Introduction: 4ARM Ver 2.0 - FABU Hands-free Door Opener

4ARM ver 2.0 Hands-free Door Opener is the second edition of assistive device we designed to support Coronavirus containment efforts by eliminating direct contact with the door handle. It works with modern lever door handle with a tube diameter range from 19mm to 22mm.

Everyday door knobs and handles are often hotspots for germs, because of the frequent and inevitable use of most door knobs/ handles. The virus is said to live on hard surfaces for up to 3 days. This mount-on door opener doesn't require drilling holes or replacing your door knob/ handle, intended to assist you to open doors without touching the knob with your hands. It is particularly helpful for you to navigate tricky moment when you need to open doors with sanitized hands. By using your forearm to operate this opener, you are less likely to transmit or to be contaminated by the virus.


To install a hands-free handle device you will need the following:

1. download our STL files

2. 3D Printer and materials

3. 4 M3 screws and nuts

4. screw driver

5. anti slip foam

Step 1: Prepare the Material

To install a hands-free door opener you will need the following:

1. our STL files

2. 3D Printer and ABS Filament

3. 4 pieces of M3 screws and nuts

4. screw driver

5. anti slip foam

Step 2: Download 4ARM Ver 2.0 3D Files & Print!

If you are familiar with 3D modelling, you can download the 3D files below and modify the 3D design to fit your requirements. Otherwise, you can download the STL file and go straight to printing it with your 3D printer. We designed 4ARM to be small enough to fit on most 3D printer build plates. Minimum print bed size is 150mm x 150mm. The design requires no support material or additional bed adhesion meaning minimal post-processing. We've mostly been producing the device in PLA with the print setting below:

1. shell size: 3

2. infill: 25%

3. extruder temperature: 240°C

*please bear in mind these are some general guidelines for temperatures and settings you should use for specific types of filament but every printer and material is different, so feel free to adjust to the configuration that best works with your printer.

We have make the files below available for you to download:

1. 4ARM ver 2.f3d (fusion 3D file if you like to modify the design)
2. 4ARM ver 2.stl (ready to print stl file)

Step 3: Wrap the Anti-slip Foam Around Your Door Handle

Cut a piece of anti-slip foam that is long enough to go around the tube of your door lever handle. Wrap the foam around the tube, you may want to use double side tape to fix the foam in place. Modern door lever handle has a tube diameter 19mm to 22mm. 4ARM ver. 2 mounting diameter size is 24 mm. You can pad additional anti-slip foam to create enough friction so the clamp is tight fit.

Step 4: Mount 4ARM on Your Door Lever Handle

Glue the nuts to the nut slots on the smaller piece of the opener to prevent the nuts from falling. Place the two parts against the tube of the lever handle, with the larger piece facing out. Most modern lever handle works by pressing the lever down to pull the door open, adjust the position of 4ARM door opener so it works with your forearm comfortably. Align the holes on 4ARM door opener and put in the M3 screws and tightened them with a screwdriver. Make sure to fully tighten the screws to prevent the device from moving.

Step 5: Test the Device by Using Your Forearm

Once the 4Arm door opener is installed properly, using your forearm, press on door lever handle to release the lock and pull open the door. This is to prevent the spread of COVID-19 by stopping the user from transmitting the virus by touching the handle with their hand. If you find this useful, step up to fight against COVID-19 by printing and distributing this device wherever possible. Stay safe, and together we can beat Coronavirus.

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