Hydraulic lathe not working.

Hi, I finally managed to find time to connect the motor back on my Harrison 155 today for the hydraulic profiling.
Last time it was working was 8 months ago and 300 miles away!

I've checked the oil level and the filter.
The motor runs and the oil pressure is correct according to the manual.
However the hydraulics don't work, there is no movement.

I know nothing about this sort of thing. Undoing the three pipes on the back of the lathe there is only oil coming out of the pump pipe. The return and other one don't appear to have oil in them.

Any ideas on what to look at / check?

Regards,
Chris

I don't know, but have you tried bleeding the system? Usually can slacken a pipe at a cylinder and/or valve connection. Might work.

Pump going the right way ?

Hi Chris,
John makes a good point that is worth checking first. I would imagine that is is going the right way if there is only one outlet pipe from the pump and the inlet comes from the oil tank. If you can post an hydraulic diagram of the machine it would be a great help. If not what to the hydraulics do. Is it just cylinders and mechanical control valves or are there hydraulic motors and/or solenoid valves as well ? I diagram of where all the pipes are connected would also help. I would not expect any oil to come out of the return pipes to the tank except when a cylinder is moving or an hydraulic motor is running.

Les.

Closed valve, or some other blockage? - hydraulic pumps typically self adjust their capacity to maintain relatively constant delivery pressure, will back right off if nowhere for the oil to go.

Hi, I believe the motor to be turning the right way, although the switch is the other side of the lathe to the motor. Probably worth connecting it the other way just to make sure.

It is a simple hydraulic system for copying a profile that is put between two centres on the back of the lathe. A stylus on the back of the cross-slide follows the profile and adjusts the cross-slide to re-create the profile on the workpiece that is in the lathe. So basically, the stylus is attached to a cylinder which is attached to another cylinder that pushes the cross-slide in and out.

Diagram below:

http://img203.imageshack.us/img203/7721/7k1d.jpg

Edited By Chris123 on 17/02/2014 14:48:23

Filter is located on the end of the pressure feed pipe in the sump under the pump and appeared spotless

motor is definitely turning correct way.

Small amount of oil coming out of return pipe when it's undone now.

Still not working.

Filter is located on the end of the pressure feed pipe in the sump under the pump and appeared spotless

motor is definitely turning correct way.

Small amount of oil coming out of return pipe when it's undone now.

Still not working.

Chris,

As its hydraulic I assume it must have a pressure relief valve, is this stuck open because of a broken spring or dirt holding the valve open, you would still get oil from the return but no pressure to drive the system.

Martin P

Just a thought Chris, is there an interlock to prevent powered cross feed selection at the same time as copying to avoid a horrible crash?

It maybe there you should be looking for answers

Brian

Hi Chris,
The diagram shows a pressure gauge. Does this read a sensible pressure ? (I do not know what the working pressure should be so by sensible I mean the gauge is not right at the low or high limits of its travel.) Even though oil comes out of the pump when the outlet is disconnected it may may not be delivering a flow under pressure. If this is the case if could be the relief valve as Martin p. suggests or it could be a faulty pump.

Les.

My hydraulic copy unit runs at 350psi, although the Hepworth manual says that some models run at 300psi.

Regards,

Andrew

I found something on the rear of the gauge, but this turned out to be a magnet to catch metal filings.

The hydraulic unit is only connected to the workings of the lathe via a 3P+E electrical connection. The cross-feed makes no difference, although I did try it just to make sure!

Pressure in the manual is 150PSI, which is pretty much what it is. 

In the end I stripped the unit on the back of the crossslide, and the master cylinder was seized, the stylus was moving due to it being on a linkage but the cylinder wasn't.

Now stripped and rebuilt and it's working fine

thanks for your help!

Edited By Chris123 on 17/02/2014 22:46:03

Edited By Chris123 on 17/02/2014 22:48:26