Z axis Ball screw break question

[Michael Simpson Virgina]

I have a ball screw Z axis coming from Techno Inc. Linear Motions System. I will need to provide some sort of brake. Any suggestions?

[Michael Simpson Virgina]

One thing I was thinking of was to spring load the carriage. The goal is to keep the bit from crashing into the table when the power is turned off.

[Gary Campbell]

Now I get it! Brake! I have used both springs and air cylinders for this use. With both ballscrews and rack & pinion setups. BTW the air cylinders, due to adjustability, are a much better solution.

[Rob Wright]

My 10mmDIA 6mm lead per turn ballscrew will not back drive the directly connected sepper motor. I have a k2 mount on a 1/2" plate that is 7"x16" with a Hiatchi router. All this mounted to a a set of Hiwin 20 series block and linear rail. Don't have an issue with it falling.

good reading: http://www.rockfordballscrew.com/ball-screws.htm

Torque The torque produced through the screw shaft by a thrust load on the ball nut. Ball screws can coast or backdrive due to the high efficiency of the mechanism (90%). If back driving is not acceptable, a method to resist the overturning backdriving systemic torque, such as a brake, will be required to hold the load. If backdriving is desired, the lead of the screw should be at least 1/3 of the screw diameter. Ideally the lead should be equal to the screw diameter. This calculated torque is the minimum amount of braking torque to hold the load in position.

[Michael Simpson Virgina]

Once I get the unit attached to one of my CNC's I will have a better idea of what I am dealing with. I can just imagion ruining yet another bit, by crashing it into my table, when I just the machine down.

[John Beroset]

I used a 1/2 dia. acme lead screw with an anti-backlash nut and there is enough friction to prevent the z axis motion when the power is turned off.

John Beroset