K40 CO2 40W China Laser und Engraver

Building instructions Rotary Module for the K40 C02 Laser

Engraving glasses and bottles


Focus via the motor table

What is a Rotary and what is it used for? A Rotary is used to laser or label round objects such as wine bottles, glasses or aluminium thermos flasks.
A laser can only perform 4 movements: right - left and back and forth. The X-axis is responsible for the right and left movements, the Y-axis for the back and forth movements.
With round bodies such as bottles or glasses, the laser would quickly lose focus due to its round shape. That's what the Rotary is for, it turns the glass a little in the Y direction after each lateral movement.

There are several Rotarys to copy and download portals. But none of them could convince me. So then I have to do it myself.
In the K40 China Laser, there is not much height left below the laser table. This should be used to the maximum. If the height is not sufficient, the bottom of the K40 can also be retrofitted with the plasma cutter.

The first version was already fully functional. In the meantime, I have further optimised the Rotary so that the last mm in width and height can be used. Now wine bottles up to 0.7l can be engraved without removing the bottom of the machine.

Rotary ausgebautfokusierbar mit dem Lasertisch Rotary ausgebautRotary im K40 Laser eingebaut

Building instruction Rotary for the K40

Somehow you came across this article. Probably because you have a K40 laser and would like to engrave round objects like bottles and glasses.
I was faced with the same project as you and was pretty much biting the bullet. No one really wants to help you and otherwise only at horrendous prices. That's why I decided to conduct a little experiment.
I took the time to develop a rotary and share it with you. I put together a list of components and laser files and wrote this report. I spent a lot of time on this and I think that this should be rewarded. If I could help you with these instructions you are welcome to send me a small amount via PayPal to contact@cigarbox-guitars. I will then see by the number of downloads if this is only used by people
if someone thanks me for something or appreciates something. Depending on that I will continue to put projects online or do without. Of course I would be very happy if you give my Facebook page a thumbs up or even share it. Thank you and here we go.....

I use the motorised laser table that can be found on Thingverse. The Rotary is specially designed for this table. You will also find the corresponding report on these pages.
Attention: First check the dimensions of your laser table. If not, the Rotary has to be adjusted accordingly.


Parts list for Rotary

- Steppermotor 1.5A (17HS4401)
- 6 Kugellager 606ZZ 6 x 17 x 6mm
- 1 GT2 Riemen geschlossen 300mm
- 4 GT2 Timing Belt Pulley Aluminium 20 Zähne Bohrung 5mm
- 4 Gewindestange M5 je ca 300mm
- 2 Gewindestange M6 je ca 325mm (Antrieb)
- 2 Schrumpfschlauch passend zu M6 Gewindestange je ca 300mm
- 8 Gewindehülsen M5x20mm
- 4 Aluminium Rohr 7.5x1mm  ~280mm
- Aluminium Winkel 40x15x1mm  (Auflage auf Lasertsich)
- 3mm MDF
- 4 Innen 6-Kt- SchraubeM3x8mm mit U-Scheiben
- 8 Innen 6-Kt- Schraube M5x16mm
- 1 Innen 6-Kt- Schraube M5x30mm

First laser these components onto 3mm MDF

  Rotary 3Rotary 1Rotary 2

Always glue the two components together. Ideally, do this when you already have the ball bearings with you. This way you can apply the glue on one side and use the ball bearing to centre the components.
Note that one component has slightly larger holes. These are used to guide the threaded bushings. When the glue has hardened, the two lower holes must be countersunk a little on the outside so that the screws do not touch the laser table.
You are probably wondering why the motor mountings are also in the right-hand components? So that you can tension the belt without having to dismantle the whole Rotary. You only need to loosen the support bracket and then use the Allen key to loosen or tighten the screws through the holes. The slotted holes allow the motor to be pushed to the side so that the toothed belt can be tensioned.
Now you can cut the two support brackets to size and also countersink the two holes a little. Then assemble the Rotary. The threaded bushes are attached to the side parts with the Allen screws.
Does everything fit? You can now adapt the threaded rods and the lateral aluminium tubes to your table.

