Two years ago at CES, we first saw the CEL Robox Dual 3D Printer that promised to 3D print using two colors and two materials. For product designers, this is the solution to single extrusion 3D printers. You can tell that this machine is on a different league right from the label of the box that says “Micro-Manufacturing Platform.” It is recommended that you follow instructions during the hard ware setup, because there will be small inconvenient problems if you don’t. The propriety slicing and printer control software is Automaker, for which operating the functions will take a little getting used to. Learn why this 3D printer is the real deal with its claim to be the game changer of the 3D printing industry.

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It’s A Game Changer! CEL Robox Dual 3D Printer Review

This review has been a very long time coming. We first learned about the CEL Robox Dual 3D Printer over two years ago, at CES 2016. It was one of the highlights of the show for us, because this 3D Printer promised to execute two-color and two material 3D printing better than anything else we had seen or tried. The two-color samples displayed at the CEL Robox tradeshow booth were flawless, no color bleeding, no distortion, no visible signs to indicate anything other than a printer that produces quality prints. We were so excited about what this 3D Printer promised, that we talked about it at length in our CES 2016 Recap podcast and blog post. We could not wait to get our hands on this new 3D Printer, because if it was as different as the company promised, it may just be the answer to what we had been looking for ever since we started pausing prints on our very first single extrusion 3D Printer to change colors.

After CES 2016, we eagerly awaited the arrival of a sample for us to review, but it never arrived. The US representative of CEL kept delaying, and eventually informed us that no review sample would be sent, due to technical improvements that were still being made to the production model, among other details. Although we were very disappointed, we moved on to focus our attention elsewhere. At CES 2017, CEL did not show, in fact year over year there have been fewer and fewer 3D Printer manufacturers showing at CES. Fast forward to mid 2017, and we were introduced to Grant Mackenzie, a STEM Ambassador, and Sales Manager for CEL. We had a conversation about all things 3D printing and STEM education, and really hit it off, you can read or listen to that conversation on the blog post page for that episode here. Grant arranged for a sample of the CEL Robox Dual 3D Printer to be shipped to us for review shortly after.

The Robox Dual arrived in the fall of 2017, and we have spent a lot of time with this 3D printer, much more time than we usually spend with a review unit. This is due to the fact that this printer is very different than any other 3D printer we have used or tested, so it deserved more time and attention. After all of this time waiting for this 3D printer, since January 2016, would it live up to the hype, and to our ideal expectations? Would we be elated, or disappointed that we waited so long for a chance to work with this 3D Printer? Is this 3D printer really a game changer, or is it another in a long list of 3D Printers that tries to deliver more, but falls short?

Out of the Box

While the shipping carton itself is quite standard, the text printed on the outside caught my eye immediately. They do not call this product a 3D printer, like most others do. Instead, they call it a “Micro-Manufacturing Platform,” a refreshing change that is indicative of how different this product is. The box contains an inner box with filament, instructions, USB Flash Drive Warranty card, Power Cord, and USB Cable. The product itself is contained in a fabric bag with handles, which is a very different presentation than any other printer we have experienced. The handle bag makes it much easier to remove the product from the box, and is just a nice touch that elevates the experience. When the bag is removed, the beauty of the printer’s Industrial Design is revealed. It is clear that attention was given to every detail, and it does not merely subscribe to a “form follows function” philosophy. The right and left sides of the printer are made of Aluminum that has been cast into a soft friendly shape that both shines to grab your attention, and creates a sturdy frame that is the basis of the structure of the printer. The fully enclosed design resembles a kitchen appliance, and has a clear plastic door that lifts up and rotates toward the back of the printer.

