When I first started trying to print NinjaFlex with my Robo3D, there were minimal resources explaining how to do it. People said its possible, but boy did I struggle! Eventually, I got to a point where I can consistently print NinjaFlex from my Robo3D. So here are the steps. Hopefully, this will be a simple explanation :)
Feel free to comment any questions and I'll do my best to answer.
Step 1: Remove the Screws and Open the Print Head
Remove the screws completely... with a screwdriver! Trust me! You'll save tons of effort and time by not screwing and unscrewing these bolts with your fingers. Be lazy, use a screwdriver!
Step 2: Thread the NinjaFlex Through a Thin Tube
I broke apart a mechanical pencil and took out the plastic tube inside. Its a perfect fit so I highly suggest this. You can buy a huge pack of cheap mechanical pencils a local store that carries stationary products (Staples, pharmacies, supermarkets, etc).
Cut the tube to be a few inches long and slide the NinjaFlex through.
Step 3: Put a Tube in the Feed Hole
Next, find the feed hole on the print head. If you have a few inches of the tube left over from the previous step, you can use this. If not, you should use a new tube. Make sure the tube is a few inches long.
Stick the tube in the hole and push it down as far as it can go, don't use too much force.
Then, take a marker or pen, and mark a cut line. The tube should stick out of the hole just a little bit, try to roughly match the picture.
Pull the tube out and cut where you drew the line. Then stick the tube back into the hole.
Step 4: Feeding the NinjaFlex and Securing the Top Tube.
Feed the end of your NinjaFlex into the feed hole. Push it in as far as it will go without too much force.
Then, slide the top tube into the top feed guide like shown in the picture. Some people have said they glued the tube into position. Since the tube from the mechanical pencil was a perfect fit, I only had to slide it into place. If your tube slides out too easy, you may want to consider putting a dab of glue.
When closing the latch, keep tension on the NinjaFlex and don't allow it to buckle and bend, make sure it stays straight.
Step 5: Close the Print Head Latch
Making sure the NinjaFlex stays straight, close the print head latch and screw the bolts back in. Use a screwdriver! ;)
Step 6: Adjust Print Settings
I've attached an image of my print settings. Not all may be required, but these current settings are working for me :)
You can play around with some of the settings, like layer height, fill ratio, but the speed settings are critical.
I basically set all speeds to 7, except first layer speed is 3. I've seen people claim they are printing at 12mm/sec. I tried this and it looks like it can work, but it also can jam. I've never had a jam at 7mm/sec and I'm usually printing overnight so print time and speed isn't usually an issue.
I'd like to point out the setting 'Minimum Travel Requiring Retraction'. I set this setting to 200. I've read multiple places to turn off retraction when printing NinjaFlex with the Robo3D. Retraction pulls the filament back into the print head when moving large distances to minimize stringing, but this can cause the NinjaFlex to buckle in the print head and get stuck. I wasnt able to find the "turn off retraction" setting. Setting the value to 200mm is almost as long as the print bed, so it essentially disabled the retraction (you can set it to a larger number to be safe if your print takes up the hole width of the print bed). However with retraction turned off, you will get stringing if you have multiple models or multiple high parts that require print head movement without printing in the middle.
Step 7: Your Ready to Print!
Set your model up and print!
7mm/sec is very, very, very slow. So step away, go to sleep. Do whatever you want for a few hours. This print will take some time.
I like to set up my laptop's webcam to watch the print. I then use TeamViewer to log into my computer remotely from my mobile phone. Since i dont actually stream the webcam footage online, TeamViewer lets me see my computer's desktop, which lets me see the camera feed so I can monitor the print. Also, you can control your computer from your phone using TeamViewer, so if you notice the print jammed or something just isnt right, you can cancel the print without having to be at your computer.
Hope this helps some people! Best of luck!