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OhmniLabs Blog

Vacuum Forming the OhmniLabs Way

[fa icon="clock-o"] Mar 20, 2017 11:47:26 AM [fa icon="user"] Manh Nguyen [fa icon="folder-open'] 3d printing, Vacuum forming


At OhmniLabs we like to try different ways of prototyping to help us move faster with testing and developing new products. 3D printing has always been our top mean for prototyping and production. On the other hand, thermoforming is a common manufacturing process that we want to test and see if it is suitable for our prototyping needs. Thermoforming appears in everyday products including packaging, trays, bins, and disposable cups due to its aesthetic flexibility to form very organic shapes. Hobbyists like to prototype using vacuum forming machines, a simplified version of thermoforming, because they can replicate complex shapes at a much lower cost compared to other processes. While the market price of a vacuum forming machine is around $2,500, we believed we can build our own with a $300 budget.

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Cool Vacuum Forming Shapes made by hobbyists. (Source: GPerco.com / Instructables )

A vacuum forming machine consists primarily of a heat component, a frame that holds the plastic, a forming area -- a platen that looks like a pegboard, and a vacuum source.

How it works: plastic sheet is melted by a heat component to a pliable forming temperature then forced to a mold by a vacuum source to form a desired shape.

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Main components of a vacuum forming machine. (Source: allbiz)

Preparation: Designing with Fusion 360

We like Fusion 360 for design because it is cloud-based, allowing team collaboration. Think of it as a google doc for CAD files. Fusion 360 also supports top-down design. Its “As-built Joint” feature allows users to mate components designed on top of each other without having to move parts around. All components of a machine can be built and assembled in one file. Got it? We found top-down design extremely efficient and a huge time saving from a design standpoint. 

Fusion360 Design Files For Vacuum Forming Machine

Designing in Fusion360.

In this design, we placed the heating element on top due to several reasons. First is space. Having a separate space for heating element is not necessary if we could place it on top. Second, the design connects the oven with the forming area with rails, limiting the degree of freedom that the frame can travel. That way there’s no need to position the plastic frame on the platen every time.

Heating Element Mounted On Top

Heating element placed at the top.


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 Creating the Bill of Materials (BOM)

We used wood (poplar, douglas fir, and MDF) as the main material because it very forgiving, durable, and affordable. Other parts in the machine are from OPENBUILDS, Home Depot, and McMaster. McMaster provides 3D models for most of its parts which is very helpful for designers. We also saved money on parts by 3D printing them in house. 3D printed parts at OhmniLabs have reached a very high aesthetic level and exceptional quality.

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3d printed brackets and fasteners.

Heating solution -- anything that can reach 450 degree F works. This is typically the forming temperature of plastic. The size of the heating element depends on the size of the plastic being formed. Plastic sheets come with the increment of 12 inches. We chose to build the machine for a 24” x 24” plastic sheet.

For our machine we used the four Quartz Tubes in the picture below which were detached from a $30 oven from Craigslist. We also kept the oven’s control because we could alter the temperature, time, and settings if needed. So far we’ve tested “toasting” different types of plastic at 450F because the toast setting provides maximum amount of heat.

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Quartz tubes and controls dettached from oven.

Interestingly, the oven manufacturer might have set the two bottom tubes provide more heat than the top two tubes do. The plastic is heated unevenly in the first five minutes of heating but the heat is spread evenly when the plastic sheet reaches the melting temperature. We haven’t seen a substantial effect of unbalanced heating on our plastic after forming so we kept the setting.

** We kept the joints and the wiring of the tubes because those are not soldering together The manufacturer used a different technique to mount them because solder will melt around maximum oven temperature. (450F)

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Vacuum pump/air tank.

Vacuum solution -- in most DIY vacuum forming machines, the two common vacuum solutions are a shop vacuum and a vacuum pump/air tank. Shop vacuums are readily available and cheaper. They usually have higher Cubic Feet per Minute (CFM) of airflow compared to vacuum pump/air tank but very low vacuum pressure. Shop vacuum manufacturers typically do not include vacuum pressure of their vacuums in the specs. Based on later testing, we found that having a high vacuum pressure is very crucial to shape the plastic over complex molds. The vacuum in the picture can reach the pressure of 5 inches of Mercury -- good enough for prototyping purposes.

The Results!

OhmniLabs vacuum forming machine vacuum forming production parts

 

Simplified BOM

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