Better nozzle with auto change?

[JuKu]

Ok, here is what I came up with. I found a source for metal nozzles, so magnets keep unused nozzles in place.
http://liteplacer.com/phpBB/viewtopic.php?f=1&t=376

[mrandt]

Ok, here is what I came up with. I found a source for metal nozzles, so magnets keep unused nozzles in place.
http://liteplacer.com/phpBB/viewtopic.php?f=1&t=376

Hi Juha,

congrats on the new kit - looks really good and I think it is a nice upgrade for any LitePlacer user who is still using blunt-needles.

The bearings, tube, coupler and nozzle holder look familiar

I also have tried a Samsung CP40 nozzle + holder from China; but in my case there were severe problems with vacuum leakage in the holder itself.

How is your experience with the holder in terms of that? Would you mind sharing the source for (just for the holder) or would you sell one holder independently to me?

Thanks and best regards
Malte

[JuKu]

By my very scientific leakage measurement (blow into it until cheeks hurt:) ) these don't leak.

[WayOutWest]

I also have tried a Samsung CP40 nozzle + holder from China; but in my case there were severe problems with vacuum leakage in the holder itself.

How is your experience with the holder in terms of that? Would you mind sharing the source for (just for the holder) or would you sell one holder independently to me?

My solution to vacuum leakage was to use a massively overpowered vacuum pump

I actually had to deliberately create some leakage in order to get good release on large BGA components when I use the big Juki nozzle, since the vacuum in the pneumatic path from the solenoid to the needle tip wasn't repressurizing quickly enough to release the part in a reasonable amount of time.

So now my machine makes a hissing noise and wastes energy, but I don't mind

I'm totally psyched about the new nozzle holder, but kinda sad that the new needles don't have a z-sensor in the tip. Having the entire nozzle head able to move along two axes (rotation and z-axis in order to trigger the z-max sensor) seems like it would just unavoidably introduce more slack than having the z-moving part be only the very tiny tip (like Juki). But to be fair I never got the Juki z-sensor working reliably, it is still flaky to this very day.

OTOH my mechaduino boards will be here soon, so maybe I'll use their force-feedback awesomeness for Z-detection and go totally sensorless. Aw yeah. They monitor both the rotational position of the stepper (magnetic encoder) and the current delivered to the motor (series current-sensing resistor) and compare the two to detect and limit delivered torque. So I'll try setting a fairly low limit on the torque delivered by the z-axis motor and trip the switch if it loses a step (yes that's right, lost-step detection!)

[JuKu]

Release: The valve I have is three way, switching outside air to the nozzle. It seems to depressurize fast enough.

Z sensor: Please report back your experiences! My gut feeling is that you might need to slow down the Z in order not to trip at acceleration or use rather large force tolerance. But I'm guessing, it might work very well! Anyway, it will be very interesting.

[mawa]

OTOH my mechaduino boards will be here soon, so maybe I'll use their force-feedback awesomeness for Z-detection and go totally sensorless. Aw yeah. They monitor both the rotational position of the stepper (magnetic encoder) and the current delivered to the motor (series current-sensing resistor) and compare the two to detect and limit delivered torque. So I'll try setting a fairly low limit on the torque delivered by the z-axis motor and trip the switch if it loses a step (yes that's right, lost-step detection!)

I am currently working on a 4 Nozzle-Head with 4 x NEMA8 + 2 NEMA11 Steppers. Each two NEMA8 hollow shaft steppers are moved up and down by a NEMA11 stepper.

All steppers are controlled by Trinamic TMC223 stepper drivers (interconnected by I2C from an Arduino which also switches 4 solenoid valves and reads 4 vacuum pressure sensors and turns the down light on and off).

The TMC223 utilize sensor-less stall detection, lost step detection and limit-switch-less homing and has a very versatile current speed and acceleration management.

Using these on my prototype head assembly I have come to the conclusion that, if you intend to use stall-detection to "measure" Z down-force, you should keep in mind that the stepper has to overcome friction to start moving. Even a thread drive will need some higher onset initial force to start moving. You don't want to stall the stepper right from the start, so you will have to differentiate your torque settings between movement start and "touch down the component".

[JohnSL]

The TMC223 utilize sensor-less stall detection, lost step detection and limit-switch-less homing and has a very versatile current speed and acceleration management.

Using these on my prototype head assembly I have come to the conclusion that, if you intend to use stall-detection to "measure" Z down-force, you should keep in mind that the stepper has to overcome friction to start moving. Even a thread drive will need some higher onset initial force to start moving. You don't want to stall the stepper right from the start, so you will have to differentiate your torque settings between movement start and "touch down the component".

Have you gotten stallGuard to work at very slow speeds? I've been using the TMC5130A chip for a PnP machine I'm building, and I have to use about 50mm/sec (16 tooth GT2 belt). At slower speeds there doesn't seem to be enough back EMF for it to work well (unless I haven't learned the trick yet).

[Pixopax]

I changed my nozzle holder for more precision.
It is milled from FR4 board, 1.5mm thick.
It has springs holding the nozzles in place, they sit perfect now and cannot slip out.
You do not need magnets, which prevents the nozzle become magnetic.

If you like I could mill you some, and send them to you for your kit.

[mawa]

Slip out?

Never happened to me yet. I wrote a nozzle exercise loop to verify the programmed load and unload movements and regularly change nozzles during pnp operation. Until now the changer works like a charm!

But I have an other auto change problem:

If I leave a nozzle attached to the adapter for one or more days the nozzle "sticks" to the adapter (probably the rubber tightening ring).
When I then return the nozzle back to the holder the Z drive has to issue a large force to pull out the adapter.

Fortunately the Z axis has a threaded rod.
I solved the issue so far as I programmed an automatic unload when the program is terminated.

What kind of lubricant could solve that effect?

I already tried Teflon spray but that did not consist very long.

[Pixopax]

I had them slip out only a tiny bit, but that caused a jam already as the Z-Axis did not hit exactly. I had some crashes due to that, so I changed it.