypropylene production lines and

A.           Introduction

CE1.1 This first episode occurred from March 2009 to June 2009. I started to work at “ENVASES PET, C.A.” in March 2009 and I worked there until August 2010. The Company, based in Valencia City (Venezuela), was dedicated to the manufacturing of plastic bottles for vegetable oil, detergent, beverages, liquor, and so on. During this period I worked as a Maintenance Engineer, and my first task was to study the stops times of polyethene and polypropylene production lines and provide and implement solutions for downtime reduction.

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B.           Background

CE1.2 “ENVASES PET” was part of a group of companies dedicated to manufacturing plastic containers; bottles, logistic boxes, butter and soap containers, among others. The group was integrated by “ENLIVEN”, which produces thin-walled plastic containers, and “ENVASES INDUSTRIALES DEL CENTRO”, where they produce plastic boxes for logistic purpose.

 

CE1.3 In the company, they had seven main production lines; two for PET bottles, three for bottles made from polyethene, and two for polypropylene bottles. Moreover, all the machinery was from the same brand; UROLA and the process (especially in the extrusion-blow lines) was very similar, except for material used.

 

CE1.4 There was a new Maintenance Manager, so the department was changing, and they decided to make me join to study the process; to identify main failures in machinery, operations and to reduce stops time. I focused my first month on understanding the process, the mechanism and to know the personnel involved. It will be my first job as a Mechanical Engineer, and I wanted my performance was upstanding.

 

CE1.5 Among my responsibilities as Maintenance Engineer were:

·         Develop and document procedures for assembly, disassembly, start-up, operation, and shutdown of rotary extrusion blow molding machines.

·         Provide technical direction to supervisors, and technicians.

·         Continuously follow up on lines efficiency and KPI (Key Performance Indicators) for schedule compliance.

·         Ensure corrective and preventive maintenance to reduce downtime.

 

CE1.6 Since I was assigned to start with this task, I acquired the following additional duties:

·         Investigate equipment failures to diagnose faulty operation and make appropriate maintenance recommendations.

·         Optimize production lines and to reduce maintenance’s stops.

 

CE1.7 Organizational structure chart:

Figure 1. Hierarchy Diagram

C.           Personal Engineering Activity

CE1.8 Firstly, I got familiarised with the machinery, and I made a list of most common stops according to my observation. With a list of 15 common failures, I designed a report form to obtain the data for my study. After creating this report sheet, I taught supervisors and operators how to fill it up in other to start the research. I spent one (1) month in the recollection of data while I was making some procedures such a start and stop, change of presentation, parameters charts, among others.

 

CE1.9 Once I’ve got the data, next step was to analyse it and then apply the Pareto principle, which states that “for many events, roughly 80% of the effects come from 20% of the causes”. In this case, 80% of the stops are associated with the 20% of the possible failures. I’ve learnt how to use this technique while I was cursing Industrial Maintenance in the University and I find it truly helpful when you are starting in any maintenance position, as a way to improve quite a lot in a short time. By doing that, I will quickly find which causes to attack first to decrease the number of stops and, consequently, the time spent on it.

 

CE1.10 In figure 2 is showed the results of this analysis. As you can see, three main items were causing most of the loss of time in production; change of presentation, contamination of material and defects inherent to the bottle.

Figure 2. Pareto Chart

CE1.11 Every time we have to change presentation (to produce a different bottle on the same machine) we spent too much time doing so. A presentation’s change involved mould changing, parameters adjustment, colour change (if required), and dimensional conveyor adjustments to name a few. However, some of these activities were external activities; that is to say, activities that we can do without stopping the machine. So I had several meetings with personnel (operators, supervisors and mechanical fitters) to solve this problem. We did a brainstorming about the activities involved in this process and how to improve it. I taught them how to segregate an internal and an external operation to reduce the time spent on this task.

 

CE1.12 After that, I developed a step by step procedure for mould changing and conveyors adjustments to standardise it. In this method, I detailed how to do the change of moulds, which pieces they will need to use or change, and which tools they will need. Also, I was very meticulous about prior preparation (including what exact tools they might use) and the time they should spend doing so. Moreover, the prior preparation of moulds now was going to be done before to stop the machine, so the new moulds needed to be ready to be fitted into the equipment previously.

