Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Sanjay Bhatikar

#13662

Set-up times | 27 October, 1998

SMT-ers

I notice that most suppliers provide data that is eye-catching but avoid providing data of significant technical relevance, such as Cp and Cpk. It would perhaps be a wise idea for standards to be formulated in this area. For eg., manufacturers of stencil printers like to talk about how fast their machines are. This is misleading, because the throughput depends of stroke length and squeegee speed. For a board of given dimensions, the throughput depends only on squeegee speed on an automatic printer. The limitation on squeegee speed for print quality limits throughput. Therefore the claim to 'fast' cycle time made by most manufacturers, on the basis of maximum squeegee speed and some unspecified board length, is absolutely irrelevant. SET-UP TIME, which is vastly more important, is only vaguely hinted at, if at all.

What do you think?

Sanjay Baticar

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Earl Moon

#13663

Re: Set-up times | 28 October, 1998

| SMT-ers | | I notice that most suppliers provide data that is eye-catching but avoid providing data of significant technical relevance, such as Cp and Cpk. It would perhaps be a wise idea for standards to be formulated in this area. | For eg., manufacturers of stencil printers like to talk about how fast their machines are. This is misleading, because the throughput depends of stroke length and squeegee speed. For a board of given dimensions, the throughput depends only on squeegee speed on an automatic printer. The limitation on squeegee speed for print quality limits throughput. Therefore the claim to 'fast' cycle time made by most manufacturers, on the basis of maximum squeegee speed and some unspecified board length, is absolutely irrelevant. | SET-UP TIME, which is vastly more important, is only vaguely hinted at, if at all. | | What do you think? | | Sanjay Baticar | Life in the fast lane. Setup times are slow relative to production speeds once setup done properly.

For stencil printing, no matter the machine, getting it right is what is important to take advantage of machine efficiency. I know of no other way to get it done but by ensuring fiducials are clean, vision recognizable, frames fitted properly, squeegees as required, paste as required, stencils matching boards, under stencil cleaning done properly, and don't forget support tooling whether magnetic, vacuum, or? First article verification also is in the mix.

For placement, programming (after good designs) is most important. Then, kitting done right with multiple feeders and reels available for efficient change over as well as pre-production audits to ensure right feeder locations. You also have machine warm up, program verification, tooling setup, nozzle selections (if manual), nozzle verification (if automatic), and first article verification.

The oven is not a problem once dialed in. However, using sample level inspections and SPC for continuous process improvement is important.

Yes, all in all - pre-production activities (supporting each process and its sub-processes) are slow compared with a possible 25,000 cph placement capability. The thing is, how else to do it all?

I've always wanted more from suppliers when making equipment evaluations. As you, I do want more for my money and the biggest thing for me is reliability (little down time) and repeatabillity. Concerning Cpk's, each user has to do it because of the uniqueness of board designs and types.

I know but a few machines (luckily) as Panasonic, Zevatech, Fuji, and now Philips (really like these) for placement and DEK and MPM for printing, and Vitronics, Conceptronic, and BTU for ovens - it becomes easier to visualize and understand how to become more efficient and ensure consistently higher quality. It also makes buying decisions easier when there is "NO" budget. When it comes to low volume or quick and dirty, what does one do? Certainly, Cpk becomes a non-issue.

Earl Moon

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