iBox Nano - User Guide
The only way to damage the nano under normal operation is to spill resin on or in it.
Do not remove the tape from the glass dish (aka VAT). This is FEP tape and is needed to keep the resin from sticking to the VAT.
What do I do if I spill resin on the printer?
Quickly remove the VAT and wipe off the resin with an absorbent paper towel or other cloth. You can use soap and water for cleanup. Do not use Windex (or other ammonia based cleaners). Do NOT use Alcohol to clean it.
We have only damaged one Nano during thousands of test prints and that was by overfilling the VAT just a little too much and not noticing it was overflowing during the first layer. Please under-fill the VAT. It is very easy to add resin with your 100mL squirt top resin bottle and difficult to remove resin. If we work together we can get through your natural fear of running out of resin. Once you are familiar with the printer it will be a non-issue.
Always clean the VAT bottom (underside where the VAT touches the top of the printer) and sides to make sure you do not have residual resin that will bond during a print. If you have or spill resin between the VAT bottom and printer top it will bond the two together during your print cycle. This is bad but usually not destructive. Remember that cured resin is basically a powerful glue.
What if I spill resin inside my Nano?
This is very bad. The resin will ÒcureÓ and bond everything together. Think of it as spilling superglue inside the printer. The buttons will be the first failure. The acrylic will discolor from the resin as well. The printer will likely still function from the GUI.
What if I get resin on my hands?
Wash them immediately.
Always wear eye protection when working with resin or any fluid that is not eye friendly. Please read the MSDS. Resin is generally safe, but be careful especially around children.
We handle support through our support forum.
1. Forum Support: With a moderated support forum you can first search for your issue and if its common you could have an answer in seconds and be on your merry way. If you don't find a solution you can post a ÒnewÓ question. Then the moderators and other friendly and helpful users can try to provide support and assistance. Your help session is logged for others to see and possibly be helped as well. The next big advantage to a support forum is search engine indexing. Thus people just banging in their issue in ÒgoogleÓ can find the answer and find our support forum in seconds. This is what we like when we buy something and what we prefer when looking for support for our consumer electronic devices. We hope you join the forum and are happy with it.
General Operational Procedures:
1. Remove the Nano from itÕs packaging.
2. The Nano has a microB USB plug and cable, it is used only to power the unit. It will not enumerate on your computer as a USB device. All connectivity is achieved via WiFi.
3. You can power the Nano from almost any USB power source.
4. The Nano takes about 2 minutes to boot up after connecting USB power. It will beep and cycle all indicator lights at boot.
5. The network settings are displayed during boot time for N seconds on the LCD screen - on the top of the printer where the VAT is placed. We recommend that until you are familiar with the Nano, specifically how to communicate with it, do not have the VAT in place while the printer is booting.
6. The Z axis on the nano has a Carriage that holds the Build Plate. The Build Plate needs to be lowered until it is touching the VAT surface before you initiate a Print. Try this a few times with no resin in the VAT to get comfortable with the process. Once you have ÒhomedÓ this position and selected print, the position will be remembered. Once homed, the Build Plate will lower to the print position by holding the ÒDownÓ button for several seconds until you hear a double beep. After a print completes the build plate will motor up automatically to a height that will allow easy removal of the Build Plate from the Carriage.
7. Never fill the VAT more than half full with resin.
8. Seriously; Never fill the VAT more than half full with resin. Refer to ÒWarningsÓ above.
9. Always attempt to shut the Nano down gracefully if possible. It is a computer with an SSD and repeated ÒhardÓ power drops will reduce the devices reliable operation. Graceful shutdown can be achieved from the GUI (Power Button) or by pressing and holding both the UP and DOWN buttons for >4 sec until it beeps multiple times. Shutdown takes 30-45 seconds. When the lights are no longer blinking, the Nano is powered down.
10. The buttons on the front of the Nano are multi-use:
¥ Òquick pressÓ -> (starts/stops printing) Starts a print. If a print is in process, it will stop the print job.
¥ Òlong press >4secÓ -> Initiates WPS to associate with a WPS enable AP. See section on connecting the nano to the network.
¥ If Òquick pressedÓ while the Carriage is in motion it will stop the Carriage motion.
Button [UP / DOWN]
¥ Òquick pressÓ -> Moves carriage UP / DOWN one layer height OR if the carriage is currently moving it will STOP the movement.
