Touch Probe for a Noob.

[lilricky2]

I just bought a small cnc mill to try light production work. I have been a machinist for about 15 years and I am realizing this cnc stuff is an entirely different world. G code is currently voodoo to me. I am wondering if this little TP100 probe might help me get off of top dead center. I have prototypes I've cast out of plastic but I run into walls everywhere I turn when I take the dimensions and try to plot them on the computer. I just don't know enough about cad/cam yet. My machine is a three HP, 3 axis machine with ballscrews and reliance servo motors. My software is Bobcad version 19 and Mach 2 on a slow Windows XP machine. I realize practice makes perfect but I really can't wait 6 months to learn g code and start production. So if anyone has advice on this probe or maybe the Renishaw MP11 or similar devices, I would appreciate the help. While I'm thinking about it, do I need a 4th axis for a digitizer to make a complete 3D schematic of my parts? I am making parts that are roughly 6 inches by 4 inches by 2 inches or smaller out of mild steel, aluminum or plastic. Recommendations on cnc books for beginers might be nice too!

Thanks for any and all help,
Rick

[psychomill]

I am wondering if this little TP100 probe might help me get off of top dead center. I have prototypes I've cast out of plastic but I run into walls everywhere I turn when I take the dimensions and try to plot them on the computer. I just don't know enough about cad/cam yet.

Not totally sure what you mean here. Can you give more detail on what you're trying to do? "Top dead center"?

[buscht]

Rick, you've bitten off quite a chunk.
I don't know what a TP100 probe is, but digitizing on your CNC mill might be more complicated than learning your CAD/CAM.

Here are the issues as I understand them. If anyone has better information, please speak up.

When you digitize with the CNC, you need a program to move the probe around and take the point readings. I am not sure exactly where you would get this program.

The result from the digitizing is a text file that contains X,Y,Z locations for thousands of points on the model. You can set up how small you want the point grid. A smaller (tighter) grid is more accurate, but increases your file size and time expontentially.

So let's say that you are able to get the point cloud data. Now this has to be turned into a solid model or surfaced model so Bobcad can apply tool path to it. This is a difficult job in itself.

You may want to post some pictures of your models so we can respond better about the 4th axis work. If you are doing full 3D sculptures then maybe, but otherwise you can get by with some indexing fixtures.

Just think about it like you would machine it manually, the CNC just replaces you cranking on the handles. If you have a 4 axis mill, then a 4 axis digitizer would be appropriate, otherwise its probably not needed.

Kind of long winded, but here's some suggestions. Work through the tutorials with Bobcad. That won't take too long. You have to build your skills up on easier projects and then work your way up to the hard stuff. Kind of like a machine shop apprenticeship. I doubt if your first project was to make an injection mold. Probably, just cut off some stock and square it up. You have to build up your CNC skills the same way.

You are way ahead of the curve with a machining background. The CNC part is relatively easy after that.

[buscht]

Originally Posted by psychomill Not totally sure what you mean here. Can you give more detail on what you're trying to do? "Top dead center"?

TOP DEAD CENTER (TDC)

Definition: The point at which the piston reaches the top of its travel on the compression stroke.

In urban slang, it means "No power, I don't know what to do to get moving on a project and am stuck"

I guess this shows our relative ages

[itsme]

Hi there,

I don't have a probe (yet), but I've always looked at it as something to add on to my machine once I knew how to use it properly. Would you not be better off trying to learn CAD/CAM properly now, rather than trying to avoid it? I had no experince with CAD and I managed to teach myself the basics in a few days just by using the help files and some simple tutorials. After a bit more practice, I was able to do more complex objects.

BTW, if your 3hp mill is 'small', then I'm not sure what mine would be classed as...

Regards
Warren

[DAB_Design]

I don't think a probe will really do what you want it to. The probe will only give you X, Y and Z coordinates of points you take. You would still have to creat the g-code for the part.

A couple of options.....
1. Find some online references for g-code, and study the heck out of it. I'm sure you can find something, but it may be hard to find something that explains from very basic to moderately complexity. This board is a great start though.

2. Find someone to do your g-code for you, until you can figure it out. After seeing a couple of parts done, you should be able to decifer it with the information you find online. Then learn from there. I happen to do such work (shameless plug). Reverse engineering, modeling from scratch, programming, etc are some of the things I have done.

3. Find some simple programms either here, or from doing an online search, that explains line by line what the code does. Again, I'm not familiar with any such places, but this board would be a great start. I would think throwing a couple programs together to do simple stuff (squares, circles, simple parts with steps, etc) would be kind of fun for most people here.

4. Ask, ask, ask. Everyone here is great with helping those that need help. If you find something that you don't exactly understand, post here and you'll get more than enough help.

[psychomill]

Buscht.... hell, I would've figured "BDC" to be used like that. Thanks for the info though.

I agree with with DAB, digitizing with a probe on a machine can be done. But to go as far as reverse engineering an entire part in full 3D will take some serious programming. If you need this to be flexible (the probe on the cnc), it will take even more serious programming.

You'd be better off mechanically reversing the part for geometry until you get to that point. Or, looking into actual digitizing equipment to render in 3D. Pricey though...

