SteveL (Customer) asked a question.
How to control a cylinder two directions and then stop in the middle?
I'm a Newbie and l am looking to control a cylinder that would extend fully, then retract fully, then extend about 1" and rest. What type of cylinder and controls would I be looking for to accomplish this.
Thanks
There's quite a bit of additional information that is needed:
1) Hydraulic or pneumatic?
2) Do you need exact positioning?
3) Do you need force feedback?
4) Cycle rates?
5) Force requirements?
6) Cylinder rod configuration?
7) Safety considerations?
8) Stroke length?
As described with no additional information, assuming a pneumatic cylinder with a reasonable stroke length, one way to accomplish this is with a double acting pneumatic cylinder with magnetic piston, compressed air supply with necessary filter/dryer, valve manifold with flow control valves, three cylinder mounted prox switches and any one of the three flavors of PLC's offered by AD.
We would need a lot more info on what kind of force is needed and how much room you have to mount the cylinder to select hydraulic, pneumatic, or electrical actuator.
Sorry, I told you I was new...
The machines I would like to adapt these to are router and a drill combination pocket hole cutter they are shop made similar to Castle machines. First direction plunges a router into the part then the opposite direction pushes a drill into the part. When the cycle stops both router and drill are clear from the part.
1) pneumatic
2) Do you need exact positioning? Not exact, but within 1/4-1/2" at the middle stop pos. (This amount of slop could be increased if I needed to) I have hard stops at both ends of travel.
3) Do you need force feedback? Yes it needs force in both directions
4) Cycle rates? Ea. cycle takes about 1-2 seconds
5) Force requirements? All I can say is we do it by hand now. Doesn't take a lot. Maybe 1" bore? I could test it out.
6) Cylinder rod configuration? I don't know?
7) Safety considerations? I have guards in place now and it is safe I don't really know what else could be of concern by adding power.
8) Stroke length? 4"
I have quite a bit of space and options to work with under the machine to mount the cylinder to the carriage that moves the router and drill.
Is there springs that currently keep it in the center position now? if so you may be able to get away with a valve with a float center and the springs would move it where it needs to be
edit I found a better link comparing valve types
https://www.lunchboxsessions.com/materials/flow-directional-control-valves/intro-to-directional-control-valves-lesson
I'd like to see a Link or Pic of the Design..
However.. to 'Stop' an air cylinder in the 'Middle' is tricky.. another option is to have TWO air cylinders working in a series length.. Generally think of it as TWO Air Cylinders with the Blind Ends hooked ( Bolted ) Together.. Cylinder 1 Has its Rod Bolted to the Machine Frame.. Cylinder two has it's Rod Bolted to the Slider Part of the Machine..
1) To Retract the Cylinder 'Set' to Min Stroke, Air up the Rod end of Cylinder 1, and the Rod End of Cylinder Two. This will Tuck the Pair to as Short as it will Go.
2) To Extend to 1/2 Stroke, Either Pressurise the Blind end of Cylinder 1, OR the Blind End of Cylinder Two. IF the Cylinders are the Same Length, then it won't matter which one you'll do.. If the Cylinders are Different Length, then do the Math..
3) To Extend to MAX Length, Pressureize the Blind End of Cylinder One, AND Two.. this will force the Rods to Max Length..
Custom Cylinders can be Made to do this in ONE Body.. it makes the Install Easier.. HOWEVER Repair Parts can be a Problem..
Cap
To effectively "stop" a rod cylinder, you'd either need a brake, or as another has suggested, two cylinders in series. A rodless cylinder is another route, with the below valve, BUT you won't get accurate sub stroke positioning.
https://www.automationdirect.com/adc/shopping/catalog/pneumatic_components/pneumatic_solenoid_directional_control_valves_-a-_accessories/5-port_(4-way),_3-pos.,_body_ported_-z-_manifold_(avs-5,am_series)/avs-513c1-24d
when the OP said castle machine this is what came up. if i recall correctly from seeing similar tools you pull the black lever it dose one operation and when you push it it dose the other and there is a set of springs that move it back to the resting position when not being pushed or pulled.
https://castleusa.com/products/tsm-12-benchtop-pocket-cutter-machine.html
with a float center valve you may be able to use the springs to pull the cylinder to the resting position and set the cylinder up so retracted is one operation and extended is the other.
Here is a link to the Castle machine I was referring. Both directions are operated by one push of the foot petal. Page 7 shows that they use proximity switches to control the directions.
Yes, the way I have it set up now (manually operated) is to hold the stop position with springs. I am not apposed to keeping it that way as long as the last stroke is able to be pulled back up rather quickly. I don't know how long it would take to evacuate the air out of the cylinder without any help other than a spring.
Keeping the spring in play with the double cylinder would probably work.
Sorry. Here is the link to the site and I was looking at the operator manual link at the bottom
Castle Pocket Cutter Machine - TSM-22 Machine | Castle, Inc. (castleusa.com)
Steve:..
There is a 'Dump Valve' or a 'Quick Exhaust Valve'
https://www.mcmaster.com/air-flow-control-valves/elbow-air-exhaust-control-valves-8
These are mounted at the Cylinder.. The Air is allowed to enter from the 'Valve', but the Exhaust Air is 'Dumped' to the Atmosphere at the Cylinder.. Allows the Cylinders to move Faster..
Cap