Eccentric Press Disengage problem

Hoping someone with ecc. press experience can point me in the right direction.

I have just commissioned a roll forming line forming angle iron out of coiled flat strip (50mm wide x 2mm thick material). The line was bought second hand and was originally used for a larger and heavier section than what I am doing. At the end of the line is an eccentric press, actuated by a limit switch, large solenoid and lever system, which cuts the angle iron to the required lengths. The press has an apparently complex mechanism at the flywheel end of the rotating shaft which engages the shaft to the continuously rotating flywheel to execute one stroke of the tool and then disengages until the next engagement.

The press copes easily with my application, but is pretty worn on the brass/bronze bush in the flywheel, and was a bit noisy and rattling while freewheeling. I decided to run one job through it to establish whether there are any other functional problems, before attempting a repair/maintenance operation.

After about 150 cuts, on and off between roller settings and tweaking the line, I am suddenly having problems with the flywheel engagement system. The press strokes once and the actuating lever then appears to return to the freewheel position, but there is a hell of a clattering from the shaft engaging mechanism as if a dog or pawl hasn't completely disengaged inside. The machine does not keep cycling however. This then goes back to normal after 5 - 10 revolutions of the flywheel.

My question is, can I remove the flywheel and expect to be able to perform a repair in my home machine shop or is this a specialist only function? I have no idea what to expect once I strip the assembly having never seen the inside of this mechanism before.

Any suggestions or advice will be greatly appreciated.

Tony in Darkest South Africa. "What did South Africans use before candles??" Electricity!!

Tony
The clicking noise is the clutch dog, not disengaging fully. The tip id the dog is bouncing off the drive lugs in the flywheel. It can really make a heck of a rattle. The main thing that causes this is the adjustment of the brake. The crankshaft needs to stop on the top of the stroke in order for the dog to be fully disengaged. Most of the time the brake has gotten to oily or wore down just a little and lost adjustment. Or someone adjusted the brake and made it to tight and its stopping to soon. Once you see if its stopping early or late you can adjust the brake, a slight turn can make a giant difference. Usually we make 1/6th of a turn adjustments (1 flat of the hex bolt). If you are not successful you may have a worn dog, pick out lever, drive lugs, or dog slot.

And another thing that can make a press act funny, lack of lubrication, be sure its getting grease and or oil at the shaft bearings and the flywheel bearings. also be sure you can pull the machine thru a cycle by hand (no material) looking for mechanical binding. Like a bend crank, over tight ways, etc

Let us know how you make out

what is the make, model, age, and size? I have some press manuals, Bliss, Hein, Roussell, etc. Above comments are correct. Those trip dogs get mysterious.

Tony,the clutch key is "nibbling".It is caused by a lot of things but you may find that tightening the brake slightly stops it.That is the most common cause.It`s also possible that someone has overtightened the brake.The next most common is wear on the key extractor,this withdraws the key in the clutch sometime after bottom dead centre and before top dead centre.If it`s worn or loose due to wear etc it extracts the key too late in the stroke so the crankshaft comes to rest past top dead centre and the key is trying to engage.Leaving it nibbling is very bad practice and also dangerous.On an operator controlled press it must be stopped straight away.The reason for this is that the key and clutch ring should have been made from steel which will not chip or splinter but it is still possible and chips of the key can cause the flywheel to partially seize and stroke the press.The other reason for fixing it is because when it`s nibbling it`s knocking hell out the key and clutch ring.Clutch rings are expensive.The first thing really is to sort out the wear in the bush,while the flywheel is off check the key and the extractor for wear.It will either be a rolling key or a sliding key.Don`t know about the laws in your country but in the UK press flywheels must be pulled every six months for inspection on machines with opening guards and twelve months for fixed guards.In addition a certified person must sign a safe to operate sheet for each press at the start of the shift and again halfway through the shift.
Mark
www.ems-fife.co.uk

Sorry to repeat what Tom said,he must type faster than me.

counterbalance air cylinder pressure adjustment

Not enough info in your post, but a quick idea comes to mind. It really sounds like your press is not stopping in the proper place in the stroke. Usually these presses have a or a pair of air cylinders that attach to the ram that can be adjusted for air pressure to make up for different weights of the dies mounted on the top platen. Should be a placard on machine that says how much pressure needs to be applied to make the press ballance properly. (35lbs for 2000lbs, 40lbs for 3000lbs) If not set right you will always have top stop problems.

Thanks for the great info

The machine is stopping way before top dead centre, like 90 degrees!!. I wondered about the "up stroke" at the beginning of each stroke cycle, but didn't recognise the problem. As soon as I get to it I will adjust the brake and see if things improve. Unfortunately no plates, pressures, instructions anywhere on the machine! Direction of flywheel rotation on the guard is all I have.

The press is old, no name plate or ID of any kind that I can find. Comparing to other machines i've seen I'm guessing it is about a 20 tonner. Motor 2,2 kW, 1430 RPM, 720mm diameter flywheel weighing about 100Kg, 2 belt drive on 10:1 ratio, shaft 90mm dia. at output end.

I will post within a few hours with results. This forum is amazing, "rephrase that, son!" -The members of this forum are amazing. This is only my second post, the first was about building/rebuilding hydraulic cylinders and great responses from you guys got me going on it, now cylinders are about 25% of my business. I will post soon with an "explanation" and photos of my homeshop/business shop.

Feedback

Confirmed that the press is stopping 90 degrees before TDC! Loosened the brake gradually, but it's still stopping in the same place, and banging like something's got to give! The brake is now really "loose". Checked lube on ways, shaft and flywheel, all OK. I can manually engage and cycle the press without much effort (one hand pushing on the side of the flywheel).

I suppose I will have to strip?? At the flywheel end of the crank, intersecting the crank OD and the steel bush there is a conventional key, opposite that key is a +-30mm dia round "key", midway beteen the two and also intersecting the crank and bush is a tapped hole (10mm dia). What is the stripping procedure? There is no obvious securing mechanism holding the flywheel on the crank!!

Taking another look, there is a spring loaded "dog" projecting below the crank which is held stationary by a lever. The actuation mechanism retracts the lever momentarily, freeing the crank and dog to make one rev. The dog then stops against the lever, which has returned to it's position, thereby disengaging the crank. At this point the offset on the "ram" end of the crank is in the position I have described, about 90 degrees before TDC! Hah!! Found it!!

The brake is too loose. When the dog returns to "battery" the slack brake allows it to roll back slightly under the spring tension, thereby putting it in a knocking position against the clutch. Tightened up the brake by feel on manually engaged flywheel rotation and tested under power. Quiet as anything!! Not a rattle to be heard.

What can I say. Would probably have paid a bomb, and waited a month!, for some tech. guy to do a whole lot of unnecessary work. I'll keep an eye on the wear though and still plan to open up sometime, so I would still like some info on stripping the clutch mechanism.

Thanks to all.

Tony

Before you strip anything check the direction of rotation.Engage the clutch with the power of and bar it around by hand so you can see what`s happening with the extractor.