¥ Òlong press >1secÓ -> Double Beeps -> Starts the carriage moving for a long distance (configurable in Nano GUI settings)
¥ Press BOTH UP+DOWN buttons for >4sec -> Gracefully shuts down the printer. You can also shutdown or reboot from the Nano GUI.
11. If the resin in your VAT has been sitting for more than a few hours, take a small paintbrush or stir-stick (take care not to puncture or scratch the FEP tape in the Vat) and stir the resin. This will ensure your pigment is evenly distributed and your cure agents are as well. If your cure agents separate you will see this as warping of the first (lowest) layers printed. If you see warping it is because the resin has settled. One other method to ensure a well mixed resin is to pour it into a ÒusedÓ resin bottle through a fine strainer. Then you can shake the bottle to ensure a well mixed resin. Never add used resin to the ÒnewÓ resin bottle.
12. In between prints make sure a film of resin has not cured to the bottom of your VAT. If so, carefully remove it with a sharp edge tool. The VAT is quite durable, but the FEP Tape (teflon tape) is not durable and can be scratched easily even by a fingernail. If the tape is scratched there is a chance it will distort the image and cause the resin to cure to the VAT or prematurely fail if resin gets under the FEP tape.
13. If you are using the default Acrylic build plate, it is best to not leave it in the resin for extended periods of time. The uncured resin can etch the acrylic, which will eventually damage the acrylic build plate resulting in its replacement.
The tape on the bottom of the VAT is a special tape called FEP tape. It is a normal adhesive based tape with a Teflon layer on the surface. This teflon layer makes it slippery and reduces the chance for Resin to bond to the VAT+FEP_Tape. The resin should only bond to the Build Plate.
The FEP Tape will last for a very long time if you use care when touching it. It scratches easily especially if you are using tools near it. If you are careful you can get 25-50 prints from onne piece of FEP tape.
To replace the FEP tape you should watch our youtube video [link to our channel at the beginning of this document]. The process is simple:
1. Remove all resin from VAT. Wipe with paper towel.
2. Clean VAT with Alcohol (Alcohol is fine for the VAT but keep it away from the Acrylic)
3. Wipe out with lint free cloth
4. Peel back part of the new FEP tape at one corner.
5. ÒcarefullyÓ stick the FEP tape to the VAT starting on one side and moving toward the other.
6. Press with your fingers on the tape to make sure it is completely stuck to the glass VAT.
7. Add resin and print.
We have experimented with >20 VAT clamp types. All of our configurations work, but vary in tightness. In general it is ok to have the VAT loose, with about 1mm or less clearance between the VAT Clamp and the top of the glass VAT. The build plate will lift the entire assembly >1mm during the peel process. At the point the VAT touches the VAT clamp this is known as the PEEL, the the force exerted by the build plate motoring up will separate the VAT from the Build Plate by using the VAT Clamps as leverage.
We have also used shorter clamps that can hold the VAT with no gap, this was also fine. We have also used foam spacers under the VAT clamp to keep the VAT from rotating at the PEEL stage. The foam adhesive is degraded by the resin, but we are still investigating a potential solution.
Getting your Nano on the network
¥ WPS - Pressing the WPS button on your Access Point (assuming it has this feature) and then pressing and holding the ÒPrintÓ button (3-5 seconds) on the Nano until you hear multiple beeps will put both devices in WPS mode and they should automatically connect.
¥ Set your local AP to SSID ÒnanoÓ with no security (aka No WEP/WPA, etc). Then connect and use the Settings->Network tab to add your APs SSID / Security Info
¥ USB Stick : Rebooting with a USB Stick in the Nano with a minimum of the file wpa_supplicant.conf.txt that has been edited to include your network information.
¥ GUI+WiFi : Connect the Nano to a monitor [HDMI or Composite NTSC], and insert a USB Hub with [Keyboard, Mouse, WiFi adapter (from the Nano)]. Then just use the Nanos GUI to input your WiFi SSID and Passphrase/Key. The heart of the Nano is the Raspberry Pi, and there are hundreds of articles and youtube videos on getting it on the network.
