Mdc 7722FV alignment problems
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Re: Mdc 7722FV alignment problems

by vincentp on Mon Oct 29, 2012 5:08 pm

see my point above about the loose belt. Yes stacking part can be the reason if the belt tensioner was a bit loose.

bmw330i wrote: I'm at a loss how it just suddenly stopped placing a simple part like a 300R resistor.


I've explained this to you earlier : you nozzle height is now wrong and your nozzle tip isn't aligned with the reference anymore in flying vision, reason why you can't place anything (and it's also off in bottom vision). Check belt tensioner, secure with epoxy as suggested by MDC, re calibrate the nozzle height for both flying vision and bottom vision (scrub / focus).

I'm reading here Vincent about "Posi2 calibration (no chip picked up)". Which screen? The nozzle chg menu? F8 for train? I'm unsure where "Posi2 calibration" is in the software menus.


I can't resist to suggest you RTFHB (HB standing for handbook) as it's there now. Have you read it a bit ? There's a complete section about calibration and another one about the nozzle changer. Make sure you use the latest version of the software too.
http://forums.adafruit.com/viewtopic.php?f=42&t=32723&start=15#p166886
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Re: Mdc 7722FV alignment problems

by bmw330i on Mon Oct 29, 2012 6:38 pm

vincentp wrote:see my point above about the loose belt. Yes stacking part can be the reason if the belt tensioner was a bit loose.


bmw330i wrote: I'm at a loss how it just suddenly stopped placing a simple part like a 300R resistor.

vincentp wrote:I've explained this to you earlier : you nozzle height is now wrong and your nozzle tip isn't aligned with the reference anymore in flying vision, reason why you can't place anything (and it's also off in bottom vision). Check belt tensioner, secure with epoxy as suggested by MDC, re calibrate the nozzle height for both flying vision and bottom vision (scrub / focus).


Ok, I get it. I do remember you mentioning it but do not remember a diagram or image. Which belt? There are belts all over this thing. I just did a search in the Manual you wrote for the word belt. It appears 2x and neither mentions a diagram or photo or mention how to set it. BTW, none of the belts feel very loose. The ones around the head are very tight. What is the right tention? Do I need an instrument to measure the tension?

bmw330i wrote:I'm reading here Vincent about "Posi2 calibration (no chip picked up)". Which screen? The nozzle chg menu? F8 for train? I'm unsure where "Posi2 calibration" is in the software menus.

vincentp wrote:I can't resist to suggest you RTFHB (HB standing for handbook) as it's there now. Have you read it a bit ? There's a complete section about calibration and another one about the nozzle changer. Make sure you use the latest version of the software too.
http://forums.adafruit.com/viewtopic.php?f=42&t=32723&start=15#p166886


I have RTFM and I got to page 39 now. Thank you. I now know what Posi2 is...I think. I was able to go there and yes it was not centered. I fixed that. I'm not sure about stroke though. I tried U and shift-U and saw the head was going up/down. I set the value to 280 (strk/U). I pressed escape and then went back in and the value of 280 was saved.

So, continuing on..
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Re: Mdc 7722FV alignment problems

by bmw330i on Mon Oct 29, 2012 8:07 pm

I have a question. I have tried p131 Luna test. I am in the feeder menu and picked up the 33R 0603 resistor by going to the line, moving cursor to the X box, pressed F8, then pressed 9, then R to move the head down, V to turn on the vacuum, then R again to bring the head up. Finally "F" to do the luna check. At the prompt I told it 21,0 (21 is the part number and 0 for rotation). It then gave me the image attached. Also F6 in the PCB menu it fails to place the part and rejects it to the dump bin.

I tried 2 things to correct this prior to this test.
1) I went into the constant menu and changed K10 #2 to 320 (default was 270). The position of the head in the image was unchanged.
2) prior to that edit I went into the nozzle changer menu, edit 2, chg 2, F8, then using U/shift-U moved the value from 270 to 280.

How much must this value change to see a difference in the Luna check? I can't see any change from the 270, 280, 320 values in this image. Using 270 or 320 I visually see no difference and the F6 placement test fails both cases.

I'm reading your manual page 132/133 right now...maybe an answer is in there?
Attachments
33R_LunaCheck.jpg
Luna Check of 33R with value set to 320 in K10#2 (Factory set it to 270).
33R_LunaCheck.jpg (376.94 KiB) Viewed 993 times
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Re: Mdc 7722FV alignment problems

by bmw330i on Mon Oct 29, 2012 9:10 pm

Eureka! I found it. Page 154 at the top. I was changing the wrong value. I really needed to change K6#1 and K6#2. When my factory value for K6#1/2 was 826. I changed it to 815 and it was almost perfect. Maybe 1mm more needed.

So I changed K10#2 back to the 270 that was set at the factory and set the K6#1/2 to the new value of 815 to get this image. I think I'll go a little more and see if I can get it more exact.

