Some doubts and problem with picking and placing components

[android]

Hi,
I almost finished making my machine. I tried the hello world job, but there is problem. Machine perfectly finds the tape holes but it's not picking up the components correctly and not placing in the correct location. It misses the components and placement location by few mm,sometimes it touches the edge of the component.i think I've done needle calibration correctly.
Is there any way to automatically centre the impression needle makes on a carbon paper by circle finding algorithm when doing needle calibration. I've read about in a post but don't know how to do it.
Is there any way to automatically centre the needle when doing the final step of needle calibration(when software instructs to jog the needle to up cam)?
Is there any thing like "wobble calibration" other than needle calibration in the "set up camera" tab?
How can I know if the machine is calibrating needle accurately?
I've read about it in assembly instruction but have some doubts.i found probe(nc), needle to cam, probe down.
Can any one tell what will happen if I do any of these?does needle rotate when doing any of these?
It'd be great if any can explain about needle calibration in detail.
Thanks in advance

[JuKu]

> It misses the components and placement location by few mm,

Way too much, something is missing. Have you set the camera box sizes? Are you using slack compensation (in the basic setup page)?

> Is there any way to automatically centre the impression needle makes on a carbon paper by circle finding algorithm when doing needle calibration.

No, you have to do that manually.

> Is there any way to automatically centre the needle when doing the final step of needle calibration(when software instructs to jog the needle to up cam)?

No, but this is not a bad idea.

> Is there any thing like "wobble calibration" other than needle calibration in the "set up camera" tab?

On the Run job page, there is a "'Measure needle" button. (Note, that earlier software versions used "needle calibration" for two different things, neither being a very good term. Now, the software talks about needle setup and needle measurement, hopefully being less confusing.)

> How can I know if the machine is calibrating needle accurately?
> i found probe(nc), needle to cam, probe down.
> Can any one tell what will happen if I do any of these?does needle rotate when doing any of these?

Probe down takes the needle to the point where the down looking camera is pointing, applying wobble correction. Probe (n.c.) does the same m, with no correction. Needle to cam takes the machine in to position so, that if you do needle down, the needle tip will be in the center of up looking camera view, wobble correction applied. The needle does not rotate, but when wobble calibration is applied, it takes the current rotation position in to account.

> It'd be great if any can explain about needle calibration in detail.

This is my job, but it is too late tonight. I'll see if I could do a more in depth writing on this and maybe a general troubleshooting guide.

[android]

I've done setting box sizes, for accuracy I used a caliper instead of normal scale.I'm not using slack compensation.

[android]

I've done setting box sizes, for accuracy I used a caliper instead of normal scale.I'm not using slack compensation.

> Is there any thing like "wobble calibration" other than needle calibration in the "set up camera" tab?

On the Run job page, there is a "'Measure needle" button. (Note, that earlier software versions used "needle calibration" for two different things, neither being a very good term. Now, the software talks about needle setup and needle measurement, hopefully being less confusing.)

So there are two calibrations for needle ,
1.'needle setup' and
2. 'needle height'
So I hope I don't have to do anything specific for wobble correction other than these two(Please mention if any).[/quote]

Probe down takes the needle to the point where the down looking camera is pointing, applying wobble correction. Probe (n.c.) does the same m, with no correction. Needle to cam takes the machine in to position so, that if you do needle down, the needle tip will be in the center of up looking camera view, wobble correction applied. The needle does not rotate, but when wobble calibration is applied, it takes the current rotation position in to account.

For clarification, consider , when doing "needle setup"(jog the needle to cam), i jogged the needle to camera position-->needle down and set the needle at the corner of the cross point of up cam(not at the exact centre)-->'Up Camera' set.
So when I click "Needle to Cam", does it come to the same position as I set above or does it come to exact centre of the cross?

[JuKu]

> So I hope I don't have to do anything specific for wobble correction other than these two(Please mention if any).

You still have to set the video processing so, that the wobble correction algorithm recognizes the needle tip. (I think you have done that, but I mention this for completeness.)

> For clarification, consider , when doing "needle setup"(jog the needle to cam), i jogged the needle to camera position-->needle down and set the needle at the corner of the cross point of up cam(not at the exact centre)-->'Up Camera' set.

You should have the needle tip at the center.

> So when I click "Needle to Cam", does it come to the same position as I set above or does it come to exact centre of the cross?

Not sure in this case. If you set the up camera position with the needle at the center of the cross so that the system gets the camera position correctly, "Needle to Cam" + needle down takes the needle to the center.