Rotary LinksAufhängung Links mit versenkten Löcher Rotary RechtsAufhängung Rechts mit versenkten Löcher

 Rotary MotorRotary mit seitlichem Ausschnitt für grüsse FlaschenRotary komplMDF Teile mit grösseren Bohrungen

A larger recess is provided on the right-hand suspension and on the motor mounting. This makes it possible to insert larger bottles into the Rotary. The bottle neck then lies under the aluminium profiles of the truck table.
So I could optimise the last mm and even bottles with a length of 330mm fit into the Rotary.

Adapter for conical glasses

Of course, there are also champagne glasses that do not fly cleanly on the Rotary due to their conical shape. For this I have built an adapter. This can be moved on the Rotary. There are some slotted holes for ball bearings.
are provided. So it should also be possible to put conical glasses straight on.

Rotary AdapterAdapter für konische GläserRotary Adapter eingebautAdapter zu Rotary Rotary Adapter mit Ausparung MotorAusschnitt für Motor für optimale Ausnutzung

What is a stepper motor?

The stepper motor is a stepper motor that moves by its step angle with each control. This step angle is indicated on the type plate, i.e. a 0.9° makes 400 steps and a 1.8° its 200 steps for one revolution.
The steps can then be specially controlled for whole-step operation, half-step operation, quarter-step operation or eighth-step operation,
Nema is a well-known cheap Chinese manufacturer and the number Nema17 that follows is only the size of the motor 42x42mm.

StepperStepper Motor als Antrieb für den Rotary

Where is the Rotary connected?

The rotary is driven by a stepper motor. This can be connected to the existing M2 Nano Board. For this purpose, the Y-axis (y-axis) that is not needed is unplugged and the retoary is connected to the socket that has become free. Attention: The stepper used should have a rated current < 2A. The Nano Board is not designed for higher currents and can otherwise be overloaded or even destroyed.

M2 Nano BoardStandard M2 Nanoi Moard

Help the Rotary turns continuously after switching on

No problem. In standard mode, the laser head always returns to its original position first. However, since we have exchanged the Y-axis for the rotary, the control expects the laser head to move to the end position in the Y-position and actuate the limit switch. So we have to trigger the limit switch manually. Some have a mechanical limit switch. My machine has an optical sensor. This is normally triggered by the metal construction. Take a piece of metal and hold it briefly between the two poles. The control system is already tricked and the Rotary moves into the start position.

Endschalter Y Axisoptischer Endschalter Y-Axis K40 CO2 LaserWhisperer

Attention: Before you move the laser head, you must always press the "Unlock Rail" button in the K40 Whisperer. This will unlock the stepper motors. Otherwise you will damage the mechanics.

The calibration

For calibration, it is best to draw a few squares and then send this file to the laser. I used a tin can for this and bordered it with masking tape.
Measure the caro after printing. Is everything correct? If the y-axis is not correct you can adjust it in the K40 Whisperer Settings. To do this, open the Settings > Rotary Setting tab or call it up directly with F4.
Select "Use Rotary Settings" and adjust the Rotary Scale factor if necessary. Then you can test the canister and the squares again and measure again.

Rotary K40ale Blechdose zur Kalibrierung des K40 RotaryRotary y AxisK40 Whisperer Rotary Settings

Prepare graphic for the Rotary

How can we determine the maximum size of the bottle surface to be engraved? We'll have to resort to the mathematical bag of tricks. What was that again. Calculate the circumference of a cylinder?
2* π *r. r stands for radius or half the diameter. This can be measured exactly with a caliper. For example, a bottle with a diameter of 70mm has a radius of 35mm. This results in 2x3.14x35 = 219.8mm.
The maximum width of the bottle or glass to be engraved can be measured directly.
Now a new sheet can be created in the graphics program with user-defined dimensions.

