Shear wont run when it gets hot outside.

Portable Welder · Jun 22, 2020

I have a 1989 Accurshear 25010, meaning it will shear 10' of 1/4" plate.
I've been plagued with this problem since I bought it used from Roush Racing 5 or so years now.
The problem is that when it warms up outside, it quits working, I will use it for 15 - 30 minutes, it will run normal, then I will hit the pedal and it will start giving a delayed reaction before the hold down pistons come down allowing it to shear.
So, the motor will start up and run just fine, nothing changes with that, its just when I hit the pedal, it wont respond, the plungers wont come down and it wont shear.

I've had the authorized Accurpress repair guy, he changed the pumps and other valving, when he left it worked just fine, but same thing, it failed on a warm summer day, so he said I should replace the oil and do a flush, I did that, with same results, I had my electrician out that works in control panels in industrial plants all over MI, he couldn't find the problem.
I dont use the shear everyday, but I do use it on a consistent basis through out the year and this only happens when its warm outside and it been doing this approximately 5 years now.

atomarc · Jun 22, 2020

That's a weird one. I'll ask, what 'didn't' the factory tech replace? If the shear is getting the electric/electronic GO signal but isn't going, then it's not electrical which means it must be in the hydraulic system, obviously.

If heat truly is the culprit, and it's affecting the hydraulic system I would think some component is binding or sticking, a pilot valve or some device like that..so, I wonder what the tech didn't replace, because the problem is still there.

Electronic components can be heat sensitive as well, but if you're sure that the press is getting the GO signal then that rules it out.

Stuart

DDoug · Jun 22, 2020

What pressures are you seeing on the gage ?

atomarc · Jun 22, 2020

Does your shear have the light curtain guard feature? Is the shear inside a building or located outside under a lean to?

Stuart

Portable Welder · Jun 22, 2020

AtomArc I dont remember the names of the valves, but there were 2 pcs. $ 1200.00 worth not including labor, then they sold me a cleaner to add to the old oil to cycle through the shear prior to doing a complete oil change, 55 gallons worth.
The shear is inside a heated insulated building, so it is not out in the elements, the temperature never falls below 55 degrees.
Digger Doug, the pressure shearing 1/4" plate with dull blades would hit 2500 psi, I have since flipped and gaped the blades.

Portable Welder · Jun 22, 2020

Atom Arc, no, it does not have a light curtain.

Scottl · Jun 22, 2020

Have you tried blowing compressed air over the components to see if localized cooling makes it work?

What I'm thinking is try a stream of air on various components, one at a time, as an aid to localizing the problem. If it is truly a case of something failing when it's hot that might narrow the suspects.

Higher humidity might be causing cooling problems.

Milland · Jun 22, 2020

Do some testing of the supplied electrical voltage, it's possible that during warm/hot weather the grid voltage goes down due to demand and increased resistance in the cables.

If there's a voltage-sensitive component in the control that doesn't like a V-dip, perhaps that's what's causing the issue?

Yes, it's a long-shot, but might as well check it out...

Portable Welder · Jun 22, 2020

Scottl I have not tried blowing cold on it.

GregSY · Jun 22, 2020

Good example of 'factory techs' not knowing as much as they should.

Portable Welder · Jun 22, 2020

GreggSY Yes, a couple grand spent not including the oil change I did and I still has the same problem.

atomarc · Jun 22, 2020

Unless the hydraulic system involves a servo valve it should be fairly straight forward to diagnose..but difficult to do on a forum in front of a keyboard.

There should be a way to jumper (trick it) around the hold down safety circuit and dry cycle the shear, which would prove that the glitch is in hold down hydraulic circuit/valving and nothing else.

You stated above that when this problem initially occurs, the hold downs don't immediately react when the pedal is pressed, then when they do, they will come down slowly. To me, this would indicate a problem with the oil supply through a valve, or a massive dump that's shunting oil away from the supply side of the hold down.

If these are simple solenoid directional control valve, often they have small buttons on each end of the valve that can be pushed in manually to shift the valve to help troubleshoot the system.

The bottom line is that I find it amazing that the technician couldn't discover the problem...unless it wasn't glitching when he was there. I sure would call those folks back and see what they had to say about this issue. They should be able to make some kind of financial adjustment as the work they did before got no results.

Stuart

Portable Welder · Jun 22, 2020

Atomarc, after the work was done it worked fine, the temperature got colder and it didn't show back up until the next summer, that's when I did the cleaner and then changed the oil.
when it starts acting up, there's a delay from the time I hit the pedal and it finally getting the signal to cycle, once it gets the signal, it cycles at proper speed, the delay time starts to increase after a couple times of doing this until it wont do anything.

Rob F. · Jun 22, 2020

Can you add a temporary push button to the pedal circuit? so next time it acts up you can push the button and see if bypassing the foot pedal helps. Wire from power source,to new button then direct to solenoid valve, bypass everything if possible.
I agree with others that it sounds more likely to be in hyd system though.

e-fishin-c · Jun 22, 2020

Milland said:
Do some testing of the supplied electrical voltage, it's possible that during warm/hot weather the grid voltage goes down due to demand and increased resistance in the cables.

If there's a voltage-sensitive component in the control that doesn't like a V-dip, perhaps that's what's causing the issue?

Yes, it's a long-shot, but might as well check it out...

I’d check this out as well, years ago I was troubleshooting a hyd baler in a grocery store and I detected too much voltage drop because of an air conditioner unit that was wired improperly (undersized wiring). The voltage drop was just barely enough to power the motor but not enough to shift the solenoid valves.

Richard Winn · Jun 22, 2020

a picture of the pump would help

sounds like the sequential valve has a prolem

if you can find this valve unbolt it from its mounts just loosen the

bolts even if the valve is new it could be bolt bound

depending on type pump type also could be not geting a sence signal

atomarc · Jun 22, 2020

A wild ass guess. It almost sounds like it's a piloted solenoid valve in the hold down circuit that isn't leaking off fast enough to shift properly, then not bleeding off and shifting at all.

Is there a schematic of the hydraulic circuit in the manual I know you have hidden on the shelf?

What doesn't make sense is that the oil temp after running for awhile should be much hotter than the ambient air temp, even on a hot day. If the oil were to reach 100 degrees one would assume all components in contact with that oil would also be at 100 degrees..so what difference would it make if it were a hot day? This is going under the assumption that the increase in temp is causing a valve to stick and bind.

Is there a thermometer stuck in the side of the hydraulic tank?

Stuart

Bill D · Jun 22, 2020

How hot does it get? I doubt if you get over 100 in Michigan inside an insulated building. I vote for a poor connection that creeps under heat or a stuck valve. But a stuck valve should move easier as the oil warms up.
Bil lD

DDoug · Jun 22, 2020

Portable Welder said:
Digger Doug, the pressure shearing 1/4" plate with dull blades would hit 2500 psi, I have since flipped and gaped the blades.

Now this is a start.
When it won't shear, does it still build pressure ?

mnl · Jun 22, 2020

Since it works correctly for the first fifteen or so minutes you have a chance to look for changes. Start by instrumenting voltage and current in likely places. Have someone watch and write down numbers as you cycle it. Once you get to the misbehaving phase the change, or lack thereof, should give a good idea if there is an electrical problem.

Shear wont run when it gets hot outside.

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