On Tue, 04 Jun 2013 18:45:37 -0400, Tom Gardner Mars@Tacks wrote:

On 6/4/2013 9:59 AM, Pete C. wrote:

Tom Gardner wrote:

I'm designing a new generation machine that will need to push a 5/8" rod
two inches with about 600 lbs of pressure. It also needs to be a bit
"springy". The new machine is only about 5 cubic feet in volume and
will replace current machines that are 4' x 5' x 6' in volume. The old
machines use hydraulic power for the pin push. I want the entire
machine to use 120VAC only. One option is a small pump and an air
cylinder, another is a linear actuator with an in-line die spring or
something I haven't thought of. The rest of the machine is most of the
way there and rather clever...for me, anyway. What pitfalls can I
expect with a linear actuator?

Not sure what the control / timing requirements are. Would this be
something best done with a continuously running motor, an electric
clutch and a gear drive to a cam type setup?


Plenty of time, 3 seconds to extend or retract. The rest of my staff is
all for air, it just simplifies things and is cheaper. And, air can be
used for clean-up and other things

Air is fine, but it's not so good where you need positive control on
the stroke of that push, so you don't have a Tool Crash when the
follow-up operation tries to happen - unless it has enough brute force
to clear a misshaped or mispositioned workpiece out of the way, and/or
you put a limit switch to make sure it went far enough to do what you
want.

And those truck brake units are handy things - and consider the Spring
Brake ones. You have to apply pressure to release the parking brake
springs, and then you apply air to the other half to get normal
braking. But when it absolutely positively has to fail safe, the
spring (and a dump valve of some sort) makes sure of it.

I notice you deliberately haven't said what this actuator is doing...
Yeah, distributing 5,000 copies of the NDA and making sure they all
got signed and returned would be a problem.

-- Bruce --