Cycle Time Reduction: Indexing Turret

In my last blog post, I highlighted a few ways to increase production on Okuma CNC lathes using cycle time reduction when commanding the spindle/M-spindle (see here to review those topics), all without spending a dime on hardware. I will continue that topic by discussing techniques that can be used when indexing a lathe turret, again referencing the “OSP-P300L/P300S Operator’s Pocketbook.”

Set the turret to index on the shortest path
If the parameter “Turret short path control A-side” is checked, turret indexing time is reduced automatically. This parameter is unchecked by default. To set the turret to index on the shortest path, go to Parameters - MACHINE USER PARAMETER - TURRET/DOOR and put a check in the box next to “Turret short path control A-side” as shown in Figure 1. You can see the difference this makes in Figure 2 below.

NOTES:

• The “A” in “Turret short path control A-side” represents turret-A. Thus the parameter will need to be set independently for each of the turrets A, B and C if applicable.
• Leaving this parameter unchecked does allow designating the turret index direction within the part program using M86 and M87.
• Setting this parameter to ‘checked,’ will ignore the M86 and M87 commands.

Index the turret off the Z-axis limit
This one may be obvious to some, but most Okuma lathes only require that you be on the X-axis limit in order to index. I see many times where the turret is sent to the Z-axis limit also, which may be safer in some cases, but if it’s not necessary, indexing off the Z-axis limit, closer to the workpiece could save the most time out of all these options. Just be careful that the Z-location you choose allows all the tools on the turret to clear any interferences.

Use M203 to unclamp the turret during rapid retract
Add M203 to the rapid retract block so the turret unclamps on its way to a safe turret-index location, thus reducing cycle time (see Figure 4). On the next line, command a turret index, which will rotate the turret and clamp automatically.

Example: G00 X500 Z800 M203 (←Make sure you are clear of interferences first!)
T020202

NOTES:

• M203 unclamps the turret regardless of the current turret position when combined with a G00 rapid move. For a 2-piece type turret (lift-up turret), interference may occur when the turret unclamps. Move the turret away from any interference before adding the M203 to the rapid retract move.
• There is a parameter to control the turret unclamp confirmation timer, but is not discussed here as the default value should be adequate. Contact your distributor for help with this setting if necessary.
• M203 can only be used on the same line as a G00 command. It cannot be used with any feed move command.

CAREFULLY* use M65 to index the turret during axis movement
M65 ignores the answer signal for the turret indexing command, which means turret indexing and axis movement can be done simultaneously as long as the turret is on the X-axis limit to begin with. Without M65, the turret will complete indexing before axis movement begins. In either case, rapid movement is allowed before the turret clamp confirmation is received. Feed movement is restricted to only after the turret clamp confirmation is received.

Example: G00 X500 Z500
G00 X50 Z50 T030303 M65
T030303
G01 …

NOTES:

• *Use M65 with extreme caution! Indexing the turret without confirming adequate clearance can cause the turret or installed tools to interfere with the workpiece, workholding, tailstock, etc…
• *When proving out this process, understand that feed override does have an effect on clearances and interferences. Prove this first with a slow override, then again slightly faster, and so on until you are confident there will be no issues at 100%. Take your time with this process. Saving time is not worth crashing your machine!
• Add an additional turret indexing command before a feed command is given or an alarm may occur (see example above). This will ensure the turret is fully indexed and clamped before feeding begins.
• M65 is non-modal, meaning it only affects the blocks in which they’re included.

Request more information
There’s one additional method to reduce cycle time when indexing a turret, but it’s more complex than can be explained here on our blog. If you’re interested in learning more, please comment below and someone will follow up accordingly.

Using the techniques above, combined with those outlined in my previous blog on commanding your spindle/M-spindle, will save valuable time and increase productivity. There’s a lot to cover and a lot more time to save with my next couple topics too: Fixed Cycles, and LAP Cycles (Lathe Automatic Programming). As always, feel free to comment below with any questions you may have.

Cooper Ferguson is Applications Engineer, Okuma America Corporation.

Please Note: As with any parameter setting, G-code, or M-code, improper use can result in “troubles, losses or damages.” Take all possible precautions when using cycle time reduction techniques.