Will this Z axis anti backlash nut improve your 3D printer accuracy?
Summary
TLDRIn this video, the creator explores the issue of backlash in the z-axis of a 3D printer, even after upgrades. Backlash, the play between parts, can affect precision, especially in the first layer of printing. While anti-backlash nuts are designed to eliminate this by keeping threads always engaged, they may not be effective under the weight of the printer's gantry. The video suggests that instead of relying on mechanical solutions like anti-backlash nuts, which can add unnecessary friction, it's better to focus on aligning the axis and removing binding points to minimize backlash and improve z-axis accuracy.
Takeaways
- 🔧 Backlash is the play between two parts that should be fixed together, often caused by loose fits, improper machining, wear, or design clearances.
- 🔄 It's a common issue in mechanisms like gears, where a small movement of the drive gear doesn't immediately move the driven gear due to clearance.
- 🖨 In 3D printers, backlash in the z-axis can cause inaccuracies, especially noticeable during the first layer print or when homing the printer.
- 🔩 The z-axis backlash is due to the clearance between the lead screw and the lead nut, which can increase over time due to wear.
- 🌀 Spring-loaded anti-backlash nuts are designed to keep the threads of the nut always engaged with the screw, minimizing backlash.
- ⚖️ However, in applications with heavier loads, such as a 3D printer's z-axis, the weight can compress the spring, causing disengagement and backlash.
- 🔩 A stiffer spring could theoretically handle the load, but it would increase friction, overwork motors, and accelerate wear on components.
- 📈 Mounting the nut above the gantry can use gravity to help maintain thread engagement, but it's not always necessary if screws are properly aligned.
- 🔒 Anti-backlash nuts can add friction, which might prevent the z-axis from dropping when the printer is powered off, but they don't improve accuracy.
- ❌ The video concludes that anti-backlash nuts do not improve the accuracy of the z-axis in 3D printers and that other mechanical adjustments are needed to minimize backlash.
Q & A
What is backlash in the context of machinery?
-Backlash is the undesirable play between two parts that are supposed to be fixed together, caused by loose fits between parts due to improper machining, normal wear and tear, or design clearances necessary for a part to function.
Why is clearance necessary between the teeth of two gears?
-Clearance between the teeth of two gears is necessary to achieve smooth operation and minimize wear, but it can lead to backlash, which is the movement of the drive gear without the driven gear moving when the direction changes.
How does backlash affect the z-axis of a 3D printer?
-Backlash in the z-axis of a 3D printer can cause the printer to assume movement has occurred when in reality there is no movement, especially during the first layer print or when the direction of movement changes, which can lead to inaccuracies.
What is the role of the lead screw and lead nut in the z-axis mechanism of a 3D printer?
-The lead screw moves the gantry, and the lead nut engages with the screw to ensure movement. However, there can be clearance between them, which can cause backlash when the direction of movement changes.
How does a spring-loaded anti-backlash nut theoretically eliminate backlash?
-A spring-loaded anti-backlash nut uses a spring to force the nut's parts to always be engaged with the screw, ensuring thread engagement in both directions of movement and theoretically eliminating backlash.
Why might a spring-loaded anti-backlash nut not be effective in a 3D printer's z-axis?
-The weight of the gantry in a 3D printer's z-axis can be greater than the force of the spring in the anti-backlash nut, causing the nut to lose engagement with the threads and not eliminate backlash.
What is the potential downside of using a stiffer spring in an anti-backlash nut?
-Using a stiffer spring can increase friction, overwork stepper motors, wear out brass nuts faster, and potentially cause binding in the mechanism.
Why might mounting the nut above the gantry help with thread engagement?
-Mounting the nut above the gantry allows gravity to work in favor of thread engagement, as the weight of the gantry helps keep the threads engaged even when the direction of movement changes.
Can the anti-backlash nut increase friction to prevent the z-axis from dropping when the printer is powered off?
-Yes, the added friction from an anti-backlash nut can help prevent the z-axis from dropping when the printer is powered off, although it does not improve the accuracy of the z-axis.
What is the final verdict on using anti-backlash nuts for improving the accuracy of the z-axis in a 3D printer?
-The video concludes that anti-backlash nuts will not help improve the accuracy of the z-axis if the goal is to reduce backlash. However, they can be beneficial for increasing friction to prevent the z-axis from dropping when the printer is powered off.
Outlines
🔧 Understanding and Addressing 3D Printer Z-Axis Backlash
The video begins with the host discussing a persistent backlash issue in the z-axis of a 3D printer, even after several upgrades. The term 'backlash' is explained as the undesired play between two parts that should be fixed together, often caused by loose fits. This can result from improper machining, wear and tear, or necessary design clearances for functioning. The video uses the example of gears to illustrate how backlash can occur when changing direction. The host then relates this concept to the z-axis of a 3D printer, explaining how the lead screw and lead nut mechanism can also exhibit backlash due to the necessary clearance for smooth operation. The video suggests that while a spring-loaded anti-backlash nut might theoretically eliminate backlash by keeping the threads always engaged, in practice, the weight of the printer's gantry can compress the spring, causing disengagement and thus not eliminating backlash. The host concludes that anti-backlash nuts may not improve the accuracy of the z-axis but could increase friction to prevent the gantry from dropping when the printer is powered off.
