What a zero-point system is, and what it is not
A zero-point system is a clamping interface: a base plate permanently mounted on the machine table, with one or more repeatable clamping modules, each of which pulls a pull-stud-equipped sub-plate down and locates it in X, Y and Z simultaneously. Release and clamp are powered by hydraulic pressure or, on some designs, by spring force with hydraulic release.
It is not a fixture. It is the thing a fixture bolts to. This distinction is where most purchase decisions go wrong, because the system is usually presented as an alternative to dedicated fixtures when it is in fact a foundation that dedicated fixtures sit on — and the fixtures still have to be designed and built.
The changeover arithmetic
The standard sales case is straightforward: a dedicated fixture takes 25 to 45 minutes to swap and re-zero; a zero-point system takes 1 to 2 minutes. On a machine billed at 180 CNY per hour, saving 30 minutes per changeover is worth 90 CNY of machine time.
At six changeovers a week, 48 weeks a year, that is 288 changeovers and roughly 25,900 CNY a year. Against a four-module base plate at 60,000–90,000 CNY plus a sub-plate for each of ten jobs at 5,000–10,000 CNY, the total is 110,000–190,000 CNY, and the simple payback is four to seven years. That is not a business case; it is a wish.
At twenty changeovers a week, the same arithmetic gives 86,300 CNY a year of released machine time, and payback lands at 15 to 24 months, before counting the second and third effects below. That is a business case.
The three effects that change the answer
Effect one: engineering capacity. With a zero-point base, a new job can go onto the machine with a sub-plate rather than a full dedicated fixture. A sub-plate is 600–1,500 USD and two to three weeks; a dedicated hydraulic fixture is 7,000 USD and six weeks. If you introduce eight new jobs a year, the base plate has paid for itself in avoided fixture spend before a single changeover is counted.
Effect two: set-up error. A dedicated fixture re-installed by hand carries a real risk of being clamped on a chip or indexed one slot off. The failure is silent until the part is measured. Zero-point modules are self-cleaning to a degree and, more importantly, give a positive confirmation that the pallet is seated. On tight-tolerance work this alone justifies the system.
Effect three: pallet pooling and unattended running. A zero-point interface is what makes a pallet pool practical. If the system is the enabler for two extra unattended hours a night, the capacity value dwarfs the changeover saving and the decision is really about lights-out machining, not about workholding.
Repeatability: read the number carefully
Zero-point systems are typically specified at 0.005 mm repeatability at the pallet interface. Buyers read that as "my part repeats to 0.005 mm". It does not. The chain is: machine positioning error, plus base plate mounting error, plus module repeatability, plus sub-plate manufacturing error, plus the fixture's own locating error, plus part-to-fixture seating. In practice a well-built chain lands at 0.015–0.030 mm on the part, and the module is only one contributor.
Where the system genuinely helps is repeatability between set-ups — the same job on Tuesday as on Monday — because it removes operator judgement from the re-zero step. Where it does not help is the absolute accuracy of the fixture itself, which is still a jig-boring problem.
Holding force and services
| Module size | Typical holding force | Pull stud | Typical base plate price (USD, FOB China) |
|---|---|---|---|
| Small, 100 mm square | 6–12 kN | M12 | 2,800 – 4,500 per module position |
| Medium, 138 mm square | 15–25 kN | M16 | 3,500 – 6,000 per module position |
| Large, 176 mm square | 25–40 kN | M20 | 5,000 – 9,000 per module position |
Two service points get skipped in planning. Hydraulic systems need 60–100 bar supply and clean oil; a dirty circuit will eventually stick a module, and a stuck module on a loaded pallet is a disassembly job, not an adjustment. Pneumatic-release designs need dry air at 6 bar and a reservoir if the release has to be held against a pressure loss. Neither is difficult, but both need to exist before the plate is bolted down.
When the system is not the right purchase
- One part, one machine, one set-up. Nothing to change over, nothing to gain.
- Fewer than six changeovers a week. The released machine time will not cover the base plate inside a reasonable horizon.
- Very heavy parts. Above roughly 400 kg the pallet handling problem dominates, and the ergonomics of a crane-loaded pallet usually cost more than the changeover saved.
- No engineering resource to build sub-plates. The system converts fixture work into sub-plate work. If nobody owns that work, the base plate becomes an expensive table.
The migration path we recommend
Do not buy a system and a set of new fixtures at the same time. Liuzhou Dongben Machinery Equipment Co., Ltd. recommends three stages. Stage one: install a single-module base plate on the machine that changes over most often, and retrofit the two highest-running existing fixtures with pull-stud sub-plates. Stage two: add modules as new jobs arrive, using the sub-plate route rather than dedicated fixtures. Stage three: only when changeover frequency has been measured for a quarter, invest in a multi-module plate or a pallet pool.
That sequence costs less in the first year, produces real changeover data before the big commitment, and leaves the shop with fixtures that are useful regardless of which system ends up standard.