¥ GUI + USB Ethernet Module : Connect the Nano to a monitor [HDMI or Composite NTSC], and insert a USB Hub with [Keyboard, Mouse, Ethernet USB adapter (User Supplied - Make sure it is one that works easily with a Raspberry Pi)]. Then use the NanoÕs GUI to verify you are connected via Ethernet via your Ethernet LAN. You can actually do this without accessing the GUI if the Raspberry Pi recognizes your ethernet adapter and has drivers for it. If so you can just boot the Nano with the Ethernet adapter inserted in the USB port and the IP address will display on the Nanos screen (where the VAT goes).
Start with he Nano OFF (not connected to USB power). Now put the USB stick in the iBox NanoÕs USB port. This will require you to first remove the WiFi adapter. Now reboot. Let the Nano fully reboot ~ <3min. Then remove the USB memory stick and reinsert the WiFi USB module. Now reboot the Nano again. The Nano should gain access to your network and display its IP address and other information on the screen during the next reboot.
Download these files and put them on a USB Flash Drive formatted as FAT (typical format)
¥ wpa_supplicant.conf.txt (mandatory) -> Add your access point SSID + Key
¥ hosts.txt (optional) -> Set NanoÕs network name - Default in the Nano is ÒNanoÓ. You do not have to change this name unless you have multiple NanoÕs on your network and you want to use ZeroConfig. If you have one Nano you can use ZeroConfig with the default name.
¥ hostname.txt (optional) -> Set NanoÕs network name (second place it needs to be set. Needs to match the ÒnameÓ in hosts.txt.
¥ interfaces.txt (optional) -> Set NanoÕs advanced network properties
The files can be found at: files.iboxprinters.com
Only one of these files needs to be changed to get the Nano on your WiFi network. The other three are for setting the NanoÕs network name (handy if you have several iBox NanoÕs), and for advanced users.
Example 1. Your home/work Access Point has an SSID of ÒHomeAPÓ and Passphrase of Ò1234567890Ó
Add this to the wpa_supplicant.config.txt file on the USB stick: (you can just cut and paste it)
You need to change ssid=Òyour_ap_nameÓ to
your WiFi SSID
You need to change psk=Ò1234567890Ó to your APs Key/passphrase
You might have to change pairwise=CCMP to TKIP if so you need to add a new line:
group=TKIP WEP104 WEP40
proto options: RSN (WPA2) or WPA (WPA1).
key_mgmt options: WPA-PSK (most likely) or WPA-EAP (enterprise networks)
pairwise options: CCMP (WPA2) or TKIP (WPA1)
auth_alg is almost always OPEN but other options include LEAP and SHARED
NOTE: The Nano will not connect to your access point if you have spaces in your SSID.
The second way to setup the WiFi network is a fairly recent feature called WPS. WPS allows you to press a button on your Access Point and a button on a device within a short period ~1-2minutes and have them associate with each other. On the Nano the WPS button is accessed by holding the ÒPrintÓ button (front - right button) for 5 seconds. You will hear several ÒbeepsÓ. Now press the WPS button on your Access Point. They should now be linked. You can find the network information on the NanoÕs screen at every reboot and after a successful WPS connection. Please take note of the IP address from the NanoÕs screen during one of these events, it is how you will connect to the Nano.
For more advanced users you can create a DHCP reservation for the Nano once it is associated with your Access Point. This is done on the AP and the process varies from AP to AP. This will assure your Nano always has the same IP Address. This process is recommended but optional.
Configure your local AP as ÒnanoÓ
You can change your home AP SSID to ÒnanoÓ and disable security (WPA/WEP,etc). Then the Nano will associate and get an IP address from your AP. Then you can log on to the Nano using its IP Address from the NanoÕs LCD or by using http://nano.local in your browser. Then you can add your target SSID and security information in the Nano Settings -> Network page. Then you can reset your AP to its original settings. You will need to reboot the Nano for your settings to take effect.
With the Nano powered OFF; Remove the NanoÕs WiFi USB interface and insert a powered USB Hub. It needs to be powered because the WiFi adapter requests all of the power available from the USB port, thus the KB, Mouse and WiFi adapter will not likely work on a passive (unpowered) USB hub. Now plug in any mouse, keyboard and your WiFi USB adapter you removed from the Nano. Now boot the Nano.
Your TV or Monitor should show the Nano booting and eventually its GUI. From the GUI select the WiFi configuration tool from the top left quick launch bar. If the wireless card is not enumerated in the dropdown list you likely have a USB Hub issue. You can still configure the Nano even without the WiFi adapter enumerated. Just edit the wpa_configuration.conf file with your network information, then save it. Its much easier/faster if the WiFi USB adapter enumerates.