K40 Laser Table with Stepper Motor and Arduino Controller

I had already built a manual laser table for my K40 China laser. Meanwhile I would like to laser round parts like glasses and bottles. In order to use the maximum height of the laser, I decided to build a new table. This table should also have the possibility to hold a rotary. If it is not needed, it should be possible to dismantle it quickly and without tools so that it is not destroyed during normal use of the laser. The rotary should also be able to be focused with the motorised table.

Basic idea table from Thingverse with slightly modivised control system

What is needed:

- 3D Druckteile
- Steppermotor
- Trapezspindeln
- Arduino Nano
- Klemmbord für Arduino nano
- Stepper- Treiber
- Klemmbord für Stepper
- Kugellager 608 ZZ
- 5 Widerstände 10 K Ohm
- 1 Endchalter
- 4 Taster
- Litze und diverse Schrauben
- GT2 Zahnriemen
- GT2 Zahnriemenscheiben 8mm Borhrung
- GT2 Pulley
- Alu Profil 15x15mm

Height adjustable table with stepper motor

I bought a 3D printer to produce the necessary parts myself. The remaining parts such as trapezoidal spindles, ball bearings, toothed belt and stepper motor have been ordered. I still have a few days to print the plastic parts.

3D Druckteile K40 Lasertisch3D Druckteile für den Lastertisch

After printing the corner parts and motor mount, the table can be assembled with the aluminium profiles.
Built-in truck table. A piece of expanded metal is used as a cover to achieve the smallest possible reflection. Instead of expanded metal, a honeycomb table can of course also be used.

K40 LasertischLasertisch zusammengebaut Lasertisch eingebautLasertisch für K40 CO2 Laser mit Streckmetall Abdeckung

In the first step, an arduino nano is installed to take over the control functions of the table. 2 up and 2 down buttons are installed. I have found space for them on the side next to the temperature monitor.
The left buttons are responsible for the microstep function for the fine adjustment and the two on the right side for the fast up and down movement of the table.

Laser Control BoardK40 Laser Control Board

I installed the control for the table in the laser's power supply. For the Arduino Nano and the stepper driver, I also used a board with terminals.
This way, the Arduino can be plugged into the designated pins and the connections do not have to be soldered directly to the electronic components. The stepper motor can be plugged directly into the driver.

Wiring K40 Laser TableVerdrahtung K40 Laser Tisch

Arduino Nano BoardArduino Nano Board  A4988 Stepper Motor DriveA4988 Stepper Motor Drive

Board mit Arduino NanoBoard mit Arduino Nano Klemm Board Arduino3D Druck Gehäuse für Platinen

Pull-up and pull-down resistance

What are the resistors in the diagram for?
So that electronic components receive a clear signal, so-called pull-up and pull-down resistors must be installed. In our control system, this is the case with the 4 manual switches and the limit switch.
When the contact is opened, the pull-down resistor pulls the voltage at the input down to GND, so there is clearly no signal on the input pin of the Arduino Nano. Without this resistor, the input pin does not receive a clear signal. With this circuit, the signal is clearly

Remote Desk Connection K40 Laser with Raspberry Pi 4

Raspberry Pi Remote Desktop Connection K40 Laser

First, the required software must be installed on the Raspberry Pi. First, update the Raspery Pi to the latest version.

sudo apt-get update
sudo apt-get upgrade -y

 Anschliessend mit dem Befehl

sudo apt-get install xrdp

install the required software. Now the Raspberry Pi is ready for remote desktop access.

To access the K40 Laser Cutter and Encraver modified with a Raspberry Pi4 from a laptop or desktop you need a remote desktop connection.
To connect, simply type Remote Desktop into the Windows search box.

Remotedesktop Verbindung

Under Computer you enter the IP address of the Raspberry Pi. If you do not know this, log into your modem, e.g. Under Network Connections you can find all devices with their IP address in the network.
Then press the "Connect" button. The following login screen should now appear.

