Every term on this page appears somewhere in our machine specifications. Each entry opens with a one-line definition, then explains why the term matters when you are choosing between two machines. No term is used here before it is defined.
If a specification cannot be explained in one sentence, it is usually being used to hide something.
The short version. Full explanations follow below.
| Term | One-line definition |
|---|---|
| CNC | Computer Numerical Control — the controller that turns a program into coordinated axis motion. |
| Five-axis | Simultaneous motion along five axes, so a complex curved surface can be machined in one setup. |
| Gantry | A bridge-type frame spanning the table, so very large parts can be machined without a very large column. |
| Twin-drive rotary table | A rotary table driven from both sides at once, to remove torsional wind-up and hold angular accuracy. |
| Spindle | The rotating assembly that holds and drives the cutting tool; its taper, speed and torque set what you can cut. |
| Linear guide | The rail-and-block system an axis slides on; it decides how straight, how smooth and how repeatable the motion is. |
| Rigidity | Resistance to deflection under cutting force, measured in force per unit of deflection, e.g. N/μm. |
| Positioning accuracy | How close the machine gets to the commanded coordinate — a measure of correctness. |
| Repeatability | How closely the machine returns to the same point over and over — a measure of consistency. |
| Twin-spindle | Two independent spindles on one base, so two parts are machined at once or a long part is split across both heads. |
| 4-axis swing-head | A spindle head that swivels on two axes to reach multi-angle features without re-clamping the part. |
| Long-stroke VMC | A vertical machining center with extended X travel (e.g. 2500 mm) and often twin spindles, for long parts. |
| RTCP | Rotary Tool Center Point — the controller math that keeps the tool tip fixed while the rotary axes move in 5-axis machining. |
| Mineral-cast bed | A polymer-concrete base with high damping, used where vibration absorption matters more than raw mass. |
| Turn-Mill composite | A lathe that also mills, drills and taps, so a shaft is finished in one clamping instead of several. |
CNC is the control system that reads a part program and converts it into coordinated, simultaneous motion of the machine axes and spindle.
Why it matters when you are choosing a machine. The control is the part of the machine your programmers and operators actually touch every day. Changing control platform means re-writing post-processors, re-training operators and living with a slower first six months. This is why we standardise on FANUC 0i-MF PLUS and Syntec across the GA- range — in most cases your existing team can move onto a new machine without starting again.
Five-axis means simultaneous controlled motion along five axes — the three linear axes X, Y and Z plus two rotary axes — so that a complex curved surface can be machined in a single setup.
Why it matters when you are choosing a machine. The value is rarely the surface itself; it is the setup count. A part that needs four three-axis setups collects four location errors and four blocks of handling time. Machined in one five-axis setup, it collects one. This is also why five-axis accuracy should always be quoted over full travel rather than in a favourable zone — ask which one you are being shown. On the GA-FA320 we state 0.01 mm positioning and 0.006 mm repeatability over full travel, as a contract value.
A gantry machine carries the spindle on a bridge that spans the table on two columns, rather than on a single column at the back of the machine.
Why it matters when you are choosing a machine. A bridge is supported at both ends, so it deflects far less than a cantilever of the same mass. That is what makes gantry construction the standard choice once parts get large — a 2,700 mm span of travel is simply not practical on a C-frame. It also means the load path is symmetrical, which helps thermal behaviour across a long working day.
A twin-drive rotary table is driven from both sides simultaneously, instead of being driven from one end and supported at the other.
Why it matters when you are choosing a machine. Driving from one side twists the table under load, and that torsional wind-up shows up directly as angular error on the part. Driving both sides in synchronisation cancels most of it. A related idea is direct drive: the GA-FA320 uses a fully direct-driven Φ320 cradle table, which removes gear backlash entirely rather than compensating for it in software — and unlike backlash compensation, it does not drift as the gears wear.
The spindle is the rotating assembly that holds and drives the cutting tool. Three figures describe it: the tool interface (taper), the maximum speed, and the power and torque it can deliver.
Why it matters when you are choosing a machine. Taper tells you what the machine is designed to cut. BT30 and BBT30 are light and fast, for small tools at high speed. BT40 is the general-purpose interface for most milling work. BT50 is a heavy interface for high torque. HSK is a dual-contact interface used where high speed and rigidity are needed together. A quick sanity check when comparing machines: high speed and high torque rarely arrive in the same spindle. Our GA-DV750 runs 30,000 rpm with 8.1 N·m of torque; our GA-UV1050 runs 10,000 rpm with 302 N·m of peak torque. Those are two different machines for two different jobs, not a better and a worse one.
A linear guide is the rail-and-block system that an axis slides along. It carries the load, constrains the direction of travel, and largely determines how smooth and how repeatable that travel is.
Why it matters when you are choosing a machine. Guides decide straightness, stiffness in the non-cutting directions, and how well the axis behaves at very small increments — which is what matters when a finishing pass is creeping along a contour. Guides also wear, which is why long-term accuracy depends on preload and lubrication as much as on the initial specification. Where an axis is driven directly by a linear motor with a linear scale for feedback, as on the GA-DV750, the position is measured at the axis itself rather than inferred from a rotating screw.