How do you connect to your Nano once its on a WiFi network?
¥ Power up the Nano, the IP Address will be on the top Nano screen for a few seconds
¥ Access your Access Points list of associated clients, the IP address will also be listed.
You can also connect to your Nano using ZeroConfig
SSH: ssh firstname.lastname@example.org
Windows FileManager: nano.local
Mac-Finder-Connect to server: nano.local
ZeroConfig allows the user to connect to the iBox Nano from a browser using instead of where xxx is the IP address of the Nano, if you happen to be using a device that supports ZeroConfig such as Windows, Mac, iPhone, iPad, etc. Now you can connect both ways from most computers. Some atypical computing devices may still require using the IP address.
ZeroConfig can also be used to map the NanoÕs drive as a network drive. This can be handy to move files back and forth between a Windows or Mac.
Why is ZeroConfig important?
Because on some networks, the NanoÕs IP address will change periodically. By default the Nano uses DHCP (Dynamic Host Configuration Protocol) which [can] rotate IP addresses. Thus the IP of your nano may change periodically. With ZeroConfig this IP change has no affect on the ease of connectivity. Also note that Zeroconfig should also allow connectivity to your Nano via SSH and VNC for the advanced users.
My Nano worked yesterday, but it no longer works. What can I do to restore it?
Integrated Two and Three Button Restore
To restore your printer if it is bricked or to restore just your print profiles, follow these steps:
1. Unplug the power cable from your printer
2. Plug the power cable back in
3. Wait for the white lights to come one and if you want to do a full restore, immediately press and hold the physical UP, DOWN, and PRINT buttons on the top of the printer until the screen says Restoring All. If you want to restore just your print profiles, immediately press and hold the UP and PRINT buttons [outer two physical buttons] until it says Restoring JSON. If the screen says Booting...Please Wait, then it did not do a restore and you should start again from step 1.
4. After it displays the appropriate message, release all of the buttons and wait for the Nano to start. It may take a few minutes.
5. Once it does its light show and the print button is blinking blue, your Nano is ready and restored.
USB Flash Drive Restore
Some Nano packages were shipped with a USB flash drive that can be used to restore the system. The base model was not shipped with a USB flash drive, but you can create one by downloading the files needed.
Create USB Flash Drive:
2. Put the files on a USB flash drive. i.e. if your USB flash drive was F:/ you would see this in the root:
A. F:/ibox/ (this dir contains all of the files to be updated during the restore process)
Restore your Nano to its factory state:
1. Remove the USB WiFi Adapter from the Nano. It is on the left side of the unit and named Ò802.11nÓ
2. Insert the USB flash drive
3. Reboot the Nano. There are several ways to reboot:
B. Hold both the UP and DOWN buttons together until you hear multiple beeps, then wait 1 minute for shutdown
C. From the web interface, press the button labeled ÒpowerÓ then ÒrebootÓ.
4. When the Nano reboots it will automatically copy the file from the USB flash drive to the Nano and reset the system files. This can take up to 5 minutes with no user notification. After 5 minutes shutdown and reboot the Nano.
5. Remove the USB flash drive and re-insert the WiFi USB adapter.
6. Boot the Nano and it should boot with a restored set of files.
You should not lose your WiFi configuration.
Copy your Calibration data back to your default profile:
1. Check to see if you still have valid calibration data in your Settings / Advanced screen. Look at the field named: ÒOEM Calibrated UV LED PWM ValuesÓ. If these 28 numbers are all 100Õs you will need to proceed to step to and restore your OEM calibration data.
2. Your calibration data can be located in the first box in the manufacturing and test screen that is labeled ÒInitial CalibrationÓ and should have 28 numbers separated by ÒcommasÓ. Copy this string and paste it in the Settings->Advanced screen in the field labeled ÒOEM Calibrated UV LED PWM ValuesÓ. Then save this change. You should note that not all profiles will have been deleted, thus not all profiles will need this calibration restoration process.
3. Without calibration data your Nano will not print optimally. But it will still print. If you do not have access to, or have lost your calibration data please use all 100 values such as: 100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100,100
How do I change the name of my Nano from ÒnanoÓ to ÒjeffsnanoÓ?
