Two worlds of machine kinematics

Two worlds of machine kinematics

Choosing a polisher is not about brand or color. Pad kinematics — how the disc actually moves on paint — determines how much heat builds at a point, what marks remain, and how much margin you have for error.

Rotary — forced circular motion

A rotary machine drives the spindle through a geared head. The pad spins on one axis only, forced rotation; rim speed is always highest at the edge. Typical heavy-correction range is up to 1600 RPM.

What that means physically:

• 100% of torque goes into one vector. No dispersion.
• Heat concentrates at the contact point — pause for a moment and local temperature spikes.
• Abrasive trails are parallel circles following the rotation axis.

Holograms — why they form

Parallel micro-grooves in clear coat act as an optical diffraction grating. Under a strong point source (sun, LED inspection lamp), rays diffract at groove edges and create spatial spirals that seem to float above the surface. They “move” as the observer moves — hence the name.

When rotary makes sense

• Deep defects — sanding after P1000, heavy oxidation, marine gelcoat.
• Hard clear coats (BMW, Audi, Mercedes) where a DA cannot deliver enough cut.
• Wool pad + A50 — devastating combo for the hardest correction.

Rotary work demands deep experience and a paint thickness gauge. It belongs in a certified studio.

Dual Action (DA / orbital) — two axes

A DA polisher combines two motions: the pad spins freely (not forced) and orbits eccentrically around the main axis. Professional units such as FEYNMACH V3 DA run 3400–4000 OPM with 15–21 mm throw.

What that means physically:

• Pad motion on paint is random orbit — trails cross at varying angles.
• Heat spreads over a larger area. Point burn-through is rare.
• Holograms cannot form by definition — there is no parallel substrate for light diffraction.

“Stall and orbit” — the one DA scenario where burn-through still happens

A DA is thermodynamically cooler but not foolproof. If you press hard enough to stop free pad rotation, the machine only orbits on a small patch. Pressure + orbit frequency + static hot spot = over minutes you can exceed the chemical threshold of the film, especially on edges.

When DA is the clear choice

• All DIY correction — burn risk orders of magnitude lower than rotary.
• Finishing phase on every paint type — rotary trails must be finished on DA to remove holograms.
• Soft clears (Honda, Fiat, Alfa) — shorter, cooler cycles.
• Complex curves and edges — compact tools like DA MINI 75 mm with short throw.

Comparison table

Microfiber on DA — why it changed the game

The old rule “DA cannot do heavy correction” collapsed with microfiber pads such as URO-Fiber. Millions of split fibers act as individual cutting edges — paired with A50, a DA can tackle defects that once required rotary + wool.

The trade-off: higher friction, higher heat, faster pad loading. Microfiber demands brushing / air purge during the job.

Key takeaways

• Rotary = fastest cut, highest risk, highest skill demand.
• DA = balanced “forgiving / handles 90% / no holograms.”
• Rotary holograms always need a DA finish with A1000 — not optional.
• Microfiber + A50 on DA today reaches results that once required rotary only.

Further reading

• Correction triangle: pressure × RPM × time
• Polishing pads: foam, microfiber, wool
• Correction protocol: 3 phases