Here is a tutorial that I am about to cover regarding a 3D printing technique known as Velocity Painting. The idea of adding a bit of extra to your 3D prints is a simple way to add a touch of something special. Compared to lithophanes, this method is vastly different. The Velocity Painting technique is a completely separate post-processing technique that is applied to your sliced GCODE files. It does not require any kind of paint at all to make this!

Velocity Painting was created by Mark Wheadon.  It started out as an open source Perl script and evolved into a more user friendly app written by Guillaume. The basic premise of Velocity Painting is to use a high contrast black and white image or pattern and transpose it onto the exterior of your 3D prints.  It works by varying the speed on the exterior surfaces to either SLOW DOWN or SPEED UP.  The default settings are typically to slow down for the black parts of the image and to speed up for the white parts. To get this to work correctly, you need to set your slicer speeds to all the same speeds for the perimeters and disable any kind of slowing down for layer cooling or ‘quick layers’.  It is very important to have the speed set correctly or else the Velocity Painting technique will not work correctly.

Slicing Your Model for Velocity Painting

First thing you need to do is navigate to velocity painting and grab the latest version for your operating system of choice.  Next, choose a nice high contrast black and white image to paint onto your print.  I have chosen to use this black and white Inov3D logo.  Finally, choose something you want to superimpose this picture on.  I chose just a simple cylinder model that I created in TinkerCad. I use the latest Cura as my slicer of choice.  The problem with Cura, is that it doesn’t have the ability to show speeds in Gcode files.  This is important to see how your Velocity Paint project came out, before printing it.  There’s a few ways to do this.  You can navigate to the online viewer or use Repetier Host.  I couldn’t get the online viewer to work, so I used Repetier Host.  Simplify3D might also have the option to view speeds in Gcode, but I can’t confirm this.

Like I had mentioned, it is EXTREMELY important to slice your model and set the infill, top/bottom, and perimeters to ALL of the same speed.  I am printing this on my Aladdinbox SkyCube, so I chose a modest base speed of 40mm/s for printing.   Feel free to adjust this value to what you normally print at on your printer.  Next, you need to make sure that your model is centered on the build plate. This is important and you will need the center point of the bed later on for setting up the Velocity Paint app.I chose to print this cylinder in vase mode, but the process also works for solid models as well.

Settings Your Velocity Paint Settings

The Velocity Paint app allows you to adjust things like the resolution, number of layers, and print speed. It also allows you to adjust the color palette, giving you the ability to customize the look of your model. You can use each of these buttons to control different aspects of the app, allowing you to customize your experience to your particular needs.

• ‘gcode’ : This button is how you load your presliced Gcode into the app.
• ‘image’ : This button is for loading your high contrast image into the app.
• ‘Load’ : Use this button to load a saved settings profile into the app.
• ‘Save’ : This button is to save a settings profile for the app.

Setting Up Your ‘Painted’ Image

Below these four buttons are the options to configure the app for painting the image onto your model.  Under ‘Image Settings’ you will find three options: Width, Height, Z Offset.  By adjusting the Width and Height, you can configure the size and aspect ratio of the image.  You can raise the start point on the Z axis by changing the ‘Z offset’.  To keep the aspect ratio locked into the original image’s ratio, you can add a value to either the X or Y axis and leave the other value as ‘–‘

Configuring Your Print Speeds

To the right are the ‘Print Speeds’.  You will need to set the ‘Target’ speed for the speed you used EARLIER in your slicer.  Then, you will need to set the ‘Low’ and ‘High’ speeds.  I chose to use 15mm/s for the ‘Low’ and 40mm/s for the ‘High’.  Typically, you will want to have a large variance between these two numbers.

Setting your Print Area

The ‘Printer Coordinates’ are where you enter the X and Y value for the center point of your print bed.  This will be where Velocity Paint will center the image.  For my Skycube, this is set to 55 and 55.

Time for the Paint!

