The CoreXY motion system is a good solution if you’re looking to print faster. The 3d printer kinematics has become more popular in the last couple of years as users and DIY builders agree on an increase in print quality. The motion system is more lightweight compared to other 3d printer kinematics such as cartesian 3d printer kinematics. A light-weight gantry is needed to increase print speed without affecting print quality. This is all important when attempting to get a smooth finish on 3d printed parts.

A 3d printer’s Z-axis is a crucial component for successful printing. The Z-axis moves the print head up and down, which dictates how high your prints will be on the build plate (Z-height). A higher Z-height allows you to print taller objects with more details than lower Z heights.

1st Layer Extrusion Adhesion

A good first layer and surface adhesion are critical components of 3d printing. 1st layer issues increase as bed leveling fails. As the extruded layers bond together or have interrupted extrusion flow layer, delamination and clogged hotends occurs when the layers separate or don’t properly bond together. Hotend flow rate Increases part strength and stronger bond between layers. A 3d printer’s flow rate or extrusion multiplier in slicer software. As the molten filament comes out of the nozzle. 

Z-Axis Design

The SolidCore Printer’s z-axis setup uses a 3-point bed leveling system. The  z-axis design utilizes three independent stepper motors driven by a belt to lead screw mechanism for precise movement. The belt and pulley ratio gives the steppers more torque and increases resolution and also minimizes vibrations that could be transferred from the motors to the build plate and potentially affect print quality. This z-axis setup is more precise when auto leveling the build plate and calibration compared to other z-axis setups.

The 3-point bed leveling is a z-axis design that uses three independent stepper motors driven by belt to lead screw mechanism. The belt and pulley ratio gives the steppers more torque, which increases resolution and also minimizes vibrations transmitted from the motors to build plate affecting print quality. This z-axis setup is precise during auto level and calibration when compared with other setups.

The SolidCore Printer’s z axis design utilizes a 3 point bed leveling system for accurate movement of the printer head on its vertical axis (z). It has three independent stepper motors running on belts connected to a leadscrew moving up or down; this leads screws have higher torque than

What is the Z-Axis and how does it work?

The z-axis and vertical motion is a critical component in bed leveling. The z-axis typically works by using lead screws and linear rails to constrain movement.

I’ll walk you through what a z-axis is, why it’s important in 3D printing, and how to design one.

The z-axis on a printer or most other machines is the axis that moves up and down. It’s what controls the vertical motion of your printed object. The z-axis typically works by using threaded rods or linear bearings with some kind of nut at either end to constrain movement.

A 3d printer’s Z-axis is a crucial component for successful printing. The Z-axis moves the print head up and down, which dictates how high your prints will be on the build plate (Z-height). A higher Z-height allows you to print taller objects with more details than lower Z heights.

SolidCore: Independent Z-Axis Design

Currently each Z axis has its own independent stepper motor drive because we plan to scale up to a larger build format.  Although stacked idler pulleys make the belts run parallel to each other we could eliminate some weight from the z axis bed components

Cantilever Bed vs 3-point Bed Leveling

While many of the original corexy printers used cantilever beds, carriage wheels or smooth rod the newer and better corexy published designs are now using linear rails and have adopted more functional mechanisms such as belted z-axis, toolchangers and non-planar 3d printing concepts such as 3-point bed leveling or triple z with kinematic coupling bed mounts for tilting print beds for perfect bed leveling. Although the simplicity of older corexy reprap printers were less technical and easier for newbies, the increasing number of options and features can easily be adopted from corexy design platform to another, which has exponentially inspired contributors as they work to identify or fix potential issues or increase overall print volume. 3D printer designs such as the HyperCube use a cantilevered bed lifting mechanism which is fine for what is now considered a smaller print bed size. For example, most earlier designs have

Dual Z vs Triple Z

While earlier corexy 3d printers used the more common cantilever bed lifting mechanism which utilized a single stepper motor 3d printer with a dual Z axis lead screw setup mechanical layout which also worked well. However, there are plenty of Hypercube and D-Bot mods that implement dual-Z or linear rails or other components that increase accuracy and repeatability.