Hardware Setup

We always like to follow the manufacturer’s instructions when we are reviewing a 3D Printer, so we can report on the experience a typical consumer would be likely to have. This time was no exception, and pretty quickly we had an experience that was surprising, and a little amusing. After unpacking the printer and accessory pack from the carton, the Quick Start Guide instructs you to open/lift the clear plastic door and remove the 3D Printed clip that holds the print head in place. Next, you are asked to move the print head from side to side on the guide rails, and also move the print bed back and forth, sliding both by hand before the printer is plugged in or powered on. We discovered the hard way, that we should have returned the print bed back to its most forward position (closest to you) before closing the plastic door. This is because there is a locking mechanism that keeps the door shut when printing, and the print bed needs to be in the most forward position, otherwise when you shut the door it will automatically lock. The reality of this mechanism and how it works was not mentioned in the Quick Start Guide, so of course we moved the print bed by hand, did not return the print bed to the most forward position, shut the door, and discovered that it was now locked. While this was not a fatal problem, it was quite inconvenient, because when you mount a spool of filament on the spool holder, it is necessary to be able to access the filament spool spindle on the inside of the printer. We had to power on the printer, install the software, and then click a button in the software to unlock the door, which was not ideal.

The Quick Start Guide requires that you install the software prior to plugging in the printer to power, and USB cable to your computer. We followed the instructions, and recommend you do too, but then quickly continued with the Hardware Setup. The software setup is covered in detail in the next section of this review.

Once the printer is plugged in and connected to your computer, the next step is to load filament. The Robox Dual has an automatic filament loading system, all you have to do is push filament into the Filament 1 or Filament 2 slots on the left side of the printer until you hear the motor turn on and feel the filament being pulled into the machine. The locations to load filament are clearly marked on the left side of the machine, within the filament spool mount area. We found it very cumbersome, even awkward, to hold the filament in the proper orientation and push it into the two slots for loading, but once the filament reaches the sensor or switch that activates the loading procedure, the machine takes care of the rest for you. We tried mounting the spools of filament first then loading the filament into the guide slot. This process works, and in some ways makes it easier because the filament will be in the right orientation to pull off the reel and go straight into the guide slot, but if you have large hands and fingers, there is not much space to work with. Over the months we have worked with this 3D printer, we also tried loading filament before mounting the spools, which leaves a lot more room to maneuver your hands and fingers. We found that as far as the machine is concerned, it does not matter if you mount the spools of filament before or after you load the filament, the machine process is the same either way.

The CEL Robox filament spool mounting system only works with their own “Smart Reels.” These reels have a chip in them that is read by the printer as soon as they are mounted. The idea is that all of the printing data and parameters of material type, temperature, color, feed rate, how much filament is left on the spool for printing, among many others, are communicated with the printer automatically to speed up and enhance the entire printing experience. Understanding that, we have never been fans of proprietary filament spools and systems, because they often limit the user’s ability to load any filament they want, and have full control over the printer. However, with some experimenting and a little learning curve using the software (more on that later in this post), we found that we can use any 1.75mm filament we desired from our entire stock, and feed it from our generic filament rack above the printer, directly into the two guide slots.

Software Installation and Print Preparation

There is a USB flash Drive provided in the accessory box with the AutoMaker, Robox’s proprietary slicing and printer control software. We found the Automaker software on the USB Flash drive was outdated, and not compatible with our computer’s operating system (OS). So, we downloaded the latest version for our computer type and OS, which went smoothly and got us up and running quickly. At first, AutoMaker took a little getting used to, as the interface is different from all other slicers and printer control software we have used. There are three main sections of the program, starting with a Status screen that gives you the current state of the 3D Printer, and controls to operate the printer, including unlocking the door, unloading filament, changing the active nozzle, among other functions. Next, there is the Layout screen, which is where you add models to the build plate, arrange them, duplicate, group, and make sure they are flat on the build plate. The graphic display of the build plate and model(s) to be printed is very well done, as you can assign the materials to be printed on each STL file and it will show the correct color to be printed so there is no confusion about what color or material is assigned to the different parts to be made. The third major area of the software display is where you choose the settings to use for printing. You have options of selecting typical preset controls for course, medium, and fine print resolutions, Raft, Support, and Infill percentage. You also have the ability to customize settings and save your own print profiles. We will discuss more on the slicer later in this review in context of the Game Changer function of this 3D printer.

