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Front Turret Lathe and G2/G3 Reversal?

BluishInventor

Aluminum
Joined
Jul 7, 2020
Hi everyone,

We have a Trak Lathe 1630 SMX control CNC. It appears that we need to swap G2 and G3 for proper code output regarding arcs. It's almost as if it is utilizing a left handed coordinate system rather than right.

So, having X+ point towards the operator and Z+ points away from the chuck, Y should then point down. Correct?

In the case of this machine the Y points up, thus reversing the CW and CCW arc requirements.

Anyone else see this before? Our 2 other front turret 2x lathes (Fanuc and Centroid controls) do no require this.
 
Sorry, I meant the chuck was to operator left. My bad, I will reword it or remove that part.

Tools or right side up, or cutting edge up.
X+ is towards you ? That's flopped, so backwards G2 and G3 make sense.

Why is X+ towards you ? To "make it easier" ? Not following the rules makes things more difficult.

Used to see this situation on dual turret lathes where everything was written from the standpoint of one turret, which made the other turret in the wrong orientation. It's not a tremendous problem to overcome, just have to remember which turret and which direction the spindle is going or mess with the post.

But kinda silly to do this on a toolroom lathe. Maybe can change a parameter ?
 
I've seen this before on VTLs because of the right hand rule for vectors. You're 100% right that it depends which way Y positive is facing. G02 was still CW, just not necessarily from the perspective of the operator. I had to think looking from the back of the machine outward for it to make sense in my head.
 
Hi everyone,

We have a Trak Lathe 1630 SMX control CNC. It appears that we need to swap G2 and G3 for proper code output regarding arcs. It's almost as if it is utilizing a left handed coordinate system rather than right.

So, having X+ point towards the operator and Z+ points away from the chuck, Y should then point down. Correct?

In the case of this machine the Y points up, thus reversing the CW and CCW arc requirements.

Anyone else see this before? Our 2 other front turret 2x lathes (Fanuc and Centroid controls) do no require this.


Hello BluishInventor,
Are you saying that a convex radius, cut with a RH OD Turning Tool machining towards the chuck, to the left of the operator, requires a Circular Interpolation command G02, or G03?

If you consider the common lathe layout with the Cutting Tools at the back of the machine (work-piece between the operator and tool), X+ away from from the operator, a RH OD turning tool will be upside down, with a Convex Radius being cut (machining towards the chuck to the left of the operator), the command will be G03.

When the Cutting Tools are at the front of the machine, with X+ towards the operator, you look at it as if the X axis and Cutting Tools were rotated about the machine's centre line. Accordingly, the RH OD Turning Tool that was upside down at the back of the machine, will now be upside up at the front of the machine. The command to machine a convex radius (machining towards the chuck to the operator's left), will still be G03. When the Cutting Tools are at the front of the machine and X+ towards the operator, CW/CCW is determines as if viewing the tool from the floor looking up.

Regards,

Bill
 
X+ is towards you ? That's flopped, so backwards G2 and G3 make sense.

Why is X+ towards you ? To "make it easier" ?

Maybe can change a parameter ?

It's considered a front turret machine, so the tool is on the same side as the operator. M3/M4 are identical to a traditional rear turret slant bed lathe where the turret is on the opposite side of the spindle axis. Thus, X+ points to the tool, which on this machine is towards the operator. We have a couple front turret 2x lathes, so I assume it's not uncommon.

Unfortunately, there is no parameter to change in the machine to flip this. Need to do it in the post.
 
X+ is towards you ? That's flopped, so backwards G2 and G3 make sense.

Why is X+ towards you ? To "make it easier" ?

Maybe can change a parameter ?

It's considered a front turret machine, so the tool is on the same side as the operator. M3/M4 are identical to a traditional rear turret slant bed lathe where the turret is on the opposite side of the spindle axis. But on this machine, X+ points to the tool, which is towards the operator. We have a couple front turret 2x lathes that are like this, so I assume it's not uncommon. But the G02/G03 moves are opposite on this machine compared to the other two, which is odd.

Unfortunately, there is no parameter to change in the machine to flip this. Need to do it in the post.
 
Hello BluishInventor,
Are you saying that a convex radius, cut with a RH OD Turning Tool machining towards the chuck, to the left of the operator, requires a Circular Interpolation command G02, or G03?

If you consider the common lathe layout with the Cutting Tools at the back of the machine (work-piece between the operator and tool), X+ away from from the operator, a RH OD turning tool will be upside down, with a Convex Radius being cut (machining towards the chuck to the left of the operator), the command will be G03.

When the Cutting Tools are at the front of the machine, with X+ towards the operator, you look at it as if the X axis and Cutting Tools were rotated about the machine's centre line. Accordingly, the RH OD Turning Tool that was upside down at the back of the machine, will now be upside up at the front of the machine. The command to machine a convex radius (machining towards the chuck to the operator's left), will still be G03. When the Cutting Tools are at the front of the machine and X+ towards the operator, CW/CCW is determines as if viewing the tool from the floor looking up.

Regards,

Bill

The tool is on the operator's side(front turret config), its cutting side up, and X+ also points to the operator. But Z+ is the same which makes this a left hand coordinate system. Super odd.
 
if X+ is coming toward you, and Z+ goes to the right, Y+ points straight down, according to the right hand rule.

if you're doing any work in G19 plane, that one has G2 and G3 reversified from the typical views of G17 and G18.
 
No, it's not. You are supposed to look at it from underneath, looking up. Still right-hand rule, just looking from the other side of the paper.

Correct, a righthand CS is Y down if X+ points at operator and Z+ points to operator right. Then you look up at it from underneath for CW/CCW direction. But this machine behaves opposite to that. When you look from the top, CW/CCW is normal to the top view and backwards from underneath.

I must be missing something here... all I know is my post needs to have G02/G03 flipped.
 








 
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