Star pick off spindle question

[jimiscnc]

STAR SR16 B and/or SV-20.

General question.

Can the pick off spindle be programmed to pick off a part that goes until stopped by a shoulder to pick up? As opposed to no shoulder and go to hard number on Z2 on Head 2.

Because face and diameter grip is more stable and concentric than gripping on O.D. only. Especially if the O.D. is more of a ring than a cylinder.

Thanks for the input!

-jim

[cogsman1]

Get a CITIZEN L20 or M16/20/32. They have servo feedback that allows you to feed into a face and stop when the load is great enough then continue with the program. MUST be a model with servo controled, some of the older ones and some of the less expensive new ones do not have that feature.

[chet470]

Yes this is possible. Speak to a application engineer with STAR. No need to buy a citizen, they are slightly overated from what I've seen.

[steve3three]

Star for the win btw.

probably the easiest way to do what your looking to do is to put a spring loader in H2. It's a pretty simple process, if you have any questions on that just shoot away.

[cogsman1]

Like I said, Get a Citizen. They can already do what you want. No springs, just program it and go.
Not "Over rated" but sometimes OVER QUALIFIED! You get what you pay for, and with Citizen it pays you back multiple times. I have 3 12 year old M20 machines holding tenths all day everyday. Tried others and they have worn out and been replaced with Citizens.

[dookie2022]

Whats the big deal just program the axis to pickup at the right position

[steve3three]

Originally Posted by dookie2022 Whats the big deal just program the axis to pickup at the right position

agreed.

[jimiscnc]

“Program the axis at the right position”

The machined shoulder is created with a natural machining tolerance. Let’s say that the accuracy of this shoulder is held to .0005” or less. Let’s say that the machining variation is .0005” or less. If you pick off the part in Head One to a hard number and program to nominal to butt against a shoulder, there will be times when the part is fat, and the shoulder will be pressed by the pick off collet face before the Z axis final position is reached. This is not good, but if we’re dealing in a few tenths variation, the error won’t be “noticed” by the CNC. However, during first part prove out, when every feature IS NOT DIALED IN, the error could be so pronounced as to trip out the Head 2 Z servo’s, as the machine thinks it’s going into a collision.

Also, if the error is not all against the shoulder, and the hard Z number positions the pick off collet face away from the part, you no longer have the benefit of both cylindrical and face contact, for the most stable gripping possible..

I am familiar with Mazak Integrexes. They can pick off to a shoulder by EIA or mazatrol programming. This is done by the use of the G31 skip signal command, which is G01 that goes to a commanded position until it gets a signal that it has hit it’s intended position. G31 is used by touch probes on CNC. They are programmed beyond what they are trying to find, and when the probe hits the feature, it sends as signal to the control that the move is finished, even though it was stopped short of completing the full command.

I am thinking that because Star uses USER MACRO B all over the place, there could be a way to program this by using all the system parameters they use for other things anyway.

In anthropomorphic terms, Head 2 would be saying, “go towards the workpiece striving to reach the commanded pick off spindle Z position. If the load of the Head 2 Z axis servo increases suddenly, stop trying to reach the commanded Z position and consider that Z command finished. Then continue to execute the rest of the program.”

In other words, my request could be satisfied if – the G31 skip signal command is valid and usable on Stars, and if there’s enough knowledge about system parameters and User Macro Programming, it could be created.

I suspect this problem has already been solved, perhaps over 10 years ago, but the people with this solution don’t read CNC internet message boards.

-Jim

KM63 tooling, and a lot of the variants of that out there, some work with both cone and face surface contact simultaneously, as a point of information. The design of such tooling is pretty remarkable. In the sense that it’s revolutionary, and uses some pretty slick engineering concepts, that I don’t understand well enough to fully explain.

[PixMan]

Originally Posted by cogsman1 Get a CITIZEN L20 or M16/20/32. They have servo feedback that allows you to feed into a face and stop when the load is great enough then continue with the program. MUST be a model with servo controled, some of the older ones and some of the less expensive new ones do not have that feature.