The ‘Paint Type’ options allow you to change the style in which Velocity Paint transfers your image to the model.  If you choose any of the ‘Projection’ styles, it will imprint your image onto that axis.  ‘Cylinder’ will wrap your image around the entire model, as long as the image is sized correctly.  ‘Sphere will start the image on a centered point on the X axis and wrap the image around your model.  This is similar to ‘Cylinder’ but there will be a point of distortion in the center and then the image will stretch out.

After you have configured it to your liking, hit the ‘Generate’ button and save your NEW Velocity Painted Gcode!

Now, it’s time to check and see if the magic worked!  Either drop your Gcode file into the online viewer or start up your copy of Repetier Host.  If you are using Repetier Host, after uploading your Gcode, you will need to change the ‘Colors’ option from ‘Extruder’ to ‘Speed’. Your Velocity Painted image should have appeared on your model now!  If it looks fine, upload it to your printer and print it up.  Otherwise, you can tweak your Velocity Paint settings and fine tune it.  Remember to save your setting configurations, otherwise there is a high probability for failure.  Getting the ‘Image Settings’ correct is the hardest part.  Take your time, and be patient!

Velocity Paint Issue: What Happened to my Prints?

While I walked you through this tutorial on Velocity Painting using Gcodes sliced with Cura 3.6, I didn’t initially notice any problems.  You may not either depending on what you are printing. I have found some serious flaws with how the Velocity Painting app interprets travel movements within Cura sliced Gcodes.  I would suggest AGAINST using ANY version of Cura to slice any solid model files. You should stick strictly to vases with Cura.

This is a very cool concept and I applied it to a few different vases and to the ever faithful Skully.  While printing the Skully I noticed some EXCESSIVE ‘stringing’ in the infill of the model.  I thought nothing of it and sliced up a file for a 3D printed hand with a checkerboard pattern ‘painted’ on it.  This is when it became glaringly apparent that something was wrong.  Which led me to investigate what could be causing this Velocity Painting issue.

I had to stop the print.  Something was wrong, REALLY wrong.  I haven’t had a print that looked this bad in a very, VERY long time.  The amount of stringing was so bad that I thought there was something wrong with the filament.  I loaded up the original file of the UnLimbited Phoenix hand and it started to print without issue on the same printer with the same Hobby King Transparent Red filament.  Hmmm!?

While watching the modified file print, I had noticed what looked like stringing from excessive heat.  Except the problem wasn’t due to heat.  The extruder was extruding on some of the travel moves!  After opening the modified Gcode file, my suspicions were confirmed.  The Velocity Paint issue was in the modified Gcode.  I opened up the original Gcode and could see that problem wasn’t there.

Verifying Settings and Reslicing

I went back through my settings and verified that I hadn’t accidentally changed anything.  My infill, top/bottom, and walls were all set to the same speed.  I even changed my initial layer to being the same speed as the rest of the model.  The Velocity Paint issue remained. I changed the speed of the travel moves to much higher, and I changed retraction speeds.  The biggest change came from disabling retraction completely.  This cleaned up the model a little bit, as I show below, but STILL the Velocity Painting issue remained!

How About a Different Slicer?

Maybe it’s something that Cura is doing?  I decided to try out KiSSlicer.  This is a pretty rough profile, but I just wanted to see if the problem was related to some kind of wipe/retraction that Cura was doing.  I sliced up my rough draft on Kisslicer and ran it through Velocity Paint.  The problem was GONE in the layer view.  I even went back and used an older version of Cura and the problem was still there.  So the problem seems to be related to however Cura handles travels.

Final Thoughts on Velocity Painting

Velocity Painting can give your 3D prints a unique, eye-catching look that won’t be found elsewhere. This creative approach to 3D printing is sure to make an impression. With this knowledge, I was finally able to get the correct image to display properly, showcasing the impressive capabilities of 3D printing and my creative approach.