Effect Of Hardness Tolerance Of Wear-Resistant Polyurethane Products On Machining: Polyurethane Sheets And Rods

Problems encountered during machining when the hardness tolerance range is too large.

1. Poor surface quality (roughness, waviness, orange peel)

· In areas with high hardness, cutting resistance is high, and the tool tends to "skip over"; in areas with low hardness, the material is easily "torn" rather than cut.

· This results in uneven tool marks, waviness, or surface irregularities, making it difficult to achieve the required surface finish.

2. Loss of dimensional accuracy (out-of-roundness, straightness deviation)

· When turning outer diameters or inner holes, hardness variations cause uneven deformation of the workpiece under clamping or cutting forces.

· After the fixture is released, inconsistent elastic recovery leads to roundness errors, taper, or barrel-shaped profiles (if the ends are hard and the middle is soft, the middle bulges; the opposite causes a concave shape).

3. Chipping and edge fragmentation

· When local hardness is too high, the material becomes brittle, and chipping or small flakes are prone to occur at the tool entry/exit edges, potentially leading to scrapping of the workpiece in severe cases.

4. Delamination and tearing

· When local areas are too soft, the material has excessive toughness and poor shear resistance.

· Tensile tearing, delamination, or rolled-up burrs are likely to occur at milled edges or drill exits, preventing the formation of a clean contour.

5. Severe heat generation during machining, even scorching/melting

· The friction coefficient varies greatly between hard and soft alternating areas, causing localized heat buildup between the tool and workpiece.

· Low-hardness areas tend to soften, stick, form filaments, or even locally melt and scorch; high-hardness areas may experience surface oxidation and discoloration due to high temperatures generated by hard particle friction.

6. Abnormal tool wear (chipping, uneven wear)

· Hard areas act like "abrasive particles" accelerating tool wear, while soft areas tend to stick to the tool, forming built-up edges.

· The cutting edge exhibits uneven chipping or localized excessive wear, significantly shortening tool life.

7. Clamping deformation and springback leading to scrap

· When clamped with a three-jaw chuck, point contact stress in hard areas may cause cracking, while soft areas become compressed and dented.

· After machining and release, the soft areas spring back and protrude while the hard areas remain unchanged, resulting in out-of-tolerance finished dimensions (especially for thin-walled or ring-shaped parts).