Why was Stainless Steel used for the DM42?

General discussion about calculators, Swiss Micros or otherwise
zeno333
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Why was Stainless Steel used for the DM42?

Post by zeno333 » Mon Mar 26, 2018 8:14 pm

I think that Stainless steel was the best choice to use, amazing it was used...I am curious as to the thinking though that caused that choice to be made? It was the best choice, but since the case is covered with paint, one could have chosen a variety of other materials...I am curious how Stainless Steel was chosen, since it is for sure an unusual material to use even though it is the best to use.

rprosperi
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Re: Why was Stainless Steel used for the DM42?

Post by rprosperi » Mon Mar 26, 2018 9:06 pm

zeno333 wrote:
Mon Mar 26, 2018 8:14 pm
I think that Stainless steel was the best choice to use, amazing it was used...I am curious as to the thinking though that caused that choice to be made? It was the best choice, but since the case is covered with paint, one could have chosen a variety of other materials...I am curious how Stainless Steel was chosen, since it is for sure an unusual material to use even though it is the best to use.
Why do you think stainless steel is the best?

Odds are most of the reasons in your reply are the same as why it was chosen, as it was clearly not a casual decision.
--bob p

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Walter
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Re: Why was Stainless Steel used for the DM42?

Post by Walter » Tue Mar 27, 2018 8:33 am

zeno333 wrote:
Mon Mar 26, 2018 8:14 pm
I think that Stainless steel was the best choice to use, amazing it was used...
Emmh?? What did you want to tell us here?

Think about the material alternatives and about the production technologies employed, then you might know why.
DM42 SN: 00041 --- Follower of Platon.

HP-35, HP-45, ..., HP-50, WP 34S, WP 31S, DM16L

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Russel
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Re: Why was Stainless Steel used for the DM42?

Post by Russel » Tue Mar 27, 2018 6:58 pm

As I understand it, the landscape SwissMicros calculators have a titanium case. At least, the currently produced models, if I'm not mistaken. Very durable and corrosion resistant, but relatively expensive. Stainless steel is a very good alternative, durable, corrosion resistant and much less expensive than titanium. Both have their manufacturing difficulties. But, I would expect the primary reason to use stainless for the DM42 is cost. Especially when the DM42 is the most expensive calculator in the line.

(About a week till the DM42 I ordered arrives. I can hardly wait!)

zeno333
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Re: Why was Stainless Steel used for the DM42?

Post by zeno333 » Fri Mar 30, 2018 1:08 am

Stainless Steel is best since it has a very high tensile strength...It is very strong, much stronger than plain steel of the same thickness etc.

rprosperi
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Re: Why was Stainless Steel used for the DM42?

Post by rprosperi » Fri Mar 30, 2018 3:08 am

Russel wrote:
Tue Mar 27, 2018 6:58 pm
As I understand it, the landscape SwissMicros calculators have a titanium case.
I believe the early cc-sized models were made of titanium, but I do not believe any of the large (DM1xL/DM41L) models were ever made of Ti, and that even the smaller models no longer are. This was addressed in a post by Michael here a couple months ago, you can probably find it with a search.
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pauli
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Re: Why was Stainless Steel used for the DM42?

Post by pauli » Fri Mar 30, 2018 6:51 am

Why then do the stainless steel screws I use break far more readily that the plain steel ones? Stainless steel ones seem to break as easily as brass or even more easily.

Stainless has other properties that make it difficult. It work hardens quickly and my previous employer had to press enclosures multiple times in stainless whereas once would have been sufficient in steel.


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Jebem
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Re: Why was Stainless Steel used for the DM42?

Post by Jebem » Fri Mar 30, 2018 9:36 am

My less than two cents humble opinion here...

A metal back cover had to be used in this design because:

1. The way the back cover is joined to the front cover requires a material with enough strength to cope with the force applied to it when opening and closing the calculator.
A plastic cover would not resist long enough here.


2. It increases the overall case rigidity and at the same time increases the calculator weight giving a sense of a class product to many owners.


3. It may act as a RF shield if it was properly designed to operate as such.

As there is no official published documentation on hardware/firmware design, and the scarce published pictures/videos/infos from other sources are not detailed enough (if at all), it is not possible to confirm its electrical play in this design.

I believe SwissMicros is protecting its Intellectual Property here, by not publishing any details on their proprietary hardware/firmware.
They have a business to run after all, and of course the last thing a company wants is to see their intellectual property stolen by malicious opportunists out there.

So, I respect SwissMicros position here, despite it being contrary to a scientific community spirit of knowledge sharing.
I mean, as a community of calculator addicts/scientists/engineers/curious people (check as appropriate), I am sure many of us would like to have access to all SM calculators hardware and firmware design details.