At the top right of the main window there are icons that take you to some additional global settings. First is a Library of Filaments and Print Profiles. There are many filament profiles that are preset for your convenience, but they are all CEL Smart Reel profiles. They contain all of the known settings, including recommended temperatures for the bed and the nozzles (even options for the 1^st layer to be different from the rest), and the color of each material. When you select a material in the main status screen, and assign it to a model, the software knows what color to display, how to slice it properly for that material, and even the cost of the material that will be used in making the current print. For materials that are not from CEL or on a Smart Reel, you can create your own filament profiles with all of the settings, and assign a color so you can have the same user experience regardless of if you are using a Smart Reel filament or not. The Print profiles section is just what you would expect, a screen where you can create custom print settings for your specific needs, save them, and make them available from a drop down menu in the main Settings Screen.

Additional icons at the top right of the screen include global Preferences where you can enable an advanced mode that will give you complete control to enter Gcode commands, enable diagnostic tools, and access maintenance controls. AutoMaker even gives you the option to connect the Robox Dual 3D printer to a GoPro camera to take timelapse photos. If you use this function the printer will pause at the end of each layer, move the print head out of the way and the bed forward for the camera to shoot a photo. The result is a lightly longer print time, but a perfect timelapse sequence of photos that you can use to make a video.

Once you assign the proper materials that are loaded into the printer, load your models, select your print settings, you are ready to print. In AutoMaker you do this by clicking on the Make button. This 3D printer requires that it be connected to your computer by USB cable, but once the Gcode has been copied to the printer, you can disconnect the USB cable and the print will still complete.

The Big Game Changer!

Okay, now we are getting to the meat of this review, and the payoff. For some context, ever since we started using our first FFF desktop 3D printer we desired to print with more than one color or material. We bought several “Dual Extrusion” 3D Printers, and worked very closely with them to try to get over the learning curve. In every case, 3D printer after 3D printer, we were left disappointed that we could not achieve our desired results. In most cases the two nozzles are coplanar at all times, so both nozzles would regularly move over the part being printed, and inevitably cause problems by hitting and breaking a portion of the part that had already been printed, causing a failed print. The other issue with most dual extrusion 3D printers is plastic material oozing out of the dormant nozzle (the one that is not actively printing). This too caused lots of problems with material bleeding, creating messy prints. Even if we used an ooze shield, or some other printable structure to try to reduce the effect of oozing filament, it never really worked. Then we tried other 3D printers that extrude more than one filament into a single nozzle. We had higher hopes for this kind of hardware solution, but again ran into problems. This kind of print requires a Purge Tower, so the nozzle can expel the remainder of one color before trying to print the next color. In principle, this concept works, but retraction is still an issue, and we found that the prints suffer from many more strings or hairs being generated from the purge tower to the printed part. Still, the hardware solution of multiple filaments into one nozzle is a promising one. When we reviewed the Builder Dual 3D printer we came to the conclusion that the hardware was very capable, but the software to create the Gcode was the major limitation. We spent tons of hours working with Cura and Simplify 3D to create proper Gcode for our prints, but we discovered that each software left something to be desired, and often placed the different colored plastics in the wrong locations at times. It was very inconsistent, which in the world of programming prints through Gcode for accuracy, was very frustrating. Our conclusion of this technology was that the hardware within the 3D printer was capable of much more than the software could deliver.

