Pipe Thread milling on VF3

All,
I’m trying to mill a conical helix on a HAAS mill and am getting a 304 Alarm, “Radius at start must match radius at end of arc within .001”. I’ve had this trouble in the past on a Fanuc control and was able to change a tolerance value in a parameter to stop the error. I’ve contacted HAAS and they are looking into it but haven’t been able to find anything.
My question; is anyone milling pipe threads or a conical helix on a HAAS successfully, and if so how? I’m not actually milling pipe threads so I’d rather not break this into small lines if possible.

Thanks in advance,
Dave

Snippet of my code:
N268 G90 G00 G57 X-3.179 Y-4.6101 A0.0
N269 G43 H14 Z0.089 M08
N270 G17 G80
N271 G1 Z-2.861 F35.0
N272 G3 X-2.858 Y-4.6101 I0.1605 J0.0 F11.6
N273 G3 X-2.864 Z-2.881 I-0.321 J0.0A0.0 >> Cone starts here, drops .020 every revolution
N274 G3 X-2.87 Z-2.901 I-0.315 J0.0
N275 G3 X-2.876 Z-2.921 I-0.309 J0.0
N276 G3 X-2.882 Z-2.941 I-0.303 J0.0
N277 G3 X-2.888 Z-2.961 I-0.297 J0.0
N278 G3 X-2.894 Z-2.981 I-0.291 J0.0

Off the top of my head I don't think a single G2/G3 curve will work for each lead of the thread. When you have arc moves with the same center point, the start/finish XY would end up being the same. Conversely if you had different start/finish XY, the center point will get shifted all around based on the curve.

For a helical pattern like a tapered thread, a spline would fit the coordinates but the spline won't have a fixed center. If you imported that into CAM software it'd probably output a whole bunch of tiny line segments climbing around the thread.

Myself I've never milled tapered threads before, but that's what I would expect from it.

have done it many times, just use a tapered thread milling cutter.the full form style. they work just fine.

Had to do a quick emergency taper thread once w/o a thread mill. So I took a regular pipe tap and ground three of the four flutes off and used it like a tapered thread mill. Hey, it worked! :)

I guess you also narrowed down the thread since it's in a helix? Or was the slightly extra wide thread not an issue? Cool idea.

Quote:

---

Originally Posted by mtlwiz1

have done it many times, just use a tapered thread milling cutter.the full form style. they work just fine.

---

Don't do this on anything critical such as very high pressure piping. A tapered thread mill doing a single interpolation will make a thread that looks tapered to the naked eye but it is not a true tapered thread. It will screw into a tapered thread and with goop and teflon tape will make a connection that does not leak at low pressures such as 100 psi, maybe a bit higher. At high pressures which require full metal to metal contact between the two mating parts, and goop and tape is a no no, this type of botch up is not suitable because it cannot give the full metal to metal contact needed.

Here is the solution to your problem

%
O89977 (PIPE THREAD )
#144= 0.5 (DIAMETRO NOMINAL EN Z0)
#136= 20. (HILOS POR PULGADAS)
#137= 0.77 (DEPHT)
#104= 3000 (RPM)
#105= 30. (INCHES PER MINUTES)
#106= 2 (T00L)

G54




#138= 1.78 (THREAD ANGLE)

#135= 0 ( ANGULO DE INICO EN LOS 360 DEGREE )
#108= -1 ( -1 PARA TUERCA /+1. PARA TORNILLO)
#112= 1. ( -1. ROSCA NORMAL /+1. ROSCA IZQ )
#124= 4 (SECCIONAR CIRCUNF EN ESTAS PARTES)
(#124 MAYOR VALOR ES MAS PRECISION)

(EL DIAM DE LA CUCHILLA ES 0.8574)
#114= #144 + 0.8574 (DIAM NOM+TOOL DIAMETER)









IF [ #108 EQ 1 ] GOTO10
IF [ #112 EQ -1 ] THEN #145= 42
IF [ #112 EQ 1 ] THEN #145= 41
GOTO20
N10 IF [ #112 EQ -1 ] THEN #145= 41
IF [ #112 EQ 1 ] THEN #145= 42

N20 #113= [ TAN[ #138 ] ] / #136 ( CIRCLE STEP )
#125= [ [ #114 / 2 ] - [ #115 / 2 ] ] / #113 ( NO. DE CIRCULOS )
#109= 2400 + #106
#110= #[ #109 ]
#123= #119 / 100.
#121= #110 * #123 (% TOOL DIAMETER)
#122= [ #110 / 2 ]
#118= [ [ #113 / #124 ] * #108 ] ( INCREMENTOS DE RADIO )
#132= [ [ 360 / #124 ] * #112 ] ( INCREMENTOS DE ANGULO )
IF [ #112 EQ 1 ] THEN #126= 3 ( G3 )
IF [ #112 EQ - 1 ] THEN #126= 2 ( G2 )
#139= 1. / #136 (PASO EN Z)
#140= #139 / #124 (Z DE CADA SECION)
G90 G20
G00 G40 G80 G49
G00 X0 Y0



T#106 M06
S#104 M03
G43 H#106 Z0.1
/ M08
G00 G90 Z0.1
G01 X0 Y0 F#105
M97 P7218
M09
G28 G91 Z0
G28 Y0
G90
M05
M30


N7218 (SUBRROUTINE)

G90 G20
#107= #135
#130= 0
#116= #114 / 2.
#127= [ COS[ #107 ] * #116 ]
#128= [ SIN[ #107 ] * #116 ]
G01 G#145 X#127 Y#128 D#106 F#105
G01 Z0 F#105
WHILE [ ABS[ #130 ] LT ABS[ #137 ] ] DO1
#130= [ #130 - #140 ]
#116= [ #116 + #118 ] ( DECRECE O CRECE EL RADIO )
#107= [ #107 + #132 ] ( CRECE O DECRECE EL ANGULO )
#127= [ COS[ #107 ] * #116 ]
#128= [ SIN[ #107 ] * #116 ]
#129= [ SQRT[ [ #127 * #127 ] + [ #128 * #128 ] ] ]
G#126 X#127 Y#128 Z#130 R#129 F#105
END1
IF [ #108 EQ - 1 ] GOTO80
IF [ #127 GT 0 ] GOTO70
G01 G91 X-0.5
N60 GOTO90
N70 G01 G91 G40 X0.5
N75 GOTO90
N80 G01 G40 X0 Y0
N90 G90 G01 Z0.1 F50.
M99
%


ask me any doubt!!!