Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: DICKEYBIRD on February 22, 2015, 01:07:21 PM
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I use Dolphin CAM to generate the code for my lathe and have all my tools with their tip radii & direction setups saved in Dolphin. I have the tool X & Z offsets saved in the Mach Tool table but noticed today that I don't have their tip radii & directions saved. :-[
Will the Dolphin generated toolpaths (with tapers or radii in the work) all be incorrect because of that? If not, surely any Mach Wizard generated code with tapers or radii will be wrong, yes? Will I need 2 tool tables?
Just when I think I'm getting this stuff clear in my head, I realize how very little I know. ::) Fortunately, it hasn't made much difference in the low precision work I've turned out so far but I need to get this issue correctly sorted.
Also. is the Direction box in the standard Turn Tool Table screen input expressed in degrees from 0?
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I don't know if the nose rad works in Mach or not, never used it and to be honest if I was using a wizard for something it would just be a simple thing. Anything requiring complex toolpaths I would do in CAM as it not only takes account of the tools nose rad but also the shape of the tool and won't (or shouldn't) crash into stock when the tool shape does not allow it to cut there.
Trying to think how the rad would affect such as a taper and I suppose it may affect the dia slightly as it will be starting to cut slightly further on from where you asked it to start, not sure if it would be that much of a deal as it would likely be minimal and you could easily compensate with the X wear I would think.
Hood
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OK thanks my friend; I feel much better. One less thing to stress over. ;D
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Would be an interesting thing to test out though, do one taper in CAM and the same again but with the wizard and see how much of a difference there is. As said I would think very little but I may give it a go if I get a chance just to see.
Hood
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I also have never used the direction or radius in the tool table. If you have a look in the lathe manual
it will show you the different tip directions used for compensation.
BUT, like you, I use precompensated code and unless there is some G41 or G42 ....guessing....and you have tip & radius in the tool table, don't think you need to worry about it. All my tools are based on the actual cutting edge.
BUT, some other controllers use a similar but different designation for the direction if my memory is correct.
Maybe someone who hand codes for the lathe can shed a little more light on how well the tool comp works.
BTW, fooling with / creating a manual touch off of the tools in lathe and don't think we will even include any restrictions relative to the touch off surface.
FWIW,
RICH
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see how much of a difference there is.
With some hobby lathes and the way folks use them......probably not accurate enough to give a comparison.....! :o
I'll let you fool around Hood....let us know what you find. ;D
RICH
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I'll let you fool around Hood
Thats all I ever do Rich :)
Hood
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Interesting stuff; thanks for the input. The only reason I worried about it at all is I've had some parts come out really close to what I programmed and others not so much. Most likely due to problems in the machine, tooling issues or my screw-ups. I should do a better job of keeping up with the good'uns & the bad'uns & try to figure what caused each.
If what you do is fooling around Hood, I shudder to think what I'm doing. ::)
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others not so much
Just something to think about......
The tool offset can be +- .0002 but that is radius and add to that some X axis actual accuracy ( not resolution), some springing / tool and work,material being cut as compared to what was used to check the tool, a little backlash ( they all have it), spindle run out, they all add up, and the total affect becomes noticeable on the part diameter, spindle. IE. do a 1-80 thread ....just a silly little and it is a junk thread.
RICH
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Yup, I hear ya. I call it the "dynamic cutting point." On the 1st try, the size of part my machine produces varies a few thou over/under what I've asked it to make. The more time I spend using it, the closer it gets on the 1st try but it many times has me scratching my head. After firing a few bracketing shots and getting a direct hit though, it does pretty well at making subsequent parts. S.O.P. for a hobby machine I suppose, but I keep trying to tweak things & make it do better.:)
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Don't know if this is normal practice or not but what I usually do is on the first part I set a X Wear offset of just greater than the insert rad, usually 0.5mm (0.4mm rad). I will then always have the Optional Stop before the part off op. I will measure the part and see how close it is then reduce the wear offset to suit and rerun the finish, usually get the first part in spec that way. In fact most of my work is one offs so I really need to do that if it is a fairly tight tolerance part, if it is not quite so pernickity then I don't bother with the wear offset and it will usually be within +/- 0.02mm anyway.
Hood
BTW when I say greater it is actually a negative value in Machs wear offset, say for example the tool is at X5 and I set a wear offset of -0.5mm then Mach will think the tool is at 4.5mm and thus the part will come out larger than intended.
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Hmmm, gotta study that...sounds like a good plan!
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Aways better to be able to remove some. Once cut you can't add material to the piece.
Hood,
Your the boss, owner, and operator so normal is whatever you want to do. ;)
If one worked in some manufacturing place there would be some rules that one would need to abide by.
FWIW,
Have used the wear and it's easier than say creating another tool ( for whatever reason ).
I just use the tool table with the offsets mostly.
Also save the tool table to a file and keep a hard copy. From the file I maintain a spread sheet of the tools.
Note about the X offset in my spread sheet:
- Decrease the X offset if the cut diameter is larger than wanted.
- Thread tool insert allowance is 0.0035 ....they all vary a llittle and none of the sharp pointed ones have a "0" radius, SO, set the tool off the stock by allowance or use wear offset to adjust. AND remember it's radii values.Ok dummy! ::)
....the OK dummy remark is me / my reminder ( ..... just can't seem to remember what to do with them numbers
and get it backwards !) :)
RICH
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Always better to be able to remove some. Once cut you can't add material to the piece.
- Decrease the X offset if the cut diameter is larger than wanted.
- Thread tool insert allowance is 0.0035 ....they all vary a llittle and none of the sharp pointed ones have a "0" radius, SO, set the tool off the stock by allowance or use wear offset to adjust. AND remember it's radii values.
Thar be some pearls methinks!