How to tell 3D CNC from 2 1/2D on a mill
Peter Reilley
is a Bridgeport conversion job that still has the cranks.
This is just for hobby use. My question is how can I
recognize a 3D controller from a 2 1/2 D controller?
Did the same manufacturers make both types?
Are their certain G codes that indicate 3D?
Is there a certain year of manufacture that everyone
changed over to 3D?
My understanding of 3D vs. 2 1/2 D is that 3D can
move in all three axis's at the same time. A 2 1/2 D
can generally move in the X and Y axis at the same time
but the Z axis will remain stopped during the X and Y move.
Any help or advice would be appreciated,
Pete.
Bob Campbell
All of the PC controllers that I know of that use G code, let you move all
three axis at the same time. It is more a function of the cad/cam program
not the controller.
Bob Campbell
Peter Reilley <mic...@mv.com> wrote in message
news:804mvh$1nm$1...@pyrite.mv.net...
Steve Daigle
Certain CNC controls have a function called "helical interpolation". That's
what separates a 2.5D from a 3D. It's little know, but Fanuc 3M controllers
were incapable of this function, and a lot of lower end buyers and start-up
shops find this out too late. The best way to tell if you cannot get
reliable literature detailing the capabilities of the controller is to have
whomever is selling this machine to you video the machine in a 3-axis
helical move (X & Y in a circle with Z coming down). Good luck. If you
have the room in your shop and are interested, I can point you towards a 3D
CNC conversational machine for about the same as you'd pay for a CNC
Bridgeport.
--
Steve Daigle
JBM Technologies, Inc.
215-938-8900 Phone
215-938-8980 Fax
jbm...@jbmtechnologies.com
Bob Campbell <rc...@anet-dfw.com> wrote in message
news:s2cbvp...@corp.supernews.com...
Doug Goncz
>what separates a 2.5D from a 3D.
Yes, you must be right. The separate Z axis move, and its relative, the
separate X and Y moves, followed by Z axis drilling only, are more the mark of
a point-to-point controller than a continuous path type. There's a better name
for the continuous path, I think. Helical interpolation is an advancement of
continuous path.
Spherical interpolation would be next. Various types of robots would be more
likely to use that than a machine tool would be. An axis would more likely be
added to a machine tool to form spherical and similar surfaces.
Yours,
Doug Goncz, A.A.S.M.E.T.
Experimental Machinist ( DOT 600.260-022 )
Replikon Research ( USA 22044-0094 )
http://users.aol.com/DGoncz
(Can't afford letterhead so I use this signature. :)
No longer reading mail sent to ReplikonVA
Gary Sweatt
>
><SNIP>
> My understanding of 3D vs. 2 1/2 D is that 3D can
> move in all three axis's at the same time. A 2 1/2 D
> can generally move in the X and Y axis at the same time
> but the Z axis will remain stopped during the X and Y move.
>
>
Pete -
It even gets doggier than that -- for example -- some of the older
(1978ish) Hurco machines that were built on Bridgeport iron with the
Hurco KM1 control - did - with the right executive program - do true
three axis motion just so long as a move was linearly interpolated.
They reverted back to 2 1/2 axis if a circular interpolation was
involved. With these machines you did have a mode set option for the
circular plane (which two of the three axes the circle would be
interpolated in - with the other held at position). This was all done
with a strictly conversational control based on a Motorola 6800
processor. Typically this control was not designed to accept offline
info but as the on board tape drives failed (and became either
prohibitively expensive or simply unobtainable) Hurco sold an expensive
(IMHO) tape emulator system which replaced the Raymond cassette drive
that would allow you to store the executive and part programs off line
on a DOS based PC. AFAIK no one other than us ever went so far as to
manage to program these beasties off line but I'd be surprised if we are
the only outfit that has done it. Dunno if this helps ya any or not but
that's the way it was.
Gary
ha...@pacbell.net
>Peter Reilley wrote:
>>
>><SNIP>
>
>> My understanding of 3D vs. 2 1/2 D is that 3D can
>> move in all three axis's at the same time. A 2 1/2 D
>> can generally move in the X and Y axis at the same time
>> but the Z axis will remain stopped during the X and Y move.
>>
>
>Pete -
>
> It even gets doggier than that -- for example -- some of the older
>(1978ish) Hurco machines that were built on Bridgeport iron with the
>Hurco KM1 control - did - with the right executive program - do true
>three axis motion just so long as a move was linearly interpolated.