The CEL Robox Dual 3D printer is different, in fact it is so different from any other FFF 3D printer, that we are calling it a Game Changer, and we do not make that statement lightly. Since we are product designers, and inventors, we cannot help but think of solutions to problems we see. Years ago, we had identified two major machine improvements that could be made to dual extrusion 3D printers to make them work better, the first was to lift the dormant nozzle up and out of the way when it is not printing so it would not interfere with the part being printed. The second was to somehow completely stop the flow of plastic material oozing out of the dormant nozzle to prevent the typical mess that seems inevitable. Well, the folks at CEL must have identified these same issues years before we did, and they actually did something about it.

To solve the problems, they built two key mechanical features into their print head. First, the head contains two nozzles, but they are not coplanar with the print bed. Instead they are mounted on a rocker arm, with one nozzle on either side of the pivot point. When one nozzle is in proper printing position, the other nozzle has been rotated up and out of the way so it does not interfere with the print. It is a very simple motion, over a short distance, that takes place once for each layer of the print that requires both materials. We found the action and motion to change nozzles to be smooth and incredibly accurate. Second, they created custom nozzles that function as needle valves. There is actually a pin shaft at the center of each nozzle that moves up and down to open and close (respectively) the flow of plastic material. This positively shuts off the flow of plastic when it is not wanted. Brilliant!

Additionally, we learned that the needle valves do not just close to shut off the flow when the nozzle is inactive. The needle valves open and close throughout the printing process to shut off the flow at times when the nozzle is actively printing, moving distances across the print, so that plastic does not ooze out when it is not wanted. This function replaces the function that is performed through retraction in most FFF 3D printers. Retraction has always been one of those settings that requires a lot of experimentation, especially when changing materials. Different plastics flow differently, and require varying amounts of retraction. The structure of a 3D printer, including the filament drive motor location relative to the nozzle, can also make retraction settings very different from machine to machine. Since retraction is one of the most time-consuming variables for 3D print technicians to deal with, eliminating this variable yields a much more efficient experience, with predictable print results.

After setting up the printer and installing the software, we jumped right in printing two color objects, and had great success from the first print. We printed some older objects that we had printed on other dual extrusion 3D printers, and created some new objects to further test the capabilities of this 3D printer. We also started with the two Smart Reel spools of filament provided with the printer, and then moved on to use pretty much any material we had on hand. The first object we printed is a two color “Ring Box” design we created and tested on the Builder Dual 3D Printer. The structure of this design makes it appear as though the different colors are weaving in and out of each other. We had never been able to get this object to print properly on any other 3D printer. However, the CEL Robox Dual 3D printer did a great job of printing this object perfectly the first time, with no color bleeding, and each color printed where it was supposed to be. Now that may not seem like rocket science to most of you reading this, but in our experience attempting with two-color and two material 3D printing with other machines, this was a pleasant and exciting surprise. We expected it to take a lot more experimentation, and trial and error before we got any good prints off of the Robox.

As we got to know and understand this printer and its software better, we began to push the envelope some more, started using our own materials, and created new objects. We even printed flexible filament in the Robox Dual with ease. Recently we have been creating some custom USB flash drives as giveaways to promote our brands, which are great objects to print. The USB flash drive designs are each adaptations of business logos, with shapes and text that have been a challenge for us on other printers. Again, the CEL Robox Dual was impressive, and did a great job, exceeding our expectations. This 3D printer is the real deal.

Interchangeable Print Heads

Key to the flexibility of this 3D printer is its interchangeable heads. They do not pop off as easily as the MakerBot Smart Extruders do, but they are easy enough to remove and reinstall. This allows you to choose from the Dual Material Head, and a Quick Fill single material head. While the Dual Material Head is for printing with two different colors and or two different materials (even printing at two different temperatures), the single material head also has two nozzles, but of different sizes for printing one single material. One nozzle is larger for printing more quickly in areas that do not require fine detail, and the other is smaller in diameter for printing smaller detailed areas.

