first of all, I would like to wish a happy new 2017 year with lots of reliably, trouble free and accurately placed SMDs, as well as many Liteplacers sold to Juha.
Now, I have to say that the post title was a bit provocative to catch attention because my post will be somewhat loooong... I also thought about "Pick or Place, pick your choice". Sorry for that, but I'm having real hard time with, I figure now, the software.
First of all let me state that the machine has been carefully built, squared, calibrated, etc... and long movements have been repeatedly done and checked with garanteed no step loss. Checked with PCB fiducials spread here and there on the table.
- The squareness factor corrects for less than a 0.4mm build squareness error (corrected down to better than 0.02mm)
- In order to avoid additionnal errors the two Y belts tensions were matched (audibly tuned to the same note - Hey I'm a guitarist ). Some experiment showed me this could matter for ultimate precision.
Now for the provocative title, I mean I can't reliably pick up, place 0603s, SOT23s, not even speaking of 0402 for which I got the machine...
Let me now explain all that in details.
First, the machine configuration is as follows: The board to be stuffed is the lower left one, while the 3 others are for test conveniency (they provide 1mm fiducials which are ideal with the pink 0.8mm needle for pickup accuracy test).
The small brass piece at main PCB lower left corner is the "home target" and allow excellent homing repeatability.
The machine is carefully calibrated it according to Juha's instructions.
Some (2) 0603 placing tests lead to the following conclusion:
- Components are not picked up. Missed by about 2x1mm, offset that seems to change, depending on the tape position on table.
- Should the needle carry a component it would have been placed accurately. At least that one's good.
So I did put even more efforts into diagnosing, thinking I was doing something very wrong. Eventually, I came to the conclusion that the software almost certainly has some more bugs, and possibly (I underline the conditional) some flaws designed in.
After all the efforts that's real frustrating, given the feeling I have that the mechanic is capable of reliably placing even 0201s.
First the problems with components pickup, and pickup consistency across the machine table:
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The board has 70+ different references per side, most 0402, so the table is cluttered with tapes.
Unfortunately components pick up offset WRT to tape hole varies across the table. (up to preventing 0603 pick up !)
I've done a lot of test, so here are the most meaningful ones:- Start with a Liteplacer calibrated as per Juha's notice
- Notice that the components are not picked up, so trying the following...
- Carefully refine the needle/down-cam offset calibration (software "Nozzle Nominal Offset") right at a pick up point, that is [list]
- Use a 0.8mm needle which allow for easy positional error estimation, when compared to the 1mm fiducial.
- Place the down-cam on one of the top right PCB 1mm fiducials;
- Align the down-cam on this fiducial using the "Show hole" button of "Tape positions" panel. This sets the fiducial as a perfect reference point
- Press "Probe Down" button
- Estimate the offset error between the fiducial and needle
- Adjust the "Nozzle Nominal Offset" values
- Repeat two above until the needle is accurately probing the fiducial center
- Repeatedly check this positionnal accuracy, while exercising movements all over the table then returning to this fiducial and probing down. The error is estimated to be under +/- 0.02mm. (not bad )
- Have a coffee
- Now the components are reliably picked up at that table location, but unfortunatelly are not placed correctly anymore on the PCB. See the following pictures.
- Now move to the three other table corners and check the "fiducial probing" accuracy test ("Probe down" button) (of course without updating the "Nozzle Nominal Offset").
[*]Here is what I measured after a lot of efforts (it's not that easy to do)[/*]
- Top right (reference) : X0=422.88, Y0=272.165 => Pickup error = (0, 0) (obviously)
- Bottom right : X0=416.025, Y0=33.893 => Pickup error = (-0.145, -0.118)
- Top left : X0=0.452, Y0=269.148 => Pickup error = (-0.55, 0.196)
- Bottom feft : X0=14.706, Y0=27.030 => Pickup error = (-0.40, 0.16)
- I then double checked the top right reference and the error was still nicely (0, 0)
[*]0.55mm is a huge enough error to almost prevent reliable 0603 pickup (width = 0.8mm) and it could even cause issues with 0805, 0402 being totally out of question for now .[/*]
[/list]
Now, even more strange at the moment, was that after doing all that calibration/verification suff, I attempted to place two 0603 ceramics picked up from the top right region and they were not picked up and the needle placement on board was way off. But I think I've also tried to play with the up cam offset to correct for the placement problem to not avail.
It seems all those calibration variables interact, maybe needlessly...
One more attempt gave: or this: This is, well, rather disappointing...
One question bothers me, though. That is, how come that nobody had those problems? Or is that the reason of so much forks?
Other things have been noticed that could be enhanced, but I'll keep that for another post. My priority is to be able to place the board I got the Liteplacer for.
Happy new year again to every body,
Fred.