Hi, we have a 1999 Fadal 4020 HT that is having a problem with the high and low gear change. When you go to change gears both roller pistons are staying engaged. Things that have been replaced and pretty much the entire air system involved with the high/low gear change. When I go to change from low to high using S.2 in MDI the Low gear roller piston does not retract. If I disconnect the air lines from the low gear roller piston it's getting air at both ends of the piston. Which from my under standing it should only be getting pressure at one end at a time if it's either retracting or extending. Once i disconnect the line where there should be no air going to under the retract cycle the piston retacts as it should. And then it stays retracted until a tool change or gear Chang and then it's back to the same problem and you have to disconnect and then reconnect the line all over again. Only way we have been getting around this for 2 years now is to only use one gear for every program and unplug the low or high gear relay depending on which one we want to use.
Sounds like the air valve solenoids are not wired right. If I remember correctly you can go int a diagnostic mode to be able to see if the outputs for the hi/low air valves are working correctly. I think the 2 letter command is DI. I may have more info on this if you need it.
I think you have an issue with your Air over Hydraulic assy sitting on top of the tool in and out piston assy. bad seals so the air coming in is feeding both sides retract and extend. Page 4 http://www.flintmachine.com/pdfs/fad...s/VMC_4020.pdf . Also on a side note the air over hydraulics main reason was not just for heavy cutting, You would actually cut heavy with right handed cutters. They came up with the air hyd system because HT motor was too much for Left handed cutters and the cutter over powered the air cylinder. And the other major reason was for Large size Taps ... you had no problem in forward at 300 rpm but when you tried to reverse , the belts would slip because of the reversing the spindle... Any ways if you dont need the super power and just wanted to bypass the hydraulics you could just run the air coming in straight to the bimba cylinder and try that. Or you would have to fix the Air over hydraulic system. Personally if you have gone 2 years try just eliminating the air over hydraulic and see how it goes for now.
I forgot one thing the Bimba currently on your hi lo need air for the return so you could swap them with Spring loaded Bimbas similiar to the bimbas on the standard hi lo range on the fadals. Or get the repair kit for the cylinders if thats the problem ITS: Hydraulic Actuator Repair Kit, HYD-0018
Fadal 4020HT high/low gear change problem
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