- Home
- Courses
- Courses for Manufacturing
- CNC Lathe & Turning Centers
- Course Types
- Internet Course
- DVD / CD-ROM Course
- Video / Print Course
- CNC Machining Centers
- Course Types
- Internet Course
- DVD / CD-ROM Course
- Video / Print Course
- CNC Swiss
- Course Types
- Internet Course
- Precision Measurement for Machinists
- Course Types
- Internet Based Course
- CD-ROM Based Course
- Automatic Bar Machines
- Fastener Production Equipment
- Stamping Presses
- Geometric Tolerancing
- SPC
- CNC Lathe & Turning Centers
- Courses for Education
- CNC Lathe & Turning Centers
- Course Types
- Internet Course
- DVD / CD-ROM Course
- CNC Machining Centers
- Course Types
- Internet Course
- DVD / CD-ROM Course
- CNC Swiss
- Course Types
- Internet Course
- Precision Measurement for Machinists
- Course Types
- Internet Course
- DVD / CD-ROM Course
- SPC
- CNC Lathe & Turning Centers
- Courses for Individuals
- Online Courses
- Cursos De Español
- Dominio de Tornos CNC
- Automático Barra Máquinas
- De un Solo Husillo
- Brown & Sharpe
- Tornos Bechler / Strohm
- Multi-Husillo
- Acme Gridley
- Davenport
- New Britain
- Custom Development
- Courses for Manufacturing
- Quick View
- Tools & Information
- Support
- Company
Quality Control Troubleshooting Guide
CNC Machining Centers
It often takes years for a new machinist to learn all of the likely causes for the various quality problems that will arise. These troubleshooting algorithms can help your personnel by giving them the benefit of years of experience at the click of a mouse. Select the Quality Defect in the list below, then follow the links (if applicable) to learn the most likely causes.
Select Quality Defect:
Select the statement that best represents the situation:
- Several features cut by the SAME TOOL are out of tolerance by the SAME amount in the SAME axis directions.
- Several features are out of tolerance which were cut by DIFFERENT tools.
- Only ONE of the features cut by a tool during a tool path is out of tolerance.
Several features cut by the SAME TOOL are out of tolerance
by the SAME amount in the SAME axis directions.
- For New Setups:
- Check the setup documentation to be sure the correct tool is being used for the cut.
- Check the cutting edge to be sure it is not worn, damaged or broken. If so, replace the insert and adjust any CRC or Length offset as required.
- Be sure the Tool Offset for the tool is entered in the Offset Table and made active in the Program.
- Determine if Cutter Radius Compensation (CRC) is applied to the tool. If it is, be sure it is activated in the Program with the correct G41 or G42 code. If CRC is not required, be sure G40 is active to cancel any previous CRC value which may have been active for a previous tool.
- Check to see if a Fixture Offset (Work Coordinate Grid Offset) or Work Coordinate SHIFT offset, is active that should not be, or that it should be active but is not.
- Be sure the workpiece is properly positioned in the Fixture and making full contact with the locating surfaces.
- Be sure the Fixture is properly mounted to the table.
- For Maintaining an Existing Setup:
- Check the cutting Insert to be sure it is not worn, damaged or broken. If faulty, replace the Insert and adjust any CRC or Length offset as required. If the Insert is not faulty, consider calculating and entering a CRC or Length Offset.
- Be sure the workpiece is placed against the locating surfaces and it is securely mounted.
- Be sure there is no damage to the fixture or its locating surfaces.
- Be sure the Fixture remains securely mounted to the Work Table.
- Perform a Zero Return or HOME to remove any errors in the Coordinate System.
Several features are out of tolerance which were cut by DIFFERENT tools.
- Perform a Zero Return, or HOME, to remove any positioning errors that may have occurred.
- Check the part to be sure it is seated against the locating surfaces in the Fixture and that no chips or burrs are interfering.
- Check the location of Program Zero to be sure it is correct for the part.
- Check the Program to see if Cutter Radius Compensation (CRC) is either required but not active, or not required but remains active.
- Check the Length Offsets to be sure they were entered correctly and that the correct G code occurs in the Program to make them active.
