How come my circles are not perfectly round?
When you are machining circles on a CNC and your circles are not coming out perfectly round, it is commonly caused because there is some backlash developing on the machine. Backlash is a tiny amount of play that appears over time and is noticed when a drive changes direction.
When running in a positive direction, the gears/lead screw are engaged with the lead screw nut on the gantry, but when the stepper motor reverses direction there is a tiny space between the lead screw and the lead screw nut that has to be made up before there is positive engagement in that direction. After many, many hours of use or if your machine is not properly maintained and lubricated, then this backlash can develop.
If this is happening to you, please download this document: Stepcraft UCCNC Backlash Compensation.
This will show you how to setup backlash compensation in UCCNC so that you can “dial” out any backlash and go back to having perfect circles again.
Understanding the Homing Procedure
Whenever you open UCCNC, the very first movement you should make with your machine is “Home All”. On a STEPCRAFT, the homing procedure begins with the Z-Axis, then the X-Axis and finally the Y-Axis. Each axis will run towards its limit switch until it engages the switch, then will run the opposite way until the switch disengages. Once all three axis have hit their limit switch, your machine is now ready to travel the full length of each axis!
This is known as a reference movement for the machine. Without this reference movement, the machine has no idea where it is along its axis and may not travel the full length back and forth. If your machine is stopping short of the full length of travel and you aren’t noticing any binding, make sure to “Home All” and try running again.
One important thing to note is that if any axis ever travels in the opposite direction of its limit switch when homing, check to make sure a limit switch is not engaged somewhere on the machine. All of the limit switches are on the same circuit, so if you tried to home your machine and the Y-Axis limit switch was pressed, the Z-Axis would travel in the OPPOSITE direction. This happens because the machine is going through the stage of homing when it backs away from the switch until it disengages. Because the Y-Axis switch was pressed, the Z-Axis will infinitely try to move away but it will never disengage.
My machine is in reset mode and I can not get it to reset, how can I fix this?
If your machine will not come out of reset mode, there are three things to check:
- Make sure that UCCNC is not running in Demo Mode. If UCCNC is running in demo mode, the software will not reset.
- Ensure that the emergency stop button is not press in on the front of the machine. You can disengage it by simply twisting it to the right slightly and it should pop out. If it is already out, then you can move on to #2.
- Check the Y Axis limit switch wires on the back of the machine. Sometimes these wires can be accidentally knocked out and become disconnected. Be sure both wires are plugged in correctly.
- Click on the DIAGNOSTICS tab in UCCNC. Check to see if any of the limit switch lights are on in the I/O Function Monitor. (Please see the video below starting at 1:36)