Star machines with Fanuc 16, 18, 21 and 30 series controls can do the exact same thing.

[glenthemann]

Originally Posted by jimiscnc “Program the axis at the right position” The machined shoulder is created with a natural machining tolerance. Let’s say that the accuracy of this shoulder is held to .0005” or less. Let’s say that the machining variation is .0005” or less. If you pick off the part in Head One to a hard number and program to nominal to butt against a shoulder, there will be times when the part is fat, and the shoulder will be pressed by the pick off collet face before the Z axis final position is reached. This is not good, but if we’re dealing in a few tenths variation, the error won’t be “noticed” by the CNC. However, during first part prove out, when every feature IS NOT DIALED IN, the error could be so pronounced as to trip out the Head 2 Z servo’s, as the machine thinks it’s going into a collision. Also, if the error is not all against the shoulder, and the hard Z number positions the pick off collet face away from the part, you no longer have the benefit of both cylindrical and face contact, for the most stable gripping possible.. I am familiar with Mazak Integrexes. They can pick off to a shoulder by EIA or mazatrol programming. This is done by the use of the G31 skip signal command, which is G01 that goes to a commanded position until it gets a signal that it has hit it’s intended position. G31 is used by touch probes on CNC. They are programmed beyond what they are trying to find, and when the probe hits the feature, it sends as signal to the control that the move is finished, even though it was stopped short of completing the full command. I am thinking that because Star uses USER MACRO B all over the place, there could be a way to program this by using all the system parameters they use for other things anyway. In anthropomorphic terms, Head 2 would be saying, “go towards the workpiece striving to reach the commanded pick off spindle Z position. If the load of the Head 2 Z axis servo increases suddenly, stop trying to reach the commanded Z position and consider that Z command finished. Then continue to execute the rest of the program.” In other words, my request could be satisfied if – the G31 skip signal command is valid and usable on Stars, and if there’s enough knowledge about system parameters and User Macro Programming, it could be created. I suspect this problem has already been solved, perhaps over 10 years ago, but the people with this solution don’t read CNC internet message boards. -Jim KM63 tooling, and a lot of the variants of that out there, some work with both cone and face surface contact simultaneously, as a point of information. The design of such tooling is pretty remarkable. In the sense that it’s revolutionary, and uses some pretty slick engineering concepts, that I don’t understand well enough to fully explain.

For what possible reason does the part NEED to be right up against the shoulder? leave yourself .005-.010" and you're good to go. Ive never had any issues simply holding on an OD, and in fact ive never heard of any reason, nor anyone trying to butt the sub up against a shoulder.

You're gonna have to touch off the backworking tools with the part in the sub anyway to do any machining.

If you want it simply to run into the shoulder, sense it and then pick off, the part length will then be all over the place by your logic and you wont be able to hold any consistent tolerances working on the backside. Also whos to say the shoulder is 100% perpendicular to the z axis? In theory it should be, sometimes it is not. The face of collets when closed are not perfect. Collets pull back also when they close, and if you butt the part shoulder against the collect and then close the collect, guess what is likely to happen?

You guys are overthinking your requirements in my opinion. Just pick the part off on the OD and machine it. If you cant hold the tolerances you need you need to look at your guide bushing and your pickoff, You should have no problem being able to hold a few tenths concentricity, unless your guide bushing is as loose as lindsay lohan and you're using inadequate pickoff collet pressure. Unless of course you've crashed the hell out of your machine and nothing is dialed in 100%, then youll never be able to hold any super tight tolerances anyway.

Also for the record I run both star and citizen.. they both have their pros and cons. Star seperate heads and thus programs is a huge plus for me. Citizens handwheel check and tool setting are huge pluses for citizen. You set every tool in a citizen the same way on one screen.. I think we all know how you have to set almost every 'set' of tools on a star differently (gang stick tools, cross live maching, front/back mahining, head2 machining..) Both are great machines, and both do have their bad apples.