 

CE1.13 I asked the quality manager about the parameter chart for each presentation, and I made a folder with this information and kept it in every production line, so everybody will know which parameter exactly to change instead of guessing all the time. Moreover, I published the start and stop procedure that I did before, and trained supervisors and operators in these matters, in other to optimise this activity and that everybody could do it in the same way and take the same time.

 

CE1.14 The second most frequently fault was contamination of material. When a foreign substance reaches the extruder, it could allocate itself to the nozzle causing the rupture of the “parison”. Consequently, the bottles started to form in a wrong way and they needed to stop the machine to clean the nozzle. The process of cleaning it could take from 15 minutes to half an hour, depending on the skill of the operator, so we had to avoid contamination to reduce to a minimum or even eliminate this time.

 

CE1.15 As part of our process, we used a virgin material with a percentage of reused plastic, as a result of deficient bottles that we had to grind in a mill, and that was precisely the weakness or were contamination could happen. My solution was to isolate the plastic mills and to create awareness among the operators that they had to be careful in the operation of the plastic mills and to ensure that the material remained free of contaminants.

 

CE1.16 I designated an area to relocate the plastics mills and designed attachments or protections that we installed in the mills to keep them more closed and prevent the entry of foreign materials, especially when passing the ground material to storage containers. Furthermore, we had to create conscious among the workers that they had to keep an eye on the processes, and they had to be acutely aware of any possible contamination.

 

CE1.17 Finally, the last cause was inherent defects to the bottles. In this category we had several undesire appeal such as; “orange peel” (which happens when there is water on the internal surface of the mold when it blows the bottle), color out of specification (lighter or darker), volume out of spec (generally under the target), weight out specification (could be over or under the set point), unequal distribution of material (due to “parison” diverted), and so on.

 

CE1.18 The solution was to standardise all the process and the parameters involved in it. By doing that, I solved the problem of weight and volume at the same time, because we had the right parameters (such as extruder speed) all the time. We acquired an electric blender to keep the exact proportion of colour which included an alarm when the hopper had a low level of colourant (masterbatch), so we stayed the colour on track. I made procedures to align the nozzle in every machine, so it was fast and straightforward to keep the parison correctly in position, which solved the problem of unequal distribution of material in the bottles.   

 

CE1.19 The “orange peel” happens when there is condensation in the moulds, which I happened because of the weather in Venezuela. A proposed solution was to install a controlled environment system (air conditioners) to reduce humidity and control this problem, but it was too expensive. But the answer was more straightforward than that, throughout a detailed analysis of the machine’s refrigeration system I noticed that the valves to control the flow of water were on/off, and operators were continually opening and closing them with the end of keeping the proper temperature.

 

CE1.20 I proposed to change those valves to gate valves, allowing the personnel to keep an efficient flow of water in the mould’s refrigeration system. Then, was through the method of trial and error that I’ve found the correct flow of water, adapted to our conditions in the factory, diminishing in that way the times stop and the material that we had to reprocess due to the defect of “orange peel”. The next step was to install a flow meter, so I could find the exact value of this parameter to add it to the existent created chart of parameters.

 

CE1.21 After fixing these three main faults, I reduced the downtime significantly in the lines of extrusion blow for this company. Moreover, my superiors were satisfied with the results, and that allowed me to start to develop my professional career and to develop a reputation within the group of companies.

D.           Summary

CE1.22 The accomplishment of this first project was essential to put into practice all the tools and skills I developed back in the university. Furthermore, I started to understand how to apply analytical thinking and troubleshooting abilities to solve problems in a real industrial ambience. With this project, I learned how to be meticulous, and how to use the cause-root methodology in addressing issues. Also, it was my first approach to the industrial world, and to begin to develop my leadership skills throughout my actions.

 

CE1.23 Through this project, I realised how important is to think outside of the box and how a different perspective could lead to a significant improvement. During this time I’ve learned to express my ideas to others and to make them trust me besides my young age. Also, I learned so much from the people directly involved in the process which was advantageous to keep me on track years later.

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