Belted Z-Axis Drive

Z-axis belt drive can eliminate z-wobble and increase print resolution. The belt driven z-axis can deliver great results, but can become more complex as depending on the design approach as more parts are used. The belt drive system needs to have enough torque and some way of limiting it when needed. You’ll also need the bed to not drop when the motors are disabled.

Rods vs Linear Rails

Many of the earlier 3d printers were designed around cheaper mechanical parts such as carbon rods or stainless steel smooth rods which were once commonly used and recommended. As the cost of linear rails become cheaper and cheaper due to the economy of scale and increasing number of buyers and large volume production of manufactures and suppliers. 8mm steel rods and linear bearings are slowly being somewhat phased out but still used on cheap kits found on Aliexpress and Amazon. 

Kinematic Bed Mounting

SolidCore CoreXY Z-Axis Bed Leveling

We recently started working on the SolidCore 3d printer‘s bed leveling and mounting system. The z-axis uses a 3-point kinematic bed mounting with magnetic pivot spheres on each mount This properly constrains the bed at 3 points of contact. The pivot balls that attach the Z-axis bed mounts can be held into position by the weight of the bed or magnetic force. The dowel pins ensure that there is zero lateral play on the bed. You can only move it by lifting it.

3-Point Bed Leveling

Three point bed leveling uses three independently driven lead screws to automatically level the bed and compensate for a bent or uneven plate. The Z-axis lead screws are used as the 3 points that make up a triangle, defining one plane. The advantage of a kinematic bed mount is that the defined plane of the bed, a kinematic mount, is that the aluminum plate can properly expand without bending the plate. 

Bed Flatness

In a standard aluminum stock, as heat warps or cools down your aluminum build plate, it expands unevenly; this causes problems with the much needed flatness of the print bed as it will eventually bend under pressure. The bed can raise or lower without binding or twisting, keeping the bed flat.

Cast Aluminum Tool Plate

Cast Aluminum tool plate is a good solution because it has good thermal conductivity and heats up evenly without warp or twist. The bed needs to be flat and remain level In three point bed leveling, the three z-axis lead screws are used as the three points that make up a triangle and define a plane.

Three Points Define A Plane

Since 3 points define a plain 3 screws, evenly placed in a triangle will raise and lower that plain without imparting any twisting forces so the bed will stay flat.

Advantages of The Kinematic Mount

A mechanical bind can cause the bed to tilt over time. The advantage of a kinematic bed mount is the aluminum plate to expand and to be set in tram with the XY plane of the printer without causing anything to bend or flex.

SolidCore-Kinematic Bed Mount Design

Kinematic Components

The kinematic mounting system will use three kinematic mounts for the 3-point bed leveling setup.

Each Kinematic Mount Contains:

1 x Kinematic Base

1 x Neodymium Ring Magnet

2 x Dowel Pins

Magnets

Kinematic Bed Mounting

SolidCore CoreXY Z-Axis Bed Leveling

We recently started working on the SolidCore 3d printer‘s bed leveling and mounting system. The z-axis uses a 3-point kinematic bed mounting with magnetic pivot spheres on each mount This properly constrains the bed at 3 points of contact. The pivot balls that attach the Z-axis bed mounts can be held into position by the weight of the bed or magnetic force. The dowel pins ensure that there is zero lateral play on the bed. You can only move it by lifting it.

3-Point Bed Leveling

Three point bed leveling uses three independently driven lead screws to automatically level the bed and compensate for a bent or uneven plate. The Z-axis lead screws are used as the 3 points that make up a triangle, defining one plane. The advantage of a kinematic bed mount is that the defined plane of the bed, a kinematic mount, is that the aluminum plate can properly expand without bending the plate.

