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Robust components for body powered prosthetic arms

We are promoting and building relatively robust components for body powered prosthetic arms. Currently we sell a wrist unit for body powered prosthetic arms [LINK]. We do that because we feel that there is an actual need for that. Also, the sales price at 1500 CHF is less than a third of our estimate for one build (around 5000 CHF). This means that this is a rare offering which contains an in part pro bono effort as we also do not expect there to be many orders.

Existing commercial prosthetic parts are relatively weak. For that, they seem relatively expensive. They are built to sustain certain loads. These loads are rather low. Such low loads do not appear to occur too frequently over the course of a typical day. So we do not believe these loads to be too realistic.

Current prosthetic parts thus cover an unrealistically low end of the loading scale. There are no robust parts available that are built for life as we know it or that even remotely approximate that. So we start to fill that niche with open source design, new ideas and cutting edge precision manufacturing. With that, we extend the scale of available prosthetic components towards a more realistic end of loading.

But amputees are not the only ones that benefit from good engineering. Social insurances these days may have to start to pay more realistic prices for prosthetic parts – and that means that instead of replacing cheaply designed units at a dream price ever so often again and again, reasonably priced units with a very high longevity could be purchased instead.

About the term “extremely durable”

One could call our products “extremely durable”. But terms, words, adjectives and attributes are decalibrated in prosthetic manufacturing: major companies tend to call anything that wrecks their parts “excessive force”. As they may construct cables or hook joints with somewhat soft plastic parts, “excessive force” is a level that may be reached relatively early in the life of such a product.

In our language, there are no high or extreme usage patterns. We call full application of force “normal usage” – pulling trains, hammering iron bars, wrecking moving boxes and throwing shelves are all part of normal daily life. And that is really how we feel it should be.

Fragile prosthetic parts are bad. Just bad.

Failure of prosthetic parts can in fact have an emotional quality. Amputees can tend to get really angry over non-functional or ill-designed prosthetic parts.

Now, getting angry in such a moment is normal, and so would you – sudden failure of a body part is not funny.

So out of pure empathy, we decided to go for a full performance as much as material choices and product design would allow us. As that, this fills an abandoned niche. No one has gone there before with upper extremity quick lock wrist designs. So really, this is a totally complimentary offer to existing large component manufacturers, as none of them appears to cover this aspect of reality.

The level of stability of our products is still fragile enough – after all, they will probably stop being useful if filled up with too much mud, dirt, sand or glue. There will be a way to get our products to stop functioning too. In our experience, no such unit will last forever – at one point in time, they all need cleaning, servicing or replacement. There is probably no prosthetic quality that lasts a lifetime. And more importantly, we found that increasing durability of one component may speed up decay of the next weaker link.


Compared to our wrist ‘PUPP+CH+EN Model 1′, any deliberately chosen competitive prosthetic quick release wrist could look like a limp and cooked noodle – no matter how its manufacturer tried to name it. Yet, terms in prosthetic components are decalibrated and we find that usage of the label “robust” is applied to some manufacturers’ parts that survive only weeks.

So we decided to call our line of prosthetic components “PUPP+CH+EN” (little puppet) to reset this inflationary type of label naming. The label PUPP+CH+EN is also a reference to the art and work of Hans Bellmer. At the same time, it is a tongue-in-cheek reference to the fact that all artificial prosthetic parts appear to fail ever so early. PUPP+CH+EN should be an adequate term to remind us of that. PUPP+CH+EN is a registered trademark in Switzerland.

To allow you to obtain reasonable replacement at any later point in time, product costs will cover time and material, but design of our parts has been optimized to keep cost low and product life long. With prosthetic components for body powered arms that are optimized for price, robustness, elegance and functionality, we are probably not competing with current manufacturers anywhere – but in fact filling an abandoned niche.

Becker hand [LINK], V2P Prehensor [LINK]

A sturdy terminal device requires a sturdy wrist. Once you own a sturdy wrist why not look for useful terminal devices?

We do not manufacture or sell Becker hands or the V2P Prehensor. All we do is suggest that you take a close look and get in touch with the manufacturers yourself or via your prosthetic technician.

If you want to use any of these, make sure to let us know before ordering your wrist. Then we can set you up with the proper parts, such as a UNF 1/2-20 threaded adapter or an Otto Bock Nutzapfen ranging around 16mm diameter.

As far as cables are concerned, it would be best to discuss that with your orthopedic technician.

Who works on the Puppchen series

We are a group of dedicated individuals that try to work towards robust and precise design.

Roman Meili runs MDP Meili AG, is a real fan of precision construction and has built bone implants for surgical use himself. He is interested in designing and manufacturing useful products.

Peter Schneider is a mechanic who works – among other – with high precision milling centers. He is interested in precision milling and assembly.

Stephan Mueller is an internationally renowned mould expert who worked self employed, who worked around the Shekou/Shenzhen area plastics industry and currently serves SHL in Taiwan. He is interested in designing and drafting intricate CAD models.

Wolf Schweitzer is a forensic pathologist, a below elbow amputee and due to synaesthetic phantom pain he really suffers when his parts fail. He is after usage specifications and testing. He is not on Roman’s payroll, has no financial gain from this and he is independent enough to have differing opinions. He gets to test all of the prototypes. And he gets to type up test reports.