Going with the Flow Print E-mail
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Written by Clive Ashmore   
Wednesday, 02 February 2011 15:28

Challenges with EMS order visibility spur interest in old – but effective – techniques.

The news reported by Bloomberg late last November stated what many manufacturers enjoying a buoyant 2010 didn’t want to hear: Demand for EMS services is softening. In the piece, Deutsche Bank Securities analyst Sherri Scribner is quoted as saying that while contract manufacturers usually “have very good visibility into the quarter ahead,” now they are slightly more cautious “almost across the board.”1

This lack of order predictability, coupled with the need to realize maximum resource utilization, spurred some lively conversation within our company. But, being unable to predict order flow doesn’t necessarily mean orders aren’t forthcoming, which presents interesting balancing challenges. Our discussions centered on this question: Barring adding more lines for the inevitable gear up to feast from famine, how can customers get more productivity out of existing equipment sets? For us, that means keeping the printer occupied, even when systems down the line may not be ready for a printed board. If an issue downstream dictates that the printer must halt, that’s wasted productivity: 30 min., 40 min., maybe an hour’s worth of valuable production time lost.

But, what if you kept the printer humming even while problems down the line were being corrected? Not only does this maximize printer productivity, but it also ensures better yields. Let me explain. The print process is not like the placement process or the reflow process; it’s a bit organic in nature. Printers work best in a flow. If the placement machine has a blocked nozzle or a board gets stuck in the reflow oven, causing the line to stop, the idle time can impede print efficiency. Small, 200 µm stencil apertures start to clog; cleaning may be required, and the 30-min. stall may start pushing the process out of control. When things start back up, the first few boards off the printer may not be up to snuff. 

Continuous cycling of the printer produces far better results, and this fact leads to our efficiency solution: batch printing. Yes, you read that correctly! If you dig way back into your memory banks to the old wave soldering, glue adhesive Type 1 SMT days, you may recall the batch philosophy. It was largely forgotten as we transitioned to Type 2 SMT, but that was primarily due to material capability in terms of open and abandon times. Today’s solder pastes are far more robust in that respect and can certainly withstand significantly more air exposure before drying out. Batch printing in its simplest form can be just a buffer between the printer and placement machine or the post-print inspection and placement machine. With today’s newer, greater longevity materials, this buffering has minimum impact to the overall manufacturing process. There is one caveat: Boards must be kept in a covered batching system to eliminate exposure to dust or airborne particles.

The process is relatively simple and can be run according to the manufacturer’s preferences. Boards are printed, inspected and then loaded into the buffer racking system. The buffer software determines if/when the board is required down the line and feeds the boards back into the production flow when signaled. Of course, when the buffer is full, then the printer has to stop. The idea, though, is to have enough boards in the buffer that when the printer is required to print, there’s sufficient time to reset the printer. This could mean printing a couple of dummy prints to get it back in the flow, or doing a full clean down. In any event, the printer is kept operational, maximizing the resource and keeping the line flowing, while ensuring good yields by smoothing out the intermittent stoppages.  Ladies and gentlemen, the batch may be back!

That said, batch printing is only viable when the printer is operating as it should. If it’s not, you are flat out of luck! Getting the most out of your resource means effectively managing your assets. With print systems, this includes utilizing predictive maintenance tools like remote diagnostics to intervene ahead of a failure. And, for (large) EMS firms that move product and lines here, there and yonder, it also means harmonization of all equipment specs, recipe files, and processes for equipment around the globe. That way, when resources have to be transferred, optimum performance doesn’t take months to sort out. All of this seems logical and simple. But, you’d be amazed at the easy, preemptive actions that aren’t employed.

So, as we begin 2011 with a mixed bag of predictions from analysts, incorporating an old technique and some proactive asset management may help maximize productivity, yields and profits, even in the face of uncertain order balance.

1. T. Homan and A. Feld, “Need for QE2 Seen in Pausing Electronics Manufacturing Services,” Bloomberg.com, Nov. 29, 2010.

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 Wednesday, 02 February 2011 16:59


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