PROBLEMS |
CAUSES |
SOLUTIONS |
| CHATTER Indicated when lines or grooves appear at regular intervals on machined surface |
Lack of rigidity | Check spindle & fixture rigidity |
| Excessive cutting force | Reduce feed rate, depth of cut or width of cut if excessive | |
| Use sharp edge inserts; avoid hone or T-land | ||
| Thin-walled part | Dampen part | |
| POOR
SURFACE FINISH A) Roughness |
Insert worn | Use more wear resistant coated grade |
| Built-up edge | Increase speed, use PVD coated inserts, use coolant | |
| High tooth | Correct improper preset. Set wiper | |
| Wiper insert set too high | .0005" to .002" above high insert | |
| B) Flatness | Deflection | Check for deflection of part, cutter or spindle |
| improper spindle tilt (milling machines) | Check spindle tilt - .0015" per foot is recommended | |
| Excessive cutting force | Use a more positive rake cutter | |
| Width of cut too large for cutter | Use a larger diameter cutter | |
| C) Waviness | Advance per revolution greater than width of flat of insert | Check for deflection of part, cutter or spindle |
| Deflection | Reduced feed rate | |
| PART BURRING | Insert worn | Use more wear resistant coated grade |
| Excessive insert edge prep | Reduce or avoid hone or T-land | |
| Improper angle of entry or exit of cutter | Change position of center of cutter over part | |
| Improper lead angle | Use larger lead angle; avoid 0° lead angle cutters | |
| Chip load too great or too small | Increase or decrease chip load | |
| WORKPIECE BREAKOUT | Improper geometry | Use larger lead angle; avoid 0° lead angle cutters |
| Use inserts with double facet corners | ||
| Improper angle of entry or exit of cutter | Change position of center of cutter over part | |
| POOR
INSERT LIFE (Use 10x magnifier to identify the following typical failure modes) Flank wear |
Excessive heat | Reduce speed. Increase chip load to carry away heat |
| Use coolant | ||
| Incorrect grade | Use a more wear resistant coated grade | |
Crater Wear |
Excessive heat | Use a more heat resistant coated grade (Al2O3 layer) |
| Reduce speed | ||
| Flush with coolant | ||
| Excessive cutting force | Reduce feed rate | |
Built-Up Edge |
Insufficient cutting temperature causes chip adherence to insert | Increase speed |
| Use coolant to aid lubricity | ||
| Use sharp edge inserts | ||
| Use grades with high lubricity surfaces (PVD coated grades, Cermet grades, polished carbide grades) | ||
Chipping |
Chatter | See above |
| Insufficient edge prep | Use hone or T-land | |
| Incorrect grade | Use tougher grade | |
| Built-up edge | Increase speed, use PVD coated grade, use coolant | |
| Excessive cutting force | Decrease feed per tooth | |
| Re-cutting chips | Use cutter with chip
gullets large enough for chip clearance. Use air blast or coolant to remove chips. |
|
Depth Of Cut Notching |
Scale part, high work hardening materials | Use larger lead angle; avoid 0° lead angle cutters |
| Use more wear resistant grade | ||
| Reduce feed per tooth | ||
| Reduce speed | ||
| Use T-land | ||
| Vary depth of cut | ||
Thermal Cracks |
Heat stresses due to temperature variations | Reduce speed |
| Use cutter with more positive geometry | ||
| Use grade designed for use with coolant | ||
| Discontinue coolant use | ||
