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geekhack Community => Keyboards => Topic started by: DrinkTea on Tue, 18 June 2013, 21:19:57
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So, many of us have probably seen listings of the force required for actuation and bottoming out of various cherry mx switches, as well as ripster's tests. However, I'm wondering how these numbers were obtained, both physically as well as the sampling of switches.
If people just took one, or even a handful of the same switch and measured, this is not correct. From what I've heard there is a somewhat large allowable tolerance for the force of a given spring. What I'd like to see is a larger sample of switches and/or springs of each type tested. This way, we could get a handle on the mean and variance of actuation and bottoming out force for each type. We also should (and can easily) check the distribution of force. I would assume that for a newly produced spring it would be gaussian (easy to check with a reasonable amount of data) but perhaps the way springs wear over time would show something more interesting.
Either way, anyone want to help me gather data from a large sample of springs/switches? It's an easy analysis after that and I'd be happy to do it.
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You would probably need a force-meter. Something like this (http://www.industrial-needs.com/technical-data/point-force-meter-835.htm). Something electronic would make it much more repeatable though. mkawa had started a thread about this but it died, lack of interest.
Also, what do you think a "large sample" is?
Edit: This was the thread (http://geekhack.org/index.php?topic=40296.30) I was referring to.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
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Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
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Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Sorry to go somewhat off topic but Lysol what is the heaviest cherry switch available today?
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Grey variants are the heaviest that are standard production switch.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
I don't know where you got that 50 number. If you're thinking of the made up cutoff at which we tell students they can use a normal distribution instead of a t when computing confidence intervals and hypothesis tests, that number is 30. It's also not entirely relevant here. If you wanted to compute a confidence interval for the variance or test the hypothesis that it is ~20/3 you'd be using a chi-squared distribution anyway(still assuming normality).
While I agree that normality is reasonable assumption, why do you think 20cN is 3SDs? Is this something standard in manufacturing that I just don't know about?
Another big assumption people are making here is that each switch/spring is i.i.d (Independent and Identically Distributed). Under this model, for every spring produced we would just pick a number from a normal distribution and be done with it. However, I have my doubts as to this assumption. If I were to hazard a guess, there would be two main sources of variability. One would be intra batch, meaning that in every batch of springs they make there is some true mean actuation force that probably isn't exactly the overall mean and some small amount of variability. The other would be inter-batch. Since my guess is that springs are made in runs, you could could think of the mean actuation force for springs in a given batch was also sampled from a normal distribution. This would give you a nice hierarchical model (if you're a Bayesian).
Sorry if this seemed dashed off. I'm in a hurry. But it could be fun.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
I don't know where you got that 50 number. If you're thinking of the made up cutoff at which we tell students they can use a normal distribution instead of a t when computing confidence intervals and hypothesis tests, that number is 30. It's also not entirely relevant here. If you wanted to compute a confidence interval for the variance or test the hypothesis that it is ~20/3 you'd be using a chi-squared distribution anyway(still assuming normality).
While I agree that normality is reasonable assumption, why do you think 20cN is 3SDs? Is this something standard in manufacturing that I just don't know about?
Another big assumption people are making here is that each switch/spring is i.i.d (Independent and Identically Distributed). Under this model, for every spring produced we would just pick a number from a normal distribution and be done with it. However, I have my doubts as to this assumption. If I were to hazard a guess, there would be two main sources of variability. One would be intra batch, meaning that in every batch of springs they make there is some true mean actuation force that probably isn't exactly the overall mean and some small amount of variability. The other would be inter-batch. Since my guess is that springs are made in runs, you could could think of the mean actuation force for springs in a given batch was also sampled from a normal distribution. This would give you a nice hierarchical model (if you're a Bayesian).
Sorry if this seemed dashed off. I'm in a hurry. But it could be fun.
Well, i was trying to give you an easy way to do a guess-timation calculation, not an exact scientific number. So that we could assume for the sake of discussion that, in general 68% of all springs will have the stated mean actuation force +-5cN or something like that. And that most likely since +- 5cN is not noticeable by human fingers, so that you would only "feel" a difference in a very small number of switches (i.e., 2 or 3 sigma), and it would not affect the overall feel of a keyboard, which I think is what real-world experience tells us. Otherwise there would be threads on this forum about how funky Cherry keyboards feel.
