Old-school Modular Door Securement - Reinvented (+Fusion 360 How To)

The flat I live in has a rather weak door lock. As I wanted to reinforce the locks without changing something permanently, I came up with a 3D printed lock securement and a 3D printed door handle safer.

Please be aware that this is not supposed to be permanent solution and cannot guarantee you’re home’s security. In case of you needing a professional security system at your apartment or house, I advice you to seek out a professional security specialist.

I know that not everyone of you has access to a 3D design software, which is why I designed the parts to be almost universal. However, compare the stated sizes with your door locks to ensure they fit (see the 'technical' drawing attached). If you don’t own a 3D printer, take a look online to find printing services near you.

I have uploaded not only printable *.stl files but also *.f3d files that may be opened with Fusion 360, so you can follow-up on how I did it (workflow is reversible in the document) and change things according to your needs. If you come up with ideas on how to improve the design, be my guest :)

The only thing you will need is either two screws or a connecting piece, such as a piece of wood.

I will split up my instructable into three parts. The first part explains the lock securement with fixation on its own (option#1), the second part looks at the lock securement with fixation on the doorframe (option#2) and the third explains how to secure the door handle.

Choosing between option #1 and #2 is simple. Is there a slit from 0.7 to 4 mm between the door and its frame? Go for option 1.

Option #2 is suitable, if the part of the door frame that is attached to the outside of the wall is at least 40 mm high (let me call it the “depth” of the frame – we’ll come to it later).

Whatever option you choose, the door handle always has to be prepared the same way.

I printed this part with supports, due to the holes for the nuts. The infill should not be lower than 50% and the housing has to be thicker than 0.7 mm.

As every lock might differ in shape, I designed the handle attachment to be customized by the end-user. Due to the low glass transition state temperature of PLA (meaning the temperature causing the state of the PLA to change towards liquidity), it is now malleable. Use a lighter at the spots marked with number 1 in the picture above for around 2 seconds and then press it under your lock handle. Let it cool down for a bit. If it did not work out the way you imagined it, just reheat it and have another try. The video shows how I did it.

At the spot marked with number 2 you may want to heat up the material as well to reshape it to better fit your door handle. This depends on how well it fits without reshaping it.

Option #1 employs the lock itself. The idea is to use the slider inside the lock to hold the fixation part of the securement.

I provide two different sizes of the securement (1 mm & 2 mm), depending on the size of your lock distance.

Print with 100% infill.

If it doesn’t fit in, read the next optional step.

Insert just as in the step before until the door can’t close further. Take the securement out and watch out for the marked spots. This is where it hits the lock. Cut the piece just underneath the spot and give it another try. You might need to try several times until it fits to your lock.

If you can’t make it fit, look for screws that are not screwed in 100% or similar.

Print it detailed (I used 0.2 mm layer height) and with enough cooling because you don’t want to use support. If the screws don’t fit, just print slower. I had initially faced some troubles with the thread not staying in form.

Option #2 employs the door frame to secure the handle attachment. As explained in the very beginning, the “depth” of the door frame needs to be at least 40 mm – as shown in picture #4. If the corner is not filled by the frame, momentum pulls it towards the lock and by that, removes the grip at the frame. In case you still want to apply it that way, build a corner from e.g. wood and put it in the space. This should then prevent the part from moving.

This part needs to be infilled at least 50% as well. It consists of three different parts. A screw, a pusher and a housing. The pusher is inserted from the side of the housing. See suggestions in earlier step regarding the screws.

The diameter of the door handle hole is 250mm. I don’t think there is a lower limit to it...

Picture #4 shows how the handle is fixed. Try to install it as far away as possible from its turning point. The momentum at the handle edge is the highest but it should only act translational (down) and not rotational.

Print ‘extension’ with 100% infill. This is the part shown in picture #1. This one needs to be fitted to your needs which depend on the chair you will use for securement. Add 'extension' (50% infill, supports needed) to it.

Shorten 'extension' according to your needs.

Keep a bit overlap because we will adapt this last piece to the used chair again. Heat up the PLA und press it on top of the back of the chair. You might have to use a knife to cut out pieces to make it work. If necessary, secure the extension further with a (rubber-)band.

When all parts are printed and prepared, you should set up the lock fastener first. Then, place the handle securer on the door handle. Position the support on the back of the chair and push it towards the door until the support is parallel to the door. The door (handle) should be completely closed.

I'm obviously not responsible if you get robbed although you used the items described above. This system’s weak spots are temperature (everything above ~60°C (140 F)) and extreme force.

Be safe :)