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General Mach Discussion / Re: Height Control for Router Table
« on: August 13, 2011, 05:37:17 PM »
"The low cost THCs DO have the pid loop built in and cost around $500 or less complete ."
Which ones? Anything that interacts with Mach3 through THC UP/DOWN commands doesn't have a PID loop, or if it does, it doesn't do any good. The idea behind the PID loop is to adjust the feed rate based on the distance of travel and to control acceleration to reduce/eliminate over-travel. Most of these low cost THC's simply trigger the Mach3 THC commands, which in turn move the Z at the set THC feed rate with no acceleration applied until the input is turned off. when it's turned off, there is always some over-travel, which is dealt with by reducing THC feed rate to where the "bounce" is acceptable, which as you pointed out, is not as big a deal in plasma as it would be in routing.
Which ones? Anything that interacts with Mach3 through THC UP/DOWN commands doesn't have a PID loop, or if it does, it doesn't do any good. The idea behind the PID loop is to adjust the feed rate based on the distance of travel and to control acceleration to reduce/eliminate over-travel. Most of these low cost THC's simply trigger the Mach3 THC commands, which in turn move the Z at the set THC feed rate with no acceleration applied until the input is turned off. when it's turned off, there is always some over-travel, which is dealt with by reducing THC feed rate to where the "bounce" is acceptable, which as you pointed out, is not as big a deal in plasma as it would be in routing.