Solved 3D Printing Vacuum Forming Mold

[Inq]

I just found out today that our flying club has Vacuum Forming gizmo to make canopies. I was thinking I could CAD up a canopy and 3D Print the form. I've never vacuum formed anything. I don't know what I don't know, so any advice, references, links would be very helpful. For my first one, I'm thinking about doing a canopy that'll fit the FT Spitfire Speed. A couple of questions to get started:

1. I'm assuming the form needs to be pretty strong. Any suggestions on wall thickness and Infill density?
2. How much detail will show in a finished canopy? IOW - How much sanding of the 3D Print Layers to smooth them out will I need to do?

 

[luvmy40]

The level of detail imparted depends on the quality of the vacuform equipment, how deep a vacuum is pulled and how even the heat is applied to the plastic. But, in general, you want a very smooth form. Also make sure to make the form so it has extra material that extends past the trim lines or you may get distortion at sharp bends. I.e., don't make the form exactly the shape you want and set on the vac plate.

My vacuforming experience is with Kydex rather than thinner clear polys, but I would say 50% infill will be more than strong enough for this.

 

[cyclone3350]

As @luvmy40 stated, it needs to be very smooth. My first attempt to vacuum forming a canopy was from a shaped balsa block. It was sanded smooth but I didn't seal the grain very well & it showed up (much to my surprise) as imperfections lines in the clarity.

 

[Tench745]

My limited experience forming clear plastics tells me that it will pick up any imperfections in the mould. Like, dust can imprint itself on the plastic and cause blemishes.

 

[telnar1236]

I just found out today that our flying club has Vacuum Forming gizmo to make canopies. I was thinking I could CAD up a canopy and 3D Print the form. I've never vacuum formed anything. I don't know what I don't know, so any advice, references, links would be very helpful. For my first one, I'm thinking about doing a canopy that'll fit the FT Spitfire Speed. A couple of questions to get started:

1. I'm assuming the form needs to be pretty strong. Any suggestions on wall thickness and Infill density?
2. How much detail will show in a finished canopy? IOW - How much sanding of the 3D Print Layers to smooth them out will I need to do?

1. I use at least 5 layers (2 mm) wall thickness for PLA since the heat from the vacuum forming machine can cause the PLA to deform. Maybe you could get away with 1 fewer for ABS. Typically I would say at least 30% infill for the same reason, but I was able to get away with 10% infill on my mini F-104 canopy using gyroid infill. Mileage may vary.
2. As others have said, every little detail shows up, especially in the wrong light. I don't really mind the layer lines in my canopy and I don't think they are that noticeable, so I tend to just print with a pretty high quality and not sand, but the lines are definitely there and visible. I've never had anyone comment on them unless looking at the canopy from a few inches away though. If you are trying to put a camera under the canopy, then the layer lines are a serious problem.

The only other advice is to make sure that you have plenty of space on all sides of the mold and to print the mold with some extra height, since the molded plastic curves slightly at the bottom and being too close to the edges will make it worse. Vacuum forming is pretty easy, just time consuming if making the perfect mold.

 

[Inq]

My limited experience forming clear plastics tells me that it will pick up any imperfections in the mould. Like, dust can imprint itself on the plastic and cause blemishes.

Beats the heck out of my experience level... "I buy lots of stuff I don't need that comes in clear vacuum formed packaging."

 

[Merv]

...I was thinking I could CAD up a canopy and 3D Print the form...

Question, why vacuum form at all? Why not just 3D print canopy, paint it if necessary and use it?

 

[Inq]

1. I use at least 5 layers (2 mm) wall thickness for PLA since the heat from the vacuum forming machine can cause the PLA to deform. Maybe you could get away with 1 fewer for ABS. Typically I would say at least 30% infill for the same reason, but I was able to get away with 10% infill on my mini F-104 canopy using gyroid infill. Mileage may vary.
2. As others have said, every little detail shows up, especially in the wrong light. I don't really mind the layer lines in my canopy and I don't think they are that noticeable, so I tend to just print with a pretty high quality and not sand, but the lines are definitely there and visible. I've never had anyone comment on them unless looking at the canopy from a few inches away though. If you are trying to put a camera under the canopy, then the layer lines are a serious problem.

The only other advice is to make sure that you have plenty of space on all sides of the mold and to print the mold with some extra height, since the molded plastic curves slightly at the bottom and being too close to the edges will make it worse. Vacuum forming is pretty easy, just time consuming if making the perfect mold.

WOW! I'm glad you chimed in... I was basically going with maybe 3 walls (1.2 mm) and @luvmy40 suggestion of 50% Infill.

