questions on rapids and the trajectory planer
18 Feb 2013 03:53 - 18 Feb 2013 03:54 #30224
by danemc
questions on rapids and the trajectory planer was created by danemc
i'm about to convert a knee mill to cnc and i am examining the option of driving the knee instead of the column for more travel. if i do this it would be supported/counterweighted with regulated air pressure and air pistons so there is minimal added mass. but there will still be a speed limit lower than the other axises. i want to know the behavior of the rapid moves. if one axis is slower will the trajectory planner try to make linear moves and limit the faster axis as would happen in g1 mode? or will each axis move at it's speed limit until the commanded position in each plane is reached? if you command a move on x and y in g0 of equal distances so it travels at 45 degrees will the total linear speed be at the set rapid speed? or will each axis reach max rapid so the measured speed would be 1.414x the set rapid speed? i know how it will behave in g1 but i'm wondering about g0.
i have run hass lathes that don't maintain full coordination between axises at 100% rapid so an x,z g0 move would sometimes make curved moves rather than angular and a move with more travel in one axis at a low rapid would move 45deg till one axis reached it's target then continue to the other target along the axis with the longer move. the machine would run each axis at it's speed and acceleration limits so moves were not direct. this is what i would prefer so the machine is not limited to the z speed limits for x/y moves.
i have run hass lathes that don't maintain full coordination between axises at 100% rapid so an x,z g0 move would sometimes make curved moves rather than angular and a move with more travel in one axis at a low rapid would move 45deg till one axis reached it's target then continue to the other target along the axis with the longer move. the machine would run each axis at it's speed and acceleration limits so moves were not direct. this is what i would prefer so the machine is not limited to the z speed limits for x/y moves.
Last edit: 18 Feb 2013 03:54 by danemc.
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18 Feb 2013 05:31 #30228
by BigJohnT
Replied by BigJohnT on topic questions on rapids and the trajectory planer
All moves are coordinated so all axes involved reach the end point at the same time. How long could a knee mill take to go from one extreme to the other a few of seconds? Some have converted the knee but on mine I find it is plenty fast to just crank the knee as needed for each different part as it is a new setup anyway. If your doing high speed production it ain't on a knee mill any way.
John
John
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18 Feb 2013 07:53 #30237
by danemc
Replied by danemc on topic questions on rapids and the trajectory planer
well the knee may be difficult to move more than 50 ipm. that may be fine to get to a clearance position but i'd like the xy plane to move a bit faster and if i need tool changes there could be coordinated xyz rapid moves with a lot of z travel.
ok now that most of what i was wondering was answered, is there a way to set separate maximum speeds for different axises? or is there just one setting for the rapid speed? can i have 50ipm rapids on the z and 100+ ipm on the xy plane?
maybe 50 ipm sounds fine for a knee mill but if i can get more i'd like to.
ok now that most of what i was wondering was answered, is there a way to set separate maximum speeds for different axises? or is there just one setting for the rapid speed? can i have 50ipm rapids on the z and 100+ ipm on the xy plane?
maybe 50 ipm sounds fine for a knee mill but if i can get more i'd like to.
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18 Feb 2013 08:07 #30238
by BigJohnT
Replied by BigJohnT on topic questions on rapids and the trajectory planer
Each axis has settings for acceleration and velocity. My BP knee mill can do 200IPM on the X and Y and 150IPM on the Z (quill) so if I'm doing a rapid move in the X and Y only I can actually go faster than 200IPM on a diagonal move. If a Z move in included and it is proportionally smaller than the X and Y moves then it will not slow down the rapid move of the other axes.
You mention tool changes do you have a Kwik Switch or something other than a R8 spindle?
John
You mention tool changes do you have a Kwik Switch or something other than a R8 spindle?
John
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18 Feb 2013 08:42 #30239
by danemc
Replied by danemc on topic questions on rapids and the trajectory planer
i may be getting one from a co-worker.
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25 Feb 2013 03:29 #30532
by andypugh
Replied by andypugh on topic questions on rapids and the trajectory planer
Maybe do both? The knee could be the W axis and the quill Z.i'm about to convert a knee mill to cnc and i am examining the option of driving the knee instead of the column for more travel.
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26 Feb 2013 08:42 #30586
by danemc
Replied by danemc on topic questions on rapids and the trajectory planer
that's also on my mind... use the quill for peck drilling and moves to clear the part. the knee for rough positioning and milling in situations where i want the quill retracted for rigidity or need travel...
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26 Feb 2013 15:52 #30598
by Rick G
Rick G
Replied by Rick G on topic questions on rapids and the trajectory planer
That seems to work best for me.use the quill for peck drilling and moves to clear the part. the knee for rough positioning and milling in situations where i want the quill retracted for rigidity or need travel...
Rick G
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