My BTTF Inspired Bag V2 Page 4

2nd heat test. Took a bit longer but wow, it is hot enough.
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Plastic!

Hopefully I will be able to make the first pull tomorrow. https://uploads.tapatalk-cdn.com/20180430/2b803db651cdd04b92d205f0fcafaf7f.jpg
And nope. I had to basically rebuild the heat box after seeing how far out the alignment was with the frame. Originally I had this attached to the hot box but I noticed that the alignment with the platen was out and I don't have time to mess around lining up the frame.

Fixed and ready for tomorrow.

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Most impressive prop build I've seen in a while! I'm half expecting to find out that this is a prototype build for an actual Nike shoe case that'll be on the shelves in time for Christmas.


Thank you @compucrap

I am hoping before Christmas.

Shhh, don't jinx it.

And too late. Can we all say EPIC FAIL!

So the plastic slumped beautifully over the heater box, but when I flipped it over to the platen, I could get a seal. Suction is fine. WTF!?! So I did a cold plastic test and seal is no problem and it dishes in under suction.

So back to the drawing board.

If I can get a seal when cold, and apply the correct amount of heat, the moment the plastic is soft enough to move, it is going to be drawn into the tool. That is how the small set up worked anyway.

So I knocked this up today. Stay tuned.
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"Some times I amaze even myself". My May the 4th SW quote for the day.

Well a much better day today that 2 days ago.

So the issue I have faced with this project has been a lack of heat. So today I bought a rig that would make Boba Fett jealous. Heat problem solved! This heat unit can drain that bottle in 20min.

2 days ago I made the new heat box but it was not working with the 3 ring burner. Works a charm now.

The trick is to fire the flame unit into the hot box and aim at the corners but not hot the plastic. It takes just 2min from cold to over 150 degrees C. I destroyed 2 sheets of plastic learning this.

So unlike normal vacuum forming, I can make a seal with cold plastic. I only need a few inched of Hg to do this. Run the timer at 2min, turn on the heat and watch the magic happen.

When I buy more plastic, I am going to have to shoot video because it was super cool to see this working.

So the results are in and I have a list of things I need to fix.

1. Use thicker plastic. The pull is not 100 percent and I had to back off the suction at 25"Hg when it broke my tool. Seriously this thing snapped 16mm MDF. See image 6. It cracked right along the side of the sand/epoxy mix. Unbelievable!

2. Fix the tool. I need to add supports under the sides now. The crack is OK.

3. I also have to make up a new handle part. So I knew at some point that I would have to replace the plastic tool parts of the handle with aluminium. I didn't figure it would have to be done after the first pull.

So over all, pretty happy about this.
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Thank you. It has been a long, bumpy ride but I hope to have all issues sorted and a cool product available soon.

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So I am waiting for a 2nd quote for a sheet of silicon for thermoforming. $330 for 1200mm x 1200mm by 3mm thick.

Bit of an expense up front, but will save me in plastic and give nicer parts.

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And more delays as the "expert" on this silicone sheet I need is away on holidays until next week.

If anyone knows about this stuff, please feel free to chime in.

The product I am looking at is rated to 230 C and has 250% stretch before it tears. No one can answer if it will stretch enough to push the plastic into the 130mm deep tool. I think it will, but not too keen on throwing $330 at a maybe. If I need to revise the tools to male, then so be it. I just want to know so I move forward.
 
Still no further on the silicon sheet, but did meet someone today that knows his stuff about male tooling and vacuum forming. He looked at what I had done and suggests that making male tools will give me a better result. He didn't quite seem to get female tooling during the conversation, though he did have some pointers that make sense.

So tomorrow, I will take his advise and lose the 90 degrees at the ends of the tool and hollow that out. He said I'd be better off with these parts at angles given the depth. Basically he said that what I have done is good but I am overs stretching the plastic at these points.
 
Had a productive day on this project.

I still don't have the proper silicone sheet, but may have found an alternative.

You can read about it in more detail in my other thread HERE.

This is how I think the best way to design the new tool would be. This will allow me to use the machined aluminium part as a buck.
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Another day and more pics of the progress.

I got game today and took suction right up to 20"Hg.

The smaller piece of rubber is being used to simulate the plastic. It also shows how I will be able to use smaller pieces than the form and still get a full seal.

The images show all the variations this could work. Based on what I observed today, image 6 is probably how I will use this. Notice that the rubber has pulled tight like a drum? Not sure what is going on there. I am hoping that with hot plastic this pulls down.

The last two images show that it does indeed pull down but the rubber does not stretch as much as hot plastic.

So tomorrow I will make plugs for the body and lid tools and then I should be able to make some parts.
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What a day.

First up, I have a puncture repair kit so should be able to fix that hole in the vacuum mat.

I spent most of today designing and building male tools.

I still have to skin the handle recess but this should work alot better on my form.

I still have to add some more reinforcement parts but basically it is one tool that I can change a skin on to make two different tools.

I have also found my original MDF buck for the end cap but it needs to be hollowed out and I am not sure if I can do that with my basic router.
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Another what a day.

Image 1. Was looking so good...

Image 2. Then this happened. Ahh!
And I honestly thought it was all over, then I thought I'd test out good old gaffa tape.

Image 3. All repaired and holding at over 15"Hg. It seemed good at 20"Hg.

Image 4. is a recycled failed pull. I figured I would just heat and flatten rather than throw it away. The idea of forming under the mat works. What this means is that it is possible to create thicker parts from smaller sheets of plastic and have less waste. I'd like to test this using the female tool now.

So based on what I have seen so far, full sheet forming of the lids in the female tool is going to give the best result.

Stay tuned for more...

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This image is proof of enough heat.
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This image is proof of a good seal and enough suction.

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The only way to move forward on this project is to now use thicker plastic. The pull in the first image was using female tooling and granded that causes thinner walls anyway. I used 3mm ABS for that and it really needed 4.5 or maybe even 6mm.

The problem with going to thicker plastic is the price goes up, way up. This is why I wanted to go the silicone sheet method. But that is $900, so given what I have spent so far, will have to wait a bit.
 
This thing rocks! Image 3 shows that it was no fluke.

I have discovered an issue that I need to correct in the tool, but once done, this project should be a go.

Still have to make the new end cap and bodies will be easy given I have had success with the lids. Experts by the way have said that it is a very complex part to vacuum form, so feeling quite good about this result.
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On any other day, these would be considered failed vacuum formed parts.

But not on this day...

I am recycling once again for R&D.
Image 1 is an over cooked polycarb pull but the idea here is back fill this to make a female tool that I know will work in my vacuum forming rig.

Image 2 is that other part reheated and reformed. Now because it was such a deep pull, it was never going to go back to flat, I as soon as it slumped, I turned on the suction. So I would suggest that I over did it on the heat as I got two webs (a sign of the plastic being too hot) and a small blow out where the plastic was over stretched.

The point of the test was to see how it would work with the new tool and I am happy with the result.

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When I watch BTTF 2, I can't help but notice that some of the props are pretty much slapped together from what ever they could get their hands on.

Spend $300 on a machined part.
Find a $10 dog bowl with the same dimensions.

Given the tube bag was a one of, maybe this is exactly what they used to make the end caps.

So going to vacuum form this tomorrow.
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