As an Aside, I have been hearing more & more Complaints about Machines built with Hydraulic Rams
from All Manufactures. All Manufactures have been going to Hydraulic Rams, and Phasing-Out making the Mechanical (Clutch / Brake / Crankshaft) Type. The reasons are Manufactures Think its Easier & Cheaper to Build them (I Don't Think it's Really True), and Marketing & Sales can use all the Theoretical Great New Features to Sell New Machines (The "Sizzle", The Real Reason). Features like Controlling the Ram-Stroke Position for Die Penetration, Louver Adjustments, Marking & Stamping, Shear & Rib Tools, Low Tool Hover-Height for even Faster Punching, Etc. It Does Sound Great!
The Problem is, there are Questions about it Working Correctly & As Advertised, and much Worse, it may Not Even Be Technically Possible to Work Correctly at All! Hydraulics work just fine in Press Brakes at only 10 Strokes a Minute or so. But CNC Punch Press Manufactures Proudly Advertise 400 to 600 Hits per Minute and Even Faster! At Full Speed, it seems they Can Not Accurately Control the Hydraulic-Ram Position, which Negates just about All its Advantages over a Mechanical Ram.
Do the Math. Some Manufactures are Advertising 500 Hit Per Minute and More. So they are making a X & Y Axis Move AND a Full Power Punch Down-Stroke AND a Up-Stroke in 120 Milliseconds!
Finn-Power Says some of their Machines Nibble at 1100 Hits a Minute, that's Only 54 Milliseconds for the Short-Nibble X & Y Axis Move AND the Down Punch Stroke AND the Up Nibble Punch Stroke!
So, How much Time is Actually Spent in the Punch Stroke? Do You Think it's "Under Control" ?
In My (and Other's) Opinion, it's Laughable to Think you can Really Read Position-Data off the Ram Encoder, Send & Process that Data in Your CNC Control, Have the CNC Adjust your Electro-Mechanical Hydraulic Valves, and Maintain Position-Control on that Fast-Moving Punch-Ram (Some Pesky Little Laws of Physics are Involved) to a Accuracy of a Thousands of a Inch, Over & Over Again,
All in Real Time While it's Actually Moving Up & Down and Punching Metal at that Hi-Speed.
The Result is the Ram, and therefore Your Punch Tool, Is Not Where it "Should Be" & Where the CNC Control "Thinks" It Is. Sometimes, these Position Errors seem to Accumulate until something Bad Happens. The result is --- Poor Hole Position Accuracy, Poor Hole Quality, Broken Punch & Die Tools,
Ripped & Crumpled Sheet Metal Parts, Machine Breakage, Lots of Machine "Down Time", Etc.
The Manufacture's Popular Scapegoats are to Blame it on the Customer's "Bad Tooling" (Very Popular), Poor Tool Maintenance (Also Very Popular), Poor Machine Maintenance, Poor Operators,
Poor Programming Practices, Etc., --- Anything but Their Machine.
These Types of Rams also seem to Wear-Out Quickly, Blow-Out Seals, and Leak Hydraulic Oil all the time. They are also Usually Quite Difficult and Very Expensive to Repair.
Manufactures "Get Away" with this because:
--- Most Shops don't use the Special Features & Special Tools that were used to Sell the Machine.
--- Most Shops don't even Recognize where the Problems are Really Coming from.
--- Most Shops think these are just Standard Problems & Just Tolerate it as "Normal".
--- Manufactures "Help-Out" by Advising their Customer's to "Slow Down The Ram Speed", and
Various Programming Tricks like Dwelling at Top or Bottom of Punch Stroke, Dwelling Before &
After the Punch Stroke, Slowing Down the X & Y Axis Move Speed, and even Doing a Full-Upstroke
(from the Low Hover-Height) every Few Hits "Just To Re-Calibrate the Ram".
Why the Hell do you have to "Recalibrate" if the CNC Control "Knows" Where the Punch-Ram is?
There is at least 1 Law Suit Pending over these Problems & the Losses they May have Caused.
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Early 2007, Update on the Law Suit.
I've followed this Suit for Several Years, Here's the Story as I know it. You can Believe What You Wish.
Customer Said there was Machine Defect & Sued Strippit. Strippit Said there was No Machine Defect.
The Suit Centered on Whether or Not the Strippit Machines in Question, the Late 1990's Vintage Hydraulic Ram Machines with P.C. Computer Controls, could in Fact Control their Punch-Ram, and there for,
it's Punching Tools. It was Alleged that Machine & Control Could Not Control the Ram Position.
This Caused Both Long Punch-Strokes and Short Punch-Strokes with No Consistency at all.