As for a manufacturing standard on sigma, there is none, which is part of the problem. The max and min tolerances should be six sigma, but that is expensive, and the only company that uses such a tolerance, that I know of, is Carl Zeiss AG (the Swiss Camera lens company), and check out their prices. Otherwise, you are lucky to get 3 sigma, usually you get 2 sigma. As for the springs, I think they are all made in China, so who knows about the quality, or the tolerances. However, there should be a normal distribution among the springs, even between batches, and I am assuming Cherry has set some min and max tolerances and some confidence interval. Of course this assumes no cheating by the manufacturer, or by his suppliers, and no defective input materiel (which is a dubious real-world assumption, especially in China, I know). As for the sample size of 50, that is what I have seen in real world testing. For some reason nobody uses the minimum of 30.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
I don't know where you got that 50 number. If you're thinking of the made up cutoff at which we tell students they can use a normal distribution instead of a t when computing confidence intervals and hypothesis tests, that number is 30. It's also not entirely relevant here. If you wanted to compute a confidence interval for the variance or test the hypothesis that it is ~20/3 you'd be using a chi-squared distribution anyway(still assuming normality).
While I agree that normality is reasonable assumption, why do you think 20cN is 3SDs? Is this something standard in manufacturing that I just don't know about?
Another big assumption people are making here is that each switch/spring is i.i.d (Independent and Identically Distributed). Under this model, for every spring produced we would just pick a number from a normal distribution and be done with it. However, I have my doubts as to this assumption. If I were to hazard a guess, there would be two main sources of variability. One would be intra batch, meaning that in every batch of springs they make there is some true mean actuation force that probably isn't exactly the overall mean and some small amount of variability. The other would be inter-batch. Since my guess is that springs are made in runs, you could could think of the mean actuation force for springs in a given batch was also sampled from a normal distribution. This would give you a nice hierarchical model (if you're a Bayesian).
Sorry if this seemed dashed off. I'm in a hurry. But it could be fun.
all moot.. no one has the time to do this. or the equipment.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
I don't know where you got that 50 number. If you're thinking of the made up cutoff at which we tell students they can use a normal distribution instead of a t when computing confidence intervals and hypothesis tests, that number is 30. It's also not entirely relevant here. If you wanted to compute a confidence interval for the variance or test the hypothesis that it is ~20/3 you'd be using a chi-squared distribution anyway(still assuming normality).
While I agree that normality is reasonable assumption, why do you think 20cN is 3SDs? Is this something standard in manufacturing that I just don't know about?
Another big assumption people are making here is that each switch/spring is i.i.d (Independent and Identically Distributed). Under this model, for every spring produced we would just pick a number from a normal distribution and be done with it. However, I have my doubts as to this assumption. If I were to hazard a guess, there would be two main sources of variability. One would be intra batch, meaning that in every batch of springs they make there is some true mean actuation force that probably isn't exactly the overall mean and some small amount of variability. The other would be inter-batch. Since my guess is that springs are made in runs, you could could think of the mean actuation force for springs in a given batch was also sampled from a normal distribution. This would give you a nice hierarchical model (if you're a Bayesian).
Sorry if this seemed dashed off. I'm in a hurry. But it could be fun.
all moot.. no one has the time to do this. or the equipment.
Someone definitely has the equipment. Time, I agree with you. It's silly. But have some fun!
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Someone? No. Some company perhaps.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Their data sheets have 2 measures, actuation and bottom with a force graph. I can't find sheet for a couple switch though, and have some for ones that aren't made anymore, like clicky greys... which I have never even seen. :rolleyes:
Cherry reports the tolerance on switch for ±20cN so it is pretty loose really.
Standard Deviation: You would need a sample size of at least 50 keyboards with the same switch type to calculate a standard deviation with a high level of confidence. On the other hand, you can reverse calculate the standard deviation for a pretty good "guess-timation", and save the money from buying 50 keyboards, and the time it will take to test every switch x 50 keyboards. If you take IvanIvanovich's 20 cN maximum differential, then you can work back under the assumption that the cherry switch manufacturing process conforms to a normal distribution (which it should, since there is no reason to believe it would be skewed.) i.e., +20cN will be your high 3 sigma, and -20cN will be your low 3 sigma.
I don't know where you got that 50 number. If you're thinking of the made up cutoff at which we tell students they can use a normal distribution instead of a t when computing confidence intervals and hypothesis tests, that number is 30. It's also not entirely relevant here. If you wanted to compute a confidence interval for the variance or test the hypothesis that it is ~20/3 you'd be using a chi-squared distribution anyway(still assuming normality).
