By VNOVO Technical Support Team
Keywords: Cost Reduction, Grease Selection, Sealed Maintenance-Free, Batch Consistency
Ruiyan Zhikong slashed 6-DOF dexterous hand price to 9,999 RMB — directly halving the industry average. This number is not explained by “domestic supply chain is cheaper” — it is supported by extreme polishing of engineering processes plus a stable, reliable mass production system.
For planetary reducers, grease accounts for less than 2% of the BOM — never the main battlefield for cost reduction. But it directly determines how long the reducer lasts in actual use and whether problems arise at the customer end. Choosing the wrong one, and after-sales costs will quietly eat up all the money saved on the design end.
In Cost Structure, Grease Is Not the Lead Role
Disassembling a dexterous hand BOM, the top three costs are: planetary gear set, bearings, and housing — these three together account for over 70% of total cost. Grease is priced by the gram. A dexterous hand planetary reducer typically uses less than 0.5g of grease — material cost per unit may be less than 0.5 RMB.
This magnitude means optimizing grease procurement price contributes within error range regardless.
But this does not mean grease can be chosen casually.
Planetary reducer working state is typical: high-frequency direction reversal, low-to-medium load, sealed maintenance-free. Each time the dexterous hand grasps an object or adjusts posture, the planetary gear load direction switches once, and friction between tooth surface micro-protrusions never stops. If you choose a grease with excessively high oil separation rate, base oil will slowly seep out of the thickener, concentrate at the bottom of the reducer chamber, and the tooth surface is actually in boundary lubrication or even dry friction state. Early on, abnormalities may not be audible, but after hundreds of hours, pitting appears on the tooth surface. Micro-cracks extend along the tooth root. The reducer at best develops increased noise, at worst suffers tooth breakage. Repair, replacement, recall — this set of after-sales costs is the real profit-eating hidden killer.
Before Batch Shipment, Grease Selection Must Answer Three Questions
Entering batch shipment stage, grease selection logic changes. During prototype stage, you can不计成本 select the highest parameter one — usage is small and problem exposure cycle is long anyway. But after batch production, every unit cost, every batch consistency, and every verification cycle must be recalculated.
Specifically, engineers at this stage must answer three questions:
1. Is it sufficient?
Dexterous hand planetary reducer working condition threshold is not high. Base oil needs appropriate viscosity with stable viscosity-temperature characteristic — not so thick it freezes at minus twenty degrees, not so thin it softens excessively when joints heat up to sixty or seventy degrees. In the additive system, extreme pressure anti-wear agent is necessary — planetary gear instantaneous pressure at the contact zone can reach hundreds of MPa. Without sufficient extreme pressure protection, tooth surface will experience adhesive wear directly.
Fluorinated oil PTFE grease formulation approach: using perfluoroether oil as base oil, combined with PTFE solid lubricant and sulfur-phosphorus extreme pressure agent, forms a stable protective film under boundary lubrication state, withstanding high-frequency reversal impact loads.
2. Can it be stable?
This “stability” refers to batch consistency. Oil separation rate, evaporation loss, cone penetration attenuation rate, and wear scar diameter — fluctuation range of these indicators between batches directly determines the reducer life离散程度. The smaller the batch, the easier this problem is to hide. The larger the batch, the harder the discrete problem is to explain to customers.
Before batch shipment, whether the grease supplier has sufficient batch quality control data is more important than the product parameters themselves.
3. Is it worth it?
The “worth it” question is harder than the first two. Grease unit price difference is at most a few RMB matter. But once wrong, you need to re-run bench verification, change BOM, and re-run reliability testing — time cost far exceeds the material price difference. Grease verification cycle is typically 3 to 6 months. During this period, the entire machine schedule is locked. For still rapidly iterating dexterous hands, a few months’ time window is worth far more than a few thousand RMB difference in grease cost.
“Just Right” Is Not Mediocrity — It Is Precise Positioning
Grease selection logic during batch shipment stage is essentially “just right”: not selecting the highest parameter in the data sheet, but selecting the one that刚好卡住工况下限, has the most stable batches, has the most verified data, and has the most reasonable cost.
Three key indicators, explained in one sentence each:
Oil separation rate: Grease in the reducer will be used for years. Excessively high oil separation causes base oil to slowly escape, tooth surface quietly degrades from lubricated state. So keep the 100°C/24h oil separation rate below 5% — leave enough margin.
Anti-fretting wear: During dexterous hand operation, joints are always in micro-vibration. Tooth surface micro-protrusions rub repeatedly, generating abrasive debris that oxidizes into abrasive oxides, gradually eating away tooth surface. Fluorinated oil PTFE grease contains solid lubricant, forming a soft cushion under boundary lubrication state, slowing this wear.
Wide-temperature stability: Working temperature ranges from minus twenty to plus seventy degrees. Base oil viscosity change amplitude with temperature determines whether the lubricating film is thick enough. Fluorinated oil viscosity-temperature characteristics are more stable across wide temperature ranges — this is the key reason it adapts to dexterous hand working conditions.
Closing
Ruiyan priced the dexterous hand at 9,999 RMB. Grease is not the lead role behind this — but it determines whether batch products can run stably at the customer end without creating trouble for the after-sales service system.
When selecting, chase high parameters or meet the threshold? The answer is clear: meet the threshold, select the batch-most-stable one, and save the verification cycle for what truly needs iteration.
Currently there are fluorinated oil PTFE greases on the market specifically designed for dexterous hand working conditions, optimized for oil separation rate, extreme pressure, and wide temperature range — such as X500 (VNOVO), which can serve as a selection reference.
Search “VNOVO” or visit our website for more information.
