Better Depth Control on Hydraulic Press
Better Depth Control on Hydraulic Press
(OP)
Hello,
I need to come up with a way to control a very large press to get precise depth control. I need a resolution of 1/1000th of an inch and if not to $$ , 1/10kth of an inch. I was looking at an absolute encoder but I would like to explore other paths. The press is very old ~50 years so the controls on it are nil to none. We did add a Rockford safety device but thats about it.
I need to control har far down the press will go (I will have a block back up to prevent die damage). It seems that the full travel of the press is 3 feet but in use 2 feet would be the max I would think. Any ideas?
I need to come up with a way to control a very large press to get precise depth control. I need a resolution of 1/1000th of an inch and if not to $$ , 1/10kth of an inch. I was looking at an absolute encoder but I would like to explore other paths. The press is very old ~50 years so the controls on it are nil to none. We did add a Rockford safety device but thats about it.
I need to control har far down the press will go (I will have a block back up to prevent die damage). It seems that the full travel of the press is 3 feet but in use 2 feet would be the max I would think. Any ideas?





RE: Better Depth Control on Hydraulic Press
http://www.star-techno.com/info.htm
There quite a few optical encoders available at Mill Supply Houses.
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
Checking out Stegman and Heidenhain, thing is even if I get the control precision I need, how inthe heck am I going to control it? These presses are 50 years old and there are no "controls" on it I dont think.
If I get a good encoder, what price range would I be looking at to control the thing. hence stop at a certain depth etc.
:)
RE: Better Depth Control on Hydraulic Press
There are just way too many variables in the control loop.
I would think about using a hard-stop. Set up a controller system that will slow the press way down when it gets close, and then reverse it when the position sensor no longer shows any movement.
RE: Better Depth Control on Hydraulic Press
Thanks
RE: Better Depth Control on Hydraulic Press
Could you use two valves? One high flow and the other low flow for the positioning. They make this combination of valves.
Please describe a little more about the problem with the Star product if possible.
RE: Better Depth Control on Hydraulic Press
http://www.keyence.com
RE: Better Depth Control on Hydraulic Press
A simple lever type multiplier may work in conjunction with a suitable limit switch to provide adequate resolution. The signal from the switch would be used to unload the press ram and begin retracting the ram. Assuming that there's no need for a dwell....
Alternatively, contact a builder with experience in closed loop servo hydraulic control?
What is the problem with advancing against the hard stops your shop is currently using?
RE: Better Depth Control on Hydraulic Press
I have used several Parkers D1FX---- valves in the past that worked well and had all the electronics on self contained on the valve.
I think the most common method is to make an adjustable ram head. This allows the cylinder to stroke full length or against a stop then adjust the ram up or down with a screw or screws. You should be able to some graduated nuts for this purpose for a std. 16tpi thread. This allows you to stroke as fast as possible.
Barry1961
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
If you have three layers of solid steel(ram, platen, die)bolted together and hanging from the cylinders, there will be significantly more than 1/10,000 compression at the end of each stroke.
Sounds like time to shoot engineers and git on with production.
Griffy
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
Thanks
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
RE: Better Depth Control on Hydraulic Press
At this point in this discussion, I'm guessing that what you are doing on this press is some type of forging or cold heading operation and your designers are trying to get as close to net form as possible to eliminate some secondary operation.
If this is true, then you are chasing a will-o-the-wisp. Thermal issues alone will drive the operator crazy whether cold or hot.
The best thing you can do if you succeed in mounting such a control is to chain the designer to the machine until he can either run the process reliably to the specs (six sigma) or gives up.
'Nuf said.
Griffy