While I agree that normality is reasonable assumption, why do you think 20cN is 3SDs? Is this something standard in manufacturing that I just don't know about?
Another big assumption people are making here is that each switch/spring is i.i.d (Independent and Identically Distributed). Under this model, for every spring produced we would just pick a number from a normal distribution and be done with it. However, I have my doubts as to this assumption. If I were to hazard a guess, there would be two main sources of variability. One would be intra batch, meaning that in every batch of springs they make there is some true mean actuation force that probably isn't exactly the overall mean and some small amount of variability. The other would be inter-batch. Since my guess is that springs are made in runs, you could could think of the mean actuation force for springs in a given batch was also sampled from a normal distribution. This would give you a nice hierarchical model (if you're a Bayesian).
Sorry if this seemed dashed off. I'm in a hurry. But it could be fun.
Well, i was trying to give you an easy way to do a guess-timation calculation, not an exact scientific number. So that we could assume for the sake of discussion that, in general 68% of all springs will have the stated mean actuation force +-5cN or something like that. And that most likely since +- 5cN is not noticeable by human fingers, so that you would only "feel" a difference in a very small number of switches (i.e., 2 or 3 sigma), and it would not affect the overall feel of a keyboard, which I think is what real-world experience tells us. Otherwise there would be threads on this forum about how funky Cherry keyboards feel.
As for a manufacturing standard on sigma, there is none, which is part of the problem. The max and min tolerances should be six sigma, but that is expensive, and the only company that uses such a tolerance, that I know of, is Carl Zeiss AG (the Swiss Camera lens company), and check out their prices. Otherwise, you are lucky to get 3 sigma, usually you get 2 sigma. As for the springs, I think they are all made in China, so who knows about the quality, or the tolerances. However, there should be a normal distribution among the springs, even between batches, and I am assuming Cherry has set some min and max tolerances and some confidence interval. Of course this assumes no cheating by the manufacturer, or by his suppliers, and no defective input materiel (which is a dubious real-world assumption, especially in China, I know). As for the sample size of 50, that is what I have seen in real world testing. For some reason nobody uses the minimum of 30.
You sound like you might be familiar with manufacturing. If so, I have a project that could use your help.
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Now I'm imagining the new niche wave in mechanical keyboards is spring force consistency. Oh, I can see the marketing catch phrases now.... :))
In all honesty though, I can imagine why someone would be curious about this, I noticed in the keys to my Storm Trigger (w/ MX Greens) that the springs on some of the numpad switches are noticeably stiffer than then the main typing area, which can lead to some mistakes.
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Now I'm imagining the new niche wave in mechanical keyboards is spring force consistency. Oh, I can see the marketing catch phrases now.... :))
In all honesty though, I can imagine why someone would be curious about this, I noticed in the keys to my Storm Trigger (w/ MX Greens) that the springs on some of the numpad switches are noticeably stiffer than then the main typing area, which can lead to some mistakes.
One issue there is that you're not using the same fingers on each key. So the perception of resistance is higher on weaker fingers. I suppose that's an argument for ergonomically weighted switches.
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Now I'm imagining the new niche wave in mechanical keyboards is spring force consistency. Oh, I can see the marketing catch phrases now.... :))
In all honesty though, I can imagine why someone would be curious about this, I noticed in the keys to my Storm Trigger (w/ MX Greens) that the springs on some of the numpad switches are noticeably stiffer than then the main typing area, which can lead to some mistakes.
One issue there is that you're not using the same fingers on each key. So the perception of resistance is higher on weaker fingers. I suppose that's an argument for ergonomically weighted switches.
Very valid point, I'd be interested in trying an MX Green board with certain switches being lighter just for ease of use, specifically the backspace key.
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I just go by what Cherry datasheets tell. I don't have any interest in guesswork or measuring myself. I would assume their information about their own product should be correct.
Statistics isn't guesswork. Their data sheets are likely accurate but probably only report the mean force. What's interesting to me is the standard deviation. Since if their tolerances are high, it could lead to inconsistent typing experiences across different boards with the same kind of switch.
Er, Cherry deviation is absolutely not high at all.
Per their website their variance for tactile is +-0.7oz out of 2.3oz - that's about 30% at already tight tolerances - and +-0.5oz at 2.1oz for tactile. A much lower 25% or thereabouts.
Compare this to the Alps Simplified White: rated for 75g +-25g. Or, you guessed it, about +-33%.
