The cooling system for a 3D Printer is important to consider. Heat is the enemy to electronics. Hot electronics will eventually let out smoke, and once that magic smoke is out, it’s very hard to put back in. So consideration needs to be made on how heat will be managed in a print. Excessive heat can affect the reliability of the print head, and can produce poorly printed parts.
I believe that if you do not design to provide positive heat displacement early on in a build then you will be playing catch up. Not that I am an expert at building 3D Printers but heat management is a critical thing to most mechanical, and electric systems, so why would this be any different?
The Print Head
One of the reasons I went with the E3D Kraken Print Head, was for the multiple hotends on a single unit. The odds of me ever printing with 4 extruders at once, or needing 4 different materials during a print, is pretty low.
With that said I think it’s pretty neat to have that option and I can see utility for it. If I wanted to print out several different components all at once, and would like to tailor the material properties for each component, having options is a good thing. Or I can have different orifices and print with the orifice that is best suited for the print. There are options here, but the cost is complexity.
Hot ends on 3D printers are cooled to reduce the chance that the filament will melt before it is in the extruder itself. Premature melt causes feeding issues and will jam a nozzle mid print. To remedy this most hot ends are air cooled, but water cooled hot ends seem to be making a “Splash” and cool more efficiently, with the disadvantages being, heavier print heads, and more complexity to the printer as a whole.
With 4 hot ends being in close proximity to each other it is no wonder that E3D elected to water cool this head. It add another component of complexity to the build for me, but I feel that it is worth it to get the added flexibility of multiple print heads on one compact unit. It also allows me to control the air flow around the extruding filament more precisely. (More on this later)
If I ever do decide to make a CNC Router head for this printer, the water cooling will already be in place. Many of the spindle motors spin at high RPM’s which can quickly toast a bearing if not properly cooled. Water cooling is essential to the long time life many of these motors.
Part Cooling
Cooling of the print head isn’t the only cooling that is required. Many materials print better at different levels of cooling provided by a blower. With 4 print heads, the trick is how to direct air to where it is needed. I could mount 4 fans to the print head, or come up with the shroud that directs the air from one fan to the print.
The cost here is adding weight to an already heavy print head. Yes it’s doable, but I wasn’t sure I wanted to do that. I was pondering on the issue, and thought “Why not use an aquarium pump and mount the pump remotely?”
As with every potentially good idea…I’m quick to assume that I am not the first guy to think of it. A quick internet search turned up this article at TridiMake.com. Seems to be a reasonable build, allows me to mount the pump remotely and then pipe the air to exactly where I need it to go. The article mentions asks the question as to why this isn’t on more builds. For the time being I can’t figure it out either.
Electronics Cooling
This is a large printer. Some of the prints I may try and do could take several hours to complete, maybe as long as 20 hours or more. That is a long time, and heat builds up over time. A motor driver that is being worked hard might be fine to run for 6 or 7 hours but can break down after longer periods due to the slow build up of heat in the components. It would really suck to have a motor driver or stepper motor start to fail during the end of a long print due to heat.
People make careers out of studying airflow within enclosures, and how to most efficiently cool a CPU, or MOSFET over a long time. The version of SolidWorks I use has a Computational Fluid Dynamic module that helps to model airflow through lots of different things. (I have used it to model bullet drag, more on that in another write up.)
Most people rely on fans to provide the necessary airflow to cool the electronics. It is an easy way to do it, but air is a poor conductor of heat. Since I am already going through the trouble of installing a water cooler for printhead, and I am confident that it is oversized, I looked into cooling some of the other critical electronics with coolers rather then using fans.
There are several cooler and pads that attach to various chip sizes. They are typically pretty inexpensive. I’ll have to select the coolers and the components after purchasing the electronics to make sure everything fits. This includes looking at pads that will help cool the stepper motors.
The Cooling System
For the cooling of the print head and various other components in the system, I plan on using a closed loop system that uses some amount of water and glycol, similar to how a liquid cooled CPU system would work. I know the cooling system is going to be a little overkill but I am fine with that. The fans will run at lower speeds, and the overall noise of the printer will be lower.
For parts that I can’t download a CAD model, I will usually take the general dimensions and create and analog. Once we receive the part we can verify the dimensions and then adjust the model for mounting brackets and whatnot.
For common items such as PC Cooling Fans, I’ll search GrabCAD. There is no sense in trying to model everything if I can just download a free CAD model from somewhere else.
Another thing that is a distinct possibility is using cooling blocks to help keep the electronics and stepper motors cool.
Besides cooling, this design will allow for positive ventilation of the 3D Printer. Many fillilemants have unpleasant and sometimes dangerous fumes when printing. It is my intent to have this printer somewhat sealed. I do not have a enclosure designed for the top of the printer, but there will be something. One of the first things I will 3D print is a shroud that will will fit over the radiator and allow a vent hose to be attached and vented to an outside window.
The pumps I am looking at will need to supply positive pressure to a manifold. The manifold will have several ports that will supply the coolant under pressure to the various components and allow the low pressure side drain back to a reservoir. This all needs to be designed and will need some thought. As for the pump and reservoir placement, there is room under the bed of the printer that would be ideal for the larger bulkier components.
It will be important to make sure that all components are of similar metals. Dissimilar metals in a coolant system can result in corrosion. Typically you do not want to mix aluminum and copper components together. So we will need to be cognizant of that as we choose the components moving forward.