Spring surgeryWhile convinced of the critical importance of using low force keyswitches, I found myself disappointed with the continued lack of commercial offerings from keyboard and keyswitch manufacturers in this area.Eventually I dismantled some of my keyboards and tried my hand at some spring surgery - in an attempt to decrease the keyswitch activation forces manually. I used a dental probe (to remove the keyswitch covers), a penknife (to carve the plastic actuators), heavy duty wire cutters (to modify the springs) and a bright light (to see what I was doing). Rather to my suprise, the surgery was successful!
Cherry MXI dismantled my Cherry G80-2334 - and tried my hand at some spring surgery on the board-mounted Cherry MX switches inside.More than half of the activation force was generated by pushing a piece of moulded plastic past a bent piece of gold - to deform it and thus make the switch. I tried a combination of chopping material off the springs and shaving plastic off the key plunger with a knife in order to reduce the activation force.
A combination of removing material from the springs and from the plastic actuators reduced the activation force from 64 cN to 20 cN - without serious side effects. That's lower than the activation force on any other keyboard I own.
The resulting change in the feel of the keyboard is delightful. However the process is fiddly. It takes about three minutes per keyswitch. It probably destroys any resale value of the keyboard. Also, it can only realistically be applied to board-mounted keyswitches. Frame-mounted keyswitches need removing from their frames before they can be dismantled. That typically involves unsoldering them from their boards - and that is often a non-trivial exercise.
This was a better quality devicethan the Cherry G80-2334 I had previously operated on. For one thing, it uses signal diodes to isolate the switches. The keyswitch surgery was equally successful.
Kinesis surgeryKinesis keyboards use use frame-mounted switches under the fingers (which are very difficult to get at) and board-mounted switches under the thumbs (which can easily be modified).
Cherry MLMuch the same thing can be done with Cherry ML switches. I applied spring surgery to one of my Cherry G84-4700 keypads.These are even more fiddly than the Cherry MX switches to dismantle. Removing material from the springs is the only intervention I attempted with these switches. I see no realistic way of reducing the distance to the activation point with these switches. The overall result is inferior to what can be done with the Cherry MX keyswitches - but worthwhile if you have Cherry ML equipment in use.
Optimal activation forceAfter futher experimentation with low-force switches, the 20 cN activation force of these modified Cherry MX switches still seems to be too large.Dedicated low force microswitches offer lower activation forces - and much better tactile feedback than seems practical to obtain by starting with a Cherry MX switch. 10 cN would probably be an improvement. Perhaps even lower forces would be desirable - if they could be obtained without compromising the level of tactile feedback provided. I originally thought that the need to prevent unintended keypresses would place a limit on how low it was desirable to make the activation force - but this seems to be a remarkably minor issue - at least for me.
FeedbackThe keyswitch surgery described here largely eliminates tactile feedback at the point where the key activates.The main idea is to simultaneously reduce the activation distance and the required force, so that effectively the key activates if it moves at all. It would be nice to have proper tactile feedback at the activation point - but the possibilities for such feedback become reduced as the activation force decreases. Good computer-generated audio feedback reduces the significance of this problem to some extent.
DisclaimerWarning: Keyswitch surgery is potentially hazardous to your equipment.You may lose springs, bend gold contacts, or cause electrical damage to your board. You have been warned!
LinksThis siteFrom here you can go back to Tim's keyboard page.
DiagramsSpring surgery for Cherry MX keyswitchesPhotos of Cherry MX keyswitches Photos of Cherry ML keyswitches |