1. If you are connected to the Nano via its user browser interface, go to [Settings] then [Network Setup]. Here you can change the name of your Nano.
2. You can reboot the Nano with a USB stick containing the updated name by using the procedure in the section labeled [Configure Nano using a USB Memory Stick:] in this user guide.
3. You can SSH into the Nano and directly edit the following files:
To change the hostname you will edit both files and change the word ÒNanoÓ to your new name. The Nano is a linux device and linux has specific restrictions on the hostname.
To SSH into the Nano please see directions in the section labeled [How do you connect to your Nano once its on a WiFi network?]
Awesome I am connected to the Nano, now how do I print something?
1. Go to a browser on a Windows, Mac, or Phone, and connect to the printer by its IP address or by typing http://nano.local in your browser. You will see the printers Graphical User Interface (GUI) which also happens to be a web page.
2. Click ÒBrowse ModelsÓ, then download a model or select from models already downloaded.
3. The Browse Models page gives you the option to Select, Print, Download, and Download+Print.
4. Before we can hit print we need to lower the build platform then add resin to the VAT
5. Put your VAT in the printer and tighten the 2x philips head screws on the right and then lightly tighten the other 2x philips head screws on the left, making sure that the VAT does not lift off of the print area on the right side when you are tightening the screws.
D. Press and hold the ÒDownÓ button on the printer until it beeps twice. This is a long movement. A quick press is a small movement of one layer in height. There is also a GUI button for UP, DOWN and STOP which turn on the long movements. The printer will Beep when the long movement has stopped. The goal is to get the Build Plate all the way down and completely touching the VAT. This is the print ready position. Watch carefully as the Build Platform is moving down. Make sure the Resin is not going to overflow onto the printer. If it looks like it might overflow from the Build Plate displacing too much resin, press the UP or DOWN button again to stop the movement, then remove some resin.
E. Carefully and Slowly fill the VAT about half way full. If you overfill it, remove resin. This may be done by siphoning off resin or removing the VAT and poring out the resin.
6. Press ÒPrintÓ, this will initiate the print process. Within a minute or so the display will update with estimated print times, number of layers to print, etc. It will continue to update periodically during the print process.
7. If you need to Stop the print process, just press [Stop]. A print can be stopped but can not be restarted.
1. Start by looking through our models in the [Browse Models] area or on . You can also look for models on the iBox account on Thingiverse, where you will find models that we have successfully printed on the Nano. Get familiar with the printer before trying to create your own models or print models that are not yet formatted for the Nano.
2. Select an item and press ÒdownloadÓ. This downloads it to the device you are using, not the Nano.
3. If the item is formatted for the Nano, you can press ÒCreate ModelsÓ from the Nano GUI.
4. Press ÒChoose FilesÓ, select the file you downloaded
5. Press ÒUploadÓ, this takes the file from your computing device and uploads it to the Nano.
6. Lower the Build Plate to the print position by pressing ÒDownÓ (Build Plate touching VAT - Its the lowest position for the build plate). If you press down on the printer, press and hold it until it double beeps. If on the GUI a quick press is fine. The GUI always moves a large distance, the physical button on the printer has two modes. Quick touch->Moves only one layer Up or Down. Long_Press->Moves a large distance. Pressing any button during a long move will halt the move process.
7. Make sure you have resin in the VAT (less than half full).
How do I format someone else STL file for the Nano?
1. Download the STL to your computing device
2. Download and Launch Slic3r (free, use version 1.2.6 or newer)
3. Configure Slic3rÕs build area to 40x20mm
1. [Printer Settings] menu item (in Slic3r)
¥ Bed Shape -> [Set] button -> set to x=40 y=20, origin x=0 y=0 : rectangular
¥ Save this setting
2. [Print Settings] Menu Item (in Slic3r):
¥ Layer Height -> Change to 0.1 mm or your current layer thickness.
¥ Save this setting
¥ First Layer Height -> Set to 0.1mm or your current layer thickness.
3. [Filament Settings] Set Filament Diameter to 1mm (sometimes not necessary)
4. [Preferences] Turn OFF background processing. Sometimes background processing will crash Slicer
*Note: If you change too many parameters in the Slic3r settings interface, it could cause the SVGs to ERROR on creation. If you see this, go back to the default Slic3r settings and start over.
