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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Contract Manufacturing

Antonio

#21095

Contract Manufacturing | 9 August, 2002

Hi Guys,

Just would like to inquire about contract manufacturing costing:

a) if I send my bds. to a CM with a line of 2 chipshooter and 1 IC mounter and will use only 1 chipshooter and the ic placer for my product, do they need to charge me with the utilisation of 1 of the chipshooter when they r using it for theit product? Does the cost of placement need only to be calculated for the 2 machines they are using?

b) Id like to get Ideas on how a CM charge per component placement or per PCB and the average rate available in the market mainly in US.

c) Also when they say their line is capable of placing 55,000 CPH, how did they come to this and how do they come up to that if they have 3 machines per line.

Thanks and regards

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Melo_Guy

#21096

Contract Manufacturing | 9 August, 2002

I work for a manufacturer of electronic components and I have spoken with some CM's in the past. I have a contact for a CM and if you would like I can refer them to you. I'm not too knowledgable on CM manufacturing techniques, but if you would like some help finding a CM I'm sure that I can find one that will work for you. You can E-mail me at Tbart@ecliptek.com with any questions.

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#21099

Contract Manufacturing | 10 August, 2002

Antonio,

a) You shouldn't care how many machines they have on their line at all. Let's assume the number of parts to be placed on a pick&place is A, and the number of parts to be placed on a chip-shooter is B. They need to find the limiting machine, So, A/(p&p cph) will give them a time and the pick&place will be kept busy for that time. If this time is shorter than the screen printing time, (20-30 seconds at my times) then your screen printer is the limiting factor, you can only run 120 boards per hour, with yields and part changes, let's say 90 boards. I don't know what yield ratio they use... So, everything starts from the 90 boards per hour parameter. They know what 1 hour of line time costs to them.

If there was a case where B/cph >> A/cph, then you need a second chip shooter. Then each chip shooter will place B/2 parts and possibly catch up with the pick&place machine.

If the line has 2 chipshooters and a pick&place, it will be pretty hard to use the one unused chipshooter for another job because for a high speed production that machine has to be used as a conveyor, and if the production is too slow where the operators can walk the boards by that machine, then it shouldn't be called a "3 machine line" anyway.

If your CM is focused on the number of machines in their quote, I would look for another Cm, NOT another CM with a 2 machine line.

b) each machine has a "tact-time" for different types of components. In an ideal world, for example, a chipshooter will give a tact time of 0.18 seconds for a 1206 chip capacitor. Then the formula is adding up (tact-time for type z component)x(number of type z components) for all different types of components. Then you come up with a total time spent on a machine. Then you add feeder changes, i.e. each reel has 2500 parts, each board uses 25 parts, every 100 boards I will have a feeder replaced. if the CM puts 5 minute down time for a feeder change, then you'll question why they don't have a full feeder ready, or maybe that machine can be loaded in a way that once there's an empty feeder, it switches to the second feeder bank.

So, there are endless ways to bring the "actual run time" to the "ideal run time". CMs have their own priorities, some are high-volume/low-mix, they won't want to change a machine setup every 4 hours, once they start running a board, they run that board for days, that way they can lower the costs. Some others are low-volume/hi-mix, their offline feeder setup group will have more people than any other group.

You have to find the right CM focused on your type of work. Otherwise, anybody can run your boards but some CMs will simply say NO since it's out of their focus. (yes, even nowadays)

c) I believe they add up each machine's capacity. 2 chipshooters each 25kcph, one pick&place 5kcph, there's your 55kcph. But if all the components on your board are large QFPs or BGAs, you'd better get prepared for a 15kcph capacity, or in your case, just add the chipshooter and pick&place.

The cph values may be calculated just like the gas mileage on a car. With a skinny driver when the wind blows fromm behind on a smooth surface road, 60 miles per gallon. Not when you drive the car with a heavy foot, canoe on top, full trunk... Same idea, if the parts are placed as a matrix on a board where the board hardly moves during placement, since it's the same fastest placed component, the feeder carriage does not move either. I don't want to say car manufacturers or SMT machine makers are not telling the truth, they may be given best case scenario numbers, that's all...

I can help you further if you want off-shore manufacturing.

Regards Erhan finepitch-services@lycos.com

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#21103

Contract Manufacturing | 11 August, 2002

a: charges are typically set by how many different part numbers you have(setup).. and how many placements there are(ie number of locations parts are to be placed) if there are 3 machines inline that does not matter.. its the amount of parts placed and the time it will take which dictates cost. b: Quantity impacts cost..low volume runs cost more 1st: parts which are ordered have quantity breaks, the less you order the more you pay(from the component mfg.). 2nd: Setup time has an impact, in the case of a low quantity order,it may be more than cost of placing the parts . 3rd: Time machines take to place parts- this number is based on the cost of the machines which is overhead to the company ironically Id have to say its generally the same higher placement speed higher cost less time. lower time lower cost more time. I would say cost is the same for placement whether you can place 3cph or 30cph. c: First of all manufacturers of placement machines boast of high CPH.. which is clearly in most cases unobtainable. Since CMs have little control over board design. Optimal conditions to achieve the CPH for which the machines are rated are a dream for CMs. There are software programs which can balance a line for component placement. if there are 2 machines inline, programs can be generated to optimize placement among them. Generally CMs take an average placement time which has been proven in production and apply that cost to all boards. Placement time is dictated by,, placement machine,component packaging,design,quantity

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Ioan Tempea

#21106

Contract Manufacturing | 12 August, 2002

Hi Antonio,

you had some wonderful input from the previous mailers. They covered much of the technicalities.

What I would like to point out is that if the line has 2 chipshooters and they only use one for you, you still pay for the second one since they pay for this asset in the form of capital recovery and O/H (power, maintenance, etc).

What I would question is their efficiency, since is pretty odd to have 2 chipshooters on the same line. They either have old (so question quality) or cheap machines (quality again) since a regular feeder capacity is 100 to 140 feeders of 8mm per machine. We never had to run assemblies that have more unique parts that the joint capacities of a chipshooter and a p'n'p.

For the CPH, I think they added up the rated capacity of the machines. And this is far from the truth. I would bet on 30% of that.

But I blasted them enough. The most important factor in CM is the customer. You are the king. If you help them, discuss with them optimisation, design issues, audit them, you will work it out together. A bad design will be costly even in the most efficient CM and a good design can be successfull even with the CM down the street.

Cross that line, talk to them upfront about the particular assembly you need and you'll get great results.

Just a thought, Ioan

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