You also bring up another thing... heat. I haven't even see one of these devices. I was assuming I heat the plastic sheet in my oven and transfer it to some vacuum bed thing like the old hockey puck air tables... just reversed. What kind of temperature and time are we talking about?

If you are trying to put a camera under the canopy, then the layer lines are a serious problem.

Although FPV is on my long list, I did want to take advantage of the flat bullet proof front screen typical on WW2 fighters for that in the future and did want this one to be able to retrofit the camera at some future date. I was even thinking of embedding something nice and flat in the mold in that area.

 

[Inq]

Question, why vacuum form at all? Why not just 3D print canopy, paint it if necessary and use it?

The clear filaments... ABS, PLA etc... are perfectly clear on the roll... the layering process of 3D printer never is good enough to see through it. I do want to put a pilot/cockpit detail in a detailed war plane and mentioned above, might want to FPV through it.

It comes out like this...

 

[Merv]

...I do want to put a pilot/cockpit detail in a detailed war plane...

Getting kinda fancy now.

 

[skymaster]

for me making a vacum former just the thought of making so many holes, i am a patient person but drilling so many holes arrrrrrgggggghhhhhhh!!!!!!!!

 

[Inq]

Getting kinda fancy now.

I'd like to say I still can create a positive learning curve and that some day... I might be able to keep a plane and fly it too. There are some gorgeous planes on the forum... foam board, foam carved, balsa, 3D printed that have very nice scale details. I can print pilot with no actual skill.

 

[cyclone3350]

for me making a vacum former just the thought of making so many holes, i am a patient person but drilling so many holes arrrrrrgggggghhhhhhh!!!!!!!!

U mean like this. Yeah it was a little bit of work, but it did make these nice nacelles for my micro DC-3 along with some cowlings for other projects.

 

[Inq]

micro DC-3

Old school Pan Am! Like it!

 

[telnar1236]

You also bring up another thing... heat. I haven't even see one of these devices. I was assuming I heat the plastic sheet in my oven and transfer it to some vacuum bed thing like the old hockey puck air tables... just reversed. What kind of temperature and time are we talking about?

The heat isn't too bad. Like you said, you heat the plastic sheet away from the vacuum forming machine. PLA is just so sensitive to it and softens whenever it even gets a bit warm (I think it only needs to reach 130 F or so). It depends on the thickness of the sheet being formed, but it's a pretty safe bet that a decent fraction of the heat will be transferred into the surface of the mold and so if it's too thin it cause problems. There needs to be enough structure under the layers that get hot to hold it in place under the not insignificant force from the vacuum forming process and even slight deformations are visible in the molded part.

 

[Inq]

The heat isn't too bad. Like you said, you heat the plastic sheet away from the vacuum forming machine. PLA is just so sensitive to it and softens whenever it even gets a bit warm (I think it only needs to reach 130 F or so). It depends on the thickness of the sheet being formed, but it's a pretty safe bet that a decent fraction of the heat will be transferred into the surface of the mold and so if it's too thin it cause problems. There needs to be enough structure under the layers that get hot to hold it in place under the not insignificant force from the vacuum forming process and even slight deformations are visible in the molded part.

Is it worth sticking the PLA/ABS plastic form in the fridge and pulling it out at mold time?

 

[Tench745]

Is it worth sticking the PLA/ABS plastic form in the fridge and pulling it out at mold time?

I would say no, because it would quickly cool the plastic you're forming over it and possibly cause a partial-pull.

 

[Inq]

Getting kinda fancy now.

See what I mean? ... @shadeyB 's - https://forum.flitetest.com/index.p...h-building-tonight.60613/page-779#post-739540

 

[shadeyB]

See what I mean? ... @shadeyB 's - https://forum.flitetest.com/index.p...h-building-tonight.60613/page-779#post-739540

When vac forming a canopy,
be sure to extend the base with a skirt as mentioned above to allow you to cut very close and trim to suit 👍
1. quickest option would be a block of balsa (or soft wood) and carve it to the shape your looking for 👍 it will hold great under vac form pressure
2. Cad one up and print it but you will need to fill, sand and polish to remove layer lines that will be pulled into the vac-form.
printing the plug 5 walls are enough and 0% infil is best , while printing at best resolution, 0 bottom layers and once printed fill will plaster which will ensure no collapse under the heat and pressure of vac forming.
sanding and polishing - simple paste filler or rattle can primer filler is all that’s required, but be sure to spend time filling/sanding/repeat then final polish to get the best result you can

another tip for a clean smooth finish it to heat shrink plastic or vinyl over the plug before vac forming

the above can be done with empty clear plastic drink bottles also with. A little practise 👍

 

[Inq]

the above can be done with empty clear plastic drink bottles also with. A little practise 👍

Now there is a back-yard engineering tip!!!