Webcam centre / edge / hole finder

[alan T]

Hi there from the UK. This is my first posting, apologies if it has already been covered but I've not seen it mentioned before on here?
I am a UK based clockmaker / model engineer with an extensive workshop incl Myford S7 and Centec 2A mill, both with Ortec digital readouts (no CNC as yet:-{{ )

Model Engineers Workshop, an excellent magazine published over here recently had a couple of articles on converting cheap Webcams into centre / edge/ hole and corner finding devices, similar to centering microscopes but displaying a highly magnified image of your component on a laptop screen. I have used centering 'scopes for years but they are often difficult to use in akward set-ups. This camera REALLY solves the problems.

It uses the lens and PCB of any cheapo 640 x 480 pixel webcam ( I used a cheap Logitech, about £10.00 US$20 ish.) Machining up a simple body and and adaptor to suit your spindle is real easy and the free software download gives you several options of crosshairs, circles, parallell lines and even a distance / angle measuring option!! There is also an optiion for LED illumination of the job.

I made one immediately, it took a day to make and I can honestly say it is the best machine accessory I have made for years, real easy and VERY ACCURATE :-}} Thoroughly recommended.

Check out www.miketreth.mistral.co.uk/centrecam.htm for full description and software download.

alanT

[Geof]

Your link has an error. You need .UK not .KK

There was a thread about this type of thing a while back but the one you link seems a more complete package and description.

[ISO Coder]

Absolutley exellent hack.
But one thing that first came up in my mind, how do you make sure that the ccd centre ends up alined with the spindle centre, this is important if you cant put the camera oriented exactly in the same place in the spindle every time.

[SmartArt]

All you need is to do is add a correction offset.

[harryn]

Hi, That is a neat idea. I could really use something like that.

I looked at the pictures on the site. Very nice. This is probably obvious to an experienced machinist, but could you please provide a little more explanation of how to do the alignment of the camera so it is properly centered ? Thanks

OK, I read some more in the software area - that is a nice concept for alignment using the software.

Is it assumed that the camera will remain "aligned" if it is mounted slightly rotated from the original location ?

Any chance you are going to sell these ?

Take care

Harry

[SmartArt]

I hope I understand the process properly.
in principle, First, drill a small hole. Then, without moving in x and y use your webcam setup. The moves you do in order to center your camera are your offsets.

[alan T]

Hi again,
I'm amazed at the number of replies so far, excellent and glad you like it.

As all my machines have No 2 Morse taper spindles, I machined all the body including the mounting hole at one setting to ensure mechanical concentricity and fitted a morse taper arbor so it always relocates accurately in the spindles. Alternatively, machine as above, fit a parallell arbor and hold the camera in a collet / end mill holder.

There is a facility in the software to align the CCD accurately. Simply put a hard centre in the machine spindle, bring it down hard on to a piece of scrap clamped in the machine to make a fine "centre punch mark" replace with the cam and align the crosshairs to suit, thus automatically resolving any offset problems.

I have performed repeated point, edge, corner and hole alignments and they have been spot on if you follow the info.

Of course, camera FOCUS and DISTANCE OF THE CCD FROM THE WORK SURFACE both have an effect on accuracy, especially if the CCD is "squinting" at the job ie. not dead square on but looking at an angle.

This is easily resolved by setting up in the first place using an accurate spacer block between the end face of the camera and the work surface. I use a standard 1 inch slip gauge block but any measurement around 1" will prove OK. Keep your block with the camera and ALWAYS use the same block for setting up.

When setting up, adjust the focus / height of the camera until the image on the screen just fills the box on the screen exactly. The camera MUST BE 640 x 480 resolution then 1 pixel equals 0.001"

Hope this helps. No real poiint in selling them, they are so easy and cheap to make and set up :-}} email me or post on here if you need any further help.

By the way, the software is a free download, it just has "Demo version" across the screen, but it is so neat it is well worth registering for his efforts and any future upgrades!! ( I have no connection whatsoever, just a satisfied end user.)

Best wishes,

alanT

[scubasteve_911]

I'm currently working on the same sort of deal, but with less interface and more image processing. The program will have to run in Matlab, but it will take snapshots from any source and input the hole diameter range. Then, it will find the center of the circle automatically with the hough transform. After an offset is programmed in, it will be able to tell you the distance from center.

I have played around quite a bit, but I don't have the hardware built yet. After a lot of fooling around with relaxation parameters, I have gotten it to be very repeatable and provides accurate information about where the holes are located with respect to eachother. I will know for sure when the hardware is built and I can make real measurements. I will post the Matlab code if anyone is interested.

Regards,

Stephen M
Lakehead U

[Switcher]

How about this (Mach3)?

http://www.artsoftcontrols.com/forum...p?topic=2519.0


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[Oldmanandhistoy]

More and alternative information in this thread

Another Aussie Adventure in Optical Edge/Centre Finding

John

[scubasteve_911]

Hey,

I have to critique this hardware solution in hopes of product improvement. First of all, is this a 1.3M optical sensor? These are readily available and would provide more accuracy at little extra cost.

Furthermore, the mount should include white LED lighting run off of the USB port or external power supply. I discovered through several tests that adequate lighting around the features was indisposable for feature recognition. It's the only good way to give enough contrast to distinguish fine lines and circles.

As a followup, attached is the result from the hole finding program I have started writing. I specified a particular pixel radius and it returns all found holes displayed as a picture with the guessed radius and centers.

Here are the X and Y coordinates of each hole found.

131.7250 269.2802
382.2941 261.6078
394.4105 101.8659
586.1414 96.4520

This is my no means an optimal setup and once I get the hardware finished (another month), then it will be clear whether or not the program will work.

Steve

[Switcher]

You need to add a dimmer control to the LED lights, thats what we use on a Pro. setup at work, it works very good.

The reason for the dimmer control, is because of reflection of the light on some material.


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