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SMEMA conveyor

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SMEMA conveyor | 16 October, 2005

I have a couple of questions about the SMEMA conveyor (standard 1.2); I posted the question to them but had no answer. SMEMA says:

5) Maximum gap. The maximum gap between the in-line machine track ends is 0.375� I would suppose this gap refers to the track ends of two separate conveyors, but how can these be spaced less than 0.375�? This would require that the pulleys supporting the belt have an OD lower than 0.375.

6) Lead-in The minimum lead-in on the track ends of the conveyor is .1 25". I thought �lead-in� was the distance between the track end and the point where the board begins to lay flat on the belt, but in this case it would be a �maximum� lead-in, not a �minimum� lead-in.

Probably I misunderstood the meaning of these two points. Can anyone provide a more clear description?

Thanks, Olas

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SMEMA conveyor | 20 October, 2005

You should not be worried about these points in the SMEMA standard. You need to make it work for your application. If you are running really small boards, keep the gap between conveyors and the lead-in as tight as you can. If you are using large panels, it will not matter as much. Example: if your panels are 12" long, you could probably live with a 3/4" gap between conveyors (not that you may want to). If your boards are 1" long, you will try to but them up so they almost touch. The standard is not important as long as your boards transfer.

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SMEMA conveyor | 21 October, 2005

Exactly. Poor Olas is pulling his hair out over an issue that has no business being "standardized". The SMEMA guys with apparently way too much time on their hands couldn't simply stop at the communications protocol and leave it at that....they had to get into conveyor gaps and heights to boot. Little did they know that a guy on the other side of the world would get an ulcer taking all of it literally.

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SMEMA conveyor | 22 October, 2005

Thank you guys,

I wasn't really pulling my hair out, but I feel better after reading your point of view!

Have a good day, Olas

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SMEMA conveyor | 30 October, 2005

I am sorry for my poor english, but perhaps you will undertsand:-) The important thing is to get the conveyors straight: The front fixed rail must be parallel with the next one and also the heigt. The heihgt of the prior conveyour should be (but not necessary) just under the nexts conveyour belt, so that the pcb will be "somewhat pulled" into the next conveyour. That is for pliable board tranfer especially with large fine pitch QFP:s. The gap between the conveyours should be as little as possible and this is just a "finger tip" senstivenes. Use your common sense. The easiest way to achieve the alignment; is to use 2 pcb:s (I assume that you have good square pcb:s and the biggest avaiable) Put one pcb on the previuous/machine conveyour and pull it towards yourself (of course you need a gap between the rails so that the pcb don't get caught). Then put the other pcb on th the next conveyour in a simular matter and slowly move them together (while still gently pull them towards the fixed front rail). If You see even the smallest misaligngmet; then adjust accordingly. If You do this over the whole line, then the line with all of the machines and conveyours will be perfectly straight and without any transfering problems. Another thing; if you have several lines at your site, make all of them at the very same height +/- some 5 millimeters. This is just if you have replaceble feeder carts. /Good luck.

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SMEMA conveyor | 2 November, 2005

Thank you for the advice, Mika. My question however was not generated by a practical problem, but rather from the fact that we have to design an equipment which must interface with other conveyors. By now we�ll ignore those two points.

Regards, Olas

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SMEMA conveyor | 4 November, 2005

Always happy to share information. Perhaps other viewers on this thread, can get some ideas of "how to". /Sincerely Ps. There is a so called "standard height" which the conveours/machines from different manufactories must be able to reach; without rumbling vibrations from the machines (if they are set to high on their foot screws) and still at a working heigt for the operators. Otherwise the machine/conveours must have extra steel/rubber pad's underneath the feet. And at this moment I have forgotten that height. DS.

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