Pick and place build, openpnp

[pisoiu]

Hi,

There are some, but not very spectacular (meaning no videos).
I worked hard at mill to complete the aluminium parts required to mount everything needed for x-y assembly. There are still few parts to be built and I expect at least a month until I have something moving.
I also built a controller required to interface everything with openpnp. It will talk with servo drivers over modbus RS485 and will send all data to head assembly over CAN.
I tested a laser alignment system for small components, it works fine, basically any component with biggest cross section smaller than 7mm will use laser alignment for placing, not camera. That will be done on route from picking coordinates to placing.
The bottom camera is now in building process, and I think I will include in it, besides the coaxial illuminator, a laser displacement sensor, to measure component height in the nozzle.
That's it so far.

[Kjelt]

How does your laser alignment work, is it a oem piece or did you do something yourself?
20 years ago they did it like this
https://www.eevblog.com/forum/projects/tear-down-of-an-assembleonphilips-pp-head/msg1293815/#msg1293815

[rx8pilot]

How does your laser alignment work, is it a oem piece or did you do something yourself?
20 years ago they did it like this
https://www.eevblog.com/forum/projects/tear-down-of-an-assembleonphilips-pp-head/msg1293815/#msg1293815

On my Quad 4000C - it uses a laser scanner and a CCD line sensor. All analog upfront that gets digitized for comparison. For its age - it works really well. Guessing modern tech could do the same thing for pennies at 100x the resolution. This method is really fast and travels with the head so the up-camera only gets used for fine pitch BGA's.

Someday, I will be forced to convert my Quad to Open PNP as the old hardware dies out and the software becomes a problem. That would be a fun and exhausting project.

[pisoiu]

It is built by me. The head is not built yet, I only tested the concept on the bench, a laser diode (7mw red, nothing special about it), a lens colimator and a line scan sensor 128 pixels, 8mm active area (tsl1401). The laser light must be as wide as the sensor and it's critical to be parallel. It will work exactly as in the video shown by you.

[Kjelt]

If you would like a few of the Cyberoptics units from the Assembleon machine I can sent it to you for free, maybe some optics to be re-used? I have no idea if that would be usefull.

[pisoiu]

Hi,
Thanks, I do not want to entirely dismiss the idea, but to be honest I prefer to build everything with aliexpress components, this way, if something breaks, it will be easy to fix or cheap enough to build a new one. It is also essential to use that line scan sensor, it is the only one with low cost and SPI access, this way allowing me to control the entire head with an 8051 MCU. I have good experience with this family and I write everything in ASM to have control to the last instruction cycle. This level of control is also required because the Z actuator for head position will probably be a voice coil linear actuator, which I have to build a prototype and test yet. For that one I need also to write a control loop in 8051 firmware.

[rx8pilot]

What is the cost of that sensor?

[pisoiu]

5eur@100pcs

https://ro.mouser.com/ProductDetail/ams/TSL1401CL?qs=%2Fha2pyFaduidmTd2EaO%2FEzP5HOW4QkvofPff3ELECl8%3D

[RoGeorge]

Optical mouse sensors are cheap too, also fast, many can be used as low resolution high fps camera.  Didn't followed the thread closely, so might be a dumb suggestion. 

[rx8pilot]

It is built by me. The head is not built yet, I only tested the concept on the bench, a laser diode (7mw red, nothing special about it), a lens colimator and a line scan sensor 128 pixels, 8mm active area (tsl1401). The laser light must be as wide as the sensor and it's critical to be parallel. It will work exactly as in the video shown by you.

The resolution seems to be modest - do you suppose that will be a practical limitation? I guess it should get the alignment close enough for most parts - perhaps a challenge as the parts get small.

[pisoiu]

True. Not great but not terrible either. With this sensor I get a measuring error of +-62.5 microns. I could have used better but... bigger sensors (in terms of size and/or resolution) comes with several problems. I would need a wider laser beam, that complicates optics. Greater resolutions are much more expensive , both the sensor itself and the required interfacing. Most have analog output, they need timing circuits, adc, etc. I have also size constraints, everything must fit in a 30mm square. This one seem to fit my needs, hopefully with good results at least to 0402. When I'll have a prototype, I will see..
RoGeorge, for this kind of application, a linear sensor is required. Having 2d sensor would not help, it just complicates optics. The optic mouse sensor itself have a very low resolution (in the range of 20x20) and the array is very small. It is mandatory in this case for the sensor to have the reading area in 1:1 ratio with the object you want to analyze.

[pisoiu]

Here are the first tests with x-y assembled, one at minimum speed, another at 50% speed. Nothing is tuned, I do not dare to play more with it, as the travel limiters are not yet installed.
Test programs feeds with 96 components and places them. No head yet . Sorry for the shake especially in the second movie but I kept my foot on the table to minimize oscillations.

[RoGeorge]

That's scary fast!   
 

