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Messages - TetraLite

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31
General Mach Discussion / Re: Digitizing
« 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!

32
General Mach Discussion / Re: Digitizing
« 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.

33
I suspect that maybe every different program that saves or exports a so-called "AutoCad" .dxf may not save it exactly the same as Autocad and I also suspect that most of the testing, if not all, of LCAM has been done with files that weren't generated with ACAD (am I wrong? I don't know!). There must be some subtle differences that account for why some files load and some don't. That's my guess. And that's all it is -- a guess! Unless LCAM gets revised to except any .dxf file from any source, I'm guessing that we all have to find our own way of getting our files loaded. Once they do get in there, it sure is an easy way to get your G-code output (in spite of the bugs that still exist). Makes it all worth while!

34
You must be using a version of ACAD other than 2005. In 2005 the File, Export... option doesn't do .dxf files. I'm still pretty happy just converting my ACAD dxf files using A9tech's converter. I have found that I can create my ACAD files as .dwg files and then convert them to .dxf with the A9tech program and that works also. Being that the A9tech program is free I figure my problem is solved. Would still like to know what version of ACAD you have.

Thanks for the input, wnevels!

35
Competitions / Re: ******Guess and win a G100 Grex******
« on: May 22, 2007, 11:08:26 AM »
Okay, here's my guess:

2,312,657


36
I wonder if our different computers are handling things differently. I am running Mach3 ver. R2.0.065 and LCAM 2.02 (just released within the last few days, I believe).

Now I'm just speculating.

37
Hi Willem,

I have only tried them in mill mode (that's the only place I'd use them for now). I'm just happy I can finally get them into LCAM and work right. I can do it using a conversion done by GlobalMapper, but I wanted to find a solution that didn't require an expensive program (for the benefit of others with this problem), so I searched until I found the A9tech website and their converter, which works (for me in mill mode) and is free, a price I like a lot!

For those stuck with ACAD2005 and wanting to use plasma mode, I don't know if this fix would work or not if someone spent the time to try converting to all the various ACAD formats that A9converter is capable of doing (maybe it's a different problem related to that mode? -- who knows!).

I think I noticed that sometimes LCAM would crash differently when confronted with different ACAD formats. And I think some files loaded but lots of LCAM features seemed to not work right. But by now I have done so much fooling around I can't really say what happened when because I tried many different things. I wasn't keeping notes. Anyway, maybe what I found will help someone.

Nice meeting you, Willem!

38
Well, I'm doing pretty well in the self-help department here. I just found a free fix for getting it into LCAM starting with ACAD2005. Here is what I did:

1. Saved the original as a .dwg (drawing) file in AutoCAD 2000 format (this doesn't work if saved in 2004 format and I haven't tried other variations of conversion sources and destinations -- there are many possibilities).

2. Did a conversion to AutoCAD 10 format .dxf file using A9TECH's free conversion utility (available for FREE at http://www.a9tech.com/products/a9converter/). You just drag and drop the file you want to convert and select the output format.

Then the resulting dxf opens in LCAM with no problem.

Below is the .dxf saved as ACAD 2000 format that I can't open in LCAM (test-v2000.dxf).
Also below is the resulting file after I do the A9conversion to ACAD10 format (test-v2000toR10.dxf) that does open in LCAM. (Yay!)

Thanks to all for your input!


39
Thanks for the input Chip.

Although that probe drawing is not the one I'm trying to load it was still created in my ACAD 2005 so it should act the same way as the one I'm working on right now. At this point I am installing an older version of ACAD (2000) to see if it will export an older format file (like R11). I'll see how that goes. I have some other programs that work with .dxf files that I haven't tried yet, so I might still come up with a solution myself.

I hope I don't have to buy another CAD program!

Update to this post: Tried ACAD 2000 and it only goes back to R12 -- same as 2005. However, tried another program, GlobalMapper, took ACAD drawing in and exported it back out with no alterations and it works so far as I can tell --so far. Points came into LCAM as points instaed of tiny circles like Corel generated. There is a free version of GlobalMapper available from the USGS and it comes under a different name. I know it is somewhat crippled compared to the full GlobalMapper version, but it may work for doing this. I will try to find it (should be an easy Google exercise) and give it a try and post results in this thread. Update: Found it (http://mcmcweb.er.usgs.gov/drc/dlgv32pro/) but it does not export .dxf -- it is a crippled version of GlobalMapper which is an incredible program, btw. I am thinking that maybe there is a program out there that is capable of reading an ACAD dxf file and also saving a dxf in a format that can be read by LCAM. It works in the full version of Global Mapper, for one. Almost in Corel.

Anyway, I wonder what it is about ACAD file format that makes it not work.

Would still like to hear from others if they have found other ways to get ACAD files into LCAM.

40
Fiddled around and found one fix that works -- still requires two programs. Here it is: Import the ACAD .dfx (which was saved as version R12) into Corel Draw 11, then, with all objects selected, export using the "selected only" option as an ACAD version R11 .dxf file. I tried exporting from Corel using newer ACAD versions to see what happens, but nothing newer than ACAD R11 worked. R13, R14 and V2000 exports from Corel all hang the program on loading the file when the progress comment reads "Duplicate Entitiy Removal". The processor seems to be very busy doing something (don't know if the computer is hung or just doing infinite computations or something) and I don't have the patience to wait any longer than I already tried waiting, which was a couple of minutes at the longest. The R11 Corel copy loads immediately.

I can get out of that hung state by closing LCAM and Windows claims that the "program has stopped responding", but of course Windows does that a lot when a program is just really busy and not crashed.

Perhaps my biggest problem here is that I am using AutoCad 2005. It only saves .dxf files back to version R12 format, but then again, in other places in this forum I hear of people saving as R12 and having it work. And could that be some difference between ACAD 2005 and whatever version they are using? Ah, technology!

One problem remains: Points were converted into small circles when importing into Corel, but since they are just points where a drilling operation is going to happen I can tolerate editing the G-Code (as long as there aren't too many. Still need a better fix!

Okay, so I didn't give up! ;D I'm still hoping for a more direct way to get from ACAD2005 to LCAM so if you have a technique I would love to hear it!

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