Re: [CAD_CAM_EDM_DRO] Bridgeport Tracer?

e.heritage@... wrote:

> I've been looking about and found a Bridgeport duplicator mill, it comes with the Tru-Trace 3D hydraulic controller and 2 J style heads. I've never seen this particular mill before, I'm very new to the whole idea of mills (I don't own one yet). So, prepare youself as I unlesh an entire universe of questions:
>
> 1.)
> Is there any possible way to fool the tracer on the mill so's the mill can be controlled by CNC? The tracer runs heavy looking hydraulic cables to the ?pump? that I assume ramps up the pressure for the mill's hydraulics. Does the tracer press into the pattern it's tracing and when the pressure reaches a point the control moves the mill's hydraulics?
> I was thinking that maybe I could make something like a brick of metal with little pistons inside that feed into the tracer's hydraulic cables. Then fit a set of steppers, or maybe even ?selenoids?, to control each piston which would then supply the pressure for the mill's hydraulic controller. Then I could put the steppers / solenoids on a cnc controller and have it move the pistons for me, as if the tracer probe was bumping into the pattern.

Yes, in theory. Some large machines in the past used CNC-hydraulic drives, either
hydraulic motors turning leadscrews, or direct movement by hydraulic cylinder.
They are expensive, maintenance intensive, very touchy, and I can't recommend
this system for anyone but an expert in CNC, control systems theory, and hydraulics.
You would need to buy a multi-thousand $ Moog proportional servo valve. Don't think
you can make one work well in less than one lifetime.

> 2.)
> If I bought the mill could a wip off one of the mill head and sell it on so I just have one?

Yes, the J head is a very salable item!

> 3.)
> How accurate are hydraulic mills like this? The guy says it's the most accurate tracer they've ever run but they've replaced it for CNC machines.

In proper tune, they can do well, holding a few thousandths reliably with a well-designed master
pattern.

> 4.)
> How noisey are the controllers if they run a compressor of sorts?

They use a hydraulic pump. Fantastically noisy! Generally, the hydraulic power pack
is placed in a separate, sound-conditioned room, or surrounded with acoustic baffles.
Also, they are massively inefficient. If you had a several Hp hydraulic pump, it would
be drawing full load whether the machine was moving or not (mostly because everybody
seems to be too cheap to use variable displacement pumps).

> 5.)
> Approximately, very approximately, hiw much would a mill like this weigh? A few thousand lb's, tens of thousands or simply concrete destroying lb's? The table would be about stomach height from the pictures so I think it might just go in the garage! `.^)

The Series I would be about 2000 Lbs for the machine, and about 1000 Lbs for the power pack.
A series II would be about 4800 Lbs for the machine.

> 6.)
> How much would one of these beauties be new? Are they even still made? If they're not how much would have been when they were? My mum has noticed me reading the Gingery lathe book and has been asking 'How much would it be to just buy one instead?'. She sees lathes being useful artistically because you can make table legs etc. on them but I don't think she has realised what a mill can do yet! I suggested a mill would be of more use and if there is a large enough saving on what it would be new she may... buy it for me and have it sent over here. A few hundred and I don't think so but a thousand or a bit more and she might.

These machines haven't been made since the late 60's, I think. They did have optical tracing
with electric axis drives that were made into the 70's. Nobody is using this technology anymore,
to my knowledge.

> Hmmm.... well that's just about it for this installment. I'm sorry I don't have a model number for you I only know it's a dublicating mill by Bridgeport with hydraulic control and two heads. I'd be willing to have it sent over taking a month or two to get here but if it's going to take a large enough chunk out of the saving I'll forget it. It's going to have to travel from Davenport in the great USA, 3000 or so miles over the blue lake Altantic to rainy England where it will take refuge in my garage with the rabbit, ghost mice and four cans of hammerite. To recap:

This is insane! It does not make any sense to ship such a bad start at a home shop machine
across the ocean! Did it ever occur to you WHY the price of this machine is so low?
It is because nobody wants it! Note that this machine does not have leadscrews, so it is
either difficult or expensive to convert it into a manual mill, or a leadscrew CNC machine.

>
> Bridgeport dublicating mill with two J style heads, dublicating probe and table. Tru-Trace 3D hydraulic controller. Stylii and hold down set. No mill collets. 220V on 3 phase (We have 220v here anyway, need to get a 3 phase transformer though). I'm willing to pay $2000 or so for the mill which is no where near what they're asking for it right now ($900).
>
> Am I rambling on and dreaming here or is there a possibilty for CNC, and am I going to save anything buying it for under $2000? Sorry for all the questions, anwser as many of them as you feel comfortable doing and if you need to know anything else please tell me.

You will NOT save money! You will most likely end up with a boat anchor!
While it is possible to get proportioning valves and make it work, you will be
very much on your own. I don't know of any modern CNC controls that support
hydraulic motion control, certainly not well-known PC software. The Allen-Bradley
7320 did have that option, but you better be a darned good electronics technician
to keep one running (as I discovered the hard way), and you will devote one week
in 4 to repairing the control. That was not a good use of my time, and probably not yours.

Look for a BOSS machine already rigged for CNC, but with a shot control.
There are many of them, and they can be had for the kind of money you are
talking about. But, the machine itself needs no conversion, and there should be
some MUCH closer to you.

Jon