Anmeldung Remote Desktop

Here you enter the username of your Raspberry Pi (normally = pi) and the corresponding password under Username. If everything is entered correctly, the desktop of your Raspberrty Pi appears on your laptop or desktop.

 Desktop Raspberry PI


Share folders on the Raspberry Pi

In order to access the folder structure of the Raspberry Pi with the laptop or desktop, the Samba software must be installed on the Raspberry Pi.
For this you open the terminal and enter the command sudo apt-get install samba samba-common-bin

Now you have to set a user for samba with "sudo smbpasswd -a pi". This must also exist as a user on your Raspberry Pi. In the following example, we use the user "pi".

Then open the configuration file with sudo nano /etc/samba/smb.conf.
A folder share can look like this


comment = Laser-Share

Then save CTRL / O and confirm with Enter.

Finally, you only have to restart the service with "sudo /etc/init.d/samba restart".


Connect network drive

Now the folder on the Raspberry can be connected as a network drive on the desktop or laptop.
Open the Explorer. Right-click on the "This PC" icon.
Connect network drive

Select the desired drive letter
For the folder, enter the IP address or the name of the Raspberry PI followed by the folder name.
Now you will be asked for a password, enter the user and password of Samba (not the Raspberry password).

Now your Raspberry folder should be visible in the explorer.


Netzlaufwerk Verbinden

Installing Fonts on the Raspberry Pi

sudo apt-get install ttf-msccorefonts-installer

Controlling the laser with Rasberry Pi 4


Raspberry PI China Laser K40Raspberry PIRaspberry PI in Box

Who doesn't know the Raspberry Pi? The small computer developed by the Raspberry Pi Foundation is the size of a credit card and has sold millions of units. The latest version, Raspberry Pi 4 Model B, has just been released.

raspberry pi 4 model bRaspberry Pi 4 Model PRaspberry Pi Logo

This small computer has 2 micro HDMI connections, 2 USB and 2 USB3 interfaces. It also has a GIGA LAN connection and can also be equipped with a WLAN adapter.
I would like to install the Raspberry Pi in my China laser and install K40 Whisperer on it so that I don't have to set up the laptop every time I want to laser something. With the LAN connection I have access to the home network where all the laser data can be found.

The following components are used: (some components can be omitted)

  • Raspberry Pi 4 Model B/4GB
  • Raspberry Pi 15W Netzteil, EU, Schwarz
  • 32GB MicroSD-Karte (Class10)
  • Original Raspberry Pi 7" Touchscreen
  • Raspberry Pi 4 Kühlkörper - Heatsink
  • Miniature WiFi (802.11b/g/n) Modul für Raspberry Pi
  • Drahtlose Tastatur - Wireless Mini Keyboard

Prepare SD card

First, the SD card must be formatted. To do this, you can download SD Formatter from the following link.

First read through and accept the licence conditions. The file is downloaded and can then be installed.

SD Card Formatter licens SD Card Formatter

install Raspbian

Download the latest version of Raspian. It must then be unpacked.


Raspbian auf die SD Karte schreiben

The best way to do this is with win32Diskimager.exe, which is available on Sourceforge. Install Diskimager and then call it up. The programme is self-explanatory. At the top, select the image file in the folder you have just unpacked and select the data carrier. Then press the button "write". Now the image file is copied to the SD card.


Once the write process is complete, the SD card can be inserted into the Rasberry Pi.
- Connect the LAN cable
- HDMI cable to screen
- keyboard
- ev WLAN adapter
- Power supply unit

to the Rasberry Pi. Plug it into the socket and Raspian will start.

After starting, you will be asked to select the country / region / language and keyboard language.
Another step is to set up the WLAN. Select the WLAN and enter the password. The active WLAN is indicated by the 2 flashing arrows.
Bravo, the Raspi is almost set up. Now it's time to install the Whisperer software. Before that, a few basics.

Basics File Management Raspberry Pi

These commands should help you to find your way around the comand line in the Raspi.