Bed Flatness

In a standard aluminum stock, as heat warps or cools down your aluminum build plate, it expands unevenly; this causes problems with the much needed flatness of the print bed as it will eventually bend under pressure. The bed can raise or lower without binding or twisting, keeping the bed flat.

Cast Aluminum Tool Plate

Cast Aluminum tool plate is a good solution because it has good thermal conductivity and heats up evenly without warp or twist. The bed needs to be flat and remain level In three point bed leveling, the three z-axis lead screws are used as the three points that make up a triangle and define a plane.

Three Points Define A Plane

Since 3 points define a plain, 3 screws, evenly placed in a triangle will raise and lower that plain without imparting any twisting forces so the bed will stay flat.

Advantages of The Kinematic Mount

A mechanical bind can cause the bed to tilt over time. The advantage of a kinematic bed mount is the aluminum plate to expand and to be set in tram with the XY plane of the printer without causing anything to bend or flex.

Lead Screw Synchronization

3 points define a plane, therefore 3 screws need to be in synchronization. So the best way to achieve that is to drive them via a single motor and continuous belt. If designed correctly so that none of the screw or bed mounts can warp or twist, then the bed will remain level.

Bed Leveling & RepRap Firmware

Auto Leveling with the Reprap firmware uses this plane to make a heightmap, and adjust the lead screws to level the bed. With 3 independently driven lead screws that automatically level the bed before each print, and bed mapping to compensate for a bent piece of sheet metal used for the bed plate.

Mesh Bed Leveling 

Mesh bed leveling measures and compensates for an imperfect bed by collecting height points along a grid pattern overlaid on the print bed and then saves collected points to generate a heightmap. When printing, the motor movement is calculated

and compensated between heights to correct the movement in Z.

Bed Tilt

A kinematic coupling bed mount is stable, like a tripod. When you turn one leveling screw, the whole bed plate tilts on the other two screws. A kinematic 3 point mount allows the aluminum plate to expand and to be set in tram with the XY plane of the printer without causing anything to bend or flex.

Kelvin Kinematic Mount

A Kelvin kinematic mount has one reference point and allows the expanding heated print bed to slide on the leveling screws in a controlled way. Setting it level the first time is fast and easy and then it doesn’t have to be touched again, assuming the printer’s frame assembly is correct.

Cast Aluminum Tooling Plate

Tooling plates are cast so it doesn’t have the internal stresses compared to other aluminum stock. The mic6 cast aluminum is milled flat afterwards. When heated it should expand evenly and with a kinematic bed mount it shouldn’t change shape or noticeably bend in the Z-axis.

Alternative Bed Mounting Options

Solidcore Corexy Z-Axis Bed Mount Designs

The SolidCore CoreXY 3d printer also has other bed mounting options for the z-axis setup. These bed mounting options use a spherical magnetic ball to pivot the bed on three points.

Stepper Motor & Lead Screw Synchronization

3 points define a plane, therefore 3 screws need to be in synchronization. So the best way to achieve that is to drive them via a single motor and continuous belt. If designed correctly so that none of the screw or bed mounts can warp or twist, then the bed will remain level.

Bed Leveling & RepRap Firmware

Auto Leveling with the Reprap firmware uses this plane to make a heightmap, and adjust the lead screws to level the bed. With 3 independently driven lead screws that automatically level the bed before each print, and bed mapping to compensate for a bent piece of sheet metal used for the bed plate. See Electronics

Mic6 Cast Build Plate

Tooling plate is cast so it doesn’t have the internal stresses compared to other aluminum stock. The cast aluminum is milled flat afterwards. When heated it should expand evenly and with a kinematic bed mount it shouldn’t change shape or noticeably bend in the Z-axis.

Alternative Bed Mounting Options

Solidcore Corexy Z-Axis Bed Mount Designs

The SolidCore CoreXY 3d printer also has other bed mounting options for the z-axis setup. These bed mounting options use a spherical magnetic ball to pivot the bed on three points.

