A lubricated ballscrew or linear bearing turns friction into heat whenever the oil film becomes too thin, the grease cannot reach the contact, or mixed greases change consistency. The numbers that matter are drive current, component temperature, lubricant quantity, and relubrication interval. A familiar brand name does not override compatibility or application approval.
Friction, Heat, and Moisture Load
Grease supplies oil to loaded rolling contacts while its thickener holds that oil near the contact zone. Too little oil increases metal-to-metal interaction, friction, motor load, and temperature. Excess grease can also raise drag and temperature until the excess is displaced. A ballscrew may react differently from a conventional bearing because its circulation path, seals, speed, and lubricant distribution differ.
Mixing products introduces another failure mechanism. Different base oils, thickeners, or additive packages can soften, harden, separate, or lose mechanical stability when combined. The result may leak out of the bearing, resist flow through a lubrication line, or remain in the housing without releasing enough oil. This is heat, not logic: a grease that looks present can still leave the rolling contact starved.
Moisture adds corrosion and wash-off risk. If the CX 20 operates in a moisture-rich wire EDM environment, water resistance and corrosion protection become selection criteria. A sticky grease that resists water may suit some bearings or gears, but that property alone does not establish ballscrew suitability.
| Quantity or condition | Decision limit | Where to read it |
|---|---|---|
| Lubricant quantity | Use the amount specified for each lubrication point; no quantity is identified here | Machine lubrication chart or service manual |
| Relubrication interval | Use the machine interval adjusted only through an approved maintenance instruction | Maintenance schedule and lubrication label |
| Axis motor current | Compare with the machine's established unloaded baseline under the same speed and travel conditions | Drive monitor or controller diagnostic display |
| Bearing or screw temperature | Compare repeatable measurements with the previous baseline and manufacturer limit | Drive diagnostics, installed sensor, or measured housing temperature |
| Cleaning solvent |
90% alcohol was proposed for residue removal, subject to seal, coating, and material compatibility |
Cleaner data sheet and Mitsubishi service instructions |
Candidate Greases and Approval Gaps
Mobilith AW2 was already being used on the machine. Its supply status is unresolved: it was reported as still available, while its absence from manufacturer product information led others to treat it as discontinued. Independent sellers reportedly identified Mobil XHP222 as a replacement, but a seller substitution does not define compatibility with every CX 20 lubrication point.
| Approach | Known application position | Deciding limitation |
|---|---|---|
Continue with Mobilith AW2
|
Existing grease in this installation | Confirm current product identity, condition, and supply before adding more |
Change to Mobil XHP222
|
Suggested for bearings, taper-unit linear bearings, and split gears | Ballscrew approval was not established; switching requires compatibility confirmation and removal of the old grease |
Change to Mobilux EP2
|
Raised as a possible alternative | No application approval, equivalence, or compatibility information is identified |
The application point controls the decision. Approval for a split gear or linear bearing cannot be transferred automatically to a ballscrew. Each point can impose different requirements for consistency, oil release, pumpability, speed, load, seal compatibility, and water exposure.
Recommended Selection Rule
Keep Mobilith AW2 in service when it remains obtainable, is in usable condition, and matches the lubricant already present. This avoids an uncontrolled mixture and the difficult task of clearing grease from distribution lines, fittings, bearings, and internal passages.
If Mobilith AW2 cannot be sourced, obtain the Mitsubishi lubricant specification for the exact CX 20 lubrication point before selecting a replacement. Ask separately about ballscrews, linear bearings, taper-unit bearings, and split gears. Accept Mobil XHP222 only for locations Mitsubishi identifies as suitable; its reported bearing and gear use does not answer the ballscrew question. Treat Mobilux EP2 the same way until its application and mixing compatibility are confirmed.
When comparing technical data, match the grease consistency, base-oil type and viscosity, thickener, additive system, water resistance, corrosion protection, operating-temperature range, and delivery method. For a centralized system, pumpability through the installed line length and fittings also matters. A grease can be acceptable at a hand-greased bearing yet fail to move reliably through a distribution circuit.
Controlled Grease Changeover
A full changeover is required when compatibility has not been documented. Adding the new product until its color appears at an outlet may leave pockets of the old grease in lines and bearing cavities.
- Identify every lubrication point supplied by the reservoir or fitting. Record which points serve ballscrews, linear bearings, taper components, gears, and conventional bearings.
- Record the installed grease from the cartridge, container, service log, and reservoir label. If identity is uncertain, treat the contents as an unknown lubricant rather than assuming it is
Mobilith AW2. - Obtain Mitsubishi approval for the proposed grease at each point and obtain compatibility guidance from the lubricant manufacturer. Separate approval for direct application from permission to mix residual products.
- Isolate the machine according to its service procedure. Empty and clean the reservoir, then clear the old grease from accessible lines, metering fittings, ports, and bearing spaces.
- Clean accessible components to a residue-free condition. Use
90% alcoholonly where Mitsubishi and the component material permit it; alcohol can affect some seals, coatings, plastics, and retained lubricant. - Replace blocked or impractical-to-clean tubing and fittings where residual grease would defeat the changeover. Reassemble without introducing lint, abrasive material, or solvent into the rolling contacts.
- Fill with the approved product and purge each circuit using the machine's prescribed service method and quantity. Confirm delivery at every accessible endpoint rather than judging the reservoir alone.
- Label the reservoir and update the maintenance record with the product, serviced points, and change date.
Post-Service Verification
Run the affected axis or mechanism without production load using the normal service test. Traverse the usable range so lubricant distributes across the contact path. Watch for abnormal drag, noise, vibration, leakage, and missed lubrication delivery.
Compare axis motor current with a pre-service or known-good baseline at the same speed, direction, position, and mechanical load. Record component temperature at repeatable locations and times. A sustained increase after lubrication can indicate overpacking, restricted delivery, incompatible residue, seal drag, or mechanical damage; a falling current and stable temperature after distribution support a successful service.
Inspect each outlet and lubrication point after the first run. Confirm that the grease reached the component and remained where intended. Recheck after the next maintenance interval for separation, hardening, water contamination, corrosion, blocked fittings, or unusual consumption.
Recurring Service Pitfalls
- Treating “bearing grease” as universal: ballscrews, linear bearings, and gears can require different lubricant behavior.
- Using availability as proof of equivalence: a distributor replacement statement does not establish Mitsubishi approval or mixing compatibility.
- Cleaning only the reservoir: old grease remains in lines, metering fittings, ports, seals, and bearing cavities.
- Choosing only by stickiness: water resistance is useful in wet service, but excessive drag or poor pumpability can starve a remote point.
- Skipping the baseline: without matched current and temperature readings, gradual friction increases can pass unnoticed.
FAQ
What happens if I mix Mobilith AW2 and Mobil XHP222?
Without documented compatibility, the mixture can soften, harden, separate, leak, or stop moving through the lubrication circuit. Clear the reservoir, lines, fittings, and accessible bearing spaces before changing products.
What happens if I use Mobil XHP222 on the CX 20 ballscrews?
Mobil XHP222 was suggested for bearings, taper-unit linear bearings, and split gears, but ballscrew approval was unresolved. Obtain Mitsubishi confirmation for the ballscrew lubrication point before applying it.
When should I stop a Mitsubishi CX 20 grease changeover?
Stop when the existing grease cannot be identified, the proposed product lacks approval for the exact lubrication point, or the circuit cannot be fully cleaned and verified. Also stop for rising drive current, abnormal temperature, noise, blocked delivery, or visible lubricant separation. Escalate with the machine serial information, lubrication-point list, existing grease identity, proposed replacement, and measured current and temperature data to official Mitsubishi support.