As eth0s pointed out, they're not six sigmas of confidence - lucky to get three, but as far as I know Cherry was actually five prior to being sold - due to relationships with their spring supplier and controlling the keyboard and keycap manufacturing. Meaning they could determine end-state and control the entire process. That makes a huge difference. Cherry can't even tell you with two sigmas how a given keyboard will behave unless they made it themselves - keycap weight, installation method, handling, those all affect the mean activation points.
And yes. Most of the difference on a single keyboard using switches from the same batch is perception rather than actual difference. Given their competitors though, three sigma confidence at a 50 interval is still higher than most of their competition. I mean Alps is not a small company or imprecise and they were at +-33% tolerance! I'm not going to complain about <25% on the clicky switches for base actuation.
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Thank you for such a detailed reply?
You wouldn't happen to have any similar information about the tolerances for the Korean springs on Originative, would you?
I'm curious because, as was pointed out earlier, "most consistent typing experience" could be an interesting niche product.
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Thank you for such a detailed reply?
You wouldn't happen to have any similar information about the tolerances for the Korean springs on Originative, would you?
I'm curious because, as was pointed out earlier, "most consistent typing experience" could be an interesting niche product.
Well, gets back to what I said about whole process/completed product. Within a given batch you're going to have a very high (read: lower than stated numbers) level of consistency. The switches will generally be closer to probably +-5% - which is lower than you can perceive realistically.
So when people complain about inconsistency what they're actually complaining about is perception or additional factors which affect the operation. Absolutely we could produce switches with a higher level of consistency between batches - that's not a huge thing to do other than the costs of achieving and maintaining it. Then you go to install them in two GH60's and everyone will say the same switches from the same batch feel completely and totally different. Why? Different keycaps, different installation, different handling. (And we haven't even gotten into the lube versus no-lube religious debate!)
If you wanted to fill the niche of 'most consistent' you'd be spending thousands upon thousands upon thousands of dollars in tooling and QC to start with. Several tens of thousands to engineer a chassis and PCB and plate and then a lot more to ensure there's +-1% variances there. Then you'd need to spend thousands of dollars and hours doing research to come up with the right keycap weights for every single key, with variances measured in tenths or hundredths of grams. And then you'd have to spend millions for the tooling to make these keycaps and ensure these extremely tight tolerances - no small feat with injection molding when a sprue can throw off your weight.
Welcome to precision engineering! Hooray! (For the record: I know a thing or four about precision manufacturing. I know several machinists who regularly turn parts with +-0.003mm tolerances and make use of their services not infrequently.)
Don't get me wrong - it would be nice to have some more consistency between various batches of Cherry MX switches, or any switches. But it's just too expensive. And by the time you're typing on them, there's too many dozens of other variables that have a greater effect on the feel.
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Thank you for such a detailed reply?
You wouldn't happen to have any similar information about the tolerances for the Korean springs on Originative, would you?
I'm curious because, as was pointed out earlier, "most consistent typing experience" could be an interesting niche product.
Well, gets back to what I said about whole process/completed product. Within a given batch you're going to have a very high (read: lower than stated numbers) level of consistency. The switches will generally be closer to probably +-5% - which is lower than you can perceive realistically.
So when people complain about inconsistency what they're actually complaining about is perception or additional factors which affect the operation. Absolutely we could produce switches with a higher level of consistency between batches - that's not a huge thing to do other than the costs of achieving and maintaining it. Then you go to install them in two GH60's and everyone will say the same switches from the same batch feel completely and totally different. Why? Different keycaps, different installation, different handling. (And we haven't even gotten into the lube versus no-lube religious debate!)
If you wanted to fill the niche of 'most consistent' you'd be spending thousands upon thousands upon thousands of dollars in tooling and QC to start with. Several tens of thousands to engineer a chassis and PCB and plate and then a lot more to ensure there's +-1% variances there. Then you'd need to spend thousands of dollars and hours doing research to come up with the right keycap weights for every single key, with variances measured in tenths or hundredths of grams. And then you'd have to spend millions for the tooling to make these keycaps and ensure these extremely tight tolerances - no small feat with injection molding when a sprue can throw off your weight.
Welcome to precision engineering! Hooray! (For the record: I know a thing or four about precision manufacturing. I know several machinists who regularly turn parts with +-0.003mm tolerances and make use of their services not infrequently.)
Don't get me wrong - it would be nice to have some more consistency between various batches of Cherry MX switches, or any switches. But it's just too expensive. And by the time you're typing on them, there's too many dozens of other variables that have a greater effect on the feel.
What you're suggesting probably isn't even possible using mainly plastic parts