Add-ons: feeders

[WayOutWest]

- Tapes are of variable thickness. If the slot that holds the tape edge is loose enough for paper tape, it is too loose for plastic tape. if the tape is not firmly held, the pickup height becomes arbitrary. Just using the lowest position (value that is good when the thin tape edge rests against the bottom surface of the side groove) slams the tape to the bottom when the tape happened to curve to the topmost position, knocking parts out of their pockets. This is a general problem. => The basic principle needs to be thought over.

Does the availability of thereza's vacuum sensor change this?

i.e. position needle over tape, turn on vacuum, lower head until needle occlusion triggers. It might be necessary to put the lower-test-lower-test loop inside the TinyG; doing the test on the host would require very slow motion.

[mrandt]

position needle over tape, turn on vacuum, lower head until needle occlusion triggers

I am afraid that the airflow will suck smaller parts out of there pockets before the needle actually touches them - resulting in arbritrary part orientation, even upside-down or tombstoned parts.

At least that is what happens with 0603 or smaller when I use my manual vacuum pickup tool and do not turn off vacuum before lowering the needle on a part...

Variable tape thickness is definetely a challenge. The tape must not bounce during pickup or tape advance, otherwise small parts will jump everywhere.

I have looked at many open-source feeder designs recently - most of them work in progress. The most common solution seems to be using some springloaded mechanism to either push the tape down onto a rail or the tape up against a guiding plate which keeps parts in their pockets.

[JuKu]

Yes, some kind of a spring mechanism is needed to hold the tape in place. I've seen a video of a super high speed feeder, that had a piece of metal over the exposed components when tape is moving; when tape movement stops, the cover piece slides away exposing one component. I like that idea, and it should not be very difficult to implement and would definitely solve the problem of components being shaked off their pockets.

[WayOutWest]

position needle over tape, turn on vacuum, lower head until needle occlusion triggers

I am afraid that the airflow will suck smaller parts out of there pockets before the needle actually touches them

Well, that was sort of the idea.

resulting in arbritrary part orientation

Personally, I don't mind checking orientation in the up-camera. I know it slows things down to have to do that for every single passive.

even upside-down or tombstoned parts.

Assuming that the up-camera can reliably detect this (big assumption, I know) does it happen often enough that you'd be throwing out more than 5-10% of the passives? They are so ridiculously cheap, at least the ones small enough for this to be a problem.

[Spikee]

Here is my feeder idea:


The smt reel is advanced via pulling the tape. The tape is ~0.1mm thick according to vishay so i made the slot where the tape goes trough small.
Immediately after the tape is pulled of the top is closed so components cant fly out of the carrier. At the end there is a slot where the components can be picked via the pnp.

I have looked at rotary encoders , magnetic encoders ... but they are all to expensive. There is also the button method or IR port method. But I think there are things that can go wrong with that setup.
A small and cheap stepper motor + driver (with microstepping) is one of the best solutions I can think of at the moment. I currently do not have smd components with me so I cant test it at the moment.
But the files are here (stl):
https://www.youmagine.com/designs/smd-8 ... eeder-test

Currently printing and probably modding it.

Based on this design:

Rx8Pilot from eevblog forum

[JuKu]

This looks great! I bet it would work as-is or at the most, with some trial and error. (Note to self: Buy that 3D printer already!)

Throwing some more ideas:

I didn't quite get how the cover tape peeling would work. Maybe a scheme where first tape and lid are advanced together, and then tape is held in place, and lid and cover tape is pushed back.

When looking at feeders, the cost of each multiplies. Stepper motor + driver is costly, but maybe it would be possible to develop a scheme where a "feeder advancer unit" moves along a row of feeders, pushing each feeder when necessary. there would only be a slider unit, two stepper motors and some additional mechanics for a whole row of feeders.

Alternatively, the feeder could have a lever mechanism (to set the amount of travel) and a solenoid to advance it. A solenoid costs about as much as a motor, but it would not need a driver and would be easier to drive. Can't tune the speed, though.

[Spikee]

A lever with solenoid might introduce a shock / vibration that might upset some component's location.
A printer stepper motor with driver is about 2 dollar in single quantity. Quite hard to beat that:
http://www.aliexpress.com/item/Smart-El ... .81.JkpAaw

The design is based on this:
https://www.tindie.com/products/FemtoCo ... 12mm-16mm/

There was also a kickstarter about it and it seems to work fine.

My plan is to make the trays and the corresponding base plate modular so you can just plug them in a random order next together.

I did a small test with the first 3d printed prototype and it seems to work good. The components stay in the tape no issue.
I had to make the side rail a bid wider because the plastic tape occasional wanted to go sideways.

And the tape width went form 8.13mm to 8.07 mm to make it fit a bit more snug. In the vishay tape document it does not state a tolerance for the tape it just says 8mm.

[JuKu]

A printer stepper motor with driver is about 2 dollar in single quantity. Quite hard to beat that:
http://www.aliexpress.com/item/Smart-El ... .81.JkpAaw

Wow, I had no idea.

[Spikee]

Top plate is transparent plastic (for now) so you can see whatever goes on. The top plate is separate so multiple versions can be made to see which one is best.
Also allows easy customization.
I'm now designing the base plate where multiple trays can be mounted on.

You can put a sticker with some component details on the top.

[Spikee]

First idea was to make trays that could be joinded together:


The problem with that is it works fine for 8mm tape. But when you go 12mm or 16mm the base plate won't fit anymore.
The new idea is to make the trays from delrin / nylon or whatever and have two steel rods sticking trough it sideways. You can just add different sizes and whatever next to each other. Designing that now ...

3d printed tray:

Works fine with thin plastic tape now

one thing i'm not sure of yet is how big to make the part picking hole. The 0805 1uF cap has some space to spare but not a lot?