Okuma Machine Tool Power Function and Basic Operation Function

• 1
  What an Okuma machine tool power function actually controls
• 2
  Rapid traverse: per-axis speed, not a group race
• 3
  Spindle power, torque and where the ceiling shows up
• 4
  Basic operation functions: feed hold, dry run, single block, override
• 5
  Interlocks, soft limits and why the machine refuses to move
• 6
  Which function limits your cycle, and when

On an Okuma control, the power function covers the drives and the motions they produce: rapid traverse, spindle rotation, feed axes under load, and the interlocks that stop them. It is not one button. It is the set of machine-side behaviors that the control can switch on, limit or suppress.

That distinction matters when you read a cycle time estimate. A CAM simulation usually assumes every axis reaches its commanded feed. A real Okuma machine tool power function has acceleration limits, per-axis rapid rates and spindle torque ceilings that the simulation never sees.

So when a quoted cycle is shorter than the floor time, the gap is almost always in the power side of the machine, not in the toolpath geometry. The control is doing exactly what it was told. The drives simply cannot do it as fast as the software assumed.

This page explains the power function and the basic operation functions together, because they share the same hardware. Feed hold, dry run, single block and override all act on the same servo loop that the power function governs.

In rapid traverse mode, each axis moves at its own set rapid speed. Axes do not wait for each other. A short Z move and a long X move that start together will finish at different times, and the control does not slow the fast one down to keep them in step.

This is why a diagonal rapid can feel longer than the geometry suggests. The path is not a straight line. Each axis runs at its own rate, so the tool reaches the corner when the slowest axis gets there.

Rapid rates are a machine specification, not a program value. A compact 500 × 500 × 450 mm machine and a 4,000 × 400 × 150 mm gantry do not share the same numbers. Check the specification sheet before you build a cycle-time model.

For most jobs this is fine. It only becomes a problem when a rapid segment sits inside a tight loop, or when a tool change position is far from the cut and the return rapid dominates the cycle.

Spindle power is rated at a base speed, and torque falls off above it. Below the base speed the spindle can hold torque and the limit is the drive. Above it, the limit is power, and torque drops as speed rises.

For aluminum at 6061 or 7075, this rarely bites. High spindle speed plus light chipload keeps the load low. The ceiling shows up in titanium TC4, Inconel and 17-4PH, where the material needs torque at moderate speed.

A practical check: read the spindle load meter during the first pass of a roughing cycle. If the needle sits above roughly 80 percent for more than a few seconds, the next step is a smaller radial depth, not a higher feed.

The power function also governs how the control reacts to an overload. It will fold back the feed before it trips the drive. That fold-back is invisible in the program listing and invisible in the simulation.

These are the four functions most operators touch every shift. Feed hold stops axis motion but leaves the spindle running, so the tool stays in the cut. Use it to check a dimension or clear a chip, not to change an insert.

Dry run moves the axes at a feed you set, without cutting. It is the fastest way to prove a new program on the machine before the first part. Run it with the tool offset cancelled and the work offset verified.

Single block executes one block per press. It is the standard way to walk a new setup through the first approach moves. Most crashes happen in the twenty lines before the first cut, not in the cut itself.

Feed override scales the programmed feed from roughly 0 to 200 percent on most Okuma controls. It does not change spindle speed unless you use the separate speed override. Treat a 150 percent override as a temporary test, not a production setting.

An Okuma control will refuse a move that breaks an interlock. Door open, chuck unclamped, tool not seated, axis outside a soft limit. The refusal is not a fault. It is the power function protecting the machine.

Soft limits sit inside the hard limits. They are set per machine and per axis, and they usually account for the tool change position and the tailstock travel. If a program asks for a move past a soft limit, the control alarms out before the axis reaches the hard stop.

This matters for long parts. On a machine with 4,000 mm of travel, the usable length is shorter once you subtract the chuck, the tailstock and the safe clearance at each end. Plan the setup around the usable envelope, not the travel figure.

When a machine stops mid-cycle, read the alarm number first. Nine times out of ten the answer is in the interlock list, not in the program.