Rigidity is a machine’s resistance to deflection under cutting force, expressed as force per unit of deflection — for example N/μm, newtons per micrometre.
Why it matters when you are choosing a machine. Cutting force pushes the tool away from the workpiece. A rigid machine deflects less, so the cut stays where the program put it, and vibration is less likely to build into chatter. Rigidity comes from mass, from structural geometry and from the guide and spindle system. It is the reason a 17,000 kg machine such as the GA-UHD500 holds a finish through heavy roughing that a lighter machine cannot, and the reason we quote bed rigidity of ≥265 N/μm on the GA-UV1050. Rigidity is also the one specification that cannot be improved by a control upgrade after delivery.
Positioning accuracy is how close the machine actually gets to the coordinate it was told to move to. It is a measure of correctness.
Why it matters when you are choosing a machine. This is an error band, so smaller is better: 0.003 mm is tighter than 0.01 mm. Two questions are worth asking about any figure you are given. First, is it stated over full travel or over a partial length? Second, is it the brochure figure or the figure in the technical agreement? Those two are not always the same number, and the second one is the one you will be measured against at acceptance. Every accuracy figure on our model pages is labelled with its basis for exactly this reason.
Repeatability is how closely the machine returns to the same point when commanded there repeatedly. It is a measure of consistency rather than correctness.
Why it matters when you are choosing a machine. A machine can be consistently slightly wrong — good repeatability, poorer positioning accuracy — and that case is workable, because a consistent offset can be compensated. The reverse cannot. For batch production, repeatability is usually the figure that decides whether every part in the run is in tolerance. To put the numbers in context: the GA-DV750 holds 0.0024 mm as a contract value, which is roughly one thirtieth of the thickness of a human hair.
Two independent spindles share one base, so two identical parts are machined in parallel, or one long part is split across both heads.
Why it matters when you are choosing a machine. Throughput is the obvious win — two parts at once. The subtler win is on long parts: a 2500 mm X envelope can be covered by two 1700 mm zones without re-clamping. Gree uses twin spindles on the GA-MVD2560 (long-stroke VMC) and the GFD variants of the high-speed gantry range.
A spindle head that swivels on two axes, so it can approach a part from many angles and machine complex curved surfaces without re-clamping.
Why it matters when you are choosing a machine. Where a 5-axis machine reaches multi-angle positions through a rotary table, a swing-head reaches them through the head itself. That matters for very large parts — a trunnion table big enough to hold them would be impractical. The GA-GFU3755 is Gree's 4-axis swing-head gantry.
A vertical machining center with an extended X travel (Gree's GA-MVD2560 runs 2500 mm) and often a twin-spindle layout, built for long, multi-hole, thin-wall parts.
Why it matters when you are choosing a machine. Standard VMCs top out around 1500 mm of X travel. Once the part is longer than that — rails, beams, extrusions — you either re-clamp mid-part (collecting location errors) or move to a long-stroke machine. The long-stroke VMC closes the gap before you need a full gantry.
RTCP (Rotary Tool Center Point) is the controller calculation that keeps the cutting-tool tip fixed in space while the rotary axes rotate during 5-axis machining.
Why it matters when you are choosing a machine. Without RTCP, programming a 5-axis move means hand-computing where the tool tip ends up after the head and table rotate. With it, you program the tip and the controller resolves the axes. It is the difference between 5-axis being a daily production tool and a specialist chore — Gree's 5-axis models, including the GA-FA500, run RTCP.
A mineral-cast (polymer-concrete) machine bed, used where vibration absorption matters more than raw mass.
Why it matters when you are choosing a machine. Cast iron is stiff; mineral cast is damped. On a high-speed 5-axis finishing pass, damping kills the chatter that stiffness alone cannot. Gree uses a mineral-cast bed on the GA-FA500, aimed at impellers, molds and complex curved joints.
A lathe that also mills, drills and taps, so a shaft-shaped part is finished in one clamping instead of moving between a lathe and a machining center.
Why it matters when you are choosing a machine. Every extra setup is a handling step and a location error. A turn-mill composite collapses several setups into one, which is why Gree lists the GA-TMY6555 (with a Y axis) for shafts, discs and EV parts that need both turning and milling.
Every specification we publish carries its basis on the same row.
| Label | What it means |
|---|---|
| Verified per signed technical agreement | The figure is taken from the contract version of the technical agreement for that model. You can check it line by line against the agreement before you order, and it is the figure you will be measured against at acceptance. 22 of our 36 models are in this category. |
| Subject to final technical agreement | The figure is brochure-level data. It is given for reference and is not a contractual commitment. We mark it rather than mixing it in with contract values. |
| Source: GREE CNC official brochure | Company-level information such as patents, facilities or service coverage. A technical agreement governs machine specifications only — it never governs how many patents a company holds, so we cite the source instead. |
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