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SMT electronics assembly manufacturing forum.

Line Capacity

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Line Capacity | 9 July, 2010

I am working on some capacity issues and I have been reading some of the other treads, but I am still struggling with the idea of machine downtime. We have a lot of older equipment that does not consistantly run from day to day. How do I factor that into my capacity figures. Do I need to use a weeks work of time studies and get an average? Thanks for any help on this topic.

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Line Capacity | 9 July, 2010

I hope I understand your question, but are you saying you're having trouble meeting demand? Keep a log of the time that the machines are down, probably for 4-6 weeks would be good and this may give you a good idea of what kind of downtime your working with and this will give you your hours of machine operation (Of course your efficiency can be gauged by your weakest link. You may need some new equipment to meet the demand). If demand is the issue, how about building up a safety stock? We try to maintain a four week stock on all products in our shipping dept. This helps us fill any large orders that my come through but also helps alleviate the effects of machine downtime. That's not Lean, but I never said I was fit.

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Line Capacity | 12 July, 2010

Thanks Reese.

Right at the moment we haven't ran into big capacity issues, but I can foresee it coming if we continue to grow. I was just looking for some other opinions from everyone as to how they handle process complications with older equipment. I know that things are tight and buying equipment is not always an option. Thanks in advance for any opinions.

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Line Capacity | 12 July, 2010

That said, having some sort of buffer to meet demand in case of machine downtime will probably be your best bet. It doesn't hurt to have spare parts on hand to mimimize downtime either. We do both. With some parts it may be economically unfeasable to keep them in stock depending on cost. Take your most common failures and get parts on hand for those.

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Line Capacity | 12 July, 2010

In my experience Through Hole equipment normally racks up the downtime due to the amount of process variables. For SMT you would normally try to capture your workhorse machines Utilization. For example a chipshooter inline with glue dispenser,screen printer, conveyors and a oven. This line would be measured off the utilization of the chipshooter. We were able to capture from our machine software - Power on Time - Machine Runtime - Machine idle time, Feeder Error time - and on an on. If you take the actual running time compared to the power on time you get a good idea of what your utilization is for a day.

Also do a search on OEE (Overall Equipment Effectiveness), this has a lot to do with what you want to accomplish.

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Line Capacity | 13 July, 2010

You have to basically know how many time you will consume producting what you have in schedule (seems to be pretty basic, and it is), but you need to consider your changeover time!!! that's basically to divide your volume on the basis you want to measure (daily, weekly, etc) with your rate (pcb/hour) so you will obtain the hours required to accomplish your demand, but consider CHANGEOVER... this is, your average changeover on your measurement basis (daiy, weekly, etc) multiplied by your REAL setup time. also you need to consider your average downtime and add to that time... if the sum of Production time + Changeover + Downtime > time available then you have capacity issues... most of the time downtime is not considered for "ideal" calculation, but is highly recommended to consider it. You have to consider alternatives if your capacity is over 90 % this is where you need to break down the numbers and propose alternatives:

Is your setup time on target?? if not... improve

is your downtime on target?? if not... improve

is your installed capacity according to volumes?? if not, propose extra shifts.. line balance, add machines (the most difficult to buy).

OEE is pretty helpful to mantain your metrics on target...

if you need more info please let me know!

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