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Hello guys in this Instructable we are going to show you how to make a plastic housing from (PET) bottles. The technique we are going to use is called heat shrinking. Just to give you an idea; this method is mostly used in the sector of packaging to put labels on bottles (see photo).

As prototyping skill, this method is pretty difficult because the bottles are always having an different shrink value. In that way you will encounter much trial and error during the process. In preparation for this Instructable, even we had to do it several times. So guys, if it doesn’t work the first time, don’t give up and try it again until you have a nice result.

Optionally you can add some nice finishing techniques such as painting, more visuals, stickers,… and everything else to get a clean prototype but we won't show you that in this Instructable.

Step 1: Materials You Will Need

  • (PET) Bottle
  • Utility knife or scissors
  • Heat gun Foam / clay / … to make a 3D model
  • A small wooden stick or something like a small cylindrical file ( for holding the foam)
  • Gloves
  • Grater, files and sandpaper

Step 2: Making a 3D Model

Make a 3D model in foam (we will make a housing of a dremel/ electric multitool). On the photo, you see we didn't exactly made a cleanly sanded model but of course it is better that you do this because your plastic housing will look much better then our result. But like I already said, it is an method of trial and error.

Hint/ tip: watch out that you don’t make the model bigger than the bottle you will use.

Step 3: Choose a Good (PET) Bottle

Choose a good (PET) bottle with not to many support ribs and a bottom as flat as possible. When you think you have found a good bottle, cut the (bottom) end of the bottle off, as closely to the bottom as possible.

Hint/ tip: try NOT to use a coca cola bottle! The bottom of those bottles are way to irregular which gives you a bad result in the end.

Step 4: Begin of Process

Put the foam model, which you made, in the bottle. Put the (wooden) stick in the foam, to get the heat away from your hands when you hold the top of the bottle or just put heat resistant gloves on.

I didn't do it but nevertheless I can recommend you to do it because those heat guns can produce very hot air.

Step 5: Hints to Avoid Errors

Heat the bottle up but do not blow heat on the same spot. Otherwise you will make holes into you bottle or get some surface blistering (see photos).

Blow evenly over the whole bottle, then it will equally shrink around the foam model it’s surface.

Hint/ tip: if some areas don't shrink equally, you can manipulate the plastic manual by pulling or pressing it (with heat resistant gloves!) while it is heated. But be carefull not to burn yourself or change the surface quality.

Step 6: End Result

When the bottle is shrinked around the foam, you can cut the bottle open at one side and get the foam out. Then you have a plastic housing for a dremel which could serve as a prototype.

In the end you will always have an opening from when you have cut the bottom end away. I solved this by cutting the shrinked plastic on the back away to get a proper backside.

Step 7: Optional Post Processing

When the foam model is intact when you have extracted it from the plastic housing, you can multiple copies of it. In this case the foam model will serve as a reversed mold.

As I told told you guys in the intro, you can optimalize the housing by painting it or by putting some visuals on. This will make your housing look as a real life product.

Thank you for reading our Instructable and make sure to take a peek to the attached tags from howest, IDC, ipo, IPO and HOWEST.

If you've found your desired mold, blow molding could be employed for producing seamless shapes. All that need be done is to cast your foam core in plaster, or fine cement to create a 2 part negative mold (or one part using mildly heat resistant silicone). You can buy bottle preforms for blow molding online(25 for $8 on amazon, or even less if you search online), they look like plastic test tubes with screw on lids. <br>When heated to around 350&deg;F the plastic softens enough to expand, allowing you to blow it to the shape of your mold(preferably using a heat resistant adapter, unless you have asbestos lips). Add vents to your mold anywhere air could be trapped keeping the bottle to expand properly.
<p>Very interesting ideas! Thank you for sharing this. </p>
<p>Thank you for your comment. I hope you enjoyed it! </p>

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