Advanced and Technical Details

We have experienced the entire range of slicing software, from 3^rd party software like Cura, 3D Printer OS, AstroPrint, and Simplify 3D, to proprietary software like MakerBot Print, and Polar 3D’s Polar Cloud. I would prefer to use a program like Simplify 3D with the CEL Robox Dual, because of how you can more easily apply settings to different regions of a print, slowing it down for one material vs. the other, among other settings. However, because of the needle valve function, which is completely unique to this 3D printer, 3^rd party slicing software will not work. CEL uses Cura as the backbone of their AutoMaker software, but Cura (and typical Gcode commands in general) do not consider or even understand needle valves. So, after all settings are selected, and you tell the software to “Make” your part, the AutoMaker software takes the Gcode created by the Cura engine and alters it to add all of the commands at all of the required points in the printing process, to properly operate the needle valves. This is a critical step that is necessary for proper operation of the printer, and a logical reason why you cannot use 3^RD party slicing software. For now, if you use this 3D printer you need to accept this reality. We put AutoMaker through the paces, testing all of its functions, and we have to say that it is very well done.

The print bed is heated, so you can print without a raft easily, and use pretty much any material you want to. When you change materials, you need to run a purge cycle to completely expel the old colors or materials, and prime the nozzles with the new ones you intend to print. This process takes longer than I would like, and occasionally did not work when I experienced a filament jam in the print head. While there are software tools built-in to AutoMaker to help you clear such a jam, I found that in some cases they did not work. CEL has a good customer service help ticket request system that you can use to get technical help with any issues you have. In our case, we were faced with delaying our testing to send in the print head for service, or we needed to help ourselves, outside of the official “system” and warranty requirements. After considering the pros and cons, we decided to get brave, and go beyond what was recommended. We removed the print head from the machine and opened it up to see if we could clear the print jam. There is an area of the print head that contains the filament path leading to the nozzle, which is not easy to get to. It requires removing several screws, and a snap ring, in a delicate process to access the filament path. Once we opened this area up we found the filament jam, a small piece of plastic that had broken off in an area that was not going to be removed any other way. Ultimately, going beyond what is recommended enabled us to keep moving forward. Snap ring pliers are not a common tool to most toolboxes, but we happened to have the proper one on hand, and recommend that if you own one of these 3D printers, that you purchase one so you have it when you need it.

The model of this 3D printer that has been available, and that we tested, does not have WiFi Capability, nor does it have a flash drive or SD card slot to print stand alone. In order to print you need to connect your computer to the printer via a USB cable. We were disappointed to learn this when we were getting acquainted with the printer. In the past, we have not experienced the best performance with printers that can only connect with a USB Cable. However, we did not experience any communication issues, and learned we could disconnect the USB cable once the print was transferred to the printer.

The build volume of the Robox Dual is 210 x 150 x 100mm, with a fully enclosed chamber that locks for safety. The enclosed chamber also provides a very consistent environment for making consistent parts. While the Robox Dual is a smaller build volume 3D Printer, CEL just released a new larger version of this printer in January, called the Robox Pro. This newer version of the printer allows you to print objects up to 210 x 300 x 400mm in size. This new model also has more connectivity options, including Wi-Fi, USB Flash Drive, USB Cable, and Ethernet. It’s fully enclosed chamber also has replaceable HEPA filters available to eliminate the odors from printing plastics with undesirable fumes. It uses the same interchangeable print heads, and has added a third version, called the SingleX, for printing with abrasive materials, like glass filled nylon.

Conclusion

As we said earlier in this post, this 3D printer is the real deal! If you are looking for reliable two-color or two material 3D printing, look no further. The CEL Robox Dual is safe enough to allow young kids to be round it and use it, and at the same time it is advanced enough for more advanced businesses and users. We are very impressed, and pleased that this 3D printer is so capable, and produces quality with predictability. No printer is perfect, and there are things we would like to improve if we could wave a magic wand and “Make it so”, but we are putting this printer at the top of our recommendation list for anyone who is ready to go beyond a single extrusion machine.

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