Progressive Dies, Mechanical Presses, Continuous Cycles, etc.

Tharon

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I recent got to play with a mechanical press for the first time. Before all my experiences were with hydraulic presses.

I learned that this press has a "Continuous Mode" setting, where the press will continue stamping, until an outside signal tells it to stop. Talking with some of the more experienced people in my shop, I learned that these modes are used for applications where you'd have an automatic, continuous feed of material, and the press would stamp parts non-stop. I believe he called it a Progressive Die.

I got to thinking, are these progressive dies and continuous running mechanical presses still used in modern manufacturing? Wouldn't an automated line with proper handshakes between a feeder and a press be more accurate, ensuring parts are in proper locations before allowing the press to move.

Just curious.
 
I believe the main problem with what you are suggesting is that it would require stopping the press and flywheel every cycle. For large presses, this would put enormous strain and wear on the clutch system.

We have a stamping press that runs continuous but has a servo-driven infeed. When steel is fed into the press every cycle, there are sensors that detect whether it is positioned correctly. If not, the press E-stops before the dies make contact.
 
Yep, wear and tear. Had a 500 ton press many years ago initially setup to stop after every cycle (which was once/second). First clutch/brake only lasted 6 months. Switched it to continious mode and all was well. In this case, if the feeder doesn't get the material positioned in time, too bad, you get a bad part. If that happens, you manually slow the press motor down, which is on a VFD.
 
Prog dies are alive and well. My last employer makes a lot of them for themselves and other automotive suppliers. I've seen them 60 feet long just for a Ford Escort body panel (Wayne MI). Parts are formed but aren't cut from the strip until the last station; all stations are hit at once.
 
We still use mechanical presses with prog tools,it is still a very fast and efficent way of producing small stampings. control wise we use electronic automation cams hooked up to the plc and set a window in the 360 degree stroke that the feeder has to work within. if the feed pitch isn't reached and the feeder drive doesn't send the feed ok signal the press stops. Also our presses have strain gauges and mechanical overloads for when things get ugly.The continous mode doesn't really apply anymore and is more relevent to older control circuits. Its was used on manual presses aswell! the operator would hold the footpedal down and hope he got the part in the press quick enough! thankfully this mode has been removed from our manual presses
 
It has already been said in the previous posts, but just to clarify: progressive dies are not related to continuous mode: the second is the mode of press operation (it could be continuous, single stroke or what is usually called inching or creeping - very slow motion usefeul for troubleshooting).

A progressive die is a concept of punch & die design where multiple consecutive punching and forming operations are perfomed within one large die motion; the material is fed "one progression" while the die is open. So, for example, on the first progression edges are cut, on the second progression a middle hole is punched, on the third progression some slots are formed etc. - all within one punch/die set. This is a fast and effective way and the only reason not to use it would be a need to do some kind of inspection between the operations. Or, maybe, if some of the operations cannot run at the same rate.
 
Not all mechanical presses are progressive die type. I used to work in a "Powdered Metals" plant where we had mechanical presses that ranged from 10 ton to 500 ton. The larger ones were hydraulic. When these were running at capacity they must be stopped on the up stroke because if they were not powered through the compression part of the stroke they sometimes bottomed out and could not be moved in forward or reverse. Generally had to cut the tooling out and waste a lot of time and money. This was a long time ago and they had rotary cam switches to keep track of the ram position and huge cabinets full of relays and pneumatic timers. The new ones have encoders on the ram to keep track of the press position and nice neat cabinets with PLCs. I retrofitted some of them with PLC 2/15s and Cherry displays with parallel TTL inputs. Anybody remember the T1 Terminal with overlay keyboard and aluminum suitcase sized cassette tape machine for backups, I do not recall the name of it.

My how technology has improved! Sorry, didn't mean to change the subject so far off course.
 
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