- Check to see if a Fixture Offset (Work Coordinate Grid Offset) or Work Coordinate SHIFT offset, is active that should not be, or should be active but is not.
Only ONE of the features cut by a tool during a tool path is out of tolerance.
- Consider entering a second Length or CRC Offset for the tool. Make it active before the problem feature to correct the problem, then reactivate the original Offsets after the feature is completed. Notify the Programmer of the problem.
- If program editing is allowed, find the coordinates in the program that created the feature and edit them to correct the problem.
- Check to be sure the cutting edge of the Finish Tool Insert is not dull, chipped, broken, or has material build-up.
- Be sure the Finish Tool or its Inserts are correct for the type of finish cut.
- Check the size of the workpiece after the Rough pass to be sure the Finisher is not removing too much material in the finish pass, or that the Finisher is not removing enough material.
- Check the Feed Rate for the Finish pass.
- Check the Spindle Speed during the Finish pass.
- Be sure the coolant reaches the Finish Tool during the cut so that chips are flushed away from during the cut, and so that excessive heat does not build up in either the tool or workpiece.
- Make sure the workpiece material is correct as specified in the setup documents, and that the hardness of the material is within normal limits.
Select the statement that best represents the situation:
- Chatter occurs when a specific tool is machining.
- Chatter occurs when any of several tools are machining.
Chatter is isolated to a Specific tool.
- Check the cutting edges to be sure they are not dull, worn, or broken.
- Be sure it is the correct Tool and Inserts for the machining required.
- Check to be sure the tool Inserts are firmly mounted in the Tool Holder.
- When possible, reduce the length of tool that extends out of the Tool Holder and reset the Tool Length Offset.
- Check the Feed Rate of the cut.
- Check the Spindle Speed during the cut.
- Make sure the Finish cutter is not being required to remove more material than is normal for the style of cutter.
- Make sure the workpiece is securely mounted in the Fixture and that the surface being machined in supported.
Chatter CANNOT be isolated to a single tool.
- Be sure the workpiece is securely mounted in the holding device.
- Be sure the surface being machined is fully supported to eliminate vibration.
- Check the Feed Rate programmed.
- Check the Spindle Speed programmed.
- Check the workpiece material to be sure it is correct and that the hardness is normal.
- Check the coolant supply to be sure it is the correct concentration and is clean.
- Make sure the machine is securely mounted to the floor.
- Ask maintenance to check the Spindle Bearing.
- Look for an external source of vibration either inside or outside the shop.
Select the statement that best represents the situation:
It is DRILLED hole.
- Be sure the Drill is the correct diameter.
- Check the Drill Point to be sure it is sharp and not damaged.
- Check the Drill to be sure it is not bent.
- Check the Drill Collet to be sure it is clean and not not broken or damaged.
- Be sure the length of the Drill Point cutting edges are the same.
- Make sure the Feedrate is not too high causing the Drill to deflect or bend.
It is a REAMED hole.
- Oversize Hole:
- Be sure the Reamer is the correct size.
- Check to see if the tool is bent.
- Be sure the drill that precedes the Reamer is not causing an oversize hole.
- Be sure no CRC offset is active.
- Bell-Mouthed Hole:
- If a Floating Holder is used, check for excessive float.
- Be sure the preceding drill is large enough so that the Reamer is not being required to remove too much material.
- Be sure the Reamer is not hitting the bottom of the hole.
- Tapered Hole:
- Check for a worn, damaged or broken Reamer.
- Be sure the Reamer is not bent.
- Be sure no CRC offset is active.
- Check any other holes created by the drill. If all have the same problem, check the Tool Length Offset.
- Make sure the Tool Length Offset is correctly entered in the offset table and is made active by the G code in the Program.
- Be sure the Drill collet holdes the Drill securely.
- If other holes created by the Drill are correct, edit the Z axis coordinate that creates the hole if allowed by shop practice.
Select the statement that best represents the situation:
It is DRILLED hole.
- Check the drills that precede the final drill to be sure they are the correct size.
- Be sure the final drill is not dull or damaged.
- Be sure the coolant is reaching into the hole or consider using a coolant-hole drill.
