The 8 Wastes of Printing Print E-mail
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Written by Clive Ashmore   
Thursday, 28 July 2011 15:17

Or why “wait” makes waste – and what to do about it.

Life has the Seven Deadly Sins. And business processes have the Eight Wastes. Well-known among practitioners of Lean Manufacturing, the Eight Wastes apply to any manufacturing or business process and, when reduced, can vastly improve efficiency, enable faster processing and reduce cost. The statistics are eye-opening: According to Lean pundits, 60% to 70% of the actions performed in a process can be classified as a waste.

Recently, our company has been participating in Lean training. I’m very familiar with Lean and have participated in training before, but this time, the Eight Wastes really caught my attention. We apply all these principles in our facilities, and as I started thinking more about each of them, it struck me how relevant they are to the screen printing process as well. Utilizing the power of the Eight Waste model and some common sense, significant efficiency savings can be found. Let’s take a look at each:

1. Waiting. There’s a lot of waiting in printing. The printer waits for upstream systems to be ready for the printed board. Employing techniques such as batch printing (see “A New Batch,” CIRCUITS ASSEMBLY, February 2011) can help printer utilization and lower waiting time. I’ve also witnessed the printer waiting for replenishment of understencil cleaning fabric or chemistry, as well as other consumables such as solder paste. On-board software that warns of impeding fabric or cleaning chemistry replenishment requirements can go a long way toward shortening printer wait.

2. Inventory. For me, two elements of inventory cause issues with screen printing. First, the correct inputs need to be available to complete the job at hand. Sounds like common sense, right? It amazes me to see lines stopped because solder paste, solvent and cleaning fabric are not available. Second, available inventory needs to be fit for purpose. Production units that use out-of-date solder paste or cleaning fabric that produces so much lint can add more defects than they resolve.

3. Transportation.
Transport in the print process is about getting boards in and out of the printer as quickly as possible. Cycle time can be shortened by optimizing software that permits the camera to wait behind the rear rail, instead of going back to home after each print, for example, or reducing squeegee dwell heights (which tend to be preset very high). High-speed transport conveyors vastly improve board in/board out time.

4. Overproduction.
The faster changeover is completed, the less overproduction occurs. If you can changeover the printer in five minutes or fewer, then you don’t have to build extra product to cover downtime. In fact, software functions on modern print systems allow operators to preset production runs and receive estimates on the time required for those jobs. Another hidden cause of overproduction is the requirement to produce a “few” extra to cover end-of-yield loss. Those who follow this column will have picked up many tips to aid in the battle toward yield improvements and, therefore, reduce the need for the extra “few.”

5. Overprocessing.
Cleaning in printing is a huge time-waster. It’s a sub-process that is way overused, in my opinion. Consider that if understencil cleaning is taking place every second board – or even every fourth board – and each clean takes 20 to 30 sec., then the equipment is being used 25% of the time not to print but to clean! New stencil coating technologies can vastly reduce required cleaning frequency by limiting the leaching of flux and paste into the stencil web and, therefore, helping stem overprocessing.

6. Intelligence (people skills/underutilization).
Well-trained operators are far more productive and effectively utilized. But, intense training can be an expensive proposition. Robust printer software that delivers on-board instruction and help via video and animation ensures a better-equipped operator and, therefore, a more intelligent process.

7. Motion.
Motion refers to ergonomics, as well as reducing the number of steps it takes to perform a given task. There are plenty of examples of motion reduction and ergonomics in the print process. These include having the control monitor effectively positioned for easy operator access; understencil fabric changeover via a preloaded cassette to eliminate manual paper feeding; positioning the solvent tank on the printer exterior for greater accessibility; streamlined cover packages and interior cabling for faster, simplified system access for adjustments or maintenance. The list is endless, but you get the idea.

8. Rejects/scrap (defects/quality).
Ah, the golden ticket for higher yields. My columns always address defects in some way. You all know my mantra: good inputs = good outputs. Realistically, though, we know that even when we are the best in the world, variables outside of our control will cause defects. In these situations, there are control tools like post-print inspection and production safeguarding technologies that incorporate input and output verification to produce better boards and, at the very least, isolate and remove faulty ones before they move farther down the line.

I challenge you to evaluate your processes against the Eight Wastes and come up with at least Eight Saves!

Clive Ashmore is global applied process engineering manager at DEK International (dek.com); This e-mail address is being protected from spambots. You need JavaScript enabled to view it . His column appears bimonthly.

Last Updated on Thursday, 28 July 2011 18:37
 

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