How to Startup a Mori CNC Milling Machine
A step-by-step cold-start routine for Mori Seiki and DMG MORI vertical and horizontal mills. Written for machinists and process engineers who need the machine cutting good parts on the first shift, not the third.
In this article
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Key takeaways
Startup Mori CNC Milling Machine: Pre-Power Checks
Most bad starts happen before the control is switched on. Walk the machine first. Look for a pallet or fixture left on the table, a tool sitting in the spindle taper, and chips packed around the linear guides. A 0.2 mm chip under a way cover will show up as a taper in the part three hours later.
Open the main air supply and confirm clean, dry air at 0.5–0.7 MPa. Water in the line reaches the spindle air purge and the tool changer, and neither tolerates it. Drain the filter bowl before you start, not after. If the machine has a spindle oil-air lubrication unit, check the reservoir level now.
Check the coolant tank level and concentration. Refractometer readings between 6% and 10% are typical for aluminum; cast iron runs lower. A tank that sat idle for two weeks grows bacteria and the smell will tell you. Top up with premixed coolant, never straight concentrate.
Verify the emergency stop buttons are released on the panel, the door, and any remote pendant. Confirm the door interlock and light curtain are clean and undamaged. A blocked light curtain will stop the cycle mid-cut on the first automatic tool change.
For a machine that has been off for weeks, pull the way lube reservoir and confirm oil is reaching the metering units. Dry ways plus a rapid traverse equals scored guide surfaces. Manual pump the lube system two or three times before you energize anything.
Power-Up Order on a Mori CNC Milling Machine
Energize in the right order. Main breaker first, then the machine transformer, then the control. Mori controls on Mitsubishi, FANUC, and Siemens platforms all expect the servo amplifier to see stable three-phase power before the NC boots. Switching the control on first gives you an alarm you then have to clear.
Watch the boot screen and note every alarm code. A low battery alarm on the absolute encoder is not a warning you can leave for next week. If the battery dies with the machine off, you lose the reference position and the machine will demand a full zero return with possible parameter re-entry.
Let the hydraulic unit run two to three minutes before any axis move. Clamp pressure on a horizontal mill should reach its set value within that window. If the pressure gauge creeps or drops, stop and find the leak. Do not jog the pallet changer on low clamp pressure.
Release the e-stop and press reset. Confirm the control shows all axes enabled and no axis in an overtravel condition. If an axis is sitting past a limit switch, use the manual handle on the ball screw only if the manufacturer's procedure allows it. Otherwise call service.
Once the control is live, check the date and time. Sounds trivial. It is not, when you are tracing a scrap event through the alarm history three weeks later.
Warm-Up and Reference Return: The Part Engineers Skip
A Mori spindle casting is heavy, and it grows as it warms. The difference between a cold machine and a machine at thermal equilibrium is often larger than the tolerance you are trying to hold. On a job with ±0.005 mm callouts, that gap decides whether the first ten parts pass.
Run the spindle warm-up program built into the control if one exists. A typical ramp is 500 rpm for 5 minutes, 2,000 rpm for 5 minutes, 5,000 rpm for 10 minutes, then 10,000 rpm for 5 minutes, with the spindle orienting at each step. On a 12,000 rpm machine, extend the top step to 8 minutes.
Move the axes through their full travel at reduced rapid, around 25% to 50% of normal. This distributes way lube and warms the ball screws evenly. Pay attention to the sound at direction changes. A rumble on reversal is a thrust bearing telling you something.
After the spindle and axes are warm, return every axis to reference. Z first, then Y and X, then any rotary or pallet axis. Follow the machine builder's stated order if it differs. Return to reference is not optional after a power loss, an e-stop, or a battery replacement.
Re-check the work offsets and tool length offsets once reference is established. Load the tool setter and measure at least the first tool. If the numbers moved from the last job, find out why before you press cycle start.
When the Startup Goes Wrong
The most common failure is an alarm on the automatic tool change during the first cycle. In nine cases out of ten the cause is air pressure or a tool that is not fully clamped. Check the pressure gauge at the machine, not at the wall. A 0.1 MPa drop across a long hose run is normal and enough to matter.
The second is a spindle overload on the first heavy cut. A cold spindle with cold grease draws more current. If the load meter jumps past 70% on a cut that normally runs at 40%, stop and let the machine warm further. Do not push through it.
The third is a dimensional drift across the first five parts. That is thermal growth, not a programming error. Measure the parts, plot the trend, and you will see it settle. Adjust the offset after the third part, not the first.