4. Open the STL in Slicer
5. Scale the object to fit the 40x20 build area
6. Make sure the object is touching the bottom of the build area.
7. Save the STL
8. Select File->Slice to SVG from the Slic3r menu
9. Go to the Nano GUI, press ÒCreate ModelsÓ then ÒChoose FilesÓ
10. Select the SVG you just created, then press ÒUploadÓ
11. Now you are ready to print: Lower the build plate first, then add resin. Fill VAT <1/2 full.
12. Press ÒPrintÓ on the Nano GUI home screen.
An iBox Model is a compressed group of files that incorporates all of the necessary information to print a model on an iBox Printer.
In general it is an easy way to find, download, and print models that are licensed for free use. These models have been previously printed on an iBox Printer and are known to work well. You can always use [Create Model] to create one from scratch if you wish.
The iBox Models contain:
-(mandatory) : Package Information File. This file is a JSON formatted information file that tells the iBox Printer what is in the IML and what to do with it. This file is extensible, like XML.
-(mandatory) : Layer Images 0000 - NNNN. These are the actual Layer image files. Their format depends on the printer in question. On the Nano they are formatted as 128x64 PNG Images. Each image represents a layer to be printed. This list has zero base, so the first layer is Layer_Name_0.png. If you had 100 layers, the last image name would be Layer_Name_99.png.
-Suggested Print Configuration Profile : This is integrated into the Package Information File and contains the same as the profiles you create and use from the ÒSettingsÓ area of the GUI. The main goal here is to provide a known good baseline for others to use to be able to print the Model successfully.
-(optional) : The STL that was used to create the IML
-(mandatory) : Model Preview in .jpg, formatted to 240x450 and including the top view and side or isometric view. The iBox Nano will automatically generate these previews during the Create Model process.
Example IML Archive : 4 Layer Gear (most models will be 100-400 layers) - Mandatory files BOLD
Four_Layer_Gear.zip (compressed archive)
[ Uncompressed Contents ]
How do I transfer files to and from my Nano?
Use the NanoÕs web GUI Upload button. This is designed to upload print files (SVG, etc) to the Nano, not for general file transfer.
Map a network drive from Windows. Linux or Mac. This process varies from version to version and OS to OS. You can map the NanoÕs file system by connecting to the Nano from your File manager like you would any other computer to computer connection. To address the Nano you can use its IP Address or its ZeroConfig name. i.e. 192.168.1.100 OR nano.local
Windows: File Manager : Map Network Drive : [IP Address / or / nano.local]
Mac OSX : Finder : Go : Connect to server : nano.local / or / IP Address
What should I do if a print fails?
Here are some common build failures and recommendations:
1. Build sticks to VAT and not to Build Plate
¥ Make sure the build plate is down far enough before starting a print.
¥ Make sure the first few layers are over-exposed which increases the adhesion to the Build Plate. This is set in [Settings] as [First Layers : Over-Exposure Time and Count]
¥ You can also use a large Foundation to assure the adhesion favors the Build Plate. This can be found in [Settings] [FoundationÉ]. Foundation layers print before the model layers and can have a higher exposure time and drive current than the model to increase adhesion to the Build Plate]
2. Build is underexposed. Underexposed is when parts of the model are missing or partly printed.
¥ Increase Exposure Times
¥ Increase LED Drive Current
¥ Look at tables in the Manufacturing &Test button (Manuf&Test) located under [Settings]. Scroll to the bottom and look at the tables indicating what parts of the build plate are most likely to cure properly.
3. Build is Overexposed. Overexposed can be too much material thus curing resin over detail, or sheets of resin attached to the model at various and random places.
¥ Decrease exposure time
¥ Decrease LED Drive current
¥ Look at tables in Manuf &Test Tab in [Settings] for what we estimate the cure should be in that area of the build plate and see if it is ÒshouldÓ cure properly with your settings.
Sure; just make sure it is one that is known to work with the Raspberry Pi, preferably without having to install drivers. If drivers need to be installed you will need to either download the files via the factory Nano WiFi module OR via a USB stick.
This can and will vary. Raspbian from Jan 2015. If you SSH to the Nano or use the GUI from VNC or HDMI and launch Terminal: run: cat /proc/version
Result as of Feb 2015: Linux version 3.18.5+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #744 PREEMPT Fri Jan 30 18:19:07 GMT 2015