I feel better. I'll try placing a part next....and Voila!! It is again placing the parts!!! Oh Joy. I'm back in business. So, in the end it seems my K6#1 and K6#2 were no longer working from factory. This machine was placing these same parts just fine before. At least now I know how to adjust this.

In the meantime I did go through the manual and did the other calibrations. Focus, nozzle changes etc. So hopefully the placement will be more accurate now. Before the parts were off a bit. I didn't know if it was the sticky tape or what the issue was. I'll do some assemblies tomorrow (hopefully).

THANK YOU VINCENT.

-BMW
Attachments
K6_815_test1.jpg
K6 set to 815 looking bettter
K6_815_test1.jpg (132.02 KiB) Viewed 992 times
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Re: Mdc 7722FV alignment problems

by vincentp on Tue Oct 30, 2012 2:43 am

bmw330i wrote:Ok, I get it. I do remember you mentioning it but do not remember a diagram or image. Which belt? There are belts all over this thing.


It's not in the manual, I mentioned it *above* (here on the forums) like I posted.
there's only one belt and one motor involved in the Z axis / head. See directly with MDC to check / fix that. Basically you just need to check that the tensioner isn't loose and ensure it won't move anymore. MDC will send you a picture.

bmw330i wrote:I have RTFM and I got to page 39 now. Thank you. I now know what Posi2 is...I think. I was able to go there and yes it was not centered. I fixed that. I'm not sure about stroke though.

I'm not sure the stroke you set in Posi2 teaching is usable. Like explained in the calibration section, I would only use the teaching mode to put the head in focus, note the stroke, and set the value manually in the scrub constant, either in the quick settings or the constant itself.
You definitely want to read the whole thing IMO, as there are cross references everywhere despite the fact I attempted to split things into chapters. The calibration section is quite coherent though, and it's at the end of the document.

I believe your focus/scrub WAS already at 280 or so (read previous discussion about your screen captures). Check that you're in focus, note the value and change the scrub accordingly.

[addon] reading your next post.

bmw330i wrote:Eureka! I found it. Page 154 at the top.

:lol: check also page 1, *wave hand* "this is the index table you're looking for" :wink:

So, in the end it seems my K6#1 and K6#2 were no longer working from factory.

normally, the head is meant to apply "excessive" pressure on the PCB without harming anything because the head is spring loaded ; the motor can keep turning the timing belt even if the head is stuck on a part or PCB, thanks to a spring.
However, if the timing belt is loose or the tensioner isn't tight enough, the belt might have a bit of backlash and at the first obstacle, the excessive pressure can change the offset a bit. Double check this, ensure that the mechanical link between the head and the belt has no backlash, and use eventually epoxy or thread locking fluid to ensure you won't have the problem again.

I also suggest you calibration the nozzle changer depth (see section about the nozzle changer), mine was WAY too high and it was really shocking the head when changing nozzles. Again the spring loaded mechanism is supposed to compensate BUT it's not meant to absorb shocks during high speed moves.
Then head is capable however of applying pressure on purpose, and like explained in the manual, the proper definition of the the PCB stroke AND part thickness is important and mandatory, as the head usually applies a "half thickness" pressure to force the part to penetrate the solder paste and stick properly. Get the thickness wrong (or the PCB stroke) and you'll either have the chip floating on the paste or it will crash on the PCB.
See my § about setting the proper PCB stroke to have this done with accuracy.

overall, it's never a problem to apply a slight pressure at the end of the movement when the head is slowing down, but it's really a problem when the machine believe that the stop point is 3 mm later and that it's still at high speed when it's touching the obstacle. This is probably what caused your machine to lose its calibration.

In the meantime I did go through the manual and did the other calibrations. Focus, nozzle changes etc. So hopefully the placement will be more accurate now. Before the parts were off a bit. I didn't know if it was the sticky tape or what the issue was. I'll do some assemblies tomorrow (hopefully).


excellent.
you get A- for not reading the index table first place :wink:
lack of accuracy is usually wrong offsets for side vision / bottom vision placement, the double sided tape has nothing to do with this. The nozzle to top camera offset might need to be calibrated a couple of times as it's not always easy to see / find the center of the stamped circle on the DS tape, I usually do it with a medium sized nozzle then with a bigger one to check.

I see indeed your nozzle height is better now for the side vision, almost there (not 100% aligned with the horizontal ref, try with no part to better see the nozzle tip). Your vertical axis is still off though. You need to correct this before you run the general placement offset calibration (again) cause the lack of concentricity in the side vision will induce more offset as it's adding a momentum.

glad it work. Did you find it difficult ? it's really like a set of instruction to follow BUT you need to be familiar with several other things before. That's why I put the calibration at the end of the handbook, so that people read as much as possible about the machine before calibrating (you must master the teaching mode first, for instance).
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