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Author Topic: Digitizing  (Read 79339 times)

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Offline Chaoticone

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Re: Digitizing
« Reply #30 on: May 17, 2007, 10:18:12 PM »
Mark, As far as price I have no idea. The cheaper you can make them, the more you will sell but you need a profit margin. You can go fishing for free if you know what I mean. You could ask in the form of a poll here in the forum.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Digitizing
« Reply #31 on: May 17, 2007, 10:35:00 PM »
Brett,
Yes, there are many things to consider when setting a price. I will check what is available out there for starters. I am currently marketing a product that undersells all my competition (see my website for the TetraMouse.com). I like the idea of trying to keep the price as low as possible while still making a profit, but I have been told by several people that my product should cost more because people don't think it is good quality if it is too inexpensive. Lots to consider!

In the meantime I suppose I could consider taking offers and see what happens. Hmmmm...
-Mark

Offline Chaoticone

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Re: Digitizing
« Reply #32 on: May 17, 2007, 10:52:04 PM »
I didn't read it but that mouse looks like a great product for a great cause. Good job. I have sent you a personal message.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Digitizing
« Reply #33 on: May 17, 2007, 11:53:09 PM »
Yes, I am very happy with it and it is extremely rewarding for me and my customers.
Replied to your message.
I have put another picture or two on my new still-rather-sparse Mach web page at http://tetralite.com/mach
Oh Gawd! another bunch of web pages to maintain!
So many toys and so little time, money, energy, etc.

-Mark
Re: Digitizing
« Reply #34 on: May 27, 2007, 11:56:29 PM »
Well, I'm on about the fourth revision of my probe design. The object is to make it simple enough to build easily while making it sensitive enough to create precise scans and measurements. On my prototype I learned that it is practically impossible to repeatedly build the probe and have the tip of the stylus be perfectly in line with the axis of the arbor and thus, the spindle. This misalignment means you can't use the probe for x,y centering the spindle or using it for edge finding with the intention of replacing the probe with a tool and having it centered on the spot you were shooting for. So I have come up with a way to make it possible to adjust the stylus tip to center. This is done by spring loading the circuit board so it is held against the top of the bottom cap and putting setscrews at three points 120 degrees apart and threaded through the bottom cap. Three springs are added; one on each of the 2-56 X 1.25" screws and tension on the spring is achieved by adding a nut on each screw to push the spring down against the PC board.

The set screws are located directly under each of the three pairs of balls that are soldered to the circuit board. By adjusting the setscrews, the plane of the circuit board can be adjusted so that the stylus tip becomes centered along the spindle axis. The setscrews are of course, accessible from the bottom of the bottom cap, so the stylus tip can be checked for runout and adjusted while mounted on the machine.

This picture shows the setscrew locations ("B" - 3 places) and the 2-56 x 1.25" screws ("A" - 3 places) that hold everything together:


This picture shows one of three 2-56 nuts ("A") holding one of the three the springs in compression against the PC board. The "B" arrow points to the gap between the PC board and the bottom cap. This gap is adjusted by the 3 setscrews. In this picture it almost looks like the PC board is warpped, but that is just an illusion, probably due to looking through the clear polycarbonate tube (1.5" o.d., 0.125" thk wall) that I made the housing from.


And here is a shot of the probe mounted in the spindle of the Taig mill showing the 1/8" phone jack with the plug plugged in. The jack fits nicely inside the housing luckily. Unplugging the wires makes it much easier to adjust the stylus tip to the center of the spindle axis because you can spin the spindle around. The adjustment of the plane of the PC board (and consequentially, the position of the sylus tip relative to the axis) is quite easy to do. It's a bit easier than chucking something up in a four-jaw chuck.


The stylus is female threaded and screws onto the screw that passes through the hub (the part that holds the pins that contact the balls). I did it that way rather than putting female threads in the hub because the HDPE doesn't thread well and the screw cap holds the spring in place at the top of the hub. This means that I can make various types of stylii with the female thread mount and easily swap them out.

I will post new plans when I get them drawn up.
« Last Edit: May 28, 2007, 06:08:12 AM by TetraLite »
-Mark
Re: Digitizing
« Reply #35 on: May 29, 2007, 12:13:35 AM »
Amazingly a digitizing probe patent has just been issued by the US patent office: 7,202,608.
It exactly describes the Renishaw probe.  They claim their new and improved invention is to solder
a wire from ball to ball so there is no need to relay on the PCB to interconnect them.  Talk about obvious knowledge.
The patent is poorly written too and easy to design around.

