Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: tjhj on January 15, 2010, 04:55:43 PM
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Hello All,
I have a 7x14 lathe and I feel I am dealing with tool changes the really hard way. So any advice or suggestions is really appreciated.
Ok I have a Quick Change Tool Post.
So attached is a picture to help explain if I am not using the correct terms.
If my tool post is always set at a Angular offset of 0 ( 90deg to the work piece) A standard offset can be made for each tool in the X and Z. This works in my mind.
Now if the tool post is anything other than 0. Lets say 30 deg. It happens alot for me to be able to work on larger pieces.
The X and Z offsets really become a triangle depending on the angular offset. Now I cant really find a good way to measure the angle of the tool post accurately in order to just do some math to find the new tool offset and get an accurate result.
Do you all just touch your tools every time you put a new tool on the post?
Does anyone use a Electronic Method of touching off the tool post?
There has to be a better way to set this up that I am missing.
Sorry the pic has all the chips I am mid project with many tool changes, hence why I am questioning a better way to do this.
Any suggestions are greatly appreciated.
TJ
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Suppose the only way, other than touching off each time, would be to set up the tooltable with all your tools at all the different angles you use them at but obviously that would require you to be able to repeat the angular movement.
This is not a normal problem in industrial CNC lathes as they tend to have turrets with multiple tools and if a tool needs swapped for another the locating is accurate enough just to replace and then call the offset for that particular tool in combination with the slot it is in.
I have often thought about doing something similar to the industrial tool probes on my lathe but just never got round to it as its not the easiest of things to do and certainly way harder than on a mill.
Hood
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You would have to be able to accurately and i mean accurately be able to locate the toolpost at an angle of say 30 degrees or whatever.
Then if you had tool one in the post at 0 degrees and you the turned the whole post that would then that tool would become a new number.
You would set all your tools from the master tool as is the case now.
So theoretically possible, but impractical IMHO
Phil
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Ok thanks all,
Yep so there isn't really a good way.
If only I had a spare 50grand for a nice big lathe with a turret on it... :-\
TJ
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Dont need 50grand, mine only cost £300 :D fair enough I've probably spent another £1000 after that doing the retrofit LOL
You could probably design a setup similar to what you would use in mill to touch off to automatically enter your offsets but it would need carefull placement on a lathe and really needs to be retractable. Because it needs to be retractable it has to have an accurate means of positioning it, which in itself is not easy. Add to that the tools can be a long way off in two axis it would really require you to do the initial positioning of the touch off routine manually before you let the macro do its thing.
Hood
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LOL,
I payed more than that for my 7x14........
Im kinda stuck on how to isolate the tool from the work electrically. With out compromising the integrity of the lathe. Plastic has its ups and downs....
I was thinking about using some form of a paint or rubberized spray on, like that spray on electrical tape, it probably wont last forever, but should easily be touched up. On the tool holders them selves or the tool post.
Maybe a hard enamel type paint.
TJ
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Similar to Reply #4
http://www.machsupport.com/forum/index.php/topic,11244.0.html
Or you could maybe make 1 special tool holder block with an offset to the rear for the larger parts.
RC
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You dont need to insulate the tool, your probe has the insulation. I made up a thing for setting tools manually, its a piece of 75mm dia steel bored out to 50mm and in that a piece of delrin which iteslf is bored out and finally another piece of steel in that which protrudes out further. I have two small holes bored in the metal either side of the delrin and can fit a small circuit board with a battery and LED, when I bring the tool up to the frnt piece it will light the LED on contact and is extremely repeatable, I could I suppose write a macro to do the offsets automatically but at the moment I just press the buttons to enter things manually.
What I do is I chuck this up, take a facing and dia cut with the master tool, fit the LED board and zero the Z of the master tool by touching off the end. I measure the dia with a mic and it should be whatever dia my master tool was already set to as I never change it. Next index the turret and manuall position the tool to touch off on Z and enter via buttons and DROs into the tooltable, do the same for the X, then the next tool etc etc etc.
Could be done in a similar fashion by just turning the dia and measuring with each tool but it would mean lots of wasted material if replacing lots of tools and also the Z would need feelers to get set correctly.
The ideal situation for me would be to have this "probe" mounted on a slide so I could position it accurately and that way I would never need to do the initial turning and could then semi automate things, maybe one day...... ;D
Hood
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The other option is to make tool holders that hold the tools at 30 degrees and keep the tool post at zero.
Graham
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http://www.mcmaster.com/#garolite-sheets/=5eckdn
This works for a strong, insulating packing material....Grade G-9
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Hood,
Why do you need to accurately position the probe? All you have need to do is setup the tool table - each tool with respect to the master tool. Can do this with the probe mounted just anywhere. Only thing to do then would be touch of the dia of the workpiece with one of the tools.
Daniel
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Daniel have you done much lathe work. ??? ;D ;D ;D
It would be in the way where ever you put it if it wasn't removable
Phil
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Phil,
Yes I do some lathe work ;) I think you just misunderstood me - I wasn't meaning it not being removable, was just suggesting that its position didn't have to be accurate and repeatable.