Kinematic Mount Design Explained

What is a kinematic mount?

A kinematic bed coupling is designed to constrain the mechanical components with optimal precision and positional accuracy. For example a kinematic coupling uses three radial v-grooves in one part that mate with three hemispheres in another part. A kinematic mount, which is ideal for bed leveling and proper mechanical constraint. A kinematic mount is a mount in which all six degrees of freedom (three translations and three rotations) of a 3D object are restrained from moving without overconstraint.

How does a kinematic mount work?

A kinematic mount is a type of mounting mechanism used for positional accuracy. Typically, the movable frame that holds the print bed pivots on a ball bearing which is set into a hole in the fixed frame.

Kinematic Constraints

Kinematic constraints are constraints between mechanical components that decrease the degrees of freedom of rigid systems. The degrees of freedom or DOF of a rigid body is defined as the number of independent movements and determines the DOF of the body. On a two dimensional plane such as a 3d printer build plate, there are 3 DOF. The print bed can be translated along the x-axis and y-axis, and rotated about each axis.

SolidCore Kinematic Coupling Bed Mount

• kinematic bed mount
• kinematic bed leveling
• kinematic coupling 3d printer
• 3d printer bed design

kinematic coupling system to prevent any z-axis bindingBOM:

The kinematic coupling prevents over constraint of the bed allowing the z-axis to move freely 

Mechanical Arrangement

The Kelvin kinematic coupling reduces mechanical binds, increasing bed leveling repeatability.

Work in progress

Currently the bed is resting on the mounts, a significant lateral force could knock the bed off, and cause damage. 

Kinematic Bed Leveling

Kinematic mounting will help to level the bed on three points and allows for thermal expansion of the bed plate without causing anything to flex.

Three point bed adjustment – SolidCore

3 point leveling options. The most recent design used a kinematic bed setup.

• z_stepper_auto_align
• 3d printer bed design
• kinematic bed mount
• 3d printer bed design
• triple z bed leveling
• triple z axis bed leveling
• true bed leveling
• thingiverse
• bed levelling using multiple independent z motors
• z_stepper_auto_align
• PEI Sheet

Triple Z Setup

A perfectly levelled print surface becomes more challenging as the size of the build plate increases. With the Maxwell coupling applied to the Z-axis by adding a third axis and mounting it with a Maxwell coupling mechanism which provides unconstrained mounting points. The Z-axis leveling routine is implemented with the RepRap firmware on a Duet Wifi or Duet 3 Mainboard.

Bed Leveling

Bed leveling is necessary in order to print large objects. Mesh bed leveling creates a virtual grid of the print bed. As the layers are printed the motors will lower and raise the nozzle while printing to compensate for the uneven locations on the build plate. Auto Bed Leveling is a function of the Duet 2 board itself. 

Firmware

Specify at least 3 points using the G30 command and after.

Last one you need to add the S Parameter. Then it will level automatically

Heat up build plate 

Click the “Bed Leveling” button or macro on the Duet Interface. see 3D Printing Dictionary

Triplez Mechanism

The advantage of triplez is the additional degree of freedom which allows  radial movement and bed leveling. With small springs on corners and the bed fixtures of the bed. Due to thermal expansion the aluminium plate just loses the frame.

Triple Z bed leveling using the Kinematic coupling for bed leveling and mounting.

Wider belts are more rigid and reduce artifacts caused by the elasticity of the belt itself. The artifacts in prints look like the pitch of the belt itself. In addition, increasing the size of the pulleys will reduce ringing and artifacts.

Triple-Z axis With G30 Command 

Set up the measuring point with the G30 command and its P-parameter S-parameter on the last G30 command.

Triple Z-Axis-Belted Z-Motors 

The triple z-axis design used on the SolidCore Printer utilizes three independent driven stepper motors to implement auto bed leveling. Each lead screw will be constrained by a MGN12 linear rail. Originally we were working on a design that used one single z-axis motor and a belt routing the three lead screws together in sync. But after having trouble sourcing the belt that was the perfect length I decided to just go with three stepper motors similar to the HeVort 3d printer or Jubilee tool changing corexy platform.

