Issues with multi-indexing feeders

[Mike]

Multiple indexing appears to only work with the fixed camera.
The second (and subsequent indexes) only happen when a part is recognised, which makes sense to get the tape in step, however this does not appear to work with the RV4s flying camera, or when imaging is disabled.

Workaround : always use "force fixed" in the CDF.

Another issue I've noticed with double-indexing is that if the distance between feeder, fixed camera and placement location is very short, one of the indexes doesn't happen as the head is back to pick a new part too soon.
This generally fixes itself as you get alternate mis-picks and good picks - it just slows things down a bit when placing parts located very near the camera. If it's a problem, move the feeder, slow the X/Y speed in the CDF or move the PCB.

[phonoplug]

This is actually an issue with the feeder and its internal firmware. Each index command sent to it is for just a single 4mm index and if it receives a further index command before its completed one it ignores it. My guess is that if its visioning a part on the fly it sends both (or all) indexes immediately, whereas if its using the fixed camera, it sends a single index command once its picked, and the remaining ones once its visioned. If the distance from feeder to the fixed camera is short, then the part will have been visioned before the first 4mm index is completed and therefore the next index command is not executed.

I have designed a replacement feeder controller board that addresses this and several other issues. It buffers upto 8 index commands and actions them as soon as physically possible - in other words the PC can send upto 8 indexes instantly, the feeder controller stores them if its busy and actions them in order immediately after the one its currently working on.

Its also smaller, more efficient and modern than the original controller. You can remove the old board complete with its heatsink as the new board doesn't generate any heat.

Lastly the other benefit is that it has its own on-board +/-12V generator, meaning a) it can be used as a replacement in both older and newer feeders, and b) you do not need the power block fitting (modification - mentioned in another thread), or can remove it if its already fitted.

I can supply these to anyone who is interested. Message me if so.

[Mike]

That's interesting - I've not yet got around to looking at the feeder protocol ( I was consideriing making a little iinline box to allow manual indexing and translating indexes to doubles etc.)  - have you confiirmed that the OTF/no-camera issue is definitely due to this?

The too-close-to-feeder one is pretty obviously a time issue.

Any particular reason for doing a whole new board instead of just redoing the firmware for the existing one?
Why use an onboard converter instead of something like a MAX232?

[phonoplug]

I don't have an RV4. Well I did briefly but that was before I re-did the feeder controller. I've got an RV1s at the moment.

Redoing the firmware and using the original board - writing firmware from scratch for early 90's technology - eugh! If I had the source then I would have, but of course I don't. I made a while load of software  improvements in the end:
- Buffering feed commands to remove the problem already discussed
- Speeding up the feed time which could also help for example with a large component on 24mm tape that needs several 4mm feeds
- Ramping the feed travel: it actually starts slower than the original but because of the ramp in speed its overall feed time is still quicker. This is to reduce tape rippage
- Micro-stepping to make it quieter and smoother

On the board itself I used modern parts rather than the old (some obsolete) parts of the original. It needs no heatsink and doesn't create any heat. Its smaller and lighter, though still maintains the 4 mount holes of the original.

I did think about adding some extra functions using the unused dip switches but haven't got round to it (yet...)

[davidc]

This is a good mod.. Well worth getting if you running an RV4s.