By the CNL Edgeworks technical team · Orange, CA
The three common approaches
Hand finishing — scraping, sanding through grits and buffing — works for one-offs but depends entirely on the operator. It's slow, and it's hard to keep two edges looking the same.
Flame polishing is fast on a single edge, but heat introduces stress in the material. Stressed edges are more likely to craze later, especially if the part is glued or cleaned with solvents, and flame polishing doesn't make an edge flat or square.
Diamond edge polishing mills the edge flat and polishes it in one pass. A machine-held diamond cutter removes the saw marks, and a finishing cutter leaves the final surface. Because the machine controls depth, feed and angle, the hundredth part matches the first.
How diamond edge polishing works
On a machine such as the Bermaq AMI-C or Kuper Euracryl ABP 310, the part is clamped against a reference bar and the polishing head travels along the edge. The head carries several diamond tools — typically roughing or milling cutters followed by finishing cutters — turning at 6,000 to 12,000 rpm.
The milling cutters take off a small, controlled depth, usually a few thousandths of an inch per pass. The finishing cutter's geometry and sharpness decide the final surface: water-clear high gloss, gloss, a soft satin, or a flat, fine-matte surface for gluing.
Tilting heads let the same machine polish bevels. The AMI-C tilts automatically from -2° to +63°; the AM2-i tilts manually to +45°. Dedicated bevelers such as the Euracryl V30 and V20s Cube handle chamfers on smaller parts.
What affects the finish
Material: cast acrylic generally polishes to a clearer edge than extruded. Polycarbonate, PETG and SAN polish well with the right tooling but respond differently to speed and feed.
Tool condition: a dull or out-of-balance diamond tool shows up as cloudy edges, chatter marks or streaks. Keeping tools sharp is the single biggest factor in a consistent finish.
Feed rate and depth: feeding too fast or cutting too deep for the material and thickness reduces clarity. Machines with a parameter library, like the Bermaq control, store proven settings by material and thickness.
Rigidity: vibration shows up on the edge. That's why production machines use heavy frames — the ABP 310's core is technical concrete that absorbs up to 95% of vibration.
Choosing a finish
High gloss is for visible, transparent edges on displays, signage and awards. Satin and translucent finishes hide minor marks and suit frosted or backlit designs. A glue surface is intentionally flat and fine-matte so solvent and UV adhesives bond cleanly without bubbles.
Changing finish is usually a tooling change, not a new machine. Our edge finishes page shows which Euracryl ES DIA Replace cutters produce each surface.
When a machine makes sense
If edge finishing is a bottleneck, if your edges vary between operators, or if you're paying for rework on stressed or crazed parts, a diamond edge polisher usually pays for itself in labor. Start with your longest part, thickest material, bevel requirement and weekly volume — those four numbers narrow the choice quickly.
We run these machines in production at our Orange, California shop. The fastest way to know what your edge will look like is to send us material and let us polish it.