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Tool room lathe to slant bed program conversions

whodey0603

Plastic
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Jun 14, 2024
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Dayton, OH
Hello all,
We recently switched from a tool room (front feed) CNC lathe to a slant bed (rear feed) CNC lathe. I only dabble in CNC lathe programming and I have a couple questions regarding converting the programs from front to rear. Tools did switch from left-cutting to right-cutting due to the tool carousel:

I know M03 will have to switch to M04. Do I also have to switch G41 to G42 and vice versa?

What about G02 to Go3? Do I need to switch those?

I'm having trouble picturing what changes are needed to convert the programs outside of the M03. Thank you for any advice.
 
Normally it would be the same tool direction for both.
Doesn't your slant bed allow you to run the tools with the inserts facing down?
That is the common way for CNC.
I don't believe so. To turn a right hand thread, the manufacturer, EMCO, had to send me a special insert to put in the carousel to get the Top Notch insert on center and run it upside down.
 
What about G02 to Go3? Do I need to switch those?
One is for CW radius the other is for CCW radius. So, yes you'd have to change those, also your cutter comp would need to change.
Are you just planning on mass editing a program to convert it to a rear turret? That's bad mojo.
 
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One is for CW radius the other is for CCW radius. So, yes you'd have to change those, also your cutter comp would need to change.
Are you just planning on mass editing a program to convert it to a rear turret? That's bad mojo.
That's what I was planning and hoping it was that simple. What is a better solution here?
 
That's what I was planning and hoping it was that simple. What is a better solution here?
The best solution is to re-post the program from your cad/cam software.
If they were hand-written, then you might be better off starting from scratch so you don't miss anything like a rapid move in the wrong direction, cutter comp, etc...
 
I'm still not clear here. What brand and model of lathe is this?

If the tools are on the back side and facing down instead of up, nothing changes at all. If you have a turret, you won't be able to "just flip the tool" or anything like that. It's designed to run one way or the other, with tools of a particular height to get to centerline.
 
I'm still not clear here. What brand and model of lathe is this?

If the tools are on the back side and facing down instead of up, nothing changes at all. If you have a turret, you won't be able to "just flip the tool" or anything like that. It's designed to run one way or the other, with tools of a particular height to get to centerline.
The one thing that usually changes is G02 and G03 are reversed on most conversational lathes since on a tool room lathe you are looking at the top of the insert vs a slant bed where you are looking at the bottom of the insert. The Haas TL1 I have run is the only exception I have run into. It makes sense form a compatibility perspective but is is annoying to have to visualize your part from the underside of the tool to hand program.
 
The one thing that usually changes is G02 and G03 are reversed on most conversational lathes since on a tool room lathe you are looking at the top of the insert vs a slant bed where you are looking at the bottom of the insert.
Right. And he's talking about running the spindle in reverse and special inserts to run backwards. That's not passing my sniff test for a slant bed lathe.
 
I'm still not clear here. What brand and model of lathe is this?

If the tools are on the back side and facing down instead of up, nothing changes at all. If you have a turret, you won't be able to "just flip the tool" or anything like that. It's designed to run one way or the other, with tools of a particular height to get to centerline.
The one thing that usually changes is G02 and G03 are reversed on most conversational lathes since on a tool room lathe you are looking at the top of the insert vs a slant bed where you are looking at the bottom of the insert. The Haas TL1 I have run is the only exception I have run into. It makes sense form a compatibility perspective but is is annoying to have to visualize your part from the underside of the tool to hand program.
This is an EMCO Maier Concept Turn 60 and does operate with a tool turret. The chair-looking stainless adapter in the first picture is the adapter I had to buy to run my Top Notch inserter upside down for right-handed threads.

1718397477156.png 1718397394193.png
 
Wow. Just wow. Someone beat that designer with a stick. @implmex would love that machine (not).


Yeah, it looks like that machine runs everything backwards. I've seen that layout before but, it's usually the weird stuff, or machines where they use a front and back turret or something. What were they thinking?
 
What about G02 to Go3? Do I need to switch those?
If the Tool Room lathe was programmed with X+ on the operators side of the Spindle Centre Line and the Slant Bed machine, with the Tool Turret at the back of the machine and X+ is on the side of the Spindle Cemtre Line furthest from the operator, neither circular Interpolation nor TNR Compensation commands will change, spindle rotation direction also has no effect on either.

Regards,

Bill
 
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The usual convention has positive direction of the X axis towards the tool. So, it is towards the operator on a front-type lathe, and away from him on a rear-type lathe. This has the effect of the positive direction of the Y axis pointing upwards on a rear-type lathe, whereas it is downward on a front-type lathe. Therefore, everything which depends on the direction of Y axis, reverses, such as CW/CCW and left/right directions, as perceived by the operator.

Thus, with this type of axis convention, G02/G03 would need to be interchanged.

However, G41/G42 will remain unchanged in the program (skipping the explanation), though tool-tip numbers will be different on the two types of machine, as indicated in the table below:
1718424514307.png
As regards, M03/M04, it depends on how the tool is placed on the turret, upside down or the insert facing up. Therefore, M02/M03 may or may not be required to switch.
 
The usual convention has positive direction of the X axis towards the tool. So, it is towards the operator on a front-type lathe, and away from him on a rear-type lathe. This has the effect of the positive direction of the Y axis pointing upwards on a rear-type lathe, whereas it is downward on a front-type lathe. Therefore, everything which depends on the direction of Y axis, reverses, such as CW/CCW and left/right directions, as perceived by the operator.

Thus, with this type of axis convention, G02/G03 would need to be interchanged.

However, G41/G42 will remain unchanged in the program (skipping the explanation), though tool-tip numbers will be different on the two types of machine, as indicated in the table below:
Given the OP's machine is a basic 2 axes example, there is no Y axis to make the determination you suggest, therefore, if Z + is away from the head stock, with the heads stock at the left of the machine, then, if convention was followed by the machine tool builders, there will be no conversion required when comparing a machine with X+ and cutting tools at the front of the machine, towards the operator and a machine where X+ and cutting tools are at the rear of the machine, away from the operator..

The same applies with G41/G42. Accordingly, in a situation where G02/G03 would need to be interchanged, as you suggest, so does G41/G42. But in a configuration where X+ is towards the cutting tool and Z+ is to the Right (spindle on the Left), when comparing the two machines, then there is no interchange of either.

An excellent example of this is on a machine having two Tool Turrets on the same fixed X axis slide, one turret for OD Tools, the other for ID Tools, such as the early Mazac "M" Series lathe,. In this case the machine has X+ towards the Operator at the front of Centre Line for the Front Turret and X- for the Turret at the rear of Centre Line, away from the operator. With this style and configuration, the Rear Turret Tools, both G02/G03 and G41/G42 were interchanged for those used by the Front Turret Tools.

The following pictures are extracts directly from a Fanuc Manual.
X+ Towards the Front of Machine
X+ Towards the Front of Machine.JPG
X+ Towards the Rear of Machine
X+ Towards the Rear of Machine.JPG
 
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Given the OP's machine is a basic 2 axes example, there is no Y axis to make the determination you suggest,
Mathematically, the Y axis always exist, and the three axes follow the right-hand rule.
The Y axis may or may not be controllable, but that does not change axis definitions.

Following the right-hand rule, the Y axis points upward on a rear-type lathe, whereas it points downward on a front-type lathe.
 
there will be no conversion required when comparing a machine with X+ and cutting tools at the front of the machine, towards the operator and a machine where X+ and cutting tools are at the rear of the machine, away from the operator.
G02/G03 would need to be switched if the machining is being done on the positive X side in both cases.
 








 
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