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Industry Standard Acceptable SMT Component loss?

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#43910

Industry Standard Acceptable SMT Component loss? | 13 September, 2006

Is there any published info on acceptable losses in SMT assembly. Especially for small to medium sized production runs with switch overs several times weekly Different losses for component sizes and packaging?

Thx

Vaughn

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SWAG

#43913

Industry Standard Acceptable SMT Component loss? | 13 September, 2006

I don't know about industry standards - I suppose it depends on your equipment, really. We are low-volume, high-mix with many, many part numbers. Here's what we do and we have pretty good luck with it: Over-issue parts to kits; 10 over on 1206's, 20 over on 0805's, 40 over on 0603's and 60 over on 0402's. We go 7 over on reeled IC's and exact on stick or waffle pack IC's and high $ parts. Granted you are paying much $ over time for scrap that may or may not be needed but it saves on what was a horrendous number of trips to warehouse to finish a build = huge loss in production. We prescribed these numbers over time by watching scrap rates on all of our machines as well as scrap qty's needed by the operators at ends of builds. We usually don't run out of more than a couple of parts especially if a build has been run a number of times and is dialed in. We tried using %-age of parts issued but found that a flat rate of over-issue works much better and is consistent and easy for kitting people. We also tried full reel qty's with periodic cycle counts and that was a real inventory nightmare.

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RDR

#43918

Industry Standard Acceptable SMT Component loss? | 13 September, 2006

much prefer using percentage instead of fixed overage. Example.... A run needs 100,000 parts, (1% shrink is 1000 parts!) you want to only issue 60 over? I recommend 2% for popcorn and exact for retrievable/ identifiable parts like sticks and trays.

We become concerned when parts exceed 1-2% fallout without assignable cause such as damaged tape or something.

Russ

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#43927

Industry Standard Acceptable SMT Component loss? | 13 September, 2006

Search the fine SMTnet Archives for background. Try searching on => attrition

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#43949

Industry Standard Acceptable SMT Component loss? | 14 September, 2006

Thanks for the input!

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SWAG

#43951

Industry Standard Acceptable SMT Component loss? | 14 September, 2006

Good point Russ but we do builds that comprise of 50 of this and 100 of that. Our high average issue might be around 400 or 500 parts but most are under 100. 20,40,60 flat over-issue gets us set-up and error scrap. 2% of 50 is 1 part. 2% of 500 only gives us 10 extra parts. That is not enough for us. If Team Services is talking low volumes like ours, then it might be a viable way to go. This is of course only from my production angle. Purchasing folks have taken this into account but I'm not sure how it is correlated.

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RDR

#43965

Industry Standard Acceptable SMT Component loss? | 15 September, 2006

Yes indeed you make great point as well, we also run low volume production as well as some high running stuff, seems as though some type of combo nwould be best,

maybe something like 20 pieces over or 2% wichever is greater maybe?

Russ

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Steve

#43967

Industry Standard Acceptable SMT Component loss? | 15 September, 2006

SWAG/Russ, How do you guys handle the left overs that the surface mount operators are left with at the end of the job? Do they discard the excess material or return it to stock? We are a small CM and have runs similar to SWAG. 50-100pc, high mix. We do kits as well as turn-key assembly. When we turn key an assy, we have the operators pull the reels from stock, use what they need, and return it. Just curious how you handle the strips, if you have the stock room issue strips? I enjoy this forum for its unique look into how others 'do it'.

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RDR

#43978

Industry Standard Acceptable SMT Component loss? | 15 September, 2006

we do get many strips kitted to us on floor, tough one to really handle but we do something like this, if the strip has 20 parts left on it, we usually chuck it, unless e know that the next build will use 10 or something and we can get it onto feeder with the 10 parts plus a few for throw away. Normally though when we buy strips we buy enough to peel back tape and splice and then run the specific job with some amount of shrink factored in.these strips are then just thrown away. one of our other means is to determine if it will require reel change/replenish in leass than 10 mins after start of production. Of course all this changes every day too! we do run short strips though when necessary and change the feeder every 5 mins til inventory is used up, depends on part cost. I do not know what we use for break on that, probably an emotional judgement more than anything

We always count material when it is believed that there is less than 1000 pieces on reel and we adjust inventory levels at that time. and these reels are then counted after every run

Russ

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Steve

#43979

Industry Standard Acceptable SMT Component loss? | 15 September, 2006

Good info, Russ. I'm glad we aren't the only ones that go to extra lengths to use up short strips of parts, both kitted and our own supplied parts. The tought part is making the call to throw out the left-overs since the operators generally don't know the cost of any given part. Tricky having the operators make a call on this. Not to mention, if they toss the parts out, we need to make an inventory adjustment at that time. I like your process of counting the reel when it drops below 1000 parts. We try to do a rotating inventory on 50-100 parts per month. That prevents our need for an annual inventory. We also adjust as necessary when shortages occur.

Back to the initial question from the thread starter. We will normally specify to our customers supplying a kit that we require 6-8" of leader on a piece of cut tape for resistors and caps. That has always been plenty of extra for us to get the feeder loaded, and accounts for all but the most poorly setup feeders, as far as dropped parts go. For small jobs <1000 components, this is always adequate. I'll also request 1-2 extra pieces for ICs in tubes, or tape. Exact quantities for quads, or trayed items.

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SWAG

#44007

Industry Standard Acceptable SMT Component loss? | 18 September, 2006

Yea, 10,20,40,60 over or 2% for large issue qtys. would be ideal as we do run out of parts often if the issue qty. is very high.

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SWAG

#44008

Industry Standard Acceptable SMT Component loss? | 18 September, 2006

We toss extras at tear-down unless it looks like an unusually large amount which could = qty. pick error from warehouse. In that case, we do a cycle count. All overages are issued when the kit is pulled so they are already taken out of stock.

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SWAG

#44010

Industry Standard Acceptable SMT Component loss? | 18 September, 2006

Depending on what kinds of machines you run and feeder style, self adhering leaders work well to minimize the need for a long leader. We use them on every reel. We can generally load most feeders with only waste of about 4 parts by use of leaders (popcorn, small parts). (These leaders are for the purpose of getting the cover tape back to the take-up mechanism).

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