Those of you who Know Anything about Punching, can Imagine the Many Problems this would Cause.
Long-Strokes could "Blow-Up" Punch Tool as it Bottoms-Out, and of course would Jam & Ruin Piece-Part Sheet, and maybe Damage Sensors & Workclamps. Imagine what it would do to a $3000 Louver Tool, Wilson-Wheel Tools, Stamp-Tools, or other Special-Tooling where Depth Must Be Controlled.
Short-Strokes would leave the Punch Slug Half in the Die, and Half in the Partially Punched Hole.
X & Y & T Axis would then make the Next Move, Ripping & Jamming & Ruining Piece-Part Sheet,
Breaking Various Sensors and Workclamps, depending on the Direction of the next Axis Move.
Story Continues as Strippit Drags-Out the Suit for Years, Hoping that their Customer would Go Bankrupt or Give-Up Suit from the Huge Legal Fees Incurred. This Didn't Happen. Eventually, Before the Trial, Strippit Employees were Deposed, and Admitted that there was Indeed a Problem with Ram-Control on these Machines. At this Point, The Game is Over for Strippit. Strippit Settled with the Customer. In This Settlement, In Our Unique American "Justice" System, Nobody Admits any Guilt or Fault or Fraud or Problems, Money Changed Hands, Secrecy & Non-Disclosure Agreements were Signed, All Suit Documents were Shredded, Now Nobody "Knows Nothing", and The Suit "Never Existed".
My Opinion is there were some Problems with Hydraulic Rams of That Era (1996-2001) that May or May-Not have been as Bad as Alleged. Strippit has Changed Venders and Improved Hydraulics & Rams & Controls since then. I also think that Strippit was Certainly Not the only Manufacture with Hydraulic Ram Problems.
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Some Manufactures, Like Trumpf, have Always-Used Hydraulic Press Drives, and Theirs seem to Work Well. Others Like Strippit, Have been on a Learning-Curve the Last 15 Years, and have Gone-Through about 3 Generations of Hydraulics Figuring it all out. Strippit's Latest Machines (about 2002 & Up) seem to Work Well, but there were Reports of Ram-Problems on their Earlier (Pre-2002) Hydraulic Machines.
I Obviously Prefer Mechanical Press Drives, but You Need to Investigate & Form Your Own Opinion!
Another Dirty Secret that All Manufactures Forget to Tell You About, is the Very High Electricity Usage of their Hydraulic Machines. They use about 3 to 5 Times the Electricity of a Mechanical Press Drive, and all that Expensive Wasted Electricity is Spewed-Out of the Heat-Exchanger into your Shop.
Where did you Think The Energy came from, for All that Heat?
A Typical Classic Mechanical Press Drive used a 3 to 8 HP Motor that Turned a Flywheel. Once the Flywheel was up to Proper Speed, the Motor just Coasts-Along, and only draws Minimum Power to keep it that Speed. When you Punch, Stored Energy is used from Flywheel, the Motor Briefly Draws a Burst of Electrical Power to get Flywheel back up to Speed, then it Coasts at Minimum Power again, until you Punch again.
If Machine is On, but Not Punching, it Draws Very Little Power. Very Efficient!
Hydraulic Press Machines Typically have a Huge 25 to 40 HP Power-Pack sitting next to Machine.
These Hydraulic Power-Packs Run Wide-Open All The Time (No Coasting) as they Must have Full Hydraulic Pressure Available All the Time as they wait for a Punch Request from Machine. Even if you are Not Punching, if the Machine is On, the Hydraulic Pack is Running Wide Open, and Drawing Full Electrical Power All The Time. All that Wasted Electricity is Turned to Heat, and if the Manufacture Cut-Corners and put Too-Small of a Radiator on the Power Pack (Very Common), Hydraulics Will eventually Overheat, and Cause Odd Intermittent Punching Problems, or even Shut-Down Machine. Very Very Inefficient!
Recently a couple of Manufacturers (Muratec, Amada, Finn-Power) have come out with a Interesting New Concept. They are taking a Large Servo Drive (Which Can be Very Accurately Controlled) similar to the Large Y-Axis Drive on your CNC Machine, and Coupling it with a Toggle-Linkage or a Crankshaft to the Punch Ram. No Pneumatic or Hydraulic Problems, Saves Lots of Electricity, and lets them Gain Complete Position Control over the Ram's Speed-Profile & Position Accuracy. I have No Experience with this, but it Sounds Good. It will be Interesting to see how it Develops, and if it Solves some of the above mentioned Hydraulic Ram Control Problems. Check Them Out!