Will this Z axis anti backlash nut improve your 3D printer accuracy?

Summary

In 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

00:00

🔧 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.

Keywords

💡Backlash

Backlash refers to the undesired looseness or play between two parts that are supposed to be fixed together, often caused by loose fits between parts due to improper machining, wear and tear, or design clearances. In the context of the video, backlash is a critical issue in the z-axis of a 3D printer, where the lead screw and the nut have a necessary clearance for smooth operation. However, this clearance can lead to a lack of movement in the z-axis when the direction of movement changes, which is problematic for precision tasks such as the first layer of a 3D print.

💡Anti-backlash nut

An anti-backlash nut is a mechanical component designed to eliminate or reduce backlash in threaded connections. It typically uses a spring mechanism to keep the threads of the nut and the screw tightly engaged. The video discusses the use of anti-backlash nuts in the z-axis of a 3D printer to address the issue of backlash. However, the video suggests that while anti-backlash nuts can theoretically eliminate backlash, in practice, they may not be effective due to the weight of the printer's gantry and other factors.

💡Z-axis

The z-axis refers to the vertical movement axis in a 3D printer, which controls the height of the print bed. In the video, the z-axis is central to the discussion of backlash, as any looseness or play in this axis can significantly affect the precision and quality of the printed object, especially during the critical first layer of printing.

💡Lead screw

A lead screw is a type of screw that is used to translate rotational motion into linear motion. In the context of the video, the lead screw is a key component of the z-axis mechanism in a 3D printer. The video explains that the clearance between the lead screw and the nut can lead to backlash, which is a problem when trying to achieve precise vertical movement.

💡Thread engagement

Thread engagement refers to the contact between the threads of a screw and the corresponding nut. In the video, it is discussed that proper thread engagement is necessary for smooth and precise movement in the z-axis of a 3D printer. Backlash occurs when the thread engagement is not consistent, particularly when the direction of movement changes, leading to a momentary lack of movement in the z-axis.

💡Gantry

The gantry in a 3D printer refers to the structure that holds the print head and moves it across the print bed. The video mentions that the weight of the gantry can affect the effectiveness of an anti-backlash nut, as the weight can compress the spring in the nut and cause a loss of thread engagement, thus contributing to backlash.

💡Stepper motor

A stepper motor is a type of electric motor that can divide a full rotation into smaller steps, allowing for precise control of movement. In the video, the stepper motors are mentioned in relation to their role in driving the z-axis movement. The video suggests that using a stiffer spring in an anti-backlash nut could overwork the stepper motors, leading to increased wear and potential binding.

💡Binding

Binding refers to the jamming or seizing up of a mechanical system due to excessive friction or resistance. In the context of the video, binding is a potential issue that can occur if the friction is too high, such as when a stiffer spring is used in an anti-backlash nut. This can cause the mechanical system to become too resistant to movement, leading to problems like the stepper motors skipping steps.

💡Alignment

Alignment in the context of the video refers to the correct positioning and orientation of the mechanical components of the z-axis to ensure smooth and precise movement. The video suggests that rather than relying on anti-backlash nuts, it is more effective to ensure proper alignment of the axis and remove any points of binding to minimize backlash.

💡C-Hop

C-Hop is a feature in some 3D printers that allows the print head to move in a diagonal direction across the print bed. The video briefly mentions c-hop as an exception to the typical upward-only movement of the z-axis during most prints, indicating that the z-axis backlash issue is less of a concern when the z-axis only moves in one direction.

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