ERGONOMICS
Evaluation of: “Mechanical Juicer”
-ENG3059M-
Tom Tidswell – 03003326
Introduction
For this
coursework, I have decided to evaluate my design project from ‘Machine Design’.
While this may mean I cannot conduct tests, or similar, on the product (as I
don’t have a physical model), I can analyze the Senses, Psychology, Perception
and Body Space in relation to it.
This work
is to be carried out when my Machine Design project is completed, so this work
can be an extension to, but not actually contribute to that module. The product
in question is a mechanical juicer, aimed at children (aged 5-9), which needs
to be fun, safe and easy to use.
Evaluation
Senses and Perception
When
looking at my product with relation to sight, one thing is clear. There is no
obvious indication of which direction to turn the second hemisphere of the
juicer; in fact, there is no indication that it can be turned at all. A
possible way to combat this would be to install some kind of subtle pointing
device (this was overlooked as I thought it would remove from its overall
aesthetic appeal). It should be noted also that this product being for a child,
they are likely to experiment with it, so hopefully the above would not become
a problem. Staying with eyesight, not that it would be likely but, I took care
to include textured surfaces on the exterior of the product, while these were
for another purpose, I do feel that these would soften any harsh overhead
lighting that happened to be reflected by the rotating elements. One final
problem for the eyes that concerns all juicers, is the
squirting of acidic juice coming from the orange during the products
application. This has been overcome two-fold by: juicing the orange inside a
unique bag; and encasing the bag inside the juicer itself.
With
respect to haptic stimuli, the design on the juicer
revolves around keeping children interested; and this is done by including
unusual textures on the outside of the product. The generic design includes an
orange peel texture; this could be a novel way to add a stimulus, as it would
be the same as the fruit that goes inside; providing a double take effect. The
twisting action of the juicer needs to conform to peoples expectations of
turning something ‘on’ – however this could bring confusion, as the ‘on’ motion
of a tap would turn the tap thread so the handle would move upwards. The
inverse of this needs to happen – turning it ‘on’ should push the juicing
element away from the hand. User testing would probably be the most appropriate
way to iron out this problem. Touch safety problems lie with sharp edges,
tightening screws, and moving-meeting surfaces. This product has all three:
sharp edges now are the problem of the manufacture process, which would need to
be especially good to as to not harm the child. The tightening screw action of
the juicing itself is protected by clipping the two hemispheres of the product together, the product would not function without this, as
the two sections would simply push each other apart. Finally, the
moving-meeting surfaces are the biggest problem. Fingers, items of clothing, or
anything else could become caught inside, and pinched by the hemispheres coming
together; this is partially solved by having a rubber stopper on one half with
a convex face, and the meeting plastic surface having a concave one. This
dampens any impact, and stops things from being able to penetrate through
during operation.
The aspect of touch that the product seems to be lacking is any kind of molded
grip, stopping hands from twisting the item properly – especially when
wet. This should definitely be considered.
Something that also needs noting is the process by which the parent would chop
the orange prior to the child coming into contact with it – this means that any
problem with children and sharp blades is avoided.
Finally, taste should be considered when choosing the
materials which would come into contact with the fruit. This is only one
material, as the fruit is concealed inside the bag at all time.
Body Strength
The product is aimed at being exclusively for children to
use. As is obvious, children have lower capabilities when it comes to strength,
than adults do. The main interaction the child has with this product is the
juicing; this is also the most strenuous. It is convenient that the most
efficient way of applying the input effort to the method of squeezing the fruit
has been used. The screw thread is the deciding factor of how good the product
is for the child to use. If the thread is too steep, the child could have
difficulty in turning the halves – as this is effectively the child pushing the
juicing element into the fruit manually. Whereas, if the thread is too shallow,
the child could get tired before the element even reaches the orange; and
certainly if there are more than one pieces to be juiced. More technical
information needs to be gathered before deciding what angle of thread to use.
Body Size
In 1975 a collection of data was conducted of children’s
accidents due to product design. It lists in detail many measurements,
including the all important hand measurements. The 5th Percentile of
five year olds shows that 10.7cm is the largest diameter they are able to
firmly grip while the 95th percentile of nine year olds is 15.9cm.
This is a problem with regards to my design. The diameter of the product when
it is closed reaches 16cm. Clearly there is going to be a problem with the
younger children using this product, however, the data does allow for a firm
grip; when put into practice, I don’t think it is necessary for hands to
completely span the product. A twisting motion is all that is required, and as
both hands can be used to twist at the same time, they are also pushing
together, so increasing the traction the child would have on the product.
I do think that some evaluation is needed into the overall size, and any
methods of trimming of a centimetre or two would be very beneficial.
Conclusion
From all the points stated above, I do believe that the
design picked up some beneficial ergonomic aspects during the design process.
Whilst as a whole, I think the design is appropriate; more attention needed
diverting from the stimuli related aspects of the design, to fundamental
aspects like sizing.
I do think that safety was well considered during the design
process, and I cannot think of any glaring points I did not consider. The
protective nature of the product – where all the workings are concealed on the
inside is a very positive point indeed. This is however the driving point behind
the increase in some critical sizes.