Binding Y axis

[Rick]

Hi Guys,

  I've built up my printer frame and have just installed the X & Y axis. I'm getting some serious binding in the Y axis I cant seem to correct. It seems that rods are a bit closer in the front of the printer. I've got all of the extrusions tight and the frame is square best as I can tell. All the bearings were smooth on each of the individual rods by themselves.

How did you adjust the Y axis on your printers to get it smooth?

Thanks

[3DprintedLife]

The Y axis binding is usually a sign that either your frame is out of square or you installed the gantry a bit cocked causing it to bind up in places. To fix the problem, you first have to determine the cause as it can be a number of things and re-doing everything probably isn't in your best interest! I'd start trying to mess with the x gantry and see if you can align that a bit better (remember that once you tighten one of the rods, it will set the y gantry. Try setting it with the y axis in the middle of the travel or at one extreme, that may help to fix your issue!

[Rick]

I did some measuring of the frame and using the side of the frame as a reference. The rods are parallel to each other measuring from the top. Measuring from the sides I can see that the rods are 0.45 mm closer to the center on each of the front sides. So, it seems that the plastic parts don't keep the rods parallel. I think that the front blocks (A11,12) should have the same t-shape cutout as the back that would put less pressure on the front of the rod and also allow an easier way to shim the rods if needed.

[3DprintedLife]

Hm ok well that's definitely the problem then! The front don't have the same T cutout because that would restrict y movement by a significant amount. However, .4mm is easy enough to shim the rods out using something like 4 layers of paper or similar.

[Rick]

Shimming wont be so easy because the rod is inserted into the cutout in the block about 4mm. You could use the current block design and take a 5mm notch out of the main block and add it to the clamp piece, no change in size of the overall part.. Only downside is that there will be a left and right clamp.

[3DprintedLife]

Ahh ok I see what you mean. You can probably just drill out that hole a bit to allow for shimming. And yes I could do what you said and at one point I think I had it like that, but in order to minimize the number of unique parts i adjusted it so the same clamp could be used on both sides. I did want to have the same clamp for all 4 pieces but that would have required too many compromises so this is what I ended up with. You also just may have secured some of the plastic parts a bit out of alignment, it is possible since there is inevitably some slop when mounting.

[Rick]

I made new front brackets with a notch that puts less pressure on the rods. I'm also using the original clamps, and enlarged the rod hole to 10.1mm. I was able to align the Y axis rods so that they are now parallel. This made the movement much smother but if I move the rods by hand they will still "grab" occasionally. Is this OK?

[3DprintedLife]

Mar 5, 2016 4:48:59 GMT Rick said:

I made new front brackets with a notch that puts less pressure on the rods. I'm also using the original clamps, and enlarged the rod hole to 10.1mm. I was able to align the Y axis rods so that they are now parallel. This made the movement much smother but if I move the rods by hand they will still "grab" occasionally. Is this OK?

Yeah that should be ok. Bushings are pretty sensitive to torquing and they really don't like to move when under a torqued load so that is expected. With the belts installed however, the corexy belt mechanics ensure that the gantry does not torque much at all so you should never see the binding during actual use!