Application of CNC Technology in CNC Tool Grinders

Older machines used a template or a cam to trace the relief behind the cutting edge. Changing a helix angle meant changing a cam, and a new design could take hours of setup before the first part was ground. CNC control replaced that mechanical tracing with interpolated axes, so the relief is generated from the part program rather than copied from a master.

The control drives at least five axes: two linear slides, a workhead that rotates the tool, and two wheel-head swivels. A typical setup keeps the grinding wheel at a fixed contact point and moves the tool through the helix. Flute depth, rake angle and clearance are all numbers in the program. Edit a value and the next tool comes off the machine with the new geometry.

This is why regrinding and small-batch tool production fit the process so well. A batch of 20 end mills in 6 mm 4-flute geometry can run, then the cell switches to a 10 mm 3-flute rougher without a fixture change. Setup is a program load and a wheel dress.

• 1
  Axes that matterWorkhead rotation plus wheel-head swivel set helix and rake.
• 2
  Program-driven geometryFlute depth and clearance are values, not cams.
• 3
  Fast changeoverNew diameter or flute count is a program edit.

The hardest part of grinding is that the wheel is a cutting tool that shrinks. Every dress removes abrasive and changes the effective diameter. If the control does not know the new size, the flank behind the edge drifts and the tool cuts oversize. Modern machines touch off the wheel against a probe or a reference block after each dress, and the control writes the offset into the program.

In-process gauging goes further. The workhead indexes the tool to a measuring station, checks diameter or runout, and feeds the deviation back to the next pass. On a batch of 0.5–25 mm cutters this keeps edge position inside ±0.005 mm across the run. The operator sets the target and the control closes the loop.

Wheel choice follows the same logic. Diamond wheels for carbide, CBN for high-speed steel, and a finer grit when edge quality matters more than stock removal. A 400 grit wheel leaves a sharper edge but cuts slower and needs more frequent dressing. That trade is a process decision, not a machine limitation.

Use a tool grinder when the part is a cutting edge: end mills, drills, reamers, step tools, form tools, router bits. The geometry is defined by angles and helices, and the machine is built to index the tool and follow that helix. Edge quality is the payoff, and Ra 0.2–0.8 μm on the flank is realistic on carbide.

Do not send a bracket, a housing or a manifold to a tool grinder. Those parts need a machining center with a large work envelope, and the grinder cannot hold them. GreatLight runs 127 high-precision CNC machines, including 16 simultaneous 5-axis centers and 16 mill-turn centers, with a 4,000 mm maximum processing size. Cutting tools and prismatic parts are different jobs.

There is a middle case too. A form tool or a special step drill can be ground on a tool grinder and then used to cut a production part on a mill or lathe. When the tool geometry is the critical feature, controlling it at the grinder is cheaper than fighting it at the spindle.

• 1
  Good fitEnd mills, drills, reamers, form tools, step tools.
• 2
  Poor fitLarge housings and brackets that need a 5-axis envelope.
• 3
  Mixed caseSpecial form tools ground first, then used to cut parts.

Batch consistency comes from three things: a dressed wheel, a known tool position, and a control that compensates between parts. Skip any one and the last tool in the batch will not match the first. On a 500-piece drill run, wheel wear alone can move the diameter by more than 0.01 mm if nothing compensates.

GreatLight inspects 100% of parts before shipment, with raw material checks, in-process monitoring and a final inspection, and reports on request. Certifications include ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. Those systems matter when a cutting tool goes into an aerospace or medical part, because the tool geometry shows up in the finished component.

For tooling that supports our own machining, we grind and recondition in-house where the geometry is simple, and buy specialty tooling where it is not. The decision is usually cost per edge, not machine capability.