Mindmap
Keywords
💡Backlash
💡Anti-backlash nut
💡Z-axis
💡Lead screw
💡Thread engagement
💡Gantry
💡Stepper motor
💡Binding
💡Alignment
💡C-Hop
Highlights
Discovered a backlash in the z-axis despite upgrades.
Anti-backlash might not be a magic fix.
Backlash is the play between two parts that should be fixed together.
Backlash can be caused by loose fits, improper machining, wear, or design clearances.
Example of backlash in gears and its effect on operation.
Z-axis backlash in 3D printers is due to clearance between screw threads and the nut.
The z-axis backlash issue occurs when changing movement direction.
Spring-loaded anti-backlash nuts are supposed to keep threads always engaged.
Load on the z-axis can compress the spring and lose thread engagement.
Weight of the gantry can be greater than the spring's pushing force.
Testing showed that the spring couldn't move the z-axis when fully compressed.
Using a stiffer spring increases friction and could overwork stepper motors.
Mounting the nut above the gantry can solve thread engagement issues.
Proper alignment and removal of binding points are more effective than anti-backlash nuts.
Anti-backlash nuts do not improve z-axis accuracy but can prevent dropping on power off.
Lead screw is not always the cause of backlash; it can originate from any point in the mechanism.
Minimizing backlash by aligning the axis is more effective than mechanical means.
Added weight to the gantry did not eliminate backlash.
The final verdict is that anti-backlash nuts do not improve z-axis accuracy.
Transcripts
in my previous video I discovered a tiny
backlash in the z-axis even after all
the upgrades
so is the anti-backlash not the magic
fix stick around to find out more
[Music]
in order to fix it we must first
understand what is Backlash
in simple words backlash is the
undesirable play between two parts that
are supposed to be fixed together
it is caused by loose fits between parts
that can be a result of improper
Machining normal wear and tear or even
by Design clearances that are necessary
for a part to function
the most common and easy to understand
example is that of two gears some
clearance between the teeth is necessary
to achieve smooth operation and minimize
wear but notice when you change the
direction the drive gear moves to engage
the teeth on the opposite side during
this small movement The Driven gear does
not move
and that can be a problem when your
required Precision is in micrometers
so how does that relate to the z-axis of
our 3D printer
let's take a look at this mechanism
here you can see that there is some
clearance between the threads of the
screw and the nut this is necessary to
have a smooth operation and to prevent
binding depending on the Precision of
Machining this clearance can be very
small or very big but even if you start
with a small clearance over time as the
nut wears out the Gap can increase
when we try to move our Gantry the lead
screw will move until it engages the
lead nut during this short duration your
printer assumes that the z-axis has
moved but because the lead screw is
still not engaged in reality there is no
movement and that can be problematic
especially for the first layer you can
see that the problem only occurs when we
change our direction of movement in most
prints the z-axis will only move up
unless you are using something like
c-hop which is another story altogether
but when you home your printer at the
start of every print job the z-axis
moves down for the procedure then the
very first movement of the z-axis is a
change in direction as it starts moving
up
now in theory when you use a
spring-loaded anti-backlash nut the
spring forces the two parts of the nut
to always be engaged with the screw so
when you move in this direction the
thread engagement is here and when you
change direction the thread is also
engaged on the side
so again in theory there should be zero
backlash as the threads are always
engaged and that is the case when you
are using the lead screw to drive small
loads like that of a laser cutter or a
pen plotter
but let's assume the load is greater
like that of a CNC machine where the End
Mill must push against the work piece
then if the force applied is greater
than the pushing force of the spring it
will compress further and loose the
engagement with the threads
in the case of a 3D printer z-axis the
weight of the Gantry is resting on the
nut and that weight is in fact greater
than the force of the spring I made a
small test to verify this
here you can see I tried to push the
z-axis with the spring even when the
spring is fully compressed the z-axis
does not move
so that has made our anti-backlash not
useless we could try to use a stiffer
spring one which can take the load of
the Gantry but that will increase the
friction it will overwork your stepper
Motors it will wear out the brass nuts
faster and it could start binding
and if you mount the nut above the
Gantry that will solve the problem of
the thread engagement as now gravity is
working in your favor but then do you
really need the anti-backlash nut
if your screws are aligned properly and
move without any binding gravity will
always be working in your favor
the bottom threads will always be
engaged even when you change direction
of the z-axis the spring-loaded nut will
only add additional friction that
however can be desirable in some cases
if your Gantry falls down when the
printer is powered off the added
friction of the nut can prevent that but
it will not do anything to improve the
accuracy of the z-axis
so to put the final nail in the coffin I
installed the spring-loaded nuts on my
z-axis and the backlash is still there
the nuts did not have any effect
so I thought to add more weight to the
Gantry in case the thread engagement is
not ideal until the steppers started
skipping but the backlash is still
present so the important lesson to learn
here is that the lead screw is not
always the cause of this backlash it can
originate from any point in the
mechanism
so rather than trying to eliminate it
all together by mechanical means we need
to minimize it by aligning the axis and
removing points of binding so the
verdict
if you are looking to improve the
accuracy of the z-axis the anti-backlash
nuts will not help you if however you
want to increase the friction to prevent
the z-axis from dropping on power off
they can be beneficial thanks for
watching and hope you enjoyed this short
video
see you in the next one
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