The easy link to patents: http://patft.uspto.gov/netahtml/PTO/srchnum.htm

Here is a good description by Renishaw:
http://www.renishaw.com/UserFiles/acrobat/UKEnglish/GEN-NEW-0126.pdf

Bertho
Re: Digitizing
« Reply #36 on: May 29, 2007, 01:33:24 AM »
Hi Bertho,
Yes, I find that really amazing! If that's all it takes to get a patent, my version would be easy to patent with all the changes I made. I wonder why they didn't think of soldering the balls to the board. That is way easier than soldering a wire to the balls. Since I am publishing my plans right here and very soon on a web page, I will declare my design as public domain. The way I understand it is, if you publish complete plans for something and declare it as public domain, nobody can patent it. I don't hold much stock in patents anyway. All a patent does is give you the right to sue anyone that you think is violating your patent. From what I hear, you can expect to lay out $25,000 up front just to begin a patent lawsuit. So, in my opinion, it isn't worth patenting unless you think you are going to have a market big enough to expect to make millions off it. I don't think the market for digitizing probes is that big. So, just for the sake of public domain, I hereby declare my design (and as much of it as I have already published here and on my site) to be in the public domain.

I think my idea of mounting the balls on the top side of the PC board (not to mention soldering them to the board) makes more sense. And also my idea to make the plane of the PC board adjustable to compensate for the misalignment of various probes is a good idea -- it makes it possible to align your spindle with what you are probing rather than to wherever the tip of the probe is in relationship to the axis of the spindle. Without the adjustment, the probe is useless as an x,y positioning instrument and only good for scanning. It would take incredible amounts of precicion to manufacture a probe that is completely concentric to the spindle of your machine, especially if you have different stylii, so make it adjustable and save the headache!

I am considering offering probes of my design for sale at a really low price compared to what is out there now. The cheapest I've seen on the web so far are around $295. I think I can produce and sell mine for maybe $150 or less.

I just looked at the Renishaw paper you linked to. They obviously have a lot of time into making a well-built probe. It's no wonder they charge so much for them. I wonder if their probe tips are always exactly on the axis of the spindle they are mounted in?

Here's a 0.25 inch square section of the back of a dime that I scanned with my latest prototype. The scan was done using 0.001" steps in the x and y axes for a total of 62,500 elevation samples. The point cloud generated by Mach3 (using the digitzing wizard that is included with those other wizards, not the add-on one that you download from Artsoft -- I can't get that one to work at all!), was taken into Global Mapper and displayed in a 3-D projection with "Atlas Shading" which applies colors according to elevation like maps in an atlas. I also added some vertical exaggeration to emphasize the elevation differences (exaggeration here is 5.5 times). You can see the red color indicates higher elevation as you move toward the right front corner. This is because the thickness of the dime is greater toward the edges. You may also notice that the scan is cleaner looking in about the first half of the scan (the half closet to you in the image). Up about 3/4 of the way you can see where there is a stripe where the elevations were sampled wrong and there is a valley cutting through the oak leaves. I think I may know what caused this -- not sure yet though -- not going to try to guess the real reason at this point. I think this image demonstrates a good degree of accuracy -- close enough for any practical use of the probe in my opinion. We're talking errors less than the thickness of oak leaves on the back of a dime!
« Last Edit: May 29, 2007, 01:43:40 AM by TetraLite »
-Mark

Offline Chaoticone

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Re: Digitizing
« Reply #37 on: May 29, 2007, 01:44:34 AM »
Way to go Mike. I'll take one at $150.00. Thanks for the info you have declared as public domain as well. Good job. It is looking great and very funcitional. Keep up the great work.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Digitizing
« Reply #38 on: May 29, 2007, 01:57:22 AM »
Brett,

Well, I haven't committed to a price of $150 yet. That is just a guess. I *do* need to research my costs (time it takes me to make one mainly -- the materials don't cost much).

Forgot to mention that the tip I used for scanning the 1/4" square of the dime was made from an ordinary straight pin. In practical applications you would probably want a larger tip!

Which brings to mind a question that occurred to me last night -- How do they mount those ruby balls on the tips of probes?

Jeez! I sure like my adjustable PC board idea. Takes all the worry about precision out of the manufacturing as far as tip alignment is concerned.

(Correction: the name is Mark ;D)
-Mark

Offline Chaoticone

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Re: Digitizing
« Reply #39 on: May 29, 2007, 02:17:56 AM »
LOL, Sorry Mark, I'm so bad with names that I can't even type them right.  ;D No,no, you figure your price to make money, you can go fishing for free. I was simply wanting to be the first n line if you can sell them for $150.00. If it goes up, I will most likley buy one any ways. As long as I can get my accountant ( the wife ) to sign off. Anything less than my sock money, I can spend without approval.  ;D

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!