[carlnpa]

I use The CNC Workshop by Nanfara/Ucello/Murphy for learning and reference. It came with CNCez simulation software. I guess some don't care for this but I find the descriptions on the use of all the codes very usefull.

[lilricky2]

Thanks Buscht, I guess I have a habit of dating myself. I am just an old gear head. Well gang, if I were not intimidated by this before, I am now. I will try to take some digital pics, but I am essentially making American rifle parts for imported rifles. It is pretty much a niche market. You have to be able to make a few of these and several of those, but not a whole lot of anything. Clear as mud, I know. My buddy is the idea man and I'm the labor, so I'm not sure I understand the market either. Most of these parts are small, nothing larger than, say, 6x4x2 inches. Some would be as small as 1.5x.5x.5 inches. I am just prototyping right now, but I am trying to figure out the most efficient way to turn them into 3d files/g code/tool path/ finished product without having to manually cut each one. I did talk with Fred Smith about his DeskCNCsoftware and the TP100 probe. Fred is great to talk to and his equipment sounds like it might solve some of my problems. However, it does sound like I may be in a little over my head until get used to the cnc part. Sheesh, I think I'll go eat supper, scratch my head some more and see if I can revise my game plan. I might have bitten off more than I can chew.

Rick

[imserv]

Originally Posted by buscht Rick, you've bitten off quite a chunk. I don't know what a TP100 probe is, but digitizing on your CNC mill might be more complicated than learning your CAD/CAM.

TP-100 probe http://www.imsrv.com/deskcnc/probe.htm

Originally Posted by buscht When you digitize with the CNC, you need a program to move the probe around and take the point readings. I am not sure exactly where you would get this program. The result from the digitizing is a text file that contains X,Y,Z locations for thousands of points on the model. You can set up how small you want the point grid. A smaller (tighter) grid is more accurate, but increases your file size and time expontentially. So let's say that you are able to get the point cloud data. Now this has to be turned into a solid model or surfaced model so Bobcad can apply tool path to it. This is a difficult job in itself.

When a TP-100 probe is used with DeskCNC, the process of creating a CAD model is not difficult. DeskCNC is a step and direction machine controller which has a simple 3D surface scan function. It produces an .STL file from a surface scan. The .STL format is usable by any decent 3D cam program, and can be used by many 3D CAD programs for purposes of editing modification and combining with other design elements.

The DeskCNC output, .STL file, is filtered for spikes, smoothed to remove the stairstep effects from a digital measurement process, and reverse compensated for the probe tip radius to produce a smooth surface model, the same size as the original scan. DeskCNC also includes 3D toolpath creation (CAM) to directly machine the scanned model.

This process produces very good results for parts that have a decorative or artistic function. rifle stocks, hand rests, grips, packing nests, statuary and sculptures are examples of common applications for surface scanning.

For producing strictly mechanical components, it is better to draw the part details using traditional wireframe or 3D modeling Cad. A reamed or tapped hole is not a good candidate for surface scanning.

Fred Smith - IMService
http://www.cadcamcadcam.com/hobby

[buscht]

Originally Posted by imserv This process produces very good results for parts that have a decorative or artistic function. rifle stocks, hand rests, grips, packing nests, statuary and sculptures are examples of common applications for surface scanning. For producing strictly mechanical components, it is better to draw the part details using traditional wireframe or 3D modeling Cad. A reamed or tapped hole is not a good candidate for surface scanning. Fred Smith - IMService http://www.cadcamcadcam.com/hobby

Great information Fred, but can you explain some more? Rick says that he already has a CNC mill with servo motors. Does your solution require the use of your controller? Would Rick have to rebuild the electrical part of his machine to get your solution to work.

I have a 4 axis router running MACH2 and a Xylotex board. If your probe would run on my system with easy to use software, I'm ready to purchase today! (or maybe tomorrow, once I get approval from the wife)
Thanks
Trent

[imserv]

Originally Posted by buscht Great information Fred, but can you explain some more? Rick says that he already has a CNC mill with servo motors. Does your solution require the use of your controller?

Yes, the probe and software work together for the "easy" solution. The Tp-100 will work with other software controllers, but as was mentioned, it is difficut to process the resulting point cloud data.

Originally Posted by buscht Would Rick have to rebuild the electrical part of his machine to get your solution to work.

Not rebuild, but possibly modify. Our system is step and direction, the same as his, or yours. If you have room in your motor driver enclosure, you can install the DeskCNC controller inside and hookup the same step and direction signals that are now received from the parallel port. You might consider this re-building, but you can leave the parallel port wired and then can use the electronics with either DeskCNC or your present software. DeskCNC requires a Win 98 or later computer.

Originally Posted by buscht I have a 4 axis router running MACH2 and a Xylotex board. If your probe would run on my system with easy to use software, I'm ready to purchase today! (or maybe tomorrow, once I get approval from the wife) Thanks Trent

An assembled package is available that requires no electrical modifications. It plugs into a parallel port motor driver box ( like your Xylotex setup):

DeskCNC-in-a-box

Fred Smith - IMService
http://www.cadcamcadcam.com/hobby