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AX-O 02-24-2020 12:20 AM

3D printed parts and molds: A how to guide (of my experiment)
This thread is to document a project that I have been making and maybe show other folks what they can also do. I wanted to challenge myself and learn new skills.

Please lets not go into the there is no alternate air source or not enough media to filter on the air or world is going to end because there is a carbon fiber parts in the vicinity of an aluminum aircraft. This is a project to learn new skills, fail and build.

I chose to make an air filter enclosure. The reason was because the room in the cowl is restricted to the mold line, the shape would require contours, it would force me to find a way to mount the enclosure and nicely bring that air into the fuel servo. It would also force me to learn how to use technology that i don't use.

My previous version was made out of fiber glass and was made off a wooden mold that belongs to Dave Anders. Looks like this.

After lots of research, gouge aero rules from college and some personal experience.. I came up with this. Not completely optimal but within the constraints mentioned above.

I then used a 3D printer using PLA to print a mold. The printer bed was not big enough so I had to print it in 2 pieces then join them together. I used 5 minute epoxy for that job. Each piece took approx 11 hours to print. Raw printed parts below.

I then sanded the mold with different grids of sanding paper to get rid off the ridges left by the 3D printer. And since I am vacuuming the parts, I filled the inside of the mold with pour foam.

And mounted it on a piece of wood so I could get a nice edge for joining parts later and also facilitate the vacuuming process. The plan was to pull 2 halves off the same mold then joining them using the flange. Then a strip of carbon fiber inside the part, cut the flange off, and 2 layers of carbon outside the seam.

AX-O 02-24-2020 12:21 AM

Part 2

The next phase was to plan out the work. This is similar to painting. The better work you do on the front side, the better the part ends up at the end.
I cut the carbon fiber are required to cover the mold. This particular carbon fiber is the left over stuff from my Formula One race plane. Side note: This type of fiber is Bid. But not the standard Bid. It was discovered by Paulo Iscold while building one of his race planes. A boat manufacturer had excess material and they needed to get rid of it. They made Paulo an offer that he could not refuse. The nice thing about it is that the fibers are not interweaved, they are laid on top of each other then stitched. So you can cut it and pick it up as you desired and it does not lose its shape. Paulo passed the gouge to Craig Catto and the fabric is now used on all his props. And now on to an experiment for an air filter ?box?.

Once the carbon fiber and supporting material was cut, I waxed the mold 5 times and polished the wax off.

AX-O 02-24-2020 12:22 AM

Part 3

Used West system epoxy mixed 5 to 1 with slow hardener.

Items laid on the mold were:
-3 layers of carbon fiber with multiple overlaps on the nose to make that stronger for a clamp.
-1 layer of peel-ply
-1 layer of perforated plastic
-1 layer of cotton

That was placed inside a hand made bag (plastic and tape, that was another trick I learned at Catto's place).

A vacuum was placed on the bag via a pump, approx 25 inHg. That entire assembly was placed under a moving blanket and a small portable heater was placed inside. That kept the temps inside at 118 deg during the curing process despite an OAT of 55 deg.

Little dots you see is the resin coming through the perforated plastic.

Once the part was cured, the struggle began. I had to pull the part off the mold. I started at 7 am because I was so excited. Did not even brew coffee. I quickly woke up by stabbing my index finger simultaneously by 4 carbon fiber needles. It shredded my finger pretty good. Had to put the work away for a few minutes and go into the garage so I could cry and not wake up my wife.

I reattacked the issue and was able to succeed at some point. The lessons learned from that were used on the second part and that one came off in a few minutes. Pics of the unfinished parts bellow. They are perfectly smooth inside. The is one small seam from were the 2 parts of plastic were glued but the seam is wax. so no issues to get that off. The outside waviness is due to the stitching of the carbon fiber. also some time the bagging process wrinkles the outside of the parts if you don't take extra care.

I am out of pics and work done thus far. I will finish this project at some point. Trying to finish up my engine installation. I also have to make a part on the fuel servo side.

DaveO 02-24-2020 06:27 AM

The pictures of your work did not come through for me.

Janekom 02-24-2020 01:17 PM

Really nice job so far. Please continue sharing

Gash 02-24-2020 02:21 PM

Looks like this will work really well, especially as you approach trans sonic airspeeds! :D Reminds me of the SR-71 shock cone.

sblack 02-24-2020 06:11 PM

Axel what is the reason for having the center cone making the inlet annular? I have noticed a similar center part on stock supercub intakes and always wondered why it was there.

