Aligning the Y axis can be the most difficult to setup, and may cause trouble homing the machine, moving to certain points at higher jog speeds, and running projects on the STEPCRAFT.
Machine is designed to jog at 100% speed as defined in the machine parameters for the full length of each axis. This speed is 50 mm/sec (3000mm/min) for the STEPCRAFT 2 machines.
If you are not able to jog at 100% it may cause a job running at a slower speed but more load to bind and/or lose steps as well. Losing steps is when the position of the machine is thrown off because the axis has been instructed to move and has not been able to complete the move, but the signal from UCCNC has been sent already.
It is also important to pay attention also to job setup because you could have a perfectly running machine but are overloading the machine due to the speeds and feeds set in the project. For example different materials will dictate the speed that the machine could cut at. There is quite a difference between cutting foam to cutting hardwood or even aluminum. Depth per cut is also a factor in the load the machine takes on while cutting. The general rule for woods is to start with half the diameter of the end mill as the depth per pass. Using a 1/8″ end mill set the depth per pass to 1/16″.
If you are first having trouble jogging the machine at 100% or homing look to this list of possible causes first, described in further detail below.
-Front and end plate alignment (DO FIRST if not done already) Step 15
-Gantry alignment Step 8.4
-Pulley and nut tightness Step 8.3
-Belt tension Step 8.5
-Lead screw alignment Step 8.2
-Roller bearing tension Step 3.3, 3.4
Where to start in diagnosing the Y axis alignment –
-Move the Y axis near the back of the machine and press in the Emergency stop button. Pressing in the emergency stop removes power from the motors so they no longer try to hold their position.
-Remove the belt cover by taking off the two 2mm allen screws.
-Try to move the belt by hand. It should be smooth and be able to move with one hand without the entire machine sliding on the table. I will usually get a good alignment on the Y axis just by testing it by hand. The machine is designed to operate in a precise tolerance, if it is difficult to move by hand it will not be able to run by the power correctly.
-Remove the belt by loosening the 2.5mm allen screw holding the tensioner in place.
-Check pulley for looseness by holding lead screw and turning pulley. The pulley and lead screw should be move as one unit, you should not be able to turn the pulley and have the lead screw remain stationary. This could be part of your issue. While here test the tightness of the nut on the lead screw by loosening the 1mm set screw for the pulley, when it is slightly loosened it should be able to rock back and forth the nut should be just barely making contact with the pulley not heavily tightened down upon it.
-Check lead screw lateral alignment by pushing lead screw forward and backwards there should not be noticeable play of the pulley moving back and forth. This would indicate the lead screw isn’t fully seated, when this occurs it can affect the sides of the gantry causing a misalignment which can cause the Y axis to bind.
-Check the force needed to move each pulley, you only want to move each back and forth about 1/4 turn as moving too far will move the gantry out of alignment then it will definitely be more difficult to turn. You may feel one side is very smooth and the other is not. Or they both may feel tight to turn. If only one is difficult to turn concentrate efforts on looking at that side first.
-Check the tension of the bearings. Without taking apart more of the machine there is not an easy way to tell if they are too tight. You can tell if they are too loose by spinning the top bearings by hand or if you can rock the axis back and forth. If you suspect they are too tight loosen the 2.5mm allen screw then place a flat blade screwdriver on the screw and lightly tap the shaft of the screwdriver to move the bearing downward, releasing tension. DO NOT loosen the larger 4mm allen screw for the roller bearing assembly.
-Reset the lead screw and plate alignment. For this the gantry needs to be near the front of the machine. You could reinstall the belt and move it there by hand or use UCCNC to jog it forward as well. The rear plate of the machine should be tightened (in case you have had it loose in trying to align the machine already) with equal 1mm gaps between the plate and the Y axis extrusions. Follow Step 8.2 in the manual to make sure the amount of play the lead screw can move is equal between the bearing.
-Reset the gantry alignment. I will do this near the back of the machine where I can use two fixed objects of the same size between the gantry upright and rear plate. When using this method it helps keep the pulleys from moving when you install the belt starting on the side with the Y axis limit switch.
-The belt tension should be firm to press down on the belt but not take a lot of force to do so either.
These items are the main things to look over when trying to align the Y axis, there will sometimes be other things to look for as well that are best explained by contacting support directly. In some cases I will go through some of these steps more than once as changing one thing may effect another.