The fourth is a lost reference on a rotary axis. Rotary tables with absolute encoders usually survive a power cycle, but incremental ones do not. If your setup relies on a rotary zero that was set two months ago, re-establish it now.
Step by Step: Startup Mori CNC Milling Machine
- 1Walk the machine and clear the work zoneRemove fixtures, loose tools, and chips. Inspect way covers and the table surface. Confirm no obstruction in the tool changer or pallet pool.
- 2Confirm air, coolant, and lubeAir at 0.5–0.7 MPa, dry and filtered. Coolant at 6–10% concentration. Way lube reservoir above the low mark; manual pump two or three strokes.
- 3Check e-stops and interlocksAll e-stop buttons released. Door interlock and light curtain clean and functional. Pendant connected and seated.
- 4Power up the machine in orderMain breaker, transformer, control. Let the NC boot fully. Note every alarm code on the screen.
- 5Start hydraulics and let them stabilizeRun the hydraulic unit 2–3 minutes. Confirm clamp pressure reaches the set value and holds steady.
- 6Release e-stop and reset the controlPress reset. Confirm all axes are enabled and none is in overtravel. Clear any remaining alarms before moving.
- 7Run the spindle warm-up cycle500 rpm for 5 min, 2,000 rpm for 5 min, 5,000 rpm for 10 min, 10,000 rpm for 5 min. Extend the top step on high-speed spindles.
- 8Exercise the axes and return to referenceFull travel at 25–50% rapid. Then zero return Z, Y, X, and any rotary axis in the builder's order.
- 9Verify offsets and prove the first partRe-check work offsets and tool lengths. Run the first part in single block at 50% feed override with 1.0 mm stock allowance.
Startup Checks by Machine Condition
Use this to decide how much of the full routine you need.
| Machine condition | Warm-up time | Reference return | First-part strategy |
|---|---|---|---|
| Daily start, machine ran yesterday | 5–10 min | Not required if no alarm | Normal feed, inspect part 1 |
| After weekend shutdown | 20–30 min | Recommended | 50% override, inspect parts 1–3 |
| After e-stop or power loss | 20–30 min | Mandatory on all axes | Single block, verify offsets first |
| After encoder battery change | 30–45 min | Mandatory plus parameter check | Air cut first, then prove-out |
| After 2+ weeks idle | 30–45 min | Mandatory on all axes | Re-measure every tool offset |
| After a move or re-leveling | 30–45 min | Mandatory plus geometry check | Cut a test block before production |
Frequently Asked Questions
How long should I warm up a Mori spindle before cutting?
For a daily start, 5 to 10 minutes at moderate speed is enough. After a weekend or a long idle period, run the full ramp out to 20 or 30 minutes, ending at the top speed you will use in production.
The rule is simple: the spindle should be at the same thermal state at the start of every batch. If the first part of the morning is always off, your warm-up is too short.
Do I have to return to reference after every power-off?
No, not after a normal shutdown where the machine kept its absolute position and no alarm appeared. You do have to return to reference after an e-stop, a power failure, an encoder battery replacement, or any servo alarm.
If in doubt, return to reference. It costs a few minutes. A wrong reference costs a fixture and possibly a spindle.
What air pressure does a Mori CNC mill need?
Most Mori Seiki and DMG MORI mills want clean, dry air at 0.5 to 0.7 MPa at the machine inlet. Measure at the machine, not at the compressor or the wall regulator.
Below 0.5 MPa you will see tool changer faults and weak spindle air purge. Above 0.7 MPa you risk damage to pneumatic seals and cylinders.
Why does the first part always come out oversize?
That is thermal growth in the spindle and ball screws. The machine is cold at the start and warms as it runs, so the tool sits slightly further from the workpiece early on.
Warm up properly, then check the first part and adjust the offset after part three. Adjusting after part one chases a moving target.
Can I skip the warm-up for a roughing-only job?
You can shorten it, but do not skip it entirely. Roughing cuts generate heat fast and the machine will reach a different thermal state than a finishing job anyway.
If the tolerance is open and the material is forgiving, 5 minutes at moderate speed is a reasonable compromise. If the part has a tight bore or a flatness callout, run the full routine.
What should I log after a startup?
Record the date, the alarm codes seen at boot, the air pressure at the machine, and the offsets you verified. Add the first-part measurement and the time it was taken.
Three months of that log tells you whether a drift is thermal, mechanical, or operator-related. Without it, you are guessing.
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