What Parts Are Made Up Of The CNC Informatique System

• 1
  The CNC informatique system is four subsystems, not one box
• 2
  How a block of G-code becomes a finished surface
• 3
  Which parts sit on the machine and which sit in the cabinet
• 4
  Software layers you actually interact with
• 5
  What the control cannot fix
• 6
  Where the informatique layer changes the part you receive
• 7
  Which informatique parts matter for your job

People say "the control" and point at the pendant. The CNC informatique system is wider than that. It is the whole chain that turns a CAM file into a moving axis: the numerical control unit, the servo drives and motors, the feedback devices, and the machine logic that handles everything the part program does not mention.

The numerical control unit is the part that reads G-code and interpolates. It plans the path, applies cutter compensation, and hands a velocity command to each axis every few milliseconds. On a simultaneous 5-axis machine it also solves the kinematic transform between tool tip and rotary axes, which is why the control model matters more on a five-axis job than on a 3-axis one.

Servo drives and motors are the muscle. The drive takes a low-power command and delivers current to the motor. Drive tuning decides how fast an axis reacts, how much it overshoots, and how loudly it complains when a heavy cutter engages. A well-tuned drive holds position without ringing; a badly tuned one leaves chatter marks that no finishing pass will remove.

Feedback devices close the loop. Most machines use rotary encoders on the motor shaft; higher-grade machines add linear scales on the slide itself. The scale measures where the table actually is, not where the motor thinks it is, so it corrects for ballscrew pitch error and thermal growth. That difference shows up directly in your tolerance report.

Machine logic covers the rest: spindle orientation, tool changer sequencing, coolant and air blast, pallet handling, safety interlocks, probe routines and alarm handling. Two machines with the same control unit and the same drives can behave very differently because of this layer.

The chain runs one way in time and it is worth walking it once. The CAM post-processor writes a program for a specific control. The control reads a block, checks it against the active offsets, and computes the next position. It then splits that move into small increments the servo loop can follow.

Each increment becomes a position command. The drive compares it with the feedback signal and adjusts motor current. On a 3-axis mill running at 4,000 mm/min in aluminium, that correction cycle repeats hundreds of times per second. If the loop cannot keep up, the tool lags behind the programmed path.

Lag is not a fault by itself. Modern controls deliberately allow a small following error and trade it for smooth motion, because a machine that chases every micron instantly will vibrate and leave a worse surface. This is why a part can measure in tolerance on a CMM and still show witness marks on a blend.

Look-ahead is the part engineers rarely think about. The control reads ahead dozens or hundreds of blocks, works out where the tool must slow down for a corner, and plans acceleration limits. Short look-ahead on a control means sharp internal corners get rounded, and the rounding is worse on hard materials like 17-4PH or Inconel than on 6061.

The practical lesson: when a feature comes out wrong, first check whether the error is repeatable. Repeatable error points at the control, offsets or CAM. Non-repeatable error points at the mechanical side, the feedback, or the fixture.

The cabinet holds the control unit, the drives, the power supplies, the I/O modules and the safety relay. The machine holds the motors, the encoders or scales, the spindle drive, the limit and home switches, the tool setter, and the operator station. Cable routing between the two is a real part of the system, not an afterthought.

Encoder and scale signals are low-voltage and easily disturbed. In a shop with several machines on one supply, a poorly shielded feedback cable produces intermittent position alarms that come and go with the load on the neighboring machine. The symptom looks like a control fault but the fix is usually shielding and grounding.

Spindle drives are usually separate from the axis drives. On a mill-turn center the spindle must also act as a C-axis for milling, which means the spindle drive has to hold angular position under load. That capability is what allows one setup to turn an OD and then mill a flat on the same part without re-chucking.

I/O modules connect the logic layer to the physical world: solenoid valves, pressure switches, door locks and chip conveyors. When a machine stops mid-cycle for no clear reason, a pressure switch or a chip jam is a more common cause than the control itself.

Coolant and chip management belongs here too. On deep pockets in 7075 or PEEK, coolant delivery decides whether the tool survives. Through-spindle coolant is a machine option, and if the control runs high-pressure coolant, that is part of the informatique system configuration.

There are three layers. The machine control software runs the axes. The CAM system produces the toolpaths. The shop-floor layer moves files, offsets, inspection data and job status between them. Most quality problems trace back to a mismatch between the first two.

Post-processors are the usual culprit. A generic post that ignores the control's cycle definitions will produce long, safe, slow code. A correctly tuned post uses canned cycles, correct arc handling and the machine's own probing macros, so a part that took 40 minutes can come off in 25 with the same surface finish.

Offset management matters on production runs. Tool length and diameter offsets drift as tools wear. If the control holds offsets per program and the operator updates them by hand, a long run of 10,000+ parts will drift. If the control supports tool life management and automatic offset compensation, the run stays centered.

Inspection data is the third layer. When a CMM report feeds back into the offset table, the loop closes and the process corrects itself. At GreatLight every part is inspected before shipment, with raw material checks, in-process monitoring and a final inspection, and reports are available on request.

This is also where IT security sits. Programs, drawings and inspection files are the customer's intellectual property. GreatLight holds ISO 27001:2022 for information security, and uploads are kept secure and confidential, with an NDA available on request.

A good control cannot rescue a bad setup. If the fixture lets the part move under a 20 mm end mill, no amount of look-ahead will hold ±0.005 mm. Rigidity comes from the machine structure, the workholding and the tool, in that order, before the electronics enter the picture.

Thermal growth is the other boundary. A spindle running for hours gets longer; a ballscrew warms and changes pitch. Linear scales compensate for some of it, and a temperature-controlled shop reduces the rest. On a 4,000 mm part, thermal drift is often the largest single error term, larger than the control's interpolation error.

Surface finish has a limit set by geometry. Ra 0.2–0.8 μm is achievable with the right tool and finishing pass, but not on every feature. A deep narrow slot limits tool stiffness and coolant access, so Ra 1.6–3.2 μm may be the honest number for that feature even when the rest of the part is polished.

Hard materials shift the balance. Inconel and Ti-6Al-4V cut hotter and push back harder, so the control spends more time managing acceleration and the tool spends more time rubbing. Cycle times rise and tool life falls, and no control setting changes that physics.

The right question is not "how good is the control" but "is this process capable for this feature." That is what a DFM review answers.

On a 3-axis job with simple prismatic geometry, the control mostly affects cycle time and corner accuracy. A part with pockets, holes and a flat face will meet tolerance on almost any modern control if the machine is rigid and the offsets are right. Vertical 3-axis work up to 4,000 mm is routine here across 27 three-axis machines.

Four-axis work adds an indexer or a rotary table, typically Ø400 mm. The control now has to coordinate the rotary position with the linear axes and hold the part while it turns. Parts with features on four sides, like manifolds and housings, come off with fewer setups, which removes stacked tolerance from re-chucking.

Simultaneous 5-axis is where the control earns its cost. The kinematic transform, the rotary dynamics and the tool tip tracking all sit in the control. Engine parts, impellers, medical instruments and aerospace brackets that need undercut access or a continuous surface rely on this. GreatLight runs 16 simultaneous 5-axis machining centers and 16 mill-turn centers for exactly this class of work.

Mill-turn combines both. Turning, milling and drilling happen in one setup, so concentricity between a turned bore and a milled face is set by the machine, not by two fixtures. For hydraulic and engine hardware, that is often the difference between a functional part and a rejected one.

Prototypes and low-volume runs benefit most from the file-to-part loop. With no minimum order quantity, a single prototype and a 10,000+ part run go through the same control chain, so what proves out on the prototype stays valid in production.