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Revolutionary Linear Drive System
Nexen has a new revolutionary linear drive system that is similar to rack and pinion but eliminates it's short comings. This makes it a better choice for many applications that typically use traditional rack and pinion, ball screws, and linear motors. See attachment for details.
Roller chain/sprocket inside out
It's said there's nothing new under the sun...
I Look at this and I see a roller chain drive. The only difference is that the "sprocket" has been turned in to a "rack"; and the roller chain itself becomes the pinion.
Since I've had good luck in the past with roller chain drive; I'll probably just keep using that inexpensive system; knowing that this "update" confirms what I've always felt about its suitability for axes driving...
Ballendo
P.S. Allan, Are you an employeee of Nexen?
The comments farther down suggest that the pitch error of ballscrews and nuts needs to be corrected by encoders. I disagree; and feel that there is some advertorial going on here... It--lead error-- is pretty simply accounted for by adjusting the steps per unit to accomodate this increasing or decreasing error. The rolled thread techniques used for precision rolled ballscrews will favor a lead error over a cyclical error, since lead error is EASILY reduced/removed; whilst cyclical error is the bane of every linear motion drive system.
From what I can see, the nexen drive will have the same issue od "lead" error. It will be due to the pinion PD not being perfect. And can be accomodated the same way.
The problem with chain and this nexen drive is that it has an uneven speed of motion. The pinion is essentially a polygon instead of a circle; and since the effective radius changes for any polygon inversely to the number of sides, there WILL be uneven motion speed. The "Rack" tooth profile will attempt to minimise this, but it will still be there.
The epicycloidal flank shape of gears is designed to eliminate this by providing a constant diameter circle at the PD where two gears intermesh. This flank shape is also designed to minimise relative sliding motion between the gear flanks to minimise wear. The nexen drive will suffer from the same wear effects as roller chain, albeit perhaps to a lesser degree since the rollers of the pinion ostensibly have better bearings than the ones used in small roller chain. But over time the rollers will wear and their diameter will no longer fit the rack tooth profile exactly. And the rack profile will similarly wear and no longer match the roller diameter. Without a means of compensation backlash will result. Since there is not a "wedging effect" as found in "normal" rack and pinion--the root of the nexen tooth form appears to match the roller diameter exactly--there appears to be no ability to "deal with" this wear outside of replacement.
Quote:
Originally Posted by allanconway2
Nexen has a new revolutionary linear drive system that is similar to rack and pinion but eliminates it's short comings. This makes it a better choice for many applications that typically use traditional rack and pinion, ball screws, and linear motors. See attachment for details.