Thread: Blohm HFS6 surface grinder

Forgot about the valve Josh.

I messed around with it before the suction valves last night, its a pain to get to, but I pulled the spring and plunger out, flushed some oil through etc. It's dead silent with it out but the speed is roughly halved due to the constant pressure loss. With it back in and almost no pre load on the spring it is noisy again. I am wondering however if there is a second one on the other side of the pump, as most things are in pairs.

Cheers
Ew

Originally Posted by Ueee

Really need to make a box for Michael G's grinder too...

It can wait. I have other things to do to and as soon as that grinder arrives I'll be distracted by it.

Michael

Originally Posted by Ueee

Forgot about the valve Josh.

I messed around with it before the suction valves last night, its a pain to get to, but I pulled the spring and plunger out, flushed some oil through etc. It's dead silent with it out but the speed is roughly halved due to the constant pressure loss. With it back in and almost no pre load on the spring it is noisy again. I am wondering however if there is a second one on the other side of the pump, as most things are in pairs.

Cheers
Ew

Hmm... I'm pretty sure there should be a another regulating valve somewhere or like you said a pair of valves, There will be probably one main regulator and a pair of fine adjustment valves for the table. Is their any spot that looks like it would fit a gauge onto?

Hi Ewan,

Just a wild uninformed guess...

Somewhere in the hydraulics there has to be a reversing valve, which swaps over the flow direction to the main cylinder, since the pump appears to load up on the reversals, perhaps there is a problem with that valve blocking flow when it reverses... there will be a spool in the valve that has cross over channels to direct the flow either forward or back..

You might see a pressure spike on the change over...

Or maybe not...

Regards
Ray

More food for though, thanks boys.e
I pulled the y screw out and got the front cover off last night. Pretty interesting and complicated stuff going on. I'd like to disable the direction change unit and manually change the direction over via the yoke, just to see which half of the system the noise is coming from. Here is a vid of it in action.

https://www.youtube.com/watch?v=mNnM...e_gdata_player
Cheers,
Ew

Originally Posted by Ueee

More food for though, thanks boys.e
I pulled the y screw out and got the front cover off last night. Pretty interesting and complicated stuff going on. I'd like to disable the direction change unit and manually change the direction over via the yoke, just to see which half of the system the noise is coming from. Here is a vid of it in action.

https://www.youtube.com/watch?v=mNnM...e_gdata_player
Cheers,
Ew

Still thinking about this.. I will have to print off the schematic and trace it through, with the vid.

-Josh

I'll shoot another quick vid this arvo describing how it works, or should I day how I think it works.....

The Vid will be here: Blohm surface grinder hydraulics walkthrough - YouTube

My upload speed seems to have taken a dive tonight so it won't be up for a while. its saying 203 minuets at the moment!

Thanks to all for their help, i only mentioned RC and Josh in the vid.

The schematic is pretty poor, and looking at it again not correct for my machine. It only shows 4 returns and i have 5. The line running from the top of the pump, presumably a safety overload valve line is not there in the pic.

Cheers,
Ew

Nice '' Blohmin '' machine there Ewan enjoy it. hydraulic drives can be a bit o a puzzle but it all falls into place. Biggest prob with any valving any any thing hydraulic is ''U F O'S'' unwanted foreign objects.
Hydraulic drive shapers are to be avoided like the plague bit usually too big for the home body.

Originally Posted by RayG

Hi Ewan,

Just a wild uninformed guess...

Somewhere in the hydraulics there has to be a reversing valve, which swaps over the flow direction to the main cylinder, since the pump appears to load up on the reversals, perhaps there is a problem with that valve blocking flow when it reverses... there will be a spool in the valve that has cross over channels to direct the flow either forward or back..

You might see a pressure spike on the change over...

Or maybe not...

Regards
Ray

Agree there might be a micro chip of sh 1t in the shuttle valve doesnt need much assemble in a bath o dieso no rag [lint] and assemble wet.make sure no galling on spool. lap with tooth paste was off well. 2 cents worth.

Originally Posted by Ueee

The Vid will be here: Blohm surface grinder hydraulics walkthrough - YouTube

My upload speed seems to have taken a dive tonight so it won't be up for a while. its saying 203 minuets at the moment!

Thanks to all for their help, i only mentioned RC and Josh in the vid.

The schematic is pretty poor, and looking at it again not correct for my machine. It only shows 4 returns and i have 5. The line running from the top of the pump, presumably a safety overload valve line is not there in the pic.

Cheers,
Ew

Ok that makes sense now...

I think reason for the closed loop on the table cylinders is so that you can vary the table speed but maintain a fairly constant table travel. A handy feature.. but as you say it would heat up after a long time cutting, but it would dump all the warm oil as soon as you put it in neutral, and you would have to dress before that became a problem. But if you walked away and left it running it would eventually trip the overloads.

I guessing part of the priming procedure is to move the table to each end of travel with the table in neutral?

Noise.. you might be able to adjust the overload valves on the main pickups, the ones with the check valves to take a little of the load off the pump, only just enough to dump just a little oil on each reversal? or that maybe the purpose of the other overload valve you mention?

My thought is at the moment that the vibration might be something just a little wrong with the control valve, probably just gummed up a little? or pressure too high? donno for sure, could also be normal.

-Josh

So i just googled pump spool.....so thats the part that the reversing lever on the table controls, which in turn sends oil to either side of the horizontal pump. John i take it shuttle is just another term for the same thing?

To prime the table is moved against one end and the pump is turned on, with the direction switch pushing it against its stop. This forces the safety valve in the pickup open and expels any air. Same for the other end of the table.

Josh, i tried loosening the safety valves off, but the table speed slows with any oil leak, and the noise changes to more of a drawn out wail. With it set borderline you can feel the valve opening vibrating with the noise. You and RC could well be right....it could be normal. But the table change of direction is still pretty violent even with the valve (no 6 on the sketch) backed right off. I get the feeling maybe the pressure to the horizontal valve is too high, causing the reversal of the cam hence the direction change happen too quickly. But if it slows down too much the table travels well after the reversing switch is hit (this happens with the safety valve 6 taken right out).

The overload valve 6 dumps oil in the first section of the system on reversal, not the closed loop. I wonder though if the line coming from the top of the main pump (the one missing in the schematic) is supposed to do that for the closed loop, there is no oil coming out of it at all when running.

I've learnt more in the last few days than i have in a while.....

Cheers,
Ew

All I will add is that is typical german.... Overly complicated then it needs to be...

Hehe, my mother is German......this pump aint complicated at all in comparison.

Originally Posted by Ueee

Hehe, my mother is German......this pump aint complicated at all in comparison.

Agree with you there Ewan mums are more complicated than hydraulic. You can turn a machine off any time. the other well?? at 86.
But they do have one thing in common ''noise means air''. Yes spool shuttle the same thing. and if you got your pressure set too hi on pump will ring bark your check valves check the balls for ring barks. another is to run around with your gauge and measure pressure at both ends. Aeration in pumps can do damage make sure they always got its feet wet pick up in oil.only way some times to bleed air is when it is cold you can reverse bleed by priming the oil ways. 0.02cents worth. Cheers John. have fun its no fun when you aint enjoying what you do.