Constructing a Cylinder from 2 cylinders

[YGOLORTEM]

I have an 8" shaft on the machine long ways in the Y axis. I measure a Ø 3.00" X 2" deep cylinder on one side (Y+) and a Ø 4.00 X 2" deep cylinder on the opposite side (Y-). Is it possible to create 1 cylinder (centerline) out of the 2 cylinders? I've used all possible configurations (Auto, Best Fit, BF ReComp, Projection, Cast and Reverse) and it keeps telling me there is not enough features. Is there a way possible to create this?

These 2 cylinders create a datum (Datum -A- & Datum -C- or A-C as called out on the drawing) and there is a Total Run Out called out from a different diameter on the shaft back to the A-C datum.

[ThePudds]

Rather than creating 2 different cylinders, have you tried taking multiple circles on each end and creating a cylinder that way? I am not sure if that would work. That would be the first thing I would try. I'm still new though, I do things different. Sorry if it doesn't help.

[YGOLORTEM]

Rather than creating 2 different cylinders, have you tried taking multiple circles on each end and creating a cylinder that way? I am not sure if that would work. That would be the first thing I would try. I'm still new though, I do things different. Sorry if it doesn't help.

I use auto cylinders to speed up programming. I'm thinking in the future this will be the way to go

[ThePudds]

I use auto cylinders to speed up programming. I'm thinking in the future this will be the way to go

Auto features are pretty much all I use. I was just thinking that in this scenario, a couple Auto circles on each end and construct a cylinder that way. It may work, it may not. I'm not honestly to sure. Worth a shot I suppose.

[UKCMM]

As the two diameters are different then a 3D line is what should be used

[YGOLORTEM]

Unfortunately a 3D line doesn't help with the dimension

[YGOLORTEM]

Currently I have a 3D line constructed between the 2 and it's working for everything need (except TTL RO) but I believe I need the form error from the datum's to get this call out to work

[Mike Ruff]

As the two diameters are different then a 3D line is what should be used

+1

I would construct a plane at the top and bottom of each cylinder. Then construct an intersection point from the cylinder and each plane. You should now have 4 points, one at the top and bottom of each cylinder. Now you can construct a 3D line from the 4 points and use this line.

[DAN_M]

The first time I came across an "A-B" callout on a print, Hex remoted in and showed me how to do the following:

Create a 3D line using the start & end points of your desired geometry and use that line for level & origin setting. Like so:

LIN_XP_THEO=FEAT/LINE,CARTESIAN,UNBOUNDED,NO
THEO/<-0.5,0,0>,<1,0,0>
ACTL/<-0.5,0,0>,<1,0,0>
CONSTR/LINE,ALIGN,1,XPLUS
CYL_A =FEAT/CONTACT/CYLINDER/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<0,0,0>,<0,0,1>,10,1
ACTL/<0,0,0>,<0,0,1>,10,1
TARG/<0,0,0>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
CYL_B =FEAT/CONTACT/CYLINDER/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<0,0,2>,<0,0,1>,5,1
ACTL/<0,0,2>,<0,0,1>,5,1
TARG/<0,0,2>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
PNT_CYL_A_START=GENERIC/POINT,DEPENDENT,CARTESIAN,$
NOM/XYZ,<CYL_A.EX,CYL_A.EY,CYL_A.EZ>,$
MEAS/XYZ,<CYL_A.EX,CYL_A.EY,CYL_A.EZ>,$
NOM/IJK,<0,0,1>,$
MEAS/IJK,<0,0,1>
PNT_CYL_B_END=GENERIC/POINT,DEPENDENT,CARTESIAN,$
NOM/XYZ,<CYL_B.SX,CYL_B.SY,CYL_B.SZ>,$
MEAS/XYZ,<CYL_B.SX,CYL_B.SY,CYL_B.SZ>,$
NOM/IJK,<0,0,1>,$
MEAS/IJK,<0,0,1>
LIN_AB =FEAT/LINE,CARTESIAN,UNBOUNDED,NO
THEO/<0,0,-1>,<0,0,1>
ACTL/<0,0,-1>,<0,0,1>
CONSTR/LINE,BF,3D,PNT_CYL_A_START,PNT_CYL_B_END,,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,WAVELENGTH=0
PLN_TOP =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,NONE,LEAST_SQR
THEO/<0,0,4>,<0,0,1>
ACTL/<0,0,4>,<0,0,1>
TARG/<0,0,4>,<0,0,1>
ANGLE VEC=<1,0,0>,RADIAL
SHOW FEATURE PARAMETERS=NO
SHOW CONTACT PARAMETERS=NO
A1 =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
ALIGNMENT/LEVEL,ZPLUS,LIN_AB
ALIGNMENT/ROTATE,XPLUS,TO,LIN_XP_THEO,ABOUT,ZPLUS
ALIGNMENT/TRANS,XAXIS,LIN_AB
ALIGNMENT/TRANS,YAXIS,LIN_AB
ALIGNMENT/TRANS,ZAXIS,PLN_TOP
ALIGNMENT/END

Also, check this out:

https://www.pcdmisforum.com/forum/pc...ting-a-b-datum

Note:
An A-B alignment can't have a material modifier attached to it because a line is not a feature of size.

[Mike Ruff]

Isn't this the same as using a single circle for each datum? On an actual part, the coaxiality of the two datum cylinders will affect the location/orientation of the compound datum, and this method would not take that into account. It would be better to use the start and end points of each cylinder and construct the compound datum as a 3D line composed of 4 points instead of 2 points

[DAN_M]

You're right my friend! By doing it the way I have above, I am forcing the line I make my alignment through to assume the coaxiality of the datums. It is exactly what is needed to ensure that the part works.

All of my stuff that has this type of call-out will end up spinning at high RPM in an aircraft engine. Datum -A- and Datum -B- will be assembled into their mating components and my part will spin in the center. Stuff has to run true to the outside or you'll start shimmying & wobbling when you're 5 miles up. (no bueno)

[LostL]

Personally I exctracts the points into a set and construct a cylinder from the set. That way you get everything.

SCN1 =FEAT/SET,CARTESIAN
THEO/<9770.13,-528.611,4717.251>,<0,0,1>
ACTL/<9770.13,-528.611,4717.251>,<0,0,1>
CONSTR/SET,BASIC,CYL1.HITS[1..CYL1.NUMHITS],CYL2.HITS[1..CYL2.NUMHITS,,
CYL3 =FEAT/CYLINDER,CARTESIAN,IN,LEAST_SQR,NO
THEO/<9770.26,-528.484,4717.005>,<-0.019565,-0.1045285,-0.9943294>,6.5,7.3
ACTL/<9770.26,-528.484,4717.005>,<0.019565,0.1045285,0.9943294>,6 .5,7.3
CONSTR/CYLINDER,BF,SCN1,,