Hurco rotary c axis feed

[billcee]

Hi
New user of a vmx60sr. The problem I have is when programming the c axis feedrate using isnc at as little as 3.0 deg /min the table still runs at full speed (33.3 rpm) . Does anybody know the feed range and format the machine expects. The user manuals offer no help at all.
Thanks in advance
Billcee

[pjgray]

I am guessing that you want to cut with the C-axis rotating and the B-axis at a fixed angle. If you have v8 Winmax software, you can use G94.1 to rotate the C-axis and maintain a constant velocity of the tool tip relative to the rotating part. Feedrate is programmed in mm/min or inch/min. You will have to set your Part Setup and Tools correctly for 5-axis machining. It cannot be used in M128 TCPM or G68.2 Transform Plane modes. Here’s a program example:

%
G21
G00X0Y0Z0
G94.1 F1000
G01 C720
M02

This program will keep the tool tip moving at 1000mm/min relative to the rotating part. The closer to the C-axis C-centerline the tool tip is, the faster the C-table will rotate to maintain the 1000mm/min feedrate.

You can find G94.1 in the Help Index for more details.

-Paul

[billcee]

Hi thanks
dont have version 8 software but below is my code which causes c axis table to run flat out.

G0 G17 G21 G40 G80 G54 G90
(TOOLPLANE NAME - TOP)
T6 M6 (DW504-B)
S2000 M3
G53 Z0.
G0 G90 G54 B0. C0.
X-275.48 Y0.
Z140. M8
Z125.
G1 Z7. F500.
X-261.48 F33.3
C-360. F3.6
X-266.48 F1000.
X-266.38 F100.
X-261.38 F33.3
C-720. F3.6
X-266.38 F1000.
X-266.28 F100.
X-261.28 F33.3
C-1080. F3.6
X-266.28 F1000.
X-266.18 F100.
X-261.18 F33.3
C-1440. F3.6

I see you are one of the inventors of the system, what would cause it to feed at full speed on rotary move using isnc,i need very slow feed because I am grinding glass. Is F mm/min ,deg/min or something else...G94 should be active as default so g93 shouldnt be an issue
cheers
Bill

[pjgray]

G93 is another solution to the problem but it is a bit difficult to work with b/c keeping a constant surface speed of the tool to the rotating part is dependent on the radius you are cutting at and the angular step size (arc length of the move). To compute the inverse time for the move use this equation:

G93 Inverse Time Value = (Feedrate [mm/min or inch/min]) / (Radius [mm or inch] * Angle of move [radian])

Angle of move must be in radians: 1 [degree] = (Pi / 180) [radian]


Here is why G94 is moving the C-axis so quickly in your program:

G94 computes the time step for the move based on the linear distance the tool will move relative to the part for the block. It is based completely on the start and end points of the block. If you rotate C 360 degrees, the start and end points of the block have the tool at the exact same location relative to the part, so it computes a zero time step (no motion of the tool tip relative to the part) and moves the C-axis as fast as possible. This is why we implemented G94.1 tangential velocity control for v8 Winmax.

I have attached an xls spreadsheet that may be helpful. It computes a modified G94 feedrate that will generate the real surface speed you want to cut with. Enter the feedrate you want to cut with in the spreadsheet [mm/min or inch/min] and the angle of the move [degree] then use the computed modified feedrate in your program. The only caveat is that you must reduce your rotary moves to less than 360 degrees.

[Stevo]

Attached PDF may also give some insight on how to calculate the feed for a rotary axis.

Stevo

[pjgray]

I understand the calculations. However, G98 in your exerpt is for CNC Lathes and is not available for CNC Mills. That is why we have added the G94.1 Tangential Velocity Control for the mills, which is more powerful than the Lathe G98 as it maintains the correct interpolated tangential velocity of the tool relative to the part even with full simultaneous 5-axis motion. If the other options I presented are not suitable for you and you need to have G94.1, your control software can be upgraded to v8. I believe there is a nominal fee for the upgrade but it's not very expensive.

[billcee]

Hi pjgray
Thanks for your grade one assistance....makes life so much easier now I know what is causing it.