One step back in the directory structure

cd ..

Change to a specific directory:

cd /home/pi/k40_Whisperer

Download the file to the current directory:

wget {URL}

Install package as root user (put a sudo in front of it):

sudo ....

Install package:

sude abt-get install{Paketname}

Check for updates

It makes sense to update the freshly installed system.

sudo apt-get update
sudo apt-get upgrade -y

Assign static IP address to RaspberryPi

sudo service dhcpcd status
sudo service dhcpcd start sudo systemctl enable dhcpcd
sudo nano /etc/dhcpcd.conf
interface eth0 static
static routers=
static domain_name_servers=

The IP address must of course be adjusted according to your IP range. For example, is the IP address of the Raspberry and is the IP address of your modem.

Download Whisperer

Whisperer 1

Search via browser on your Rasberry Pi for the following page and download the latest version of K40 Whisperer to your Rasberry Pi.

enter the following command line (latest version name)
You can also search for the file in the browser and right-click on the file to copy the link address, which simplifies the input. This can be pasted with CTRL-V.


(X.XX is the current version number Version 0.56 is the latest version when the report is created)

After downloading, the file must be unzipped


then change to the directory.

cd K40_Whisperer-0.56_src

A query may appear between the individual installations confirm this with a capital "J" and Enter.

sudo apt-get install libxml2-dev
sudo apt-get install libxslt1-dev
sudo apt-get install inkscape
sudo apt-get install libjpeg-dev
sudo apt-get install libudev-dev
sudo pip install -r requirements.txt
sudo pip install pyusb

Starte Whisperer

sudo python k40_whisperer.pyWhen Whisperer has been started, a menu item can now be created so that Whisperer can be started more easily.

Navigation -> Einstellungen -> Menupunkt hinzufügen

name : K40 Whisperer

Command : sudo python /home/pi/K40_Whisperer-0.56_src/

Comment : blank

Automatically mount / attach USB stick with "usbmount"

Some USB sticks are not automatically integrated and therefore cannot be accessed directly.

sudo apt-get install usbmount

After the installation, a directory with the name "media" is created. You will find the attached drives in this directory.

Rotate screen

I use the 7" touchscreen from Raspberry Pi. Unfortunately, Whisperer is not pre-programmed for such a small screen. Therefore, the whole start screen of Whisperer is not displayed in normal format.
The most important buttons Raster Engrave, Vector Engrave and Vektro cut and especially the Pause / Stop button are no longer displayed on the 7" touchscreen. The following command can be used to edit the config.txt fil

nano /boot/config.txt

The config file must be extended with the following value. After a reboot, the screen is rotated 90 degrees. Alternatively, the micro SD card can also be changed with an editor on the PC. The config.txt is located directly in the root directory.

display_rotate = 1

 Touchscreen 7 Zoll

  • display_rotate = 0: Normal value
  • display_rotate = 1: Rotated 90° (clockwise)
  • display_rotate = 2: Turned 180° (upside down)
  • display_rotate = 2: Rotated 270° (or counterclockwise)
  • display_rotate = 0x10000: Picture mirrored horizontally
  • display_rotate = 0x20000: Image mirrored vertically


K40 China Laser Mirror and Focus Lens Cleaning

Maintenance and cleaning of the K40 China laser does not only include vacuuming the residual parts in the laser room. During lasing, smoke also rises in the area of the laser head and contaminates the focus lens. I use an air assist system. This constantly blows air directly onto the part to be lasered. This prevents the smoke from rising up to the lens and contaminating it. To get an optimal cut, the mirrors and the focus lens must also be cleaned in between.

AcetonAceton zum Reinigen der Spiegel und Linse

I use cotton swabs and acetone for this. Caution: Acetone is a toxic and dangerous solvent. Acetone strongly degreases and dries the skin on contact. With prolonged or frequent skin contact, the chemical can trigger dermatitis, i.e. an inflammatory skin reaction. The vapours of the solvent are also harmful to health.