Triple Z Firmware

With the Duet Wifi electronics board, we can drive 3 steppers and run an auto bed leveling routine using a proximity sensor or probe.

Many 3d printer users frown upon the idea of multiple steppers for Z-axis motion due to syncing issues. But with the 32 bit Duet3d board and RepRap Firmware keeping the three lead screws in  sync should be fine.When powered up stepper motors tend to jump to the four steps that match the phase current. Some will jump forwards or backwards after a number of power cycles.

We used RepRap firmware with bed levelling using multiple independent Z-axis motors bed levelling and RepRap Firmware Files: https://3ddistributed.com/workhorse-printer/ Dual Z Stepper motors with mesh bed leveling 

Each Z motor must be driven from a separate stepper motor output on multiple drivers for the Z axis. 

1st. Auto level

2nd. Mesh Bed Leveling

We used independent stepper motors with each motor having its own endstop switch.

Duet 3 Dual Z Motor

M584 Drive Mapping For Dual Z-Motors

; Drives

M569 P0 S1                                       ; physical drive 0.0 goes forwards

M569 P1 S1                                       ; physical drive 0.0 goes forwards

M569 P2 S1                                       ; physical drive 0.2 goes forwards

M569 P3 S1                                       ; physical drive 0.3 goes forwards

M569 P4 S1                                       ; physical drive 0.0 goes forwards

M569 P5 S1                                       ; physical drive 0.5 goes forwards

M584 X0:1 Y2 Z3:4 E5                           ; set drive mapping

M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation

M92 X64.00 Y64.00 Z64.00 E420.00                  ; set steps per mm

M566 X900.00 Y900.00 Z12.00 E120.00                ; set maximum instantaneous speed changes (mm/min)

M203 X6000.00 Y6000.00 Z180.00 E1200.00            ; set maximum speeds (mm/min)

M201 X500.00 Y500.00 Z20.00 E250.00                ; set accelerations (mm/s^2)

M906 X800 Y800 Z800 E800 I30                       ; set motor currents (mA) and motor idle factor in percent

M84 S30                                            ; Set idle timeout

M584 Drive Mapping For Dual Z Axis Motors Settings

M584 X0:1 Y2 Z3:4 E5                           ; set drive mapping

; Axis Limits

M208 X0 Y0 Z0 S1                                   ; set axis min

M208 X230 Y210 Z200 S0                             ; set axis max

Dual Z Endstop Configuration

; Endstops

M574 X1 S1 P”io1.in”                               ; configure active-high endstop for low end on X via pin io1.in

M574 X2 S1 P”io2.in”                               ; configure active-high endstop for low end on X via pin io1.in

M574 Y1 S1 P”io3.in”                               ; configure active-high endstop for low end on Y via pin io3.in

M574 Z1 S1 P”io4.in”                               ; configure active-high endstop for low end on Z via pin io4.in

M574 Z2 S1 P”io5.in”                               ; configure active-high endstop for low end on X via pin io1.in

RepRap Firmware

While a single Nema 17 stepper motor can use a continuous closed loop belt routing to all three lead screws in sync. This can be avoided by adding code in RepRap Firmware to detect a power down moving the motors to the correct position ready for power up. The Duet WiFi has two power monitor circuits on board but it doesn’t matter because the machine will run an auto levelling at start up.

Z-Wobble

Z-wobble is a common issue that many z-axis lead screw driven 3d printers experience. The z-wobble issue occurs from either bent lead screws, mis-alignment, rotational run-out or other factors on the drive mechanism such as components being overconstrained or loose. Also, check the frame of your 3d printer for squareness

Print a tall test piece to analyze the z-banding or layer lines and artifacts. The pattern of the layer lines can easily identify the frequency or pitch as the print bed moves up or down to print the object.