N269SD 02-24-2020 08:37 PM

I'll bet that carbon takes a lot of resin

AX-O 02-24-2020 09:46 PM


Originally Posted by sblack (Post 1410156)
Axel what is the reason for having the center cone making the inlet annular? I have noticed a similar center part on stock supercub intakes and always wondered why it was there.

In simple terms; In subsonic flow, the shape reduces drag (drag coefficient) and ends up aligning the flow better than just a blunt object. Different reason for supersonic flow.


Originally Posted by N269SD (Post 1410186)
I'll bet that carbon takes a lot of resin

It sure does! :D Thanks for the help with the wing and tail Goose.

sblack 02-25-2020 10:37 AM

ah ok and I didn't realize from your dwg that the cone is actually the filter element! The picture tells the story.

Regarding stabbing with cured CF - I fell your pain. I redid all the empennage fairings on my 4 in CF. I had numerous punctures. It hurts! :mad:

thilokind 02-25-2020 04:25 PM

3D printed molds
I have made similar parts using a slightly different process. In a nutshell:
- 3D print core with PLA in one piece
- sand 3D printed part to a smooth finish and apply mold release agent (i.e. wax) or slightly sand 3D printed part and cover with electrical tape.
- Lay up glass fiber or carbon fiber and epoxide resin to the 3D molded core
- Apply peel ply
- Vacuum bag (breather ply, etc.) or wrap cling wrap film over peel ply
- let epoxide resin cure
- once cured, remove peel ply
- put part including 3D printed core in oven for 1 to 2 minutes at 300 F
- the PLA core will get very soft and rubbery - it now can be easily pulled out using pliers

AX-O 02-25-2020 05:48 PM

Thanks. looks like the only difference in our process is the oven. Pretty standard process.

You should post specifics on your projects so other folks can learn and see the possibilities folks (not manufactures, companies) have.

BJohnson 02-25-2020 11:16 PM

Looks good!
You must have meant 25 inHg vacuum. You would need an autoclave to get to 25psi.;)

Do you have a preferred source for the non-crimped-fabric you were using?

AX-O 02-26-2020 01:24 PM


Originally Posted by BJohnson (Post 1410485)
You must have meant 25 inHg vacuum. You would need an autoclave to get to 25psi.;)

Do you have a preferred source for the non-crimped-fabric you were using?

Good catch on the units.


I got an email into Craig and Nicole for the part number and where to buy the carbon fiber. Will let you know.

gofly 02-26-2020 01:44 PM

Are you using Solidworks? Is that a plugin for it?

Thanks for posting!


hgerhardt 02-26-2020 04:45 PM


Originally Posted by gofly (Post 1410635)
Are you using Solidworks? Is that a plugin for it?....

Good time to remind folks that Solidworks is available free for EAA members.

Bill Rossmann 02-26-2020 05:36 PM

Hi Axel great thread could you share with us the model 3D printer you are using and any problems to look out for..

AX-O 02-26-2020 06:15 PM


Originally Posted by gofly (Post 1410635)
Are you using Solidworks? Is that a plugin for it?

Thanks for posting!


This is Solidworks. You can get it from EAA as shown on the link provided in a post above.


Originally Posted by Bill Rossmann (Post 1410693)
Hi Axel great thread could you share with us the model 3D printer you are using and any problems to look out for..

I am using an ANET 8 printer. It was a kit that you build. Took about 5 hours to set it up. When I bought it the cost was around $250 without the filament. Now you can find them under $200. I spent extra on upgrading the printing surface on the bed and had a buddy print me some upgraded cooling nozzles, stand and knobs.

The biggest thing that I hate is that the plastic filament snaps off if you don't print in a while (approx 7 days). You then have to take things apart to feed the PLA back in.

I printed in quick mode that is why it ended up with small ridges. If you print in a different mode that part will come out smoother but will take much longer to print.

AX-O 02-26-2020 11:03 PM

2 nights ago I glued the 2 half together by placing a single layer of carbon on the inside seam. I covered it up with peel ply and let it dry for 24 hrs since I did not have the heater.

The inside looks like this after peeling the peel-ply.

Tonight I cut the flanges off and sanded them flush. After that was accomplished, i placed a 1 inch wide strip of carbon fiber on the seam and covered it with peel ply. I was going to use 2 layer on the outside but with one layer on the inside, it was very rigid already. 2 layers would have been a little over done.

