Re: [CAD_CAM_EDM_DRO] hydralic bed control

Hi all.

I taught on a big Mori - Seki vertical machining centre for several years,
It used hydraulics for all high power control functions, - table movements,
head control, etc, and an electronic servo system driving the hydraulics.
It was fast, accurate and repeatable, a nice bit of gear.

The only thing that irritated me about it was that to alter an instruction
via the keyboard you had to power the lot up, as it would not do ANYTHING
until it had hydraulic pressure - and running about a 25 HP hydraulic
pump in order to type in an instruction did not make much sense!

Jim Gregg


At 08:51 AM 7/29/00 -0700, you wrote:

>Ejay Hire wrote:
>
>> Disclaimer: I haven't done specifically what you ask about, and I don't
>> know how much backlash is present in a hydraulic system.
>>
>> If I were going to attempt this, and not a lot of people had said it
>> wouldn't work, here is what I'd do.
>>
>> 1. No power steering pump. Hydraulic pumps are less than $100 and will
>> last longer, run cooler, and provide more stable volume.
>> Get them from Grainger or Princess Auto(The catalog, not the web store)
>>
>> 2. Linear encoders provide feedback to the Controller. This will have to
>> be a closed-loop system
>>
>> 3. Electrically controlled variable rate hydraulic valves.
>>
>> With the proper controls, it wouldn't seem to be very different from a

servo

>> system.
>>
>> ----Original Message Follows----
>> From: dave engvall <dengvall@...>
>> Reply-To: CAD_CAM_EDM_DRO@egroups.com
>> To: CAD <CAD_CAM_EDM_DRO@egroups.com>
>> Subject: [CAD_CAM_EDM_DRO] hydralic bed control
>> Date: Sat, 29 Jul 2000 07:38:06 -0700
>>
>> Hi,
>> I have an old horizontal mill with a hydralic bed. Has anyone tried
>> control of anything hydralic using a automotive power steering unit?
>>
>> Dave
>
>Hi again,
>Back in the dark reaches of my memory is the recollection that the first

cnc's were hydralic and while they may not have been a

>good as the electircal stuff they worked. I've spent some time talkng with

one of the electronics people at Dowty Aerospace that

>does a lot of test stuff and he assures me good hydralic servo valves are

spendy.....really spendy....which is why I'm considering

>using a power steering control unit.
>The other option might be a series of solenoid valves with binary

weighting. i.e. hydralic D/A. :-)

>
>Dave
>
>>
>>
>
>
>
>
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