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Can someone explain in layman's terms how computers are used in designing pianos? Can they actually predict how changing some part of the scale design will change the piano's sound?

CAD, or computer aided design, has been used since the 1980's for heavy commercial design (my FIL was an electrical engineer) and certainly for some time in pianos. In my personal experience with the design of the Matchless Cunningham, for instance, we were able to make adjustments to the cast iron frame virtually to make sure it had the stability we were looking for. This was 15 years ago.

I imagine that CAD could also be used to adjust the geometry in an action so it could be tried virtually as well.

When I designed the Mammoth VCG Piano, I knew nothing of CAD. Drew up the plans on paper (because that's the way I was taught) and took those down to the machinist to have the plate cut out with a water jet and then all the parts welded together. First thing out of his mouth was to send him the DXF file.
So I had to buy a CAD program, learn it (took 2 months), and then redesign the whole piano again. The file goes directly to the cutting machine. Sure was a big deal that day sending the DXF file.

The advantage of Cad is its precise, easy to share the file, and you'll get to make sure everything will fit together before the actual build.
As far as changing the string scale to change a sound. That comes from experience working on pianos and seeing what works and what doesn't. Once you have that under your belt, then you would design a piano to your specs.
Hope that helps.
-chris

About a year ago I saw a youtube video put out by Yamaha where they started out showing how they synthesized the sound they wanted from a piano in an acoustic room, then designed the parts to give them that sound and built it and compared the resulting sound to the original design to see how close they got. Of course I've never been able to find that video again but I know it's out there. It also showed how the pianos are built in the factory, it showed a huge hydraulic press that they used to bond the rim veneers together. Anyway, if you can find that video it was a good layman's view of how much they were using computer aided technology to design and build the piano, and to modify the design to get the sound they were after. The whole thing was the most impressive "factory tour" type video I've seen.

Just for fun,

I can't believe I found a photo of the CAD rendering of our 5'4" piano on my computer. We did this 2 computers ago!

Anyway, here is a photo of the design of our 5'4" frame, virtually:

pianoloverus apart from my acoustic I have Pianoteq Stage version which allows me to change most physical characteristics of several types of piano. Click on the video on this site to see what can be changed.
Even if playing Pianoteq pianos is not of interest it's adjustment to pianos does provide an education and experience. Of course the other aspect of using computers for a new scale design is to compute string thickness, windings, tension and length which traditionally was, and still is, done using tables of data.
https://www.modartt.com/home
Ian

This is all very interesting but mostly beyond my comprehension haha. Is there some basic difference in the piano sound created by Pianotek compared to top of the line hybrids like the Avantgrand and Novus 10?

You’ve peaked my interest. Back before the new millennium I did IT work for the CAD designers. They were using AutoCAD, SolidWorks, and ProEngineer. Are these programs still in use? I also remember the designers had to have a fast powerful workstations, especially for the ProE users.

As I remember it took an engineering degree to even figure out how ProE worked.

I think all the car manufacturers use advanced CAD design because building wind tunnels is expensive. Pianoloverus, you could do some searches on the new Bronco or Jaguar and there’s some explanation of how the get from a drawing to a finished production automobile showing some info how the steps between CAD design and machine production. Might be worth a look. AutoMakers and rocket builders use CAD for everything, I’m sure automakers share more information.

That reminds me of this Kawai factory video. They do some similar things to what you describe.

I'm inclined to say, "On what part of a piano's design can a computer not be used?" One could start with 3D solid modeling programs like SolidWorks, ProE, and several others. These programs allow the dimensions and shapes of every single part of the piano to be designed, and then fitted together in a virtual assembly. So, before any part has been made, the whole piano can be visualized and the fit of every part of the whole can be verified. Once done, accurate drawings and files to be used in the machinery that makes the parts can be generated. It can predict the finished weight of the piano.

But, the really exciting part is the use of finite element analysis. Such software can compute and display the stress and strain of all parts, their resonant frequencies, and how much they would bend or otherwise deform with use. It can compare the responses of various materials. It can help predict the resonant modes of the soundboard and can allow the soundboard designer to experiment with, as an example, different rib sizes, shapes, and contours in ways that would be impractical to do with real parts.

Finite element analysis is ideal for designing plates. It will predict the stiffness and resonant frequencies of the plate as a whole and all its constituent parts. It would allow the designer to know what parts of the plates should be stronger, and also what parts need less iron so as to save weight and cost.

Computer aided design has revolutionized the design and production of almost all products

Schimmel is known for using computer-aided design extensively. From Schimmel's website:

"CAPE (COMPUTER ASSISTED PIANO ENGINEERING) DESIGN SOFTWARE

"In the process of any piano manufacturing, one encounters mathematical relationships and the basic laws of physics. The Schimmel CAPE program takes all these factors further. CAPE opens up new dimensions in the area of piano manufacture. It enhances accuracy and optimises quality, programs the automatic machines, improves production methods, and implements results of research.

"The CAPE technology encompasses;

"The experience gathered over a century of piano manufacturing
The mathematical analysis of the art of piano manufacturing
The knowledge of the physics of vibrating components
The analysis of vibrating soundboards
The calculation of the stiffnesses of cast-iron plates
The results of measurements of the velocity of sound waves
The interaction of wood, metal and felt
Knowledge concerning the geometry of good keyboard and action assemblies
Complete mastery in dealing with mass and acceleration, plus much more."

Schimmel apparently still makes use of quite an amount of "hand work ". There no unnecessary hurry to get each piano individual attention by trained people.These are not mass produced pianos , although Schimmel makes many pianos
and different models of pianos .
I suppose all these European pianos have work done by machinery. It seems that some may have more work done by hand ?

As nobody has answered I'll have a shot:

Most (nearly all) digital pianos such as Avantgrand and Novus store a library of recorded notes and play those back when the keys are pressed. Better pianos store actual recordimngs for each key rather than just a few samples pitch shifted to provide all the required notes. Even better pianos store multiple samples per note as the character of a real piano's note is different between soft and loud play. Better still have even more samples so that less interpolation/guessing between samples is required, better still have longer samples to provide a longer sustain etc. etc.

Just a few digital pianos don't bother with any of that stuff and instead go back to the very first days of digital pianos and just synthesise/model the note from scratch rather than play back a recording from real piano. These days the better examples of these modelled pianos, such as Pianoteq , are said to offer more expression to the pianist but perhaps not quite such a realistic sound.

I didn't go to College because i was too busy learning stuff. So when I needed to do CAD work in order to share files with computer based machines, i searched the various CAD software out there. AutoCAD was ridiculously confusing and probably would require taking a college class. It turns out that there are Cad programs out there tailored towards the common joe entrepreneur like myself. I chose VERSACAD. I know of several instrument designers that also use it. Anyways I wanted to share a screenshot of a drawing so i had to go and clean it up a little. I hadn't touched the program for about 6 years, but i was able to pick it right back up. So that is a sign that its somewhat intuitive to use.
I recommend it.
-chris