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Subspindle Lathe (Miyano Fanuc) parting off

Pete Deal

Titanium
Joined
Apr 10, 2007
Location
Morgantown, WV
I bought a Miyano BNC-42S5 Lathe a few months ago and am working on getting some parts running on it. It's been a slow process because I've been busy with lots of stuff and also have a lot to learn. This is my first Subspindle lathe, first Fanuc, first live tooled lathe. Lots to learn. Fanuc 21 control. I wanted to put my understanding of a few things in words here and see if I have some things thought out right.

I read a post that was kind of old but Ox had a way of setting tools that I liked. As i understand it I'm going to set my tool offsets in Z so that zero is at the main spindle chuck face. Then I'll put a G10 P0 command in each program that moves that part Z0.0 out the amount of stickout of the stock. I assume the same can be done with the sub spindle where the back side working tools (the ones that face the sub spindle) they are all zeroed at the sub-spindle chuck face when the sub spindle is in B=0.0 position? then another G10 command can be used to set the part zero at the face of the part in the sub spindle.

Some of the parts I want to run first are very short (1/2" long) and 1/4" diameter. I think with these parts I'll need to machine one end in the main spindle, grab the part with the sub, pull it out some (enough to get the parting tool between the spindles), then part it off with the resulting stub in the main spindle being the right stick-out for the next part. At this point (man everything is scary tight in there photo below) It seems like I just need to do some fussing around to figure out where to grab the part with the sub, where to back it up to, and where to position the parting tool. Probably need a LH parting tool to get closer to the sub spindle face (photo below has RH parting tool).

No bar feeder installed yet. Just going to try to figure it out pulling short bars at first.

I know this isn't exactly a question post but I know lots of people on here do this all the time so hoping to steal some of your big ideas.Miyano Parting.jpg
 
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For subspindle lathe, I use the blade type parting tool with the tool block specific for the blade tool. The tool block has radial clearance for sub -spindle and allows the blade to get in between chucks at very tight space. See if your machine comes with this type of tool block or ask your machine vendor for one.
 
"Twistoff" Method:

Perform an incomplete part-off (e.g. X0.05) with the sub at home position.

Retract the turret with G28 U0 or however you want.

Come in the sub, clamp the part, and twist it off however you see fit. If your machine has spindle clamp, you can clamp one of the spindles and M3/M4 other. Or you can just spin up the sub by itself to 300-500 RPM. The main has enough inertia that the part will just separate.

Retract the sub and proceed with the backside.

 
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For subspindle lathe, I use the blade type parting tool with the tool block specific for the blade tool. The tool block has radial clearance for sub -spindle and allows the blade to get in between chucks at very tight space. See if your machine comes with this type of tool block or ask your machine vendor for one.
Yea, the one I have (shown in photo) is the Miyano parting off tool block. It's all carved out to get in very close.


"Twistoff" Method:
The machine has C positioning for both spindles and when in this mode it holds the spindle in position so should be able to twist it off by putting the main spindle in positioning mode I think then start the sub. Haven't gotten that far yet.
 
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Grab it wherever you want over the part. Pull it out part length+cutoff width+facing stock for both sides. Position cutoff tool at Z0+facing stock
 
A) Sure, you could G10 the sub as well I guess. This appears to only be a single turret machine, so that helps to keep things simple. On a single turret IDK if you would ever really git'cherself in trouble or not? But just be aware that if you don't have a G10 line below every tool change, that it would be possible to have the wrong G10 loaded, and then start mid program on a line that should have the other ZERO loaded.

Now this is not a G10 issue. It would be the same if you was using G54 and G55 in the same program.

I seldom use more than one Zero offset in a program, even on my twin turret machines. I prefer to park my sub so that the back of my part is on a nominal location, and then I program from there.

Ex:

Part is 1.675" long
Your part doesn't allow much wiggle room on where you clamp up on it at, so by default, your sub clamps up at E4.32.
So now you need to move to E5.995 for the back of your part to be at ZERO.
(You are not actually going to make that move, just helping you to wrap your mind around the shift from one end of the part to the other.)
So now I would move my sub to E23.995, and then my sub work would all be at 18".
Rapid tool to 17.9 and feed to 18.6 .. whatever...

I don't find this anymore, and maybe a little less cornfusing than calling up a nother zero, and then trying to remember to program the sub in + movements.

But there isn't a right way nor a wrong way.
I am always amazed at how many different ways there is to write code for any one part.


B) I have his and hers cut-offs. I wouldn't want a blade sticking out that far. That sounds like asking for chatter, as well as Z drift if you are using an angled insert. But then IDK as I don't doo it that way. So ....


C) The twist off method works for solid parts, and it is a prefered method for stainless, but I wouldn't recommend planning that to be your GOTO method. Doesn't work so well with a 1" through hole.


D) I pull up to 24' tubes with the sub. Just set your counter a bit short of where you expect it to run out, and even in full production, it's a good plan to set the counter 1 part short of the full bar, just in case. Depending on length of bar and parts... To pull with the sub tho, requires a bit of planning sometimes. You'll understand the first few times that you find yourself in a jackpot and need to turn the part around the other way, or ... or .. It's not as forgiving as having the feeder AND the sub, but I have ran one machine in particular that way for 20 years.

You can either pull the bar before cut-off, or you need to leave more sticking out to grab later. But if your sub collet is smaller than the bar, you're not likely gunna grab the new bar to pull it out, you're gunna need to pull first.



I assume the same can be done with the sub spindle where the back side working tools (the ones that face the sub spindle) they are all zeroed at the sub-spindle chuck face when the sub spindle is in B=0.0 position? then another G10 command can be used to set the part zero at the face of the part in the sub spindle.

Personally I really dislike this method. Especially applicable for live cross-werking toys that could be used on either spindle. This leaves the door open for trouble down the road. All of my toys have the same zero ref position. Now - with that said - no, I can't touch off my sub drill to the main chuck face, but I would stop the program after the cut-off and make sure that my sub was at 23.995, and then touch my drill off to the part, enter the W value in the Offset, and then subtract 18".

Also, having your sub tools zero'ed to the chuck face doesn't offer much benefit I don't think. Your part isn't really sticking out a "known amount" from sub zero. The back of your part really needs to be your ref surface.



------------------

Think Snow Eh!
Ox
 
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Good info! Thanks Ox.

I hadn't thought of working off the already finished face of the part that's been transferred to the sub spindle. I'm still digesting what you said above but I think that's the gist of it. I guess it would be easyish to keep track of that position.

My thinking in using two zeros, one for the main and one for the sub was that in the first part of the program I'd work on the end in the main spindle and the second part of the program work on the part in the sub. But, I guess it would be more efficient if I was say roughing the part in the main then use the same turret tool position but the tool looking toward the sub to rough that part with no turret change.

Regarding the parting tool stickout, On this machine it's not as bad as it looks. The holder Miyano carved up for the purpose does support the tool pretty well but not easy to see in that photo. It will require a left hand tool to be able to part close to the sub though.

Regarding bar pulling, I have a hydrobar gatling gun style bar feeder, still not installed but intend to. I read of people using a bar stop for feeding but I was thinking it would be better to set the push pressure for the feeder down and just pull with the sub spindle. This would eliminate the bar stop step but the bar feeder would still control the whipping 12' rod.

I really need to just get in there and setup a part but I need to do a little more wiring first. Hopefully this weekend.
 
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