Deinecke CNC machines: how they cut metal and where they stop

• 1
  What actually happens inside a CNC machine
• 2
  Axis count decides which parts are possible
• 3
  Where tolerance comes from and when it drifts
• 4
  Fixturing is where most accuracy is lost
• 5
  What drives the price of a machined part
• 6
  How to check a machined part before it ships
• 7
  Which machine class fits which part

A CNC machine is a motion system with a cutting tool at the end of it. The controller reads G-code, converts each line into axis moves, and drives servo motors that position the tool relative to the workpiece. Everything else on the machine exists to keep that relationship stable: the bed, the spindle, the ballscrews, the linear guides, the coolant.

Removing metal is not the hard part. Holding position while you remove it is. Cutting force pushes the tool away from the part, heat grows the spindle, and chips carry friction into the cut. A machine built for tight work controls those three variables rather than chasing spindle speed alone.

The practical result is repeatability. A machine that can hold ±0.005 mm on one part is useful. A machine that holds it on part 500, after the spindle has warmed up, is what production actually needs. That is why thermal compensation and rigid castings matter more than a spec sheet number.

For Dutch manufacturers working in aerospace, medical and high-mix industrial work, the deciding question is rarely machine brand. It is whether the process window of a given machine covers the tolerance, finish and geometry of the part in front of you.

Three-axis machining moves the tool in X, Y and Z while the part stays still. It handles flat faces, pockets, slots and drilled holes well. If a feature can be reached from one direction with a straight tool, three axes are the cheapest way to make it.

Adding a fourth axis rotates the part around one axis, usually A or B. This lets you machine four sides in one setup instead of four. On a bracket with holes on two faces, that removes two fixturing steps and the positional error that comes with each one.

Five-axis machining adds a second rotary axis so the tool can tilt. The payoff is not only access to angled faces. It is that a shorter, stiffer tool can reach deep features because the holder tilts away from the wall. Shorter tools deflect less, so surface finish and tool life both improve.

The limit is stiffness. Every rotary axis adds a compliant joint. A five-axis machine cutting a heavy roughing pass is less rigid than a three-axis machine of the same mass. That is why the typical workflow is rough on a rigid machine, finish on the five-axis center.

Tolerance is a stack, not a single number. Machine positioning, tool wear, fixture rigidity, material condition and thermal growth each contribute. A machine rated at ±0.005 mm delivers that only when the other four terms are small.

Aluminium 6061 and 7075 cut clean and hold size well because they conduct heat away from the cut. Stainless 316 and 17-4PH work-harden, so a dull tool pushes the cut instead of shearing it, and the wall springs back after the pass. Titanium TC4 (Ti-6Al-4V) is worse: low thermal conductivity keeps heat in the tool edge.

Thin walls are the usual failure point. A 1 mm wall on a 40 mm pocket will move as the cutter passes, then relax. Rough, stress-relieve, then finish with light passes. Measure the wall before the final pass, not after.

Surface finish follows the same logic. Ra 0.8–1.6 μm is a normal machined finish for most engineering parts. Ra 0.2–0.8 μm needs a finer stepover, a sharper tool and often a separate finishing pass. Ask for it only where a seal, bearing or optical surface requires it.

A machine holds tolerance against the fixture, not against the drawing. If the vise lifts a thin plate by 0.05 mm, every hole in that plate is off by 0.05 mm in Z. No controller setting fixes that.

Good practice is to keep the number of setups low and the datums obvious. Machine all critical features from one face when geometry allows it. Where a flip is unavoidable, cut a reference feature first so the second setup can be probed and offset.

Soft jaws machined in place beat generic vise jaws for repeat work. For a batch of 200 parts, the jaw pocket is cut once to the part profile, and every part then sits at the same height. That single change often does more for consistency than a tighter machine spec.

Vacuum plates suit thin flat parts where clamping would distort them. They trade holding force for even pressure. If the part sees a heavy cut, vacuum alone will not hold it.

Cycle time is the visible cost. Setup, programming and inspection are the hidden ones. A part with a 12-minute cycle but three setups and a custom fixture can cost more than a part with a 40-minute cycle cut in one setup.

Material is the second lever. A 7075 aluminium bracket machines fast and holds a good finish. The same bracket in 17-4PH stainless takes longer, wears tools faster and may need stress relief between roughing and finishing. The geometry is identical; the process is not.

Batch size changes the method. One prototype justifies a five-axis setup that avoids fixtures. A 10,000-part run justifies a dedicated fixture and a shorter cycle, even if the fixture costs more than the first few parts.

Lead time follows the same split. Programming and first-article inspection dominate the first part. Once the process is proven, parts ship in 3–5 days and the per-part cost drops as the run lengthens.

Dimensional checks come first. Calipers and micrometers cover most features. A CMM covers position tolerance, true position and profile of a surface, which calipers cannot resolve. For a first article, ask for the CMM report with the datum scheme marked.

Material and finish checks come second. Hardness, conductivity and alloy verification catch wrong-material errors before they reach assembly. Anodize thickness and coating adhesion matter where the part slides or seals.

Surface finish is measured, not eyeballed. A profilometer reading in Ra tells you whether the finishing pass did its job. On a sealing face, a visual check is not enough.

Ask for reports on the features that carry function, not on every dimension. A 60-page report hides the three numbers that matter. Raw material certificates, in-process records and final inspection notes are the useful set.