When Isolation Routing double sided PCB’s I drill two holes in the PCB blank (one is the datum and one the reference) to locate the work on two pins in the spoil board on the machine. This method enables good location of the tracks when machining each side and also for hole drilling etc. (always using the same datum point for X zero /  Y zero).

After reading this post and watching the video http://www.machsupport.com/forum/index.php/topic,22555.0.html  I thought I would try visual location of the datum and reference holes (using my cross hair pointer) and use ‘Local System Rotate’ just to see if it was an easier method.

Then using 3 CB buttons (at the bottom of my Mach screen) it is as easy as ABC. Well it’s almost that easy. 
Obviously this was only experimental so it is bit of a ‘quick & dirty’ solution and it needs work to tidy up the user interface side of things but it works.

Basically…

Button A turns on the cross hair pointer, sets slow jogging and brings up the status message ‘Locate Datum then click Button B’

Button B resets X and Y axis DRO’s to zero and brings up the status message ‘Locate Reference then click Button C’

Button C is where the calculation takes place – the current X and Y axis position (reference) is used to calculate ArcTan of the angle which is then used to set the Local System Rotate. The offset between the cross hair pointer position and the spindle position is factored in and the X and Y axis moved to bring the spindle to the datum position. Jog speed is reset to normal etc. and the status message ‘Complete’ is displayed.

As it turns out this method works very well and in operation is an equivalent to the system used in the aforementioned video. It can handle any rotation or position of the work (within + / - 90 degrees).
Although the accuracy I achieved is acceptable it could definitely be much improved by using a webcam for the hole location and Klaus’s video window (camera plugin). http://www.kd-dietz.com/klausphp/pages/ger/plugins/webcam/description/wcam_description.html

It is not a quicker method than my existing system of using the two dowel pins but it may have advantages with odd shaped circuit boards and possibly alteration of existing boards so definitely warrants further investigation.

My next step – fit a webcam to the Z axis.   

A short video of the result  http://tweakie.byethost10.com/rotate1.wmv

Tweakie.

Very Good Tweakie!

Brett

Pretty cool, Tweaks. Looks like you've got it figured out pretty good. Amazes me how you are able to do all the things you do. I can't even get the necessities done! "Limit switches you say? Pfffffttt... it can wait." I read about this in the digital sample issue of Digital Machinist. They have a really nice writeup on Mach 3 "How Mach 3 Continues To Amaze Me". It's a really good read, very informative. Even gives ya the VB code for several routines.
http://digital.turn-page.com/issue/17465 If your interested.

Thanks for the info Sam, much appreciated.

A Question...

Is there any way to increase the resolution (currently 0.1 degrees) of the Mach3 ' Local System Rotated' DRO as this appears to be my major stumbling block (as far as accuracy is concerned) ??

Tweakie.

Tweakie you can change the resolution of the dro with MachScreen. I have mine set to

0.0000 degs

(;-) TP

Many thanks Terry, I will give that a try. 

Tweakie.

Great work Tweakie....thank you.

WELL - fitting a USB webcam to use with the on-screen video window could be considered akin to playing the lottery – you pay your money and take your chance. I had to smile when one member commented that ‘plug and play’ should be renamed ‘plug and pray’.

As the saying goes ‘third time lucky’. After two unsuccessful attempts the third ‘plug and play’ webcam works perfectly on both my desk PC and machine PC with either Brian’s or Klaus’s video window. So now, still using the same 3 buttons, Button A opens the video window and prompts for the Datum to be located, Button B prompts for the Reference to be located and Button C closes the video window, performs the calculation, sets the Local System Rotated and moves the spindle / tool to the Datum position.

This has proved much easier and quicker than using the cross-hair pointer so I now have some more work to make this a permanent addition to my machine.

(Incidentally the cross-hairs in the video window were in the process of refresh at the instant the first snapshot was taken which is the reason they are not actually showing in the pic.).

Tweakie.

Well done, Tweakie.

What web cam did you use?  I will add one to my laser diode machine to locate the edges of material and establish center points for image burning.  No more pencil and scale 

Thanks much,
John Champlain
www.picengrave.com 

Hi John,

This is the webcam (endoscope) that I finally used. It is from China and available via ebay for < £20 UKP.

Tweakie.