VENTILATION SYSTEM V2
3D printed a large assembly in Multiple parts
Bonded ABS parts with Acetone
Sealed de-laminated layers & seams with Acetone
Fixed my mistakes with a dremel
Used a 3D pen to patch A hole and mistakes in one of my 3D prints
Assembled the Ventilation system
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I currently 3D-print indoors, right next to where I sleep. So, I made an enclosure to make sure I wasn’t inhaling plastic particle emissions while I slept or worked on my podcast. The frame is made of wood with inlaid glass panels for easy viewing – a good budget-friendly solution. I created the first ventilation system mount using Wood PLA on my RigidBot Big. Combined with a 150 cfm fan, it was exactly the solution I needed at the time.
After I started gaining confidence with 3Dprinting my ambitions grew, and so did my projects and my print times. I noticed that after the 10-hour mark, there was the faintest smell of ABS plastic near the printer. Combine a bit of paranoia with the need to solve problems, and the obvious choice was to increase my airflow to 300 cfm! Another fan and another mount were now needed. So I started designing…
The first thing I noticed was that the part would be bigger than my 3D printer could build. I tried a few different designs to see if I could make it fit. But after a few designs I decided to just print it in pieces, which is common practice in 3D printing. I split the model right in the middle, so that it was two mirrored pieces. This meant all I needed to do was build the same part twice and put them together.
At first, I was having some trouble with this part. The logic was to build the part from the bonding side, so that it would be as flat as possible when I put the pieces together. But, there was warpage on two corners of the part (see pictures of failed prints).
After the first failed print, I added a base-strip to the model to keep it down, since I could always just cut it off afterwards. When that didn’t work, I had to take a serious look at my print-surface for an answer.
Up to this point, I had tremendous success with blue painters tape and glue-stick as a build surface. But there were two things causing problems:
1. Part warpage seemed to get worse as the weather got colder. This wasn’t surprising, since my ventilation goes outside and my room is in a basement. With single pane glass, there’s no cushion of air between the panes to keep the heat from escaping.
ADDITION: After a few seasons, I've noticed the temperature can drop almost 15*F on extreme weather days.
2. My blue painters tape and glue stick solution was doing it's job – stick to the ABS. But the warpage was pulling the tape off the heated bed (90*C).
So it seemed regardless of my available options (wider tape, more glue-stick, letting the tape sit for a day) the part was still warping. I needed a better surface.
After digging through online forums, 3D printing guides and what other 3D printer manufacturers were using, I came across the PEI surface. Polyetherimide is it’s chemical name, and its molecular formula is a repeating chain of C37H24O6N2 . The 3D printing industry found it because ABS sticks VERY WELL to it. I’ve even read that if you run your heated bed at 110*C or higher, it’ll stick so much you might ruin the PEI surface getting it off!
After using it myself, I highly recommend it (but it is pricey - one 8x8 sheet cost me $16) . If you’re new to FDM 3D printing, getting your first layer to stick and stay is everything. ABS is tricky, and shrinks when it’s cooled unevenly. If you don’t get a good adhesion on the first layer, your part WILL warp. So a surface that keeps ABS down is valuable. Even better, you get this almost glass-like surface on the bottom!
FIXING MY MISTAKES...WITH A DREMEL
I do want to share the mistakes I made and the solutions I found to fix them. Even though I end up swearing up a storm when I find out I made a mistake. Failure is always a great opportunity to see what you're capable of.
This wonderful screw-up was due to the fact that I was up late designing and just wanted to get the part printing ASAP. I forgot to look at the bottom of my part, where my fan would be connected. The circle here is just the hole from the top, cut all the way to the bottom. But, it should be a 4.5" circle on the bottom surface, the same size as the fan blades.
Luckily, I had a dremel handy and used a rotary bit to slowly rip material away. I wasn't about to waste all this plastic, and no one will see this area once it's assembled.
Alas, I'm not great with a rotary tool yet and I ended up puncturing a hole through the side. Another fix. Sometimes, problems are like that cartoon where they try to plug up a hole on a sinking boat. Once you plug up one hole, another leaky hole starts.
FILLING A HOLE...WITH A 3D Pen
A 3D pen is a great tool for creating 3D objects free-hand. But it's also a great tool for filling holes, gouges, etc. with your 3D prints. Simply plug it in, heat it up, wait for the green light, load the filament and you're up and running! 3D printers are obviously better at making precise parts, and I could use some practice with my 3D pen hand.
I used a different color so the filled areas would be easier to see, but I could easily have used the same colored material as the part. The blue ABS dried quickly, and it stuck to the original print as if it was part of the original piece. The important thing to remember here is to use the same material as the part (i.e. Use ABS with ABS, and PLA with PLA, etc. Color difference shouldn't matter)
ACETONE BONDING & SEALING
*I did this part outside, while wearing a particle mask. Always make sure you are in a well ventilated space when using acetone and chemically changing any plastics - CHECK MSDS SHEETS!!!*
Acetone is a well known way to bond ABS plastic together. It can also help you smooth out build layers, seal edges, and give you a shiny finish as well. For each process, you might need a different tool to get the job done.
The first issue: There were a few layers in my print that had separated. This is called "de-lamination", and ABS is very susceptible to this, especially with a part this big. Luckily, this can be fixed up with some acetone and a smoothing pen.
The smoothing pen is simply a foam brush tip marker. Fill it with acetone, push the tip in when you need more acetone, and apply pressure as you need it. The more acetone and the more pressure you use, the more the plastic is removed and gets mixed into an ABS "juice". With some practice you get the hang of the dynamics and sealing these de-laminated layers was easy.
For bonding the two pieces together, I used a paint brush to apply the acetone. The acetone was drying VERY quickly. I only had one shot at bonding these pieces together. So I made sure to be generous with acetone to give myself time to put them together. All I needed to do was hold the parts together with some even pressure for maybe 15 seconds. The part bonded extremely well, and fast.
Then, I used the smoothing pen to fill any seals from the two part connection to ensure the air didn't escape. I also noticed that I didn't like how there were just patches of shiny areas where I spot welded. So I used the paintbrush to apply a shiny surface and give it a more "complete" look. The geometry of the part made this easy.
All in all, acetone is a very valuable and versatile tool when dealing with ABS.
In order to mount the fans, I marked and then drilled holes for the mounting bolts I had from the previous ventilation fan project. I chose a small drill bit first, to get the positioning. Then, a larger drill bit that was slightly smaller than the bolt itself. This made it easier for the bolts to catch and guide themselves in snugly.
The four (x2 per fan) mounting holes towards the center of the body simply threaded into the assembly. I used four bronze knurled hand turn nuts for the four mounting bolts on the outside of the part to keep them in place. It added a nice, professional look to the whole assembly.
The fans needed a small adjustment. With a drill bit I opened up the mounting screw holes, since they were too small for the bolts I was using. I also used a step drill bit to allow the bolts to sit flush with the surface of the fan, so they "disappeared". It also gave me the extra threads the knurled hand turn nut needed to properly catch and secure the fans.
I mounted the fan using four wood screws guided by the built-in mounting brackets on the top of the part.
NEW VENTILATION SYSTEM IN ACTION
Here is a video of the new ventilation setup in my 3D printing box.
I absolutely love the new dual mount. I look at it every time I go to 3Dprint. It's incredible that I made that - it's my design!
I learned a lot throughout this project. If I hadn't messed up a few things, I never would have needed to improvise to find solutions. With each project, I learn new things and get better as a Maker. Even quicker, if I make mistakes and learn from them
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Alex G. Orphanos