Daniel
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Daniel
I am not following how you would be able to touch off the probe if it is not accurately positioned. The distance it is at on the X would not be an issue, the distance it would be on the Z would likewise not be an issue but the orientation would be if using a cylindrical probe.
Hood
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Hood,
Now I'm not following you... :D
All I'm saying is that you could put the probe just anywhere in the space and it doesn't have to be the same point it was at the last time. Why use a cylindrical probe? Saw on another thread here someone who used a carbide square insert for his probe.
Daniel
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OK carbide square insert, doesnt matter, still has to placed accurately. If you could not position the faces true to the two axis then it would be a waste of time as being a slightly different position on the Z axis with the next tool when you touched off the X would give you a wrong diameter. Similar if the face was not true to the X axis, if you were not at the same X dia when touching off the Z would be different.
Hood
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Ah... But I thought you mentioned position accuracy in one of your first posts here, not orientation of the probe. This was why I said you didn't have to worry about position. But why not do it the way I think you said you were doing it - make a cylindrical probe that you can hold in your chuck and this way it will be perfectly true to the axes, then touch off all the tools and set up the tool table and then remove the probe. This way you can even make the position accurate if you like.
Daniel
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I am doing it the way I said and it is a manual operation, I need to chuck the "probe" and take a face and dia cut with the master tool and then I can set up any tool to that. If I have a part in the chuck and for some reason decide a tool, that I dont have set up in a slot, is needed my only choices are to estimate by touching off the part or take a light cut and measure or remove the part and replace with the probe.
What I was talking about was having a semi automated process with a probe that could be retracted and your probe was the reference so you would just put a tool in, make sure you are in a suitable position (manual part of operation) and then press a button, the probe would deploy, the tool would touch off in X and Z and the offsets would be set. No need for messing about machining the probe with the master tool first. That is why I said positioning accuracy would be the hard part and positioning in respect of not only X and Z but also in regards to trueness of X and Z axis of the probe.
Hood
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Why not make an electronic probe that you can chuck and no need to machine it each time? Still has the drawback that you can't use it if you have a part in the chuck, but at least it'd be semi-automated.
Daniel
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I basically have an "electric probe" already but to get the accuracy needed it has to be machined each time, just chucking in a 3 jaw to me is not accurate enough for something like this.
Hood
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I would assume you would use the electric probe as is, without machining it to setup the tool table and then when you're set to machine the part, take a cut and measure it.
Daniel
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Ok so say you do that, you set your master tool off the probe, set all other tools to the master via using the probe then you have to machine the part, measure then offset the master again, sounds like we are again back to a manual method.
Hood
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Why to set you master tool off the probe? Any reason it could change its position? I was actually more thinking in the way of making a macro to take advantage of the electrical probe and set all the tools automatically with respect to the master tool. You could probably use temporary DROs to store the true position of the master tool before touching off the probe and then touch it off, override the X and Z DROs with say 0,0, and set all the tools with respect to that, then return back the stored true position of the axes - all in a single macro. This way you don't need to reset your master tool each time.
If you do it this way, and considering your machine's repeatability, I think you don't even need to machine the part each time and measure it.
Hope it makes sense...
Daniel
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You seem to be moving the goal posts every time you reply ;)
Hood
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OK i have been giving this some thought and there is a solution for most tools.
Permanently attached to the headstock would be two probes one for X and one for Z this would be behind the chuck so as not to interfere with the working environment.
Great idea or what.
Phil
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You seem to be moving the goal posts every time you reply ;)
Hood
???
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You could make a probe plate from a vertical angle or square section, have this mounted to a clamp that fits to the lathe bed and a stop for the front of the gap.
If it's made with some adjustment you could get it on centre (I think mach lathe allows for this) this way it would be repeatable and accurate and no need to do the dia turn to set the final tool position.
Write a macro to do the touch off etc and you should be able to reset mid job, assuming the stock doesn't interfere.
Steve
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So maybe I am way over thinking this, but why not add the ability to measure the angle of the tool post.
Ok so here is the idea,
Take a Isolated Probe, mount it in a standard tool holder. Rounded of some kind.
Now I normally do embedded systems, so I am thinking take a potentiometer and mount it to the tool post in a manner that as the angle of the tool post is changed it changes the pot. It should not be a problem to achieve 12 bit resolution. And as most single turn pots have a rotation of 260 degrees. So considering that 10% of the ADC resolution will most likely be lost due to not getting a perfect ending on the pot. It should be quite realistic to get a position range of 0-3686 over the 260 degrees. The result is accuracy to 1/14th of a degree. If a 14bit adc was used 1/56th of a degree accuracy could be obtained.
I think the 12 bit solution would provide accurate enough angle offset to accurately position the tool.
So knowing the angle and difference to each tool from the probe in X and Y at 0, the new offset can be found using a macro.
The biggest question is how to get the information into Mach. I was thinking I could have it output pulses based on position, per angle. Maybe as an additional axis encoder? Then the macro could make a new offset based on the encoder position.
Maybe?
Does this even make sense.... Or am I missing the new point.
TJ