Re: [CAD_CAM_EDM_DRO] Re: Bridgeport CNC retrofit recommendations wanted.

On Tue, 2003-12-16 at 09:40, doug.rasmussen@... wrote:

>
> Hi Kim,
>
> First off, I didn't mean to suggest buying a machine that old, I was
> only making the statement that I feel the commercial controls of
> that age generally have more features than the current hobby PC
> based
> types.

I understand this is what you might think.

> This is not a criticism of hobby controllers, you wouldn't
> expect them to be the equals of the commercial controls that were
> developed by groups of engineers over years.

But they do...

> My advice to the OP was based on my assumption that he was more
> interested in machining than building a machine. And with a $15K
> budget it's possible to buy a fairly newish machine and be making
> parts tomorrow rather than piecing something together over the next
> several months.

Agreed, sort of... have you ever taken delivery of a used piece of
equipment and had it making parts the next day ? What is the downtime
going to be the first time it breaks down and he doesn't know anything
about the control system ? Why do you think the previous owner is
selling that 15 year old machine ?

> a. I don't know anything about TurboCNC. I think you're using it
> on a lathe, right?

3 machines now... lathes and mills. If you don't know anything about
TCNC, how can you compare it to a commercial controller ?

> Compare it to an Emco-Maier T1 control which is
> over 15 years old. How many canned cycles do you have?

G76: canned threading.

G77: canned turning/boring with taper and finishing pass parameters

G78: peck drilling with Z axis retract functionality and retracted dwell
time, in addition to the normal bottom of hole dwell time.

and a few more peck drilling canned cycles that I never use.

G202: circular milling

G212: hellical milling

G222: thread milling

G770, G771, G772, G7722, G773: custom 3 axis milling canned cycles. Ie
to machine a slot from x1 y1 to x2 y2 I issue the following command:

G0 X1 Y1
G770 x2 y2 z-1 i-0.025 f6 p2

We've got a few special operations that we've written special canned
functions for too.

> Turning
> cycle, face or longitudinal with tapers & finishing pass? Tapered
> and face threading?

Yep, all of them except tapered threading, which I haven't needed or
added, yet. I machined several internal tapers last week using our
canned G77 cycle. It worked great. Taper machining on a CNC lathe is a
huge timesaver over doing it on a manual machine and using a canned
taper routine is a huge timesaver over individual G01 commands.

All my canned routines have P parameters for the number of finishing
passes at the final OD to compensate for tool and work springiness.

> Grooving, face & radial?

Not canned, but easily done.

> CCR? Constant
> surface speed?

My *lathe* doesn't support it, otherwise I'd have it set up.

> What's your rapid speed?

150 IPM, soon to be 300IPM.

> How many tool & work
> offsets?

32. If I need more, I'll add them.

I can store multiple tool offset files, ie one for the gang tooling
setup and another for the quick change tooling. T1, for example, in
both files can be the same tool, ie a right hand cutting tool for
example. I can cut parts during prototyping with the quick change
tooling (and offset file) and use the same tool identifier (ie T1) in
the part file when we run it in production using the gang tooling. Can
you do this sort of thing with your 1988 control ???

> Do you have an operator panel or do you work off a
> keyboard?

Operator panel: yes, with a feedwheel for EACH axis, ie the mill has 3.
It has a keyboard and I take that as a plus. Most commands are a single
keystroke. We DO NOT use a mouse.

> Spindle load meter?

Yes.

> Auto lube?

On one machine, not all of them.

You are starting to get into the *machine* advantages, not the
controller advantages. My favorite machine to put a PC based CNC
controller on is a real CNC machine because of the size, screws, lube
system, etc. His Bridgeport probably has a lube system on it already.

> Those are just a few
> of the ways I'd compare the two, and keep in mind the T1 in it's day
> was not a high end control.

Agreed.

> b. Yes, older controls electronics will always be a problem.
> Repairs can be expensive, but the expenses can be offset by the
> productivity. I figure about $1000 a year in maintenance on each of
> my controls.

My lathe whole conversion only cost that much. It works great. I'm not
afraid of any part of it... I don't need to call a tech when it quits,
not that it has.

> c. Two of my controls have macro programming, so it is possible to
> make them do things the way you want. I think I've only used the
> feature a couple times out of curiosity.

My TCNC uses symbols. Between that and subroutines and good canned
cycles, it does just about anything. A symbol can be like a macro:

%operation = G77 z-%depth i-0.025 f1 p200 #1000

To use it:

N198 %depth = 0.5
N200 %operation

I can do really complicated things this way. It has subroutines as
well.

> Another point, I don't
> think most commercial controls were designed by programmers, maybe
> implemented, but not designed. More likely designed by indivduals
> who understood machining processes.

I think that there is a multidisciplinary gap between machining and
programming and it is reflected in a lot of CNC controllers. I do both,
machine and write software and thus our controllers do what we want them
to, not what someone thinks they should do. Our G2xx canned cycles came
directly from the fact that it was WAY TOO SLOW to program a series of
G72/73 commands to machine anything circular.

For example:

G200 d0.5 ; set up a 0.5" endmill
G212 d3.0 z-1 i-0.05 f8 p3

This machines a circle of ID = 3", with a depth of 1", using a cut depth
of 50 thou in a helical fashion.

That 1988 controller *might* have G72/73 routines, which will machine a
maximum of 1 revolution per command. The G212 command machines round
and round until a depth of 1" is reached.

> On the other hand I think some
> of the hobby controllers were desinged by people with little or no
> machining experience.

With open source code, you can modify it exactly like you want it. If
I'm running a machine and something isn't nice to use, it goes on a list
and gets modified. You wouldn't believe how much time these
modifications save in the long run.

> Have you ever used a modern commercial control? If so, I don't
> understand how you could make your arguments.

We run CNC equipment in a production environment, day in and day out.

I've spent a lot of time hanging around our neighbors cnc machine,
listening to their complaints, praise, etc.

I've gone through the handbooks of several CNC controllers, modern ones.

I've studied several CNC programming handbooks from cover to cover

My neighbors come over and drool at how fast/easy our equipment is to
operate and how fast we machine parts. They drool over the real
keyboard the BIG BRIGHT CRT COLOR display, etc. Their lathe controller
has a funny tool offset implementation that prevents them from actually
using it. And they have no power to make any changes. My version of
TCNC has a great Jog GUI and a really good file editor, that allows the
user to make changes to the code on the fly while running it. This is a
HUGE time saver that I am sure the 15 year old machine does NOT have.

I've been asked to do 2 CNC conversions for outside entities. This
isn't our interest, so I declined.

Doug: technology is changing VERY rapidly in the area of CNC
controllers. In my mind those older CNC controllers have been made
obsolete by modern PC based control systems.


--
Kim Lux <lux@...>