Let's talk about anti-backlash nuts, whether or not they're even necessary. Ito that question,
we really need to know what backlash is in the first place.
We're going to be using this adjustable wrench as our little demonstration.
This little worm gear right here, whether you spin it one way or another, will engage on some threads
that is attached to this particular component. As we spin it, it goes up and down. Think of
this little warm gear as your Z-axis lead screw, and think of this auto component as your gantry.
Now, what would happen is when we move back and forth when moving this worm gear?
If we move this worm gear in one direction, it'll engage one side of the teeth on these threads.
The moment we move the worm gear in the other direction, you'll notice there's a point where
it's not engaging any of the threads. That is absolutely necessary because if the threads and
the worm gear were the exact perfect fit, there wouldn't be any wiggle room to move anything.
As we move in the other direction, now we're engaging the opposite side of those threads.
As we move back and forth, this happens every time we change direction. That is backlash.
That extra movement required before you actually engage the threads to go the opposite direction.
That is why we have anti-backlash nuts. Then you might ask yourself how exactly does an
anti-backlash nut deal with minimizing, reducing, or getting rid of backlash. It's actually quite
simple. You see that spring that is connecting what is actually two separate pieces here.
This brass component is indeed two separate pieces. It is pushing these two brass pieces that
are connected but separate in opposite directions. That way, the top of this brass nut is engaging
one side of the threads on the lead screw or the bottom of this brass piece is being forced to
engage the opposite side of the lead screw. When it moves up and down on something like a Z-hop,
your backlash is minimized because the threads in either direction are always being engaged.
In essence, what is happening is you have two lead screw nuts that are connected together,
but being pushed apart by a spring. That makes it so that the top lead screw nut is
engaging the thread on one side while the exact same time, the bottom lead screw,
not as engaging the thread at the other side. That is how we use an anti-backlash nut.
However, you'll notice for this demonstration that I just showed you, we're in a horizontal
orientation instead of a vertical orientation. This is the topic of debate for a lot of people.
The question is, does it even matter when you have the entire weight of the gantry pushing
down on the lead screw nut anyway? Because what's going to cause it to have that issue when you have
the force of gravity forcing the lead screw nut, always on one side of the lead screw?
To demonstrate that, we'll put force on the part that moves here and we'll move
it back and forth either way. You'll see because we have gravity pushing down on it,
we don't really have any backlash from moving like this. Then pray tell you may ask, "If that's the
case, well, what's the point?" The answer is, it's not so clear. Here's the thing, when you Z-whop,
you are forcing an object in motion and an object in motion likes to stay in motion
unless acted upon an equal and opposite force. When you Z-hop, you bounce a little bit. That
little bit of bounce when you're moving up and down rapidly, especially during a lot of Z-hops
could cause some small artifacting. Is it a deal-breaker? No, not really,
but there are a number of people that report that when enabling Z-hop, anti-backlash nuts,
do help a tiny bit in removing some forms of artifacting in your printing.
For a few dollars, it certainly doesn't hurt, but is it entirely necessary? Absolutely not.
I suspect the anti-backlash nuts are going to come far more in handy once we start getting to a point
where 3D printing is going to get truly 3D, i.e non-planar printing. Now, I don't
have any examples of a print that is non-planar because non-planar printing is very much still
in its infancy stages at the moment, and having the right equipment to do it is very specialised.
Teaching Tech did a fantastic video on it. It's basically, instead of pancaking
a two-dimensional layer of plastic on each other, your hot end actually can move up
and down in the Z-axis as it's printing in real-time to make these beautiful finishes
at the end. It's just absolutely incredible. I suspect when we're moving up and down a
lot more than just with Z-hopping that the anti-backlash nuts will help in that regard,
that's just speculation on my part. The current situation is some people say
that anti-backlash nuts improve quality in certain guards in regards to Z-hopping. In my experience,
I have been using anti-backlash nuts for a long time and if they're giving me some benefit,
that's great and if they're not, well, it does make the rod a little more stable,
but that's the reality of it. The evidence is anecdotal. It's just one of those things.
Perhaps, in this particular case, it's not necessary.
Again, maybe not. I wish I could give you guys a more definitive answer on this, but I can't really
afford to take apart my production machine to really experiment around with this. All
I can say is, it doesn't hurt anything. Does it help? I can't comfortably say one way or another.