For most DACH and UK shops running Chinese CNC machines, the best spare parts strategy is a hybrid: keep a small two-bin stock of wear parts locally and buy high-value, low-failure parts on a written 48–72 hour air-freight agreement. The two pure choices—holding a large local stock or buying every part reactively—usually cost more than the hybrid.
This article compares two plausible strategies, gives a worked cost example, and ends with a decision rule you can use with your own downtime figures.
The Two Choices
Choice A: Local Safety Stock
You buy critical spare parts now and keep them on your shelf. The benefit is speed: a failed spindle or servo drive can often be replaced in one working day. The cost is carrying cost—capital tied up, storage, insurance, and the risk that a part becomes obsolete before you use it.
Carrying cost is the annual cost of holding inventory. A typical range is 18–28% of the inventory value per year.
Choice B: Reactive Air Freight
You hold only cheap consumables. When a part fails, you order it from the Gree central warehouse or a European depot and ship it by express air freight. The benefit is almost no inventory cost. The cost is longer downtime: typically 3–5 working days door-to-door from China to DACH or the UK, plus customs clearance.
The table below summarises the two choices.
Factor
A: Local safety stock
B: Reactive air freight
Capital tied up
High, illustrative €12,000–€25,000 for 5 VMCs
Low, under €1,000 for consumables
Repair downtime after failure
1 working day
4–6 working days
Annual carrying cost at 22%
€2,600–€5,500
€0
Best when
High downtime cost, several identical machines, long supplier lead time
Low downtime cost, limited cash, machine under warranty
All figures are illustrative typical ranges. Confirm part prices and lead times against the official Gree spare parts catalogue.
Worked Example: Five VMCs Over Three Years
This example uses a shop with five three-axis vertical machining centres (VMCs). A VMC is a milling machine with a vertical spindle. Unscheduled downtime means the machine is stopped and not earning margin.
Assumptions:
Unscheduled downtime cost: €180 per hour. This is a typical industry range of €100–€300 for a job shop. Use your own gross margin per hour, not revenue.
Carrying cost: 22% per year. Typical range 18–28%.
Air freight cost per critical shipment: €820 for a 40 kg crate door-to-door China to DACH or UK. Typical only. Confirm current rates.
Critical failure rate: 0.5 events per year across all five machines. This is an illustrative planning figure. Track your own failure history.
Cost over 3 years
A: Local stock
B: Air freight
High-value inventory value
€16,000
€0
Carrying cost
€10,560
€0
Expected critical repairs
1.5
1.5
Downtime per repair
1 day = €1,440
5 days = €7,200
Total downtime cost
€2,160
€10,800
Logistics per repair
€0
€820, total €1,230
Total 3-year cost
€12,720
€12,030
The numbers are close. That is normal. The break-even point is the useful result.
Choice A avoids 4 extra days of downtime per event, or 32 hours. At €180 per hour, each avoided event saves €5,760. But Choice A costs €3,520 per year in carrying cost.
Break-even downtime cost:
Annual carrying cost: €3,520
Extra downtime avoided per year: 0.5 failures × 32 hours = 16 hours
Break-even = €3,520 ÷ 16 = €220 per hour
If your measured downtime cost is above €220 per hour, the local stock wins. If it is below, air freight is cheaper. This is the core decision rule.
What Actually Fails and What to Stock
A two-bin system is a simple inventory method. You keep two bins of each consumable. When the first bin is empty, you reorder. The second bin covers the lead time until the new parts arrive.
Low-cost, high-frequency parts to hold locally:
Way wipers and seals
Coolant, hydraulic, and air filters
Limit switches and proximity sensors
Drive belts
Tool gripper springs or fingers, if your machine uses them
Fuses, contactors, and relays
CNC backup batteries
These parts are cheap, fail often, and stop the machine. Holding them is almost always right.
High-value, low-frequency parts to consider for air freight unless your break-even says otherwise:
Spindle cartridge: illustrative €4,000–€8,000 for a typical 800 mm VMC. A spindle is the rotating shaft that holds the cutting tool.
Axis servo drive: illustrative €1,500–€3,500. A servo drive is the electronic unit that powers and controls an axis or spindle motor.
Ball screw support bearings: illustrative €300–€800. A ball screw is a precision threaded shaft that converts rotary motion into linear axis movement.
Tool changer cylinder or cam box: illustrative €800–€2,500.
CNC control PC or screen unit: illustrative €1,000–€3,000.
Power supply unit: illustrative €400–€1,200.
These prices are illustrative only. Confirm current prices and part numbers against the official Gree spare parts catalogue.
Step-by-Step Method
Measure your downtime cost. Use gross margin lost per hour. Include overtime, late-delivery penalties, and idle labour. A typical job shop loses €100–€300 per hour.
Build a failure history. Log every unplanned stop for 12 months: part, machine, downtime hours, repair cost. If you have no history, use the Gree recommended spare parts list for your model and mark each part high, medium, or low risk.
Classify parts. A: cheap and frequent, stock locally. B: expensive and rare, use air freight unless break-even says stock. C: very rare or custom, buy only after failure and accept a longer wait or plan a rebuild.
Set stock levels. For class A parts, use two-bin or min/max. Set minimum stock equal to consumption during lead time plus safety stock. For China air freight, use 7–10 days cover because door-to-door lead time is 3–5 working days plus customs.
Write an air-freight agreement. Include part list, prices, lead time from ex-works to your door, packaging, and after-hours ordering. Use Incoterms DAP (Delivered at Place) as a baseline. DAP means the seller pays transport to your named site, and you handle import clearance, VAT, and duty. In the UK after Brexit, use a customs broker or ask for DDP (Delivered Duty Paid), where the seller handles import duties and VAT.
Review quarterly. Adjust based on real failures. If a high-value part fails twice in 12 months, move it to local stock.
When Neither Choice Is Right
Be honest about limits.
If your machines are older than about 10 years, some OEM spares may be obsolete. A local stock of OEM parts may not be possible. Then choose a local spindle repair shop or a proven aftermarket supplier.
If you run 24/7 production, downtime cost is high. The break-even rule will almost always favour local stock for high-value parts.
If the machine is under warranty, follow the warranty rules. Installing non-OEM parts can void it.
Do not buy safety-critical parts such as spindles, drawbars, tool grippers, or brakes from unknown grey-market sources. A failed spindle from a copied drawing costs far more than the saved purchase price.
Customs and VAT in DACH and the UK can add 1–2 days to air freight. Add this buffer when you calculate lead time.
Decision Rule
Use local stock for a part if:
(Failure rate per year × extra downtime hours avoided × hourly downtime cost) is greater than the annual carrying cost of holding that part.
Otherwise, use air freight.
For cheap consumables, always stock. For each expensive part, run the numbers. Re-evaluate every quarter.
What to Check Before You Buy
Confirm exact part numbers from the official Gree spare parts catalogue using your machine serial number.
Ask for the current price, availability, and lead time ex-works for each critical part.
Check whether the part is covered by a warranty or an exchange/repair programme.
Get a written air-freight rate per kilogramme and a minimum charge for a typical 40 kg crate.
Clarify Incoterms: DAP or DDP, and who pays customs, VAT, and import duty in DACH or the UK.
Confirm packaging requirements for sensitive parts such as spindles, servo drives, and ball screws.
For spindles and ball screws, ask for installation instructions, run-in procedure, and required balancing.
Keep a repair log after every failure. Record which parts worked and which did not. Use that data to update your stock levels.