One thing that can be difficult to achieve with a disabled hand, is clipping the other hand's nails.
Some commercial helpers exist, but I thought that there was room for improvement, in particular for people with weaker arms (and hard nails). This design attempts to provide a more comfortable, cheap solution to this problem, and can be customized to fit different clippers. I have put a photo of the one I got from Carrefour.
The system is made of a lever mechanism (using print-in-place hinges) to amplify a light downward force on the handle into a stronger clipping action. It was inspired by this existing design, which provides a lever action relying on a flexible handle. One issue of this existing model is that the clippers' slot dimensions cannot fit every clippers on the market. I also wanted something with a wider base for more stability. Finally, I chose to incline the clippers upwards, in a more comfortable position
To adapt to various clippers models, the design needs to be parameterized according to the clippers' geometry, as explained bellow. The values should not be too different, for a “regular” clippers (the one I used is 80mm long). I took pictures of the clippers to make the modeling and initial measurements, but it should be OK to measure directly, for example with a caliper and then adjust the values using the quick test prints until the fit is satisfactory (which I did).
Then, you just need to generate the model with OpenSCAD (uncomment the relevant lines in nail_clippers.scad
), print the two parts, assemble them with two M3x6 screws (or glue), insert the clippers and optionally secure it with one more screw. I also advise putting adhesive pads under the legs for stability (there are centering marks).
The following pictures describe the meaning of the clippers' parameters which needs to be customized so that it fits in the slot perfectly. Use the three test models to check and adjust the parameters before printing the whole part.
The clippers are approximated as a straight portion (cuboid) at the rear, followed by a "truncated pyramid" portion becoming larger towards the front.
The first picture shows the side view and the associated parameters. clippers_back_x
and clippers_z
specify the position of the bottom rear corner, with respect to the lever's rotation axis. clippers_back_h
, clippers_front_h
, and clippers_back_l
specify the slot side profile. Print the test model clippers_side_test()
to check those.
The second picture shows the top view, on which you should identify the values for clippers_back_w
and clippers_front_w
. You should also determine the distance clippers_rivet_x
between the center of the rivet and the clipper's rear and the radius clippers_rivet_r
of the hole (you should put a screw of that radius to secure the clippers).
An additional test model clippers_full_test()
is provided for a final checks. It includes a small additional tolerance to compensate for the bridge printing inaccuracy. Make sure that the fit is not too tight on the front side so that the clippers can get back to its open position when the lever is released.
Lever parameters are explained by the following picture. Again, small test models allow you to adjust the parameters.
The first picture is for the lever's tip side profile, which is approximated as a circular arc of thickness lever_t
(a straight tip profile can be represented using a large radius). lever_z
and lever_fold_x
specify a point where we put a tangential arc (again, with relative to the lever's rotation axis), while lever_back_x
is the tip X coordinate (which correspond to the length of the lever). The remaining parameters normal_angle
and lever_tip_r
specify the radius and the direction of the arc at this tangential point.
The lever's top profile is defined as shown on the second picture, with a straight front portion specified by lever_front_x
and lever_front_w
, and a narrower tip of width lever_back_w
. The straight front section is irrelevant for making the tip slot, but I found it more natural to measure the maximum width and the length of the straight section than extrapolate to get the correct angle.
The three test models should help with customization. This needs to be a tight fit (adjust the thickness accordingly), so that the lever stays in its slot.
The last parameters specify the angular range of the lever, from which the angular range of the hinges are computed (with some extra margin).
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Those do not require a very high precision. A margin of 1° is added to max_angle
, and of 5° subtracted from min_angle
(because the lever can need to be pushed further before it actually clips). And the hinge's tolerance add some more play anyway. Of course, a wider range will not hurt, except that it can make the hinges slightly weaker.
The model has many more parameters, which are not required for simple adaptation. The consistency is of course not guaranteed when playing with those. For example the “geometry” parameters define the position and lengths of the moving parts. This could be used to modify the lever amplification, handle angular range, etc.
I suggest printing at 0.15mm precision, with 3 perimeters, 1mm top/bottom, 20% infill, very slowly (around 20mm/s) to get the hinges right. No supports are needed. The parts are oriented for printing at the very end of nail_clippers.scad
.
It should not be too difficult to loosen the hinges if printed correctly.
I've tried my best to make the model “easy” to adapt to different existing clippers and detail the customization process, but I admit that there are quite a few parameters to set. The benefit of this parametric approach is that the resulting object is easy to print, and maybe less cumbersome than an mechanically adjustable version would be.
I'm always interested in getting feedback. Please send me pictures of your manicure !
The author marked this model as their own original creation.