Author Topic: Pick and place build, openpnp  (Read 6826 times)

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Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #50 on: February 15, 2020, 09:43:20 pm »
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.
« Last Edit: February 15, 2020, 10:30:17 pm by pisoiu »
 
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Offline Kjelt

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Re: Pick and place build, openpnp
« Reply #51 on: February 15, 2020, 11:08:05 pm »
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
 

Offline rx8pilot

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Re: Pick and place build, openpnp
« Reply #52 on: February 16, 2020, 12:14:50 am »
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.
Factory400 - the worlds smallest factory. https://www.youtube.com/c/Factory400
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #53 on: February 16, 2020, 02:27:36 pm »
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.
 

Offline Kjelt

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Re: Pick and place build, openpnp
« Reply #54 on: February 16, 2020, 06:42:34 pm »
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.
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #55 on: February 16, 2020, 07:07:48 pm »
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.
 

Offline rx8pilot

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Re: Pick and place build, openpnp
« Reply #56 on: February 16, 2020, 08:05:13 pm »
What is the cost of that sensor?
Factory400 - the worlds smallest factory. https://www.youtube.com/c/Factory400
 

Offline pisoiu

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Online RoGeorge

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Re: Pick and place build, openpnp
« Reply #58 on: February 16, 2020, 09:41:12 pm »
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. 

Offline rx8pilot

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Re: Pick and place build, openpnp
« Reply #59 on: February 16, 2020, 10:50:39 pm »
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.
Factory400 - the worlds smallest factory. https://www.youtube.com/c/Factory400
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #60 on: February 17, 2020, 06:55:57 am »
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.
« Last Edit: February 17, 2020, 07:05:27 am by pisoiu »
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #61 on: March 03, 2020, 05:46:23 pm »
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.



 

Online RoGeorge

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Re: Pick and place build, openpnp
« Reply #62 on: March 03, 2020, 06:34:52 pm »
That's scary fast!   :scared:
 :-+

Offline Rat_Patrol

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Re: Pick and place build, openpnp
« Reply #63 on: March 03, 2020, 10:14:46 pm »
May want to tune your acceleration profiles!
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #64 on: March 04, 2020, 06:20:36 am »
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.
 

Offline MR

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Re: Pick and place build, openpnp
« Reply #65 on: March 20, 2020, 06:44:13 pm »
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?
 

Offline Kjelt

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Re: Pick and place build, openpnp
« Reply #66 on: March 20, 2020, 07:40:18 pm »
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.
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #67 on: March 21, 2020, 09:38:26 am »
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.
 

Offline Kjelt

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Re: Pick and place build, openpnp
« Reply #68 on: March 21, 2020, 06:08:28 pm »
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.
 

Offline pisoiu

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Re: Pick and place build, openpnp
« Reply #69 on: March 21, 2020, 07:48:00 pm »
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.
 


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