But at this point, I am not buying one DM42 to have my weekends free time assigned to reverse engineering sessions to satisfy my curiosity.
Currently I have other more useful things to do on my spare time.
That said, I admire those who have the skills, the will, and the spare time to uncover any device secrets that they can share with the community.
I learn from these people and I am thankful to them.
Human natural curiosity took us to me moon (do we really got there? My hope is on Elon Musk and SpaceX now... Mars is getting closer!)


4. Why inox steel?
Well, why not, specially if it is so much cheaper to produce than using other much more "noble" and costly metals like aluminum or even copper?

We are talking about Chinese steel manufacturing skills here.
I'm sure they can produce good inox steel and use their hydraulic presses to create corrosion resistant metal back covers at the lowest cost possible when compared to any other (some better, some worse) alternatives. However, only the passing time will tell how good these metal covers are.

Few manufactures can afford to use "noble" materials these days, as it would increase the project costs substantially.
I miss those days when CASIO could afford to use first grade aluminum leagues on the battery holders and back covers able to resist corrosion year after year for more than 20 years now for their first models built like this.

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Russel
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Re: Why was Stainless Steel used for the DM42?

Post by Russel » Fri Mar 30, 2018 7:04 pm

zeno333 wrote:
Fri Mar 30, 2018 1:08 am
Stainless Steel is best since it has a very high tensile strength...It is very strong, much stronger than plain steel of the same thickness etc.
That has been my experience.
pauli wrote:
Fri Mar 30, 2018 6:51 am
Why then do the stainless steel screws I use break far more readily that the plain steel ones? Stainless steel ones seem to break as easily as brass or even more easily.

Stainless has other properties that make it difficult. It work hardens quickly and my previous employer had to press enclosures multiple times in stainless whereas once would have been sufficient in steel. [...]
I'm surprised that you say this. I find stainless steel screws very durable, both hex head cap screws and wood screws. Brass screws are much weaker, in my experience. I install stainless steel wood screws, of the same size as brass screws, to prepare a wood construction so that the brass screws can be installed and don't break off.

Of course, there are many alloys of stainless steel and "plain steel", so I guess it would really depend on the exact material the screws are made of.

In the construction of a calculator case, I consider stainless steel to be an excellent choice. Compared with aluminum or other steels, the cost of the stainless steel and the difficulty of manufacturing with it being the down side.

DA74254
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Re: Why was Stainless Steel used for the DM42?

Post by DA74254 » Fri Mar 30, 2018 7:31 pm

Russel wrote:
Fri Mar 30, 2018 7:04 pm
zeno333 wrote:
Fri Mar 30, 2018 1:08 am
Stainless Steel is best since it has a very high tensile strength...It is very strong, much stronger than plain steel of the same thickness etc.
That has been my experience.
pauli wrote:
Fri Mar 30, 2018 6:51 am
Why then do the stainless steel screws I use break far more readily that the plain steel ones? Stainless steel ones seem to break as easily as brass or even more easily.

Stainless has other properties that make it difficult. It work hardens quickly and my previous employer had to press enclosures multiple times in stainless whereas once would have been sufficient in steel. [...]
I'm surprised that you say this. I find stainless steel screws very durable, both hex head cap screws and wood screws. Brass screws are much weaker, in my experience. I install stainless steel wood screws, of the same size as brass screws, to prepare a wood construction so that the brass screws can be installed and don't break off.

Of course, there are many alloys of stainless steel and "plain steel", so I guess it would really depend on the exact material the screws are made of.

In the construction of a calculator case, I consider stainless steel to be an excellent choice. Compared with aluminum or other steels, the cost of the stainless steel and the difficulty of manufacturing with it being the down side.
Speaking as a ships engineer; here are my experiences with stsainless steel og "SS" as we refer to it as short..
There are mainly two types of "SS", first is "stainless", which is DIN 304 and "acid resistant", DIN316.
Mostly, nuts and bolts are made of 304 type steel and it has rust and seawater durability, but it does not like friction. If one use, say an air driven impact wrench the nut and screw (bolt) goes very warm and seizes. The threads will be destroyed and you will not be able to unscrew this.
Stainless in any flavor is "harder" than steel but also more brittle (and mostly non-magnetic).
Using "SS" (in SM, most probably 304 as it is much cheaper than 316) is a good thing for day-to-day use as it is extremely resistant to rust and environmental degradation, though, taking into mind the friction "wulnerability" one should unscrew and fasten the small screws with caution and really be sure the threads have entered correctly, whence no problem should occur.
Having this in mind, there should be no trouble with the SM calc with the very small screws. On a bigger scale, say M12 and up, they're, in lack of better words, crap. I, as an engineer prefer to use ordinary high tensile "rusty" bolts and replace them on a regular basis d.t rust instead of having trouble with them seizing or shearing in critical environments.
Esben
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