[Rat_Patrol]

May want to tune your acceleration profiles!

[pisoiu]

Yes, it definitely needs tuning, not only on acceleration profiles, also on servo filters. With the exception of few basic parameters (comm baud rate, direction, etc.), all servo parameters are default, not matched to this machine. Tuning will be next step after I install travel limiters, I am afraid to do more tests without those, the risk of damage is significant without protections.

[MR]

Travel limiters like for trains?
https://youtu.be/EVBdrPggXO4?t=34
I guess once the portal hits the travel limiter it will be damaged.

Or did you mistake it with homing switches?

[Kjelt]

Travel limiters like for trains?
I guess once the portal hits the travel limiter it will be damaged.

They are commonly used also in commercial PnP machines.
Here an example from Assembleon spindle. No idea where to buy them but it does not damage since it has a spring which will deaccelerate the motion and the closed loop servo driver will detect the error and stop the servos.

[pisoiu]

I wasn't very specific with travel limiters. The system has several components and is different than homing sensor.
Homing sensor is optical, that one needs to be very accurate and with low mechanical hysteresis. Currently I am playing with one which has 50 microns hysteresis and 10 microns repeatability.
Travel limiters are actually composed of 2 separate components, electrical and mechanical. There are 2 switches connected to servo drivers into protection ports. Panasonic calls them POT and NOT inputs (positive over travel and negative over travel). When those switches are actuated, whole driver immediately stops and brakes the servo. Secondary travel limiters are purely mechanical, installed at the ends of the ballscrew. I will not use springs, rather some thick rubber pieces. They are designed to minimize the damage in the eventuality that POT and NOT fails.
The system uses absolute positioning and during testing phase, there may be cases when driver software filters are off and coordinates outside the machine area can be entered. Without protections, there will be damage.

[Kjelt]

Homing sensor is optical, that one needs to be very accurate and with low mechanical hysteresis. Currently I am playing with one which has 50 microns hysteresis and 10 microns repeatability.

You already have a servo with encoder, so one of the cheaper but also very accurate methods is to use a simple proximity sensor icw the encoder.
Fast move till sensor activates, Brake, slowly move back till sensor deactivates, now continue to move till the first index pulse of the encoder, finished.

[pisoiu]

The sensor I want to use is an encoder actually. I don't need to worry about homing procedure steps, the servo driver has a separate command just for that purpose. But it works pretty much as you said.

[mendez]

The build looks great!. Which controller are you using? Smoothieboard?

The sensor I want to use is an encoder actually. I don't need to worry about homing procedure steps, the servo driver has a separate command just for that purpose. But it works pretty much as you said.

[pisoiu]

No, the controller I use is built by me because I need to control timings very precisely. Each millisecond counts. It has a ftdi and 8051 CPU on the main board with CAN interface, from there UART goes to servo controllers through RS485 interface. All data for heads are going on CAN bus and each head have its own 8051 CPU with CAN, which controls vacuum relays, vacuum sensor, voice coil actuator, laser alignment system and rotation motor.

[mendez]

Thats amazing! Could you share how you did it?

[cgroen]

Great project pisoiu!
Is it perhaps possible for you to write the exact partnumbers on the drives and motors (in fact, maybe even the mechanical parts also?) ?
I have looked at the motors/drives, and there are quite a lot to chose from, it would be great to know at least a "working combo" if possible
PS: really impressed with the speed and the mechanics !!

[pisoiu]

I cannot share design files. They are quite useless anyway because they contain many precision custom machined parts and without a mechanical workshop, it is outside of many amateur capabilities. This entire project is not a personal project, it is a company funded project. The costs are quite high, so far they are close to 10k$ in components only. But I can share implementation details and some component details.
For the x-y, motors and drivers are MHMF042L1U2M+MBDLT25SF . Iirc, I said in some post details of ballscrews, TBI2550, one is 1m, other 1.5 meters.
Controllers are configured in full closed control, they have external scales with 5 microns resolution, this is work in progress, scales are yet to be installed, configured, then both servos must be tuned to the actual mechanical parameters of the machine. I expect this to be a hard process.
The heads are not yet finished. Parts are in various design phases. I tested the rotation motor, it is a small 8x10mm stepper, 20degree step, with 1:10 mechanical demultiplication to nozzle. It works fine, so far microstepping down to 1:8 should be enough for positioning. The laser alignment system is tested as a principle of operation, it uses a TSL1401 sensor (128x1) but currently I am having trouble obtaining a parallel laser beam with good quality. I tested some configurations with plastic lenses but the quality is not ok, they produces a parallel beam but most of them have a dead spot in center due to plastic quality. I must switch to glass lenses but I was not able to find a ready made one for my needs, I need to design and build a custom one.
Voice coil actuator and vacuum system are yet to be designed and tested.
However, this entire corona situation created me some personal problems which significantly slowed the working pace. The progress is far from what I want, but unfortunately I cannot do too much about it.