- Check the Drill to be sure it is not bent.
- Check the Drill Collet to be sure it is not damaged, is clean, and firmly holds the drill.
- If chips are not breaking into small sizes that are easily removed from the hole, consider a chip-breaking or fast-spiral drill.
It is a REAMED hole.
- Be sure the Reamer is not dull, damaged or bent.
- Check the drills that precede the Reamer to be sure they are the correct size so that the Reamer is not trying to remove too much material.
- Be sure the Spindle speed is not too high.
- To increase rigidity, reduce the length of the Reamer that sticks out of the Tool Holder as much as possible.
- If a Floating Holder is being used, be sure there is not too much or too little float in the holder.
- Be sure the coolant is reaching into the hole.
- Check the Drill Collet to be sure it is not damaged, is clean, and firmly holds the Reamer.
- Roundness:
- Check for a bent Drill.
- Be sure the drill does not extend from the Drill Collet any further than necessary to create the correct depth of the hole.
- Check the length of the cutting edges of the Drill to be sure they are the same length.
- Be sure the Feedrate is not too high causing the drill to deflect or bend.
- Concentricity:
- Check the Spot Drill which precedes the Drill to be sure it is not broken, chipped or dull.
- Check the Drill collet to be sure it is not dirty, broken or has burrs.
- Make sure the Drill Collet Nut is securely tightened.
- Make sure that no CRC value is active.
- Check the programmed coordinates for each drill.
- Check the cutting tool to be sure it is sharp and not damaged.
- Be sure the correct tool is being used.
- If the Boring Bar is adjustable, make any required adjustment and be sure the lock screw on the adjustment mechanism is tight.
- Be sure no CRC Tool Offset values have been entered or are currently active.
- Check the Boring Bar to be sure it is not bent.
- Make sure the Depth-of-Cut or Feedrate is not too high causing the Boring Bar to deflect.
- If the workpiece has a thin wall, check to see if deflection in the wall is occuring during the cut.
- Check the condition of the Boring tool to be sure it is not damaged or worn.
- Be sure the correct Boring Bar is mounted and called up by the Program.
- Check that the correct Tool Offsets are entered and active.
- If all other features bored by this tool have the same dimensional problem, adjust the Length offset as required.
- Be sure the Boring Bar is securely mounted to the Tool Holder.
- If other features bored by this tool are correct, adjust the Z axis coordinate for the hole, if allowed by shop practice.
- Check the cutting tool to be sure it is sharp and not damaged.
- Check to be sure the Inserts and Holder are securely mounted.
- If possible, reduce the length of the bar that extends from the Tool Holder.
- Make sure the Depth-of-Cut is not too high.
- Use the Override control to reduce the Speed and Feed rates until the finish improves. Note the percentage used and calculate and enter new rates if allowed by shop practice.
- Incorrect Diameter or Pitch of Threads:
- Check to be sure the correct style of tap is used and it is the correct diameter and thread pitch.
- Be sure the drilled hole is not oversize or undersize.
- Be sure the correct tapping G code is active.
- Make sure the correct tool offsets are applied.
- Make sure the hole to be tapped is straight.
- Faulty Thread Form:
- Make sure the tap is sharp and coolant is reaching the hole to clear chips during the cycle.
- If a floating holder is used, make sure the proper amount of float occurs.
- Make sure the hole to be tapped is straight.
- Make sure the drilled hole is not undersized or oversize.
- If chips are packing into the flutes, use a fast spiral tap.
- Reduce the overall tapping speed and the withdrawl speed.
- Poor Thread Finish:
- Check to be sure the correct style of tap is used and it is the correct diameter and thread pitch.
- Be sure the correct coolant is used for the material being machined.
- Reduce the overall tapping speed and the withdrawl speed.
- Damaged Tap:
- Make sure the hole depth is correct.
- Select the style of tap for the blind or through-hole to be tapped.
- Make sure the hole is not undersize.
- Be sure the correct tapping cycle is active.
- Make sure the correct offsets apply to the tool.
- Make sure the correct coolant type and viscosity is being used.
- Material hardness may not be correct, or there may be hard spots in the material.