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(+)+(+) Setup Minimization Improves Line Efficiency
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(+)+(+) The Quick Changeover e-letter
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(+)+(+) Written by John R Henry, CPP
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### JANUARY 2005
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A PRESENTATION YOU CANNOT AFFORD TO MISS
The Institute of Packaging Professionals (IOPP) and Packaging World magazine will be sponsoring a 1 hour web seminar by yours truly on February 24. The title of the seminar will be “Pitstops in your Plant” and will discuss how to make changeovers more like a racing pitstop.
For more information, visit http://www.iopp.org/pages/index.cfm?pageid=740
Registration is at https://www.iopp.org/forms/form.cfm?id=23
I look forward to seeing you there.
SOME THOUGHTS ON...
STARTUP TIME
A few months ago I asked for suggestions on topics for this newsletter and Michael Mansfield responded with an interesting one. (By the way, I am always open for suggestions. Coming up with a good topic is sometimes harder that writing about it. Even better, if you would like to write something yourself...)
Readers of this newsletter or my site will know that I break changeover down into what I call “The 3 Ups”. The 3 Ups are cleanup, setup and startup. This month, at Michael’s suggestion, I want to address startup time. It is also called by other names such as “run-up” and “ramp-up” time.
Let’s start with a definition. Startup time is the period of time after the line has been restarted but before it is running at normal speed and efficiency. It is characterized by frequent stopping of the line for tweaking of adjustments, machine jams, damaged product, rejects/rework and other problems. This startup period can last anywhere from a few minutes to a few hours. In one case, a client told me that it took them 2-3 shifts to get the line “settled down” and running correctly.
Startup time is not to be confused with line acceleration time. No machine starts off at full speed. They take a certain finite amount of time to come up. In most packaging machinery, this time is negligible, lasting a few seconds. In a manufacturing line, it also takes some time to fill up the line. Again, this is normal. It should be improved if possible but there is usually not much that can be done.
Startup time is very expensive. Some people may think it doesn’t matter because, after all, product is coming off the end of the line. This is true but it may only be coming of the end of the line at 75% (or less!) of the normal rate. This is bad enough but when damaged or rejected product is factored in, the costs go up considerably. Startup time may be the most costly part of changeover and it is also a frequently ignored part of changeover. One of the reasons it is frequently ignored is because it is usually hard to measure accurately. More on that below.
The goal for cleanup and setup should emphasize reducing it’s time. The goal for startup should not be reduction, it must be elimination. It may never be possible in practice to achieve this goal completely. That does not mean that we should not continually strive for this result. The reason for startup time can be summed up in one word: “Variation”. If machines could be setup perfectly each time AND if the materials and components (bottles, cartons, stampings etc) came in perfect each time, there would be no startup time.
SETUP VARIATION
A common problem with setup is that it relies on the mechanic’s skill to carry it out. Settings may be made by eye, feel or judgement. When this happens, each person may have a different opinion of what the correct setting is. In some cases, the same person may do it differently from day to day.
The order in which the setup steps are performed is also important to achieving a successful setup. If not performed in the correct order, it may be necessary to perform some steps twice.
Proper maintenance of change parts is an important element in elimination of setup. For example, if a starwheel has sloppy mounting holes, it may be difficult to locate it precisely. If the pockets are worn, it may be necessary to tweak the adjustment to compensate.
Some machines, due to wear or perhaps to improper or weak initial design may not be able to be adjusted precisely. In these cases, think about redesign or replacement.
In eliminating startup, the critical first step is to determine the optimal way to do the setup and DOCUMENT it in an SOP (Standard Operating Procedure). There will often be variations on how a setup can be performed. These variations need to be examined and the one best way determined. The best people to do this are the people doing the setup. They are the experts and that expertise needs to be used. Additionally, if they write the SOP, they cannot say that it was not correctly written which makes for better buy-in.
I have written previously on how to write SOP’s and you can find that at
http://finance.groups.yahoo.com/group/quickchangeover/message/22 and
http://finance.groups.yahoo.com/group/quickchangeover/message/24
I have also posted on the Changeover.com website a MS-Word template for generating SOP’s with automatic checklists. This template, with instructions for use, can be found at www.changeover.com/sop.doc
Once the optimal changeover has been documented, everyone must be trained on it. The manager or supervisor must then make sure it is followed. If it is not, exceptions need to be noted along with the reason for the exception.
Setpoints must be measurable and repeatable. The height of a capper chuck, for instance, cannot be set by eyeball. The best way is a digital indicator, either mechanical or electronic. This gives a definite number to adjust to, not subject to interpretation or reading error. Scales, scribe marks and gauges are some other techniques that may be used. The important thing is that everyone can get to the same setting every time.
Don’t forget speed settings, even on something as mundane as a conveyor. Machine speed is always a critical parameter but is often overlooked. Tachometers and determination of optimal speeds is a must.
MATERIAL VARIATION
Variation of materials is usually outside the control of the folks on the floor and is often ignored. Purchasing has a set of specifications that they buy to and quality may inspect incoming materials to assure that they comply. Assuming that both are doing their job, in-spec materials can still vary. In one instance purchasing changed to a different cap supplier. The new caps met all specs but still gave a lot of trouble on the line. It turned out that the new supplier used a silicone mold release which built up in the capper chucks and caused slippage. This made it very difficult to set and maintain proper cap torques. Corrugated cases, by their nature, can often vary in various characteristics. This can make setting a case packer to a specific setpoint difficult. Most readers here will probably have other examples from experience.
The key is not, generally, that purchasing is not doing it’s job. The problem is that they are usually not aware of the problems caused by variability. More important, they are usually not aware of the costs. This needs to be explained to them. Ideally, they should be part of the changeover improvement team.
As I mentioned before, the goal needs to be elimination of startup. This can only occur when everyone recognizes it’s criticality and expense. “Quality” can be defined as the absence of variation. Work to make yours a quality process and product.
TIP OF THE MONTH...
MULTIPLE SPROCKETS
A few years ago I was working with a client who packaged pudding in pre-formed pouches (Say that fast 5 times!). The pouching machine was mechanically tied to a cartoning machine so that the two ran in sync. On different pouch sizes they needed to place one, two or three pouches per carton. This necessitated a ratio change between the two machines. As built, the respective line shafts each had a sprocket and a roller chain connected the two. In order to change the ratio, the sprockets had to be removed and a different set mounted.
A minor redesign solved this problem. Each sprocket set was bolted together to form a stack. Spacers separated them to give clearance for the roller chain side plates. Each sprocket set was then mounted and aligned. A spring loaded chain tensioner kept the chain tight. To change from 1:1 to 2:1 or 3:1, the chain tensioner is pulled back, the chain shifted between sprocket pairs and the tensioner released.
A glance at a bicycle shifter will show where the idea came from.
When doing this, don’t forget to make sure the relative position of the two machine shafts is clearly identified. This will save a lot of time getting the timing of the two machines right, avoiding startup time. Paint a tooth on each sprocket or put a dial and pointer on each shaft. Don’t rely on luck and judgement.
Another approach would have been to mount master/slave servo motors to drive both machines and control the ratio electronically. This does have advantages, especially since changeover can be done by a switch. On new machines, this might be the way to go. On an existing machine, this kind of retrofit can be a lot of work. The multi-sprocket idea can be implemented very quickly (an hour or two) at minimal expense.
It is also simpler. Remember, simplicity is your friend.
John R Henry CPP
Visit the Quick Changeover website at http://www.changeover.com
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