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Messages - TetraLite

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1
Mach3 under Vista / Re: Your opinion of Vista ?
« on: November 03, 2009, 04:23:14 PM »
Answer 1: No, it will not run on a Mac
Answer 2: The requirements are to buy a PC  :)

But the good news is that you don't need a brand new expensive PC. A computer with a 1GHz processor runs Mach quite well and you can probably find one used for dirt cheap or even free from friends or relatives that are buying a new, faster one. I use a 1GHz Dell that I got for $75 from Boeing Surplus (before they closed their retail store).

2
General Mach Discussion / Re: Setup help much abliged!
« on: September 24, 2008, 08:44:08 AM »
If you haven't already, check out these recommendations (a text file) for setting up Windows XP for Mach at http://www.machsupport.com/downloads/XP_Optimization.txt. This may not help with your shutdown problem (or maybe it will!), but it won't hurt for running Mach.

Oh! I'm assuming you're using XP.

3
I have just posted my wiring diagram on a new web page (link below). The diagram shows the inexpensive model C6 speed control board from CNC4PC.com connected to the FC250J/110V DC motor controller board that comes on many late model 7x10, 7x12 and 7x14 Sieg C2 style mini lathes. The diagram is accompanied by lots of text describing the modifications and operation and set up in Mach3 Turn. I am also offering spindle interrupter discs for sale ($5 + $2 S&H, US only) at my new lathe pages. These discs fit the 27mm spindle and are meant to be used with an opto-interrupter such as the Fairchild H21A1 (available from Digikey) or lots of similar devices. The site is at http://tetralite.com/lathe

4
I know this is a slightly old thread, but I just wanted to mention a problem I had when I set up my spindle index. This was a fresh and clean Mach3 install and I used a typical optical interrupter switch (LED and phototransistor in slotted package - Fairchild H21A1 available from Digikey) and disc on my lathe spindle. When I first tried it out I would get good readings from very low rpm to around 1000rpm and then, while still increasing the spindle speed the rpm reading in Mach would suddenly drop by roughly (very roughly) one half. I eventually found the problem and it was this: The default debouce setting for the index pulse input in Mach (in General Configuration) was set to a rather large number (it was in hundreds) and this setting is multiplied by 40uS, so I set it down to 2 (making it 80uS) and the rpm readings are now true for my full range of up to about 2800 rpm.

5
General Mach Discussion / Re: Digitizing
« on: August 23, 2008, 11:29:00 PM »
You mentioned: "They monitor the increase of resistance and at a defined point they turn off the current before the contacts actually open."

AHA!!! That could be really easily done with a very small microcontroller chip with an A to D input (I have some and I have the capability of programming them). By stopping the current before the contacts fully open it would stop them from arcing, which causes carbon to build up. And indeed, the amount of force needed to move the contacts only enough to detect increased resistance would be very small, but of course, the machine does not stop instantly, so more force would continue to be applied until the Z axis drive stopped moving. But cutting off the current before the contacts fully open is very interesting. This is a very neat idea and I just might pursue it. The PIC12F615 or PIC12F675 microcontrollers are 8-pin DIP packages with a 10-bit A/D converter and could be built right into the probe. This would require three wires to hook it up: one for +5 volts, one for ground and one for the output signal which would not need amplification and could drive a parallel port directly. A tiny potentiometer could be added for fine tuning the trigger level but may not be needed. I might give it a try soon.

6
General Mach Discussion / Re: Digitizing
« on: August 23, 2008, 09:14:40 PM »
Yes (regarding measuring and referencing), that's a good point! I don't really know how most people would use them, but as a hobbyist I think I would want to do 3D point clouds to copy shapes. Also, my tests have huge numbers of point samples and maybe the the ordinary, everyday scan that one might usually do would be a much larger grid with much fewer sample points. Maybe I've been making good probes all along and didn't know it!

From the information I've seen on commercial probes of the type that use balls and rods I don't think they are doing it any different basically. Maybe they are using some special materials? I just don't know.