The fiberglass intake you see on the background is the old one that came off Dave Anders' mold. It was used during the Reno air races and did not have an air filter.

AX-O 02-26-2020 11:22 PM


Originally Posted by BJohnson (Post 1410485)
Do you have a preferred source for the non-crimped-fabric you were using?

Nicole got back to me. They were using Vectorply carbon fiber when I was there building the wings, similar to this. Now they have changed to the same material made by a different manufacturer. It is Chomarat c-ply link

I have not had to buy it (well I did when the wing was built). Just using the scraps so far.

AX-O 03-21-2020 10:11 AM

Been working on some other projects but wanted to continue with this one yesterday.

I was trying to figure out how the air filter would seal on the cone flange. The filter has a small ridge. Figured I would mix some micro and make a perfect seal.

I put tape on the filter in case i made a mess, then waxed the rubber part of the filter.

I then mixed up micro with caboseal (spelling?) to keep the micro from running. I then applied the micro on to the cone flange and shaped the micro into a triangle. This will insure that when the 2 surfaces meet, there is squeeze out and no empty pockets form.

Then put both part together and set a 15 lbs prop crush plate on top to squeeze out the micro and keep the rubber flange straight.

Mike S 03-21-2020 10:59 AM

I have had good luck in the past using compressed air to get parts off/out of the mold.

DanNiendorff 04-10-2020 08:06 AM

Solidworks Mold Function
Hi Guys,

I've been exploring SolidWorks for a little while, for making parts, and molds for parts.

I'm not sure if everyone is aware, but SolidWorks has a function for creating a female mold for the part you have designed. You can specify the offset from the part you have designed in SolidWorks, and if will create a female mold with that offset.

For SolidWorks 2019 it is under Insert --> Molds.

Great feature.


AX-O 04-15-2020 09:39 AM

The project has been moving forward. After talking with a few folks, Tim Feeney wanted to give it a go. He is on VAF (TFeeney) and an RV-10 builder. We decided to go with aluminum as the material. There were many questions that I did not expect which required answers before moving forward. Probably pretty basic questions for folks in the machining business but not for me. Goes back to the learning part of EXPERIMENTAL.

Tim can be reached here if you need machining work:

Tim Feeney – Director of Engineering
Aerospace Solutions Group
7000 Airport Drive, Suite 204, Sellersburg, IN 47172
O: 812-246-1656

picture of current work below.

AX-O 04-16-2020 09:04 AM


Finished product. The only difference is that I decided to make the flange the same size as the filter OD.

Mike S 04-16-2020 09:06 AM

Looks good, another new skill :D

TFeeney 04-16-2020 04:56 PM

More copies
I?m looking forward to hearing how this works out for Axel.
Thanks for letting us get involved - it?s a fun project!

If there is additional interest, just let me know. We?d be happy to make more.


AX-O 05-17-2020 10:23 AM

Getting back to this project. Tim did a great job machining this part. There a few things I would do different on this part if I were to do it again. Those are a thinner flange, lightening holes and a smaller flange OD. The part is strong like bull but it is also heavier than i would like it. The transition from inside the filter to the servo is nice.

Continuing with the experiment.
I decided to mount the unit floating on the servo side and the cowl side. In order to do that I cut holes on the carbon fiber cone and filed a spot on the adapter. One of the holes was for clearance on the alternator bracket. The other one was for the starter. That will allow for clearance while components are moving around. For the first experiment, I will use a 3 inch SCAT hose. Allowing approx 1/4 inch between the parts so it can flex/float.

trying to get weight off.

After figuring out clearance and mounting issues. Pics make the part look like they need more clearance but they look ok in real life.

Cowl is kind of painful to put on now. I have to push the filter assembly towards the firewall while trying to fit the hose on the cowl inlet. But it makes for a nice transition. Future test may use different materials. I wanted something fairly strong at the beginning to make sure the filter assemble could be supported.

AX-O 05-17-2020 03:24 PM

[quote=RV8JD;1431073]I think you are getting caught by the same thing Martin ("goatflieg") was in another thread. Remove the "-no?authuser=0" from the end of the pic address

Thank you.

Pilot135pd 05-19-2020 07:54 PM

When I read "HOW TO GUIDE" I thought it was how to use the 3D printer. :( I really need to decide which one to buy for a newbie to start learning how to do these things on rainy days or this summer when it's super hot and I can't work outside on the airport.

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