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SMT tact time

#30233

SMT tact time | 25 August, 2004

Can anyone tell me what a reasonable real world percentage would be for tact time on SMT machines. If I have a machine rated at 14,400CPH what would be real world, 85%, 75%? Thanks

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RDR

#30234

SMT tact time | 25 August, 2004

This is highly dependent upon your board, vision inspection, part rotation, part type, layout, number of P/Ns per (1 pers or 100 pers) feeder layout, optimization, nozzle changes, etc... all have significant impact on placement speed. I find if you get 50% you are doing well or average. Some boards will be faster, some might actually even be slower. Placement speed is sometimes calculated by the manufacturer using the maximum speed of pick time, place time, and seek time, maybe even vision inspection time. Others will use the IPC board and under ideal conditions, (ie perfect feeders and feeder layout since they don't necessarily have to place a different P/N in each location like we do) and can only really be used to compare one machine with another, These are not real life conditions on these test boards and setups. You need to ask how the speed was calculated and have them "run your product" and tell you what they got and how fast they got it going. Did they spend two days changing feeders around? or modifying step sequence? how did get this incredible speed? Show them a typical board if you can and have them guarantee a tact time and see what they do.

Is anybody getting 75% of advertised speed out there? I'm curious.

Russ

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Loz

#30245

SMT tact time | 26 August, 2004

I think realistically any speed quoted by any manufacturer should be down graded to 80% of what they quote. This should be used as top end, then the component, feeder count and complexity will start digging into this. As for achieving 75% of book speed, nope never have.

Loz

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#30247

SMT tact time | 26 August, 2004

Machine design plays a major factor in actual placement rate vs. the published tact time max speed. For example, random access horizontal turret head machines can vary greatly depending on nr. of different components and size ranges, while the dual gantry dual vertical turret head (the collect and place design) design achieves some of the most consistent rates regardless of nr. of components and component size range. Single gantry single head designs can also vary greatly from board component mix. There are also designs such as split axis where the head moves in X and the table/board moves Y. This design allows for maximum axis speeds and delivers good performance in max. cycle rate vs. actual rates. There is also the multi-head sequential design, which is the absolute fastest with rates in the hundreds of thousands per hour. In this design the machine is segmented in stages. Each stage has its own placement head(s) and feeders. The board steps from stage to stage. The proper method to measure actual placement rate on a given board is to time the machine from the first fiducial read on board nr. 1, then complete component assembly, then stop the clock at the first fiducial read on board nr. 2. This will account for board transport time. Ensure there are no feeder re-picks or errors during this test. What you time will be �real best case� for that given board. Now, how many placements you get at the end of the day for that board will depend on how efficient your operation is. Speed of feeder change outs and re-loading, how fast operators react to a machine stoppage- these are the human factors that will effect placement rate. Machine design can effect these times as well. Not all machines take the same time to re-load a feeder and mount it on the machine. Some machines are designed to not stop for a minor error, instead it will continue picking and placing (provided there is more to do) and alert the operator to the issue. The IPC9850 spec is a good start to differentiate machines in terms of what their actual placement rate is on the IPC board vs. what their published max rate. A good machine design should deliver 80% of max cycle rate or better on the IPC9850 board.

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Dreamsniper

#30250

SMT tact time | 26 August, 2004

I've done a few capacity and capability studies and bought new SMT equipment (Pick and Place) based on the above required capacity. I did not rely on equipment manufacturer's tact time. I used only 60% of their tact time as achievable in real manufacturing world. Say an equipment supplier rated his machine as 21,000 CPH, I gauged it as only 60% of 21,000 CPH (12,600 CPH). And I never FAILED. When the machines arrived at our manufacturing floor the placement rate that we were getting based on real world manufacturing is +/- 5% of my gauge.

So if you use that, you will never fail and will not loose your face.

regards, Dreamy

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#30420

SMT tact time | 8 September, 2004

Hi Everyone, I am new to this forum. I have posted a similar question on this subject (Chipmounter Plancement Speed). Does the 60% inclusive of the PM and Downtime ? I also find that line balancing also plays a part. For example the Universal GSM II is choked with PCBA that has higher IC count.

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Rob

#30422

SMT tact time | 8 September, 2004

Hi Peter,

We're typically seeing 60% on the average subcontract job, but on high volume, high density & well laid out boards we are seeing up to 95% on our chipshooters. The things that usually kill the speed for us are:

multiple circuit panels (32 up etc) that require local fiducial reads. (Can often get around by programming panel as circuit)

Line balancing - moving bigger devices onto the chipshooters to speed up the GSM's

Lower batch sizes where running changeover (both feeder banks) is not economical

Low component count PCBs

Regarding preventitive maintenance, we do this outside of production time, & downtime due to machine failure doesn't really happen as we use Fuji's.

Hope this helps,

Rob.

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#30424

SMT tact time | 8 September, 2004

Hi Rob, Thanks for the reply. Our boards are 4 ~ 6 ups and mostly double sided. The ratio between chips and IC/Odd shape varied from products to products. So, line balancing between chipmounter and GSM is tough to do. Some boards are mirror image to reduce set.

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Rob

#30429

SMT tact time | 8 September, 2004

Hi Peter,

I've got to admit we cheated by adding another GSM per line, but that's not always the most economical option.

Cheers,

Rob.

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#30439

SMT tact time | 8 September, 2004

Hi Rob, I guess the ratio between chipmounter and GSM is very much depending on the chip to ICs ratio. This is product dependent. We use 2 HS50 to 2 GSMII, 5 S20 to 2 GSMII, 3 Sanyos to 2 GSMII, and 2 CP6 to 2 GSMII. Are these ideal ratios ?

Lean Manufacturing concept encourages U-shape line for better operator efficiency. Bad for house keeping. What's your idea ?

Kind regards, Peter

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#30442

SMT tact time | 9 September, 2004

Peter-

If you have all of these machines in your factory, why are you asking what their throughput and tact time speeds are? You should know better than anyone.

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Rob

#30445

SMT tact time | 9 September, 2004

Hi Peter,

You certainly have a selection of kit. We use 2 CP6's & 2 GSMs per line, and that balances pretty well (sometimes one of the fuji's is idle though - but we can live with that). When we had S20's we found 2 of them roughly kept up with a CP6. But again it does really depend on what you are making.

I've got to say (and I know I'm risking the wrath of the many - so please don't see this as a challenge!)that most conversions to lean manufacturing I've experienced have involved paying lots of money to people to create problems further down the supply chain. If you've got a production manager with common sense and some decent engineers you should be able to find the best solution for you.

Remember no one has exactly the same facility or requirements, so whats good for me aint neccesarily right for you.

Just out of interest, if you're running all of your chipshooters at capacity which ones give you the least trouble?

Cheers,

Rob.

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#30465

SMT tact time | 9 September, 2004

Hi Fastek, Why am I asking ? Cost pressure ! Down 10~15% every year to remain competitive. Need to do differently for better $ per unit.

Hi Rob, Thanks for your candid advice.

Kind Regards, Peter

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