Here is a link to an interesting PowerPoint presentation from Renishaw, a maker of probes. It does have a fair amount of information and its worth a look (if you haven't found it already):
http://www.renishaw.com/media/ppt/en/744f3d51d1b944caa6c8bba90515b9a8.ppt


7
General Mach Discussion / Re: Digitizing
« on: August 23, 2008, 06:25:38 PM »
Very nice, Bertho! I like the simplicity. Your questions are ones I have been asking myself for some time. The contact resistance varies dramatically with different materials and the amount of time in use (number of actuations) according to my tests. I used a circuit board in my original design and soldered the balls to the board, using small drilled holes to align the balls. The biggest problem I had with ball and rod contacts was that after about 100,000 samples (that's 100,000 switch operations) the contact resistance would increase so much that the op amp circuit would start to fail to switch its output state. At first, when I started testing my probes they were great, but after hundreds of thousands of samples they started to fail to close enough to work reliably. I couldn't accept those statistics, otherwise I would be selling them for cheap! Logic tells me that the problem is that the contacts don't wipe (self-clean) and a buildup of carbon occurs. This even happens at the extremely low current I was using (less than 10 microamps). Cleaning the contacts with some fine steel wool fixes the problem for up to another 100,000 point samples, but I still find this unacceptable.

The spring pressure is also something to be reckoned with. If it is too weak, as you know, the resistance increases. However, making it too strong means you are applying more force to the probe tip and the object being scanned. Objects made of softer material may not stand up well to these higher forces. Also, for really fine scanning with a needle-sharp tip, you will definitely leave a mark on all but the hardest of metals each time a sample is taken. Of course hardly anyone will be using such fine point probes for everyday use. I use them when I am testing my probes in order to get the finest resolution I can in my test results. If you want to scan an object that is a model and made from wood or clay, then the spring force may become a factor due to deformation of the object.

I am currently working on new designs. One uses a piezo-electric sensor and the other uses miniature off-the-shelf normally closed switches. The piezo element tends to deform over time and I have scrapped that idea for now, although it did perform pretty well for a while. The switch system is working even better than I suspected it would. Instead of using three rods I have gone to five. It still uses the rods to re-center the probe after each point sample. I use five switches that are operated by a ring that lays on top of the five radial rods. My thinking in using off-the-shelf switches is that, being made with excellent switch contact materials, they will survive longer before their resistance goes too high. I would like to get 3 million operations between servicing the probe. For my off-the-shelf switch model, servicing would mean replacing the switches or perhaps the whole circuit board with the switches pre-mounted just to make it easier for the user. Or perhaps just call the probes disposable and toss them after 3 million point samples and buy a new one.

My goal is to build and sell them for under $100, with accuracy and repeatability of under 0.0002" and have them last for 3 million operations.

8
Mach3 under Vista / Re: Your opinion of Vista ?
« on: August 15, 2008, 03:46:13 AM »
Windows has always been bloatware. Microsoft tries to make an operating system that does everything for everybody -- whether they want it to or not. So as the new versions come out, the computer is forced by default Windows installation to run a whole bunch of routines just in case someone might want to use them. For XP you are advised to stop many of the processes that Windows want to run at startup if you want to run Mach. I set up my mill on a 1GHz computer running Windows 2000 and I disabled as much of the unnecessary processes as I could. It is a very clean machine. The thing I like about it is it works. It doesn't crash. Mach 3 runs without a hitch. Windows 2000 is much less encumbered by crapware than XP. Why would anyone even want to run an OS any more complicated than Win 2K? In my opinion, running anything else on a CNC controlling computer is a serious mistake and the computer should be dedicated to running the CNC machine. As far as Vista is concerned, it is trying to do things we don't need even more than XP. Another thing that makes Win 2K attractive is it doesn't require the Windows activation. It installs much cleaner than XP. There is no advantage I can think of to using a Windows version newer than 2K if you are dedicating the computer to a CNC machine. Vista is another of Microsoft's attempts to please all the people all the time and in that attempt they have opted to run an overabundance of processes that most of the people will never use and these processes only serve to hijack computer resources and possibly conflict with what you really want to do. I recently put together a Vista computer because I need to test my products to make sure they run on Vista. I find Vista to be very annoying, much like the way I found XP to be annoying until I learned how to trim it up. So far, there is nothing about Vista that appeals to me enough to make me want to use it for everyday computing over XP. For CNC I say keep it simple and run Win 2K on a dedicated machine. Oh yeah, and whatever OS you use don't connect to a LAN or the internet with your CNC machine while you are CNCing.

