gas springs on z for heavy spidle motor

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transmon
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gas springs on z for heavy spidle motor

Post by transmon » Wed Feb 07, 2018 8:42 pm

Hey guys what do you think about gas springs to offset weight of spindle motor on Z axis on table router I know I have came across someone doing this somewhere but can't seem to find any information about doing this with router table are there any tips or negatives to doing this Thanks Dave

Gary Campbell
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Re: gas springs on z for heavy spidle motor

Post by Gary Campbell » Wed Feb 07, 2018 9:24 pm

Dave...
I've had much better luck using air cylinders. They are fully adjustable and foolproof. Plus you don't have to guess what your lift requirements are before you install them. Once installed, I disconnect the ballnut and adjust the pressure so that the up and down force feels equal. A neutral bouyacy setting?? The Z still has to work against inertia of the mass on direction change, but not gravity.
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transmon
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Re: gas springs on z for heavy spidle motor

Post by transmon » Wed Feb 07, 2018 10:04 pm

so just regulate air pressure to counteract the weight of spindle I like that thanks I think I will try that will be pretty straight forward thanks Gary !!

Gary Campbell
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Re: gas springs on z for heavy spidle motor

Post by Gary Campbell » Wed Feb 07, 2018 10:58 pm

I usually use 1" diameter cylinders. In any case its easy to calculate the pressure available.

for 1' diameter: Area * Pressure = Lift. pi * r^2=.7853 sqin. at 100 psi max 78# lift 3/4" cylinder is 44#

A look at how I mount them between 4:30 and 5:00 in this video: https://youtu.be/qtzkAExTA00
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agsweeney1972
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Re: gas springs on z for heavy spidle motor

Post by agsweeney1972 » Wed Feb 14, 2018 5:47 pm

Some large commercial CNC mills/routers use counter balance air cylinders and they work good, however they are a few components involved more than just the air cylinder.

There is of course the air cylinder.

There is a piloted check valve on the bottom of the cylinder to keep the thing from crashing down if you loose air pressure (trust me it happens) or creep down overnight when powered off without compressed air supplied.

There is also an expansion tank which has a regulated pressure and a check valve (second-order safety to maintain air pressure in the counter balance cylinder ) . Granted with a 1" bore you won't probably need much expansion but in the case of larger bores it will need it. You don't wan the air pressure rising as the Z goes down as that will just wear things out faster (especially if you are using lead screws instead of ball screws) or be too much for your stepper to handle.

frijoli
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Re: gas springs on z for heavy spidle motor

Post by frijoli » Mon Feb 19, 2018 8:59 pm

Gary Campbell wrote:
Wed Feb 07, 2018 10:58 pm
I usually use 1" diameter cylinders. In any case its easy to calculate the pressure available.

for 1' diameter: Area * Pressure = Lift. pi * r^2=.7853 sqin. at 100 psi max 78# lift 3/4" cylinder is 44#

A look at how I mount them between 4:30 and 5:00 in this video: https://youtu.be/qtzkAExTA00
The easiest rule of thumb is a 1.125 bore cylinder is 1 to "damn near" 1.
Clay
near Winston-Salem, NC
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