The Y-axis stepper only has strength counterclockwise


Since I finished the lowrider, I can not succeed cutting practically nothing. I blamed the bits, the resin of the woods, my little experience milling, etc. Today while I was still trying to cut a piece I realized that when the Y axis began to lose steps it was always in the same place, in a cut with Y going up while the X axis was going to the left. I’m running the same program again, but this time I’m empty, I went back trying to stop the bit shaft and I can do it, but doing enough strength. I still do not understand anything, the CNC has a lot of strength, the bit is new, it is sharp, the speed and the rpm are correct. While I continue to hold the path of the bit with some pressure, the Y axis starts to lose steps when it is directed upwards, making on it a very little force (I do not think more than 1 kilogram). while when the bit is going down I have to do a lot of force to make it lose steps, maybe about 7 kilograms.

I stop the program and move the axis using the display, then I confirm that by increasing the Y axis (+Y) I can very easily brake the stepper, but lowering (-Y) it makes a lot of force.

If I move the shaft by pushing it with my hand, there is no difference between taking it to one side or the other. the same as if I turn the stepper with my hand.

Does someone know why this is happening? The X axis does the same force in both directions. The Z axis is difficult to know because of the weight of the pipes.

This is on your big table? Remind me what kind of controller you have? Is it ramps, rambo, etc.?

  1. You can sometimes get more information by doing an air cut or a foam cut. That will eliminate the wood/feeds/speeds from the equation. If it’s that light, it will fail even in foam.

  2. is there any binding in Y? If the machine is unpowered, does it move smoothly in both directions?

If it’s not binding, then I would try to blame a wire or your motor drivers. The current limit should be the same in both directions. There’s no physical reason why it should be asymmetrical.

Yes, the big one. Ramps 1.4 8825 drivers.

  1. I did a test in the air and discovered the problem. there is nothing that stops the Y axis in the direction (increasing Y) in which it has no force
  2. all the axis moves smoothly in all directions. I made a drawing with a pen mounted that took several hours. The size of the drawing was 2x2 meters. the strokes coincided perfectly. The cnc is very precise.

Can you try swapping the x and y drivers? The only reason I suspect them is that they are pretty much a black box to me. You’ve adjusted the little current pots on them, right?

The other suspicion I have is that there is a wiring problem. The steppers go from coil A to coil B to coil A, and I’ve seen on my machine with one coil disconnected, it will jump the gap most of the time and be completely correct. But if you give any force, it won’t make it across to the A coil. That would be a problem in either direction, unless the wiring problem was only in direction, like some connector was being stretched in one direction.

I’m going to try changing the drivers and also with another wires.

I set the voltage of the 3 axes to 0.7. Then, noticing that the Y axis had no force, I raised it to 0.9. I’ll leave it again in 0.7.


Well, there is no an electronic problem, or wires, or drivers. The problem is strictly mechanical. The pulley that moves the router through the pipes spins. the strap was quite tight. Adjusting it more the problem is reduced, but even so, it persists. I did not have time to remove the pulley to see if it has any machining problems. What I could see is that there is a lot of wood dust between the teeth. This machine has only a few “attempts” to use it. so if this were the problem I should design something to cover this and prevent the entry of dust.

I’m going to take out the pulley, clean it, check that it’s not badly machined. Reassemble and adjust the straps as much as possible, and try again.