Rocket line starts aren’t rocket science
By John Henry, CPP
Are your line starts vertical? Vertical, in this case, refers to the time it takes to go from the line stopped to fully efficient normal production speed.
A truly vertical start goes from stopped to fully efficient speed instantaneously. The fact that this is impossible in the real world should not stop us from striving for it. The ramp-up to full speed has two components: Line charging may require some operator intervention and slow speeds until the line is full.
Once the line is fully charged, ramp-up truly begins. This period is characterized by frequent stops for fine tuning of adjustments, jam clearing, spill cleaning and removal of damaged packages. Some packages that make it all the way through may be rejected as substandard. (Even worse, some substandard packages may not be rejected.) This period can last anywhere from 10 minutes or less to 10 hours or more. In some cases, the run may finish without the line ever getting settled down.
Since the line is producing, albeit inefficiently, some may not be too concerned. “Better to have low production than none at all” seems to be the attitude. I disagree. Ramp-up is expensive, and plants will be better off without it. Direct ramp-up costs include marginal, damaged and rejected product. Indirect costs include less than fully effective operators, and mechanics who are always putting out fires.
Non-vertical start-ups are normally caused by variation in machinery, materials or both. Examples of material variations include varying viscosity of liquids or stiffness of paper and board. Material variations need to be identified, tracked and reduced or eliminated wherever possible.
Machinery related non-verticality comes from several sources:
Some machines require a thorough warmup before they will run properly. If a vertical bagging machine is run before the sealing die temperatures stabilize, problems will occur. One means of addressing this is to activate heaters well before the machine actually needs to run.
Some machine controllers may not be able to maintain the necessary degree of stability. Some machines use 0-10 potentiometers for speed control. Even with a designated setpoint, it is hard to keep the speed just where it needs to be. All moving machines in a packaging line need to have tachometers to precisely indicate speed.
Machines that have not been properly maintained may tend to have excessive play in their movements. This play means that they seldom cycle exactly the same way twice. Worn machines must be taken off-line and refurbished to allow them to operate to tight parameters.
The biggest cause of non-vertical startups in my experience is that the setup was not performed correctly. This requires both standard operating procedures and checklists that show exact settings, as well as proper tools and training to assure that the SOP and checklist were followed.
Verticality, be it after a changeover or simply after an overnight shutdown, is usually relatively simple. Not easy; simple. The principal requirements are good materials, well-maintained machinery and attention to detail.
Getting your line to take off vertically like a rocket is not rocket science.
F&BPJohn Henry, Certified Packaging professional (CPP), is renowned as the Changeover Wizard. His company, at www.changeover.com, offers workshops and other services to reduce changeover time. Contact John at firstname.lastname@example.org or 787-550-9650.
December 16, 2009