>They reverted back to 2 1/2 axis if a circular interpolation was
>involved. >
probably Times Have Changed since my day . . but can anyone
name any common controls which do three-axes circular interpolation ?
Don't all the CAM systems output three dimensional contours in line
segments because NO common control is capable of anything more
difficult than two-axis circular simultaneous plus a linear ?
An Acc220 is a 2 1/2 axis control, for sure ! And probably a Slo-Syn,
but has anyone even made a machine control recently (not retrofit thing
like the new Sony) which isn't capable of three axes simultaneous
linear motion ?
>Gary
--
h„rad ‘ngravv†d
Vincent Carknard
Peter Reilley <mic...@mv.com> wrote in message
news:804mvh$1nm$1...@pyrite.mv.net...
> I am considering getting a CNC mill. My ideal machine
> is a Bridgeport conversion job that still has the cranks.
> This is just for hobby use. My question is how can I
> recognize a 3D controller from a 2 1/2 D controller?
> Did the same manufacturers make both types?
> Are their certain G codes that indicate 3D?
> Is there a certain year of manufacture that everyone
> changed over to 3D?
>
> move in all three axis's at the same time. A 2 1/2 D
> can generally move in the X and Y axis at the same time
> but the Z axis will remain stopped during the X and Y move.
>
> Pete.
>
A true 3d control will do arcs/radii (circular interpolation) on any
combination of axes, xy, xz, yz using standard G codes. My 2.5 D machine
does xy arcs as a function of the G codes (g02,g03). On xz, yz arcs I have
to use my cad/cam program to interpolate the arcs into tiny straight line
segments. This is very easy to do. The control then uses linear
interpolation (g01) to cut the tiny lines on the xz,yz axes. The result is
an arc in the appropriate direction. This makes for long programs (no
problem), depending on the resolution you use for the lines. I cut aluminum
mold cavities using this method.
HTH
VBC
Vickers Tech Support
. . but can anyone
> name any common controls which do three-axes circular interpolation ?
I assume you're talking about helical interpolation here...
Every Vickers control (ex-Cincinnati) in recent memory was capable of this.
G2 X-- Y-- Z-- I-- J-- K--
X, Y, Z: axis end points
I, J: coords of center point
K: lead
Works in any plane according to G17/18/19. Also requires coordintion
between endpoints and lead. On more recent controls (last 15 years) you can
program it to interpolate as many helixes as desired by modifying the Z
word.
Ron
Paul Elliott
<ha...@pacbell.net> wrote...
> probably Times Have Changed since my day . . but can anyone
> name any common controls which do three-axes circular interpolation ?
> Don't all the CAM systems output three dimensional contours in line
> segments because NO common control is capable of anything more
> difficult than two-axis circular simultaneous plus a linear ?
----
Fanuc has a G02.4 command that is a true 3 axis arc.
Siemens has a CIP function.
Thermwood has a G72/G73 3 axis arc.
Selca supports rotating an arc into an arbitrary plane, as does Fanuc.
There are a few others, but I have yet to see either specs or working
examples.
All of them define their arcs differently.
all of these are MetaCut supported formats, so the CAM system doesn't have
to do it. . . ;)
----
Paul Elliott, Software Engineer
Northwood Designs http://www.MetaCut.com
Developers of MetaCut optimization software.
3 axis arcs rule.
ha...@pacbell.net
><snip>
>.. . but can anyone
>> name any common controls which do three-axes circular interpolation ?
>
sorry ron, no, I am NOT speaking of helical interpolation. I am thinking
of parabolic interpolation or cubic interpolation or interpolating an
arc in two planes simultaneously. Helical interpolation is not three
axes circular, it is two axis circular with a third linear.
>
>Every Vickers control (ex-Cincinnati) in recent memory was capable of this.
>
220 doesn't have it :-) In fact, 220 doesn't have linear interpolation, but
you can do contouring work using the same method that CAM systems use
for 3 axis work - 40 billion little moves. That was my point - how can one
label a control as 2 1/2 axis if it does 3 axis simultaneous linear moves ?
Which controls or CAM systems use anything BUT line segments for 3 axis
work ?
>
>Ron
>
do you still have cinturn II as an option on the turning centers ?
Ron P.
> >Every Vickers control (ex-Cincinnati) in recent memory was capable of this.
> >
>
> 220 doesn't have it :-)
My qualifier was 'recent memory.' :p I think those 220s are nearly as
old as I am... But there are a noticeable number of them still
running!
Ron