Some users attempt to constrain the lead screws with a bearing or idler mount but that will transfer the wobble into the mounting point. If over done it could also cause damage to the rails or premature wear. Rely on the straight rods with linear bearings for Z stability. Anti backlash nuts will eliminate much of the wobble. Disassemble the Z-axis assembly to check if the lead screw is straight. Roll the lead screw on a flat surface such as a very flat table. If the lead screw is not straight, replace the lead screw from a reliable source.

Oldham Coupler

A Oldham coupler is an attachment that can minimize or eliminate the run out at the bottom and no bearing at the top to overconstrain it. If lead screws may be somewhat bent. The run out can cause imperfections and may transfer to the prints. If  lead screws are causing Z wobble due to not being straight, they are overconstrained – This is a common problem on cheaper 3d printers. 

If you’re struggling with a bent lead screw check to see if it’s over constrained and sifting along the x and y-plane. Z-wobble is common on low quality machines but can easily be fixed by attaching an Oldham Coupler.

Print Surface

A sheet glass with blue painters tape can be used as a removable print surface. Although the glass print surface could be bad for heat conductivity as it needs to make contact between bed and surface. It’s flat and a cheap solution. Swap between sheets of glass in between prints so the printed part can be removed without waiting for the bed to cool. 

PEI Sheet

Machining a sheet of mic6 aluminum to make a heat bed.

Press fit the magnets vs epoxy

• The round magnets with a hole in the middle to put a small screw to secure in place but that depends on how thick the mic6 plate.
• Use high temp rtv silicone sealant, it’s cheap and can take 200 Celsius.

• High temp magnetic stickers adhered to mic6. When it gives up, peel it off and replace it. The magnetic stickers won’t compromise bed integrity from machining pockets in it for magnets.
• 3m high temp no77 glue

Nozzle Diameter & Layer Height

Nozzle diameter and layer height plays a critical role in overall print time. The more material that flows through the print head, the faster a print will finish. The quicker you finish a print the less likely you are to have a failed print. A wider nozzle will also increase print temperature and flow rate. This will allow you to print wider layers, which should result in better layer adhesion. 3d printing large parts can take days to weeks and can use a great amount of filament. Print time is directly related to nozzle flow rate. Print speed is a healthy balance of X and y-axis travel speed and extruder flow rate. 

Non-Planar 3D Printing

In the future, we may see more non-planar printing. This would allow you to print a part in vertical mode and add another component at an angle without need of support materia. With non-planar printing becoming more and more popular, it’s not surprising that slicer toolpaths are available. This means you can optimize how your layers are printed and reduce support needed thanks to angled orientation.One problem with 3D printing is that it can be difficult to support overhangs.

The Hevort 3-point bed tilt also changes the way parts need to be supported so for models with overhangs facing ‘uphill’ into the angle, supports aren’t needed. Although non-planar printing is not really widely implemented yet, their software for printing at fixed angles other than 90 can generate optimized toolpaths for printing fixed angles.

3 point bed leveling can tilt the bed at an angle printing along a slope.  

Although non-planar printing is not really widely implemented yet, there are new slicer post and processor components for printing at fixed angles other than 90. In some cases the prints come out stronger due to layers not being on 90 degree plains.

The Hevort’s 3-point bed tilt also changes the way parts need to be supported so for models with overhangs facing ‘uphill’ into the angle, supports aren’t needed. if we say 45 degrees is possible on a normal printer now, it allows 45+35(=80) in that direction, without support. Although non-planar printing is not really widely implemented yet, there is a post processor and custom Cura version for printing at fixed angles other than 90. I think this would make it quite easy to combine the g-code of two models to print a part in the regular vertical mode, then add a second component at an angle, allowing optimization of layer orientation to an extent, and again reducing support.

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SolidCore Thingiverse 3D Printer Build Plans

SolidCore Kinematic Bed Mounting System Setup