The Machine is Not Level - Lathe
To operate correctly, the machine must be level. An out-of-level machine can have problems such as poor surface finish, tapered parts, accuracy and repeatability issues, out-of-round circular motion, and out-of-true linear motion.
Watch the Lathe Leveling video to learn how to properly level your Haas lathe, or contact your Haas Factory Outlet to have your machine’s level checked.
Thermal Growth in the Linear Axes (X, Y, Z)
Warm up the spindle and all of the axes for 20 minutes before you set the work coordinate and tool length offsets.
You should also warm up the spindle and all of the axes before you check the machine for accuracy.
Electronic Thermal Compensation - Lathe
Electronic Thermal Compensation (ETC) uses a proprietary algorithm to compensate for the expansion and contraction in linear axes caused by the heating and cooling of the ballscrews. The ETC algorithm uses a model of the ballscrew, and it estimates expansion or contraction based on the distance traveled and the torque applied to the motor. Heat is represented by a thermal coefficient of expansion, and the axis distance is multiplied by the coefficient to get the amount of correction needed. A real-time clock monitors in-motion time and non-motion time (e.g., lunch, breaks), and compensates accordingly.
Remember that ETC does not correct for thermal growth due to changes in ambient temperature, growth due to part expansion, or growth due to spindle expansion/contraction.
The X, Y, and Z Screw Thermal Comp % settings let you adjust adjust the existing screw thermal compensation by -30% to +30%. If these values are incorrect, you can have accuracy errors.
Start each setting with a value of zero, and then adjust as needed.
These are the settings:
Setting 158 - X Screw Thermal Comp % (-30 to 30)
Setting 159 - Y Screw Thermal Comp % (-30 to 30)
Setting 160 - Z Screw Thermal Comp % (-30 to 30)
If the parameter values used in the ETC algorithm are incorrect, you can have accuracy errors.
If you suspect the ETC parameters are incorrect, contact your Haas Factory Outlet to have the machine parameters checked and corrected if needed.
On Haas lathes, ETC uses a thermal sensor on the X-Axis ballscrew to help ETC compensate the axis. If the thermal sensor on the ballscrew is faulty, this compensation can be incorrect. This causes accuracy errors.
To check for a faulty sensor, find the axis thermal sensor status on the DIAGNOSTICS screen. If the temperature status does not stay constant, the thermal sensor should be replaced.
The Workpiece Moves in the Chuck
If your workpiece moves in the workholding during the cut, you will have accuracy issues, difficulty holding tolerances and chatter issues.
Incorrectly bored chuck jaws can let the workpiece move. The soft jaws should be machined to match the nominal size of the part being held.
Be sure to use a chuck jaw support slug (1) or adjustable boring ring (2) in the center travel of the jaws, before you machine the jaws. If the Jaws are too close to the top of the stroke you will have diffucalty loading and unloading your workpiece in the jaws, if the jaws are too close to the bottom of the stroke the full clamping force will not achieved.
Use a 0.001" (0.03 mm) feeler gauge to check for gaps between the workpiece and the chuck jaws. Check both the front and the back. The jaws may have deflected from the clamp force, in some cases you may need to machine a slight taper in the jaws to compensate for the jaw's deflection allowing for full jaw contact with the workpeice .
Make sure that the chuck jaws are tight, and that the screws do not bottom out on the T-nuts or T-slot. The T-nuts should not extend outside the T-slots.
When OD clamping parts, the centrifugal forces generated at high RPMs will reduce the clamp force and may allow the part to move. Use this chart to determine the if you need to increase the clamp force on the chuck or reduce the max RPM during your program. You can find this chart on a sticker near the hydraulically pump on your lathe.
Refer to the How to Properly Cut Lathe Soft Jaws — Part 1: Fundamentals and OD Gripping and How to Properly Cut Lathe Soft Jaws — Part 2: ID Gripping, Re-cutting, and Adding a Taper videos for more details on cutting soft jaws.
Note: Be sure to clean and deburr you workpiece before you clamp it into your workholding device. A dirty surface, chips, or burrs can let the workpiece move during the cut.