Caution: Mirrors and lenses are sensitive products and should be handled with care.
Furthermore, it should be noted that the mirrors and the focus lens should not be held with bare fingers. Our skin is kept moist by a kind of oil film. This moisture immediately leaves a fingerprint on the mirror or focus lens which is burnt into the mirror by the laser beam. So only touch the mirror and lens from the side or wear gloves.


Read more: K40 China Laser Mirror and Focus Lens Cleaning

K40 Check laser mirror settings and focus

Um das "Beste" aus dem K40 China Laser herauszuholen müssen die Spiegel und der Fokus überprüft und gegebenenfalls nachjustiert werden. Durch den Umbau des Lasers musste ich die ganze Mechanik aus dem Gerät aus- und anschliessend wieder einbauen. Ein nachjustieren der Spiegel ist also unumgänglich. Wenn beim lasern festgestellt wird das auf der einen Seite die Teile korrekt durchgelasert sind und an einer andern Stelle die Schnitte nicht gänzlich ausgeschnitten wurden, deutet dies darauf hin das entweder der Lasertisch nicht an allen Orten die gleiche Höhe ausweist oder das die Spiegel bzw der Fokus nicht korrekt eingestellt ist.

Das Prinzip:

Der Laserstrahl wird von der Laserröhre nach links auf den ersten Umlekspiegel gerichtet. Dieser leitet den Strahl auf den vorderen fahrbaren Spiegel. Dort wird der Laserstrahl zum Laserkopf umgelenkt.
Ziel ist es das der Laserstrahl möglichst mittig auf den Spiegel auftritt. Um dies in jeder Position sicherzustellen ist dies an diversen Punkten zu überprüfen. (mind. 4 rote Punkte) Trifft der Laserstrahl nicht mittig auf den Spiegel, driftet der Laserstrahl anschliessend seitlich weg. Somit ist es möglich das der Laser an einer Position sehr gute Ergebnisse erziehlt und an einer andern Position kein Laserstrahl mehr ankommt. Mit den 3 Justierschrauben kann der Spiegel exakt einjustiert werden.

Laser Einstellungkorrekt eingestellte Umlenk Spiegel  Laser Einstellung korrektLaserstrahl an allen 4 Punkten überprüfen

Laser Einstellung leftLaserstrahl nicht korrekt  Laser Einstellung rightLaserstrahl nicht korrekt

What is the best way to proceed:

After the first mirror, the laser beam is redirected to the front through the opening in the housing. An adhesive tape can be attached to the opening and then the test button pressed. Be careful not to reach into the unit and take care of your eyes. A small burn mark will be visible in the adhesive tape after it has been triggered.
Laserstrahl KlebebandKlebeband an der Gehäuseöffnung Laserkopf KlebebandKlebeband am Laserkopf

This is helpful to determine the position for the next mirror. For the second mirror, also stick a piece of tape or a small piece of wood with double-sided tape in front of the mirror. Then move the slide to the rearmost position. Release the test button, then push the slide all the way forward and release the test button again. The two points should be exactly on top of each other and centred in the mirror. If this is not the case, the mirrors can be adjusted with the 3 adjustment screws. It is a matter of patience, but you will be rewarded with a good result

Adjust focus:

The laser beam is directed from the left movable deflection mirror directly onto the inclined mirror in the laser head through the lens onto the workpiece. Normally the distance from the lens is 50.08mm.
The laser beam should be as bundled as possible onto the workpiece.

Fokus LaserkopfK40 China Laser Fokus Einstellungen

Adjusting the focus is no magic. Simply place a remnant on the laser table and place something underneath on one side. Then send a job with a line to the laser. The focus must then be determined on the piece of wood and the height of the laser table adjusted accordingly. With an adjustable laser table, this can be done in no time at all.

Fokus TestenTestlinie schneiden  FokusFokus bestimmen anhand der Testlinie

Download the test line here


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