Try switching the slack compensation on. Then redo the needle setup again, and set the up camera position with the needle tip at the center of the cross. This should ge the system behave correctly. If unchecking slack compensation significantly changes it, we have another unrelated issue.

[mrandt]

So I hope I don't have to do anything specific for wobble correction other than these two(Please mention if any).

Yes, there are more steps

Also, it is important to run the calibration steps in the right sequence.

Unfortunately, the functions are distributed over multiple tabs and the necessary order is not obvious from the UI.

See this post for a quick list of what I am doing:
http://liteplacer.com/phpBB/viewtopic.p ... =181#p1185

Once your machine works mechanically (i.e. jogging by 10mm moves it 10mm and squareness is OK), you calibrate software parameters.

Don't forget to home machine everytime you turn off motor power.

You start with needle height calibration (Basic setup tab) - because pixel to mm (box size / camera calibration) is dependent on correct Z-level due to projection error.

Next, you configure the cameras and set the correct Box sizes (determines px-mm ratio) for up and downlooking cam (Setup cameras tab) - and make sure to put your ruler, caliper or mm grid at PCB level (!). Exact measurement is important here as the measures px will be caculated to mm offsets when compensating needle wobble.

Another approach that works well for me is to move needle overhead up camera, lower the needle to PCB level, jog the needle tip to the lower left corner of the box, note X and Y coordinate, jog it to upper right and note X and Y again - with simple substraction you can now figure out exact box dimensions. RMod (Ver2) of software does this automatically by the way.

Once box sizes are accurate, click "Needle setup" (Setup cameras tab) to calibrate distance between needle center and camera center. This will allow machine to place the needle at exact location the camera is looking at later.

I do this by putting a piece of carbon paper on the table top, lowering the needle so it leaves a mark and then jogging the camera exactly above the mark. Finally, you move the needle above up camera, lower it to PCB level and jog it center and set up cam position (Still setup cameras tab).

Last and final calibration step is to calibrate needle wobble, which is called "Measure needle" in latest software release - the button is on "Run job" tab.

Obviously you have to repeat needle height and needle wobble calibration whenever you change the needle.

Good luck and have fun!

[JuKu]

Thank you for the detailed procedure, you explained it better than I could!

> Obviously you have to repeat needle height and needle wobble calibration whenever you change the needle.

I'm not sure that height needs to be calibrated. The wobble is done automatically or with one click. (And writing this I got the idea that needle height recalibration (if found necessary) can be automatic as well, either set a position where you keep a piece of PCB (home mark?) or by probing a fiducial.

[mrandt]

I'm not sure that height needs to be calibrated. The wobble is done automatically or with one click.

If needle has different length, height needs to be calibrated I guess... Otherwise the wobble calibration would not work correctly, as needle tip would be farther away and thus px-to-mm ratio would not be accurate - would it?

needle height recalibration (if found necessary) can be automatic as well, either set a position where you keep a piece of PCB (home mark?) or by probing a fiducial.

I like the idea of doing that automatically - probing a fiducial is probably fine.

Btw, have you looked at the calibration routines in Reza's or Karl's fork lately? I think they found great ways to efficiently calibrate px-mm ratio using machine movement, added automatic needle centering above up camera and also implemented a nice way to validate wobble calibration.

I think Karl slightly changed the way the "virtual" needle center position is handled, but IMHO that is fine as long as it is consistent across the application.

The only other automatic calibration I am missing is camera-to-needle distance - using the carbon paper method it should be possible to automatically home in on the mark which could further improve accuracy.

A wizard which lists all those calibrations in the right sequence combined with short explanations is still on my usability wishlist - although I think new users would benefit more than those who already mastered the calibration routines

[android]

Next, you configure the cameras and set the correct Box sizes (determines px-mm ratio) for up and downlooking cam (Setup cameras tab) - and make sure to put your ruler, caliper or mm grid at PCB level (!). Exact measurement is important here as the measures px will be caculated to mm offsets when compensating needle wobble.

How can I place my caliper at the exact PCB level. If I use a caliper to set box size(that I did),it's height will obviously higher than that of PCB .Couldn't it affect when determining box size?????

[JuKu]

If needle has different length, height needs to be calibrated I guess... Otherwise the wobble calibration would not work correctly, as needle tip would be farther away and thus px-to-mm ratio would not be accurate - would it?

In theory, you are right. In practice, you would turn the needles more or less the same into the Luer lock, and therefore, the difference in height is small. I think the difference is small enough not to matter - but this is my feeling only, I haven't run any tests!