9
General Mach Discussion / Re: Digitizing
« on: November 07, 2007, 01:49:32 AM »
Mark,
What input format are you using for global mapper. Seems they have a lot of them.

Roger

Hi Roger,
Under the File menu the click on "Open Generic ASCII Text File(s)..." and it prompts you for the location and filename of your point cloud text file. When you select your file it then comes up with a window where it asks for some settings. The first setting is "Input Type" and you want to choose "Elevation Grid from 3D point data". Set "Coordinate Column Order" to the "X..." option and set "Coordinate Line Prefix" option to "None..." (I think those are the defaults). You can click on the "Select Coordinate Offset/Scale" button to scale up the image. I usually scale things up with those settings. Leave the "Coordinate Delimiter" setting on "Auto" or select "Comma" -- it works either way. Leave the slider on the "Loose" setting since you are dealing with absolute points. Or experiment. Setting it tighter takes more time.

When it asks for a projection (in the next window) select "Equirectangular" from the list. This is because the sampling points are a square grid. The other projection types take into account various distortions in the various map type projections and have no use in this type of purely regular 3D plotting where we don't have to account for things like the curvature of the Earth.

There are many ways to project and scale and alter the display of the resulting image in Global Mapper and I can't even begin to go into what I know about it here. It just takes a lot of trial and learning and exploring.

10
General Mach Discussion / Re: Digitizing
« on: June 08, 2007, 11:38:53 PM »
I used the digitizing wizard that is clumped in with the other wizards under the "Wizards" menu in Mach3, version R2.0.065 and not the digitizing plug-in.

Yes, I too have noticed that it skips a point on each row, but the software that I am bringing it into (Global Mapper) does not expect any particular values in any particular order, but rather just interprets the points as absolute points with their respective elevations. It doesn't matter what order they are in because a location is a location and not dependent on which location you last looked at. I can mix up the lines in the point cloud file in any way and Global Mapper will still map each point independently from the others and end up with the same grid of x,y points at their respective elevations and use it to generate the output, which is a 3D image consisting of points and their elevations and interpolated elevations between the points. Obviously, this is not quite the same as interpretting points as adjacent locations like you would want to do in order to ultimately generate efficient G-code. To get to G-code would require another step for me that would go from point to adjacent point in the output from Global Mapper with no missing points in the grid. Global Mapper fills in the missing points as well as filling in the elevations between points, so I could generate a new point cloud by exporting one from Global Mapper that would tend to have smoothed out the original input and also filled in missing points. Of course, this doesn'tg really help the problem of the wizard skipping points to begin with, which it does in my copy of the program. You can see where the points are missing in the Mach3 toolpath display on my copy. There is a diagonal line from the end of one line to the beginning of the next line, instead of a perpendicular line like you would see if it didn't skip a point. So the wizard is in error and is decrementing or incrementing the x value (depending on which direction change you are at) at the same time it increments the y value to start the next line.

This file is probably not a good one to work with because the elevations are very small. The lowest point is (-0.012") and the highest point is (-0.006"). The image I created had a vertical exaggeration added to it in order to visualize and emphasize the elevation differences, while in reality, the max difference in elevation from the lowest to highest points is only 0.006". (I may have those numbers wrong, but it was something like that.)

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