Centre point or Axes

[Anonymous]

Hello, Every sketch I start, I'll project something if there isn't something to work from to begin with. Your first sketch, what do you project and why? Me, well I always start with projecting the Centre point, however I'm begining to question it, I'm thinking that the projection of both the X and Y axis will be better as I'll then be able to use Colinear constraints to nail it down as opposed to a Coincident constraint holding everything to the Centre point. I've just had to move an entire sketch, the Coincident constraint applied to the centre point has forced me to break the loop by removing more than two constraints, I believe the centre point has also been consumed by the line, hence removing the constraint and moving the entire sketch I've found to be impossible, under the same circumstances using Colinear constraints I could have removed two constraints, moved the sketch without having to rebuild the loop during the process. Thanks and take it easy Scott

[Anonymous]

Scott, I'm not saying you're wrong, but excuse me if I ask a few questions or make a few points. I currently use a projected Centre Point. From there Inv automatically places a coincidence constraint, followed by a horizontal or vertical constraint, followed by parallel or perpendicular constraints. I believe iFeatures or Design Elements don't like vertical or horizontal constraints. So this method could have some benefit with iFeature design. Two collinear constraints with any number of parallel, perpendicular, horizontal &/or vertical constraints won't nail a sketch down to one particular place. I'm sure you'll need at least one coincident constraint. That said, it's definitely worthwhile looking into this method a bit further. Thank you for sharing it with everybody. Duncan -- "Humour ... is one man shouting gibberish in the face of authority, and proving by fabricated insanity that nothing could be as mad as what passes for ordinary living." (Terence 'Spike' Milligan K.B.E., 1918-2002) "Scott Stubbington" wrote in message news:4177658f_2@newsprd01... > Hello, > Every sketch I start, I'll project something if there isn't something to work from to begin with. Your first sketch, what do you > project and why? Me, well I always start with projecting the Centre point, however I'm begining to question it, I'm thinking that > the projection of both the X and Y axis will be better as I'll then be able to use Colinear constraints to nail it down as opposed > to a Coincident constraint holding everything to the Centre point. > > I've just had to move an entire sketch, the Coincident constraint applied to the centre point has forced me to break the loop by > removing more than two constraints, I believe the centre point has also been consumed by the line, hence removing the constraint > and moving the entire sketch I've found to be impossible, under the same circumstances using Colinear constraints I could have > removed two constraints, moved the sketch without having to rebuild the loop during the process. > > Thanks and take it easy > > Scott >

[Anonymous]

Gathering experience, that's all. :-) Programming IV defines a sketch line cannot exist without two end points, IV also has a habit of combining sketch points. When moving my sketch I'd have liked to remove the original projected point, move the sketch, however it didn't work that way, I had to remove two coincident constraints, break my sketch loop, move the sketch geometry, apply a coincident constraint to re-join the loop and then apply colinear constraints to nail it down again I'm not suggesting we can replace Coincident constraints with Colinear, however it with respect to nailing down your first sketch, I'm wondering if people do use X-Y axes projections as opposed to just the centre point, I know that if I were to try and remove the constraints holding the sketch to the origin it will be easier to isolate the Colinear constraints than the Coincident constraint. I suppose I'm niggled by blurring of constraints that hold the sketched loop together and constraints that hold the sketch loop in position, couple that with the circumstances of what you're sketching I suppose I've asked "how long is a piece of string". Thanks "Duncan Anderson" wrote in message news:41777178$1_3@newsprd01... > Scott, > > I'm not saying you're wrong, but excuse me if I ask a few questions or > make a few points. > > I currently use a projected Centre Point. From there Inv automatically > places a coincidence constraint, followed by a horizontal or vertical > constraint, followed by parallel or perpendicular constraints. I believe > iFeatures or Design Elements don't like vertical or horizontal > constraints. So this method could have some benefit with iFeature design. > > Two collinear constraints with any number of parallel, perpendicular, > horizontal &/or vertical constraints won't nail a sketch down to one > particular place. I'm sure you'll need at least one coincident constraint. > > That said, it's definitely worthwhile looking into this method a bit > further. > > Thank you for sharing it with everybody. > > Duncan > > -- > "Humour ... is one man shouting gibberish in the face of authority, and > proving by fabricated insanity that nothing could be as mad as what passes > for ordinary living." > (Terence 'Spike' Milligan K.B.E., 1918-2002) > > > "Scott Stubbington" wrote in message > news:4177658f_2@newsprd01... >> Hello, >> Every sketch I start, I'll project something if there isn't something to >> work from to begin with. Your first sketch, what do you project and why? >> Me, well I always start with projecting the Centre point, however I'm >> begining to question it, I'm thinking that the projection of both the X >> and Y axis will be better as I'll then be able to use Colinear >> constraints to nail it down as opposed to a Coincident constraint holding >> everything to the Centre point. >> >> I've just had to move an entire sketch, the Coincident constraint applied >> to the centre point has forced me to break the loop by removing more than >> two constraints, I believe the centre point has also been consumed by the >> line, hence removing the constraint and moving the entire sketch I've >> found to be impossible, under the same circumstances using Colinear >> constraints I could have removed two constraints, moved the sketch >> without having to rebuild the loop during the process. >> >> Thanks and take it easy >> >> Scott >> > >

[Anonymous]

"Scott Stubbington" wrote in message news:4177854a_1@newsprd01... > Gathering experience, that's all. :-) Same here. Duncan -- "Humour ... is one man shouting gibberish in the face of authority, and proving by fabricated insanity that nothing could be as mad as what passes for ordinary living." (Terence 'Spike' Milligan K.B.E., 1918-2002)

[ArtC]

You can use 2 dimensions to constrain to the organ point. The dimensions can be 0. You can also fix any point and not use the organ point.

[Anonymous]

I almost always project the two axes, but rarely use collinear constraints. Most parts that I create are symmetric in at least one direction, so I often constrain the midpoint of an edge to a projected axis. If it's a cylindrical part, the circle is coincident to the origin. If it's a revolve, one of the projected axes is the axis of revolution (hint: change it to a centerline if you want to dimension as diameters instead of radii). In other words, if I know ahead of time that my part will be symmetric, I try to constrain the first sketch so that the part is symmetric around the origin. Helpful for mirroring features, and later on in an assembly, the origin planes of one symmetric part can be constrained to the origin planes of another symmetric part while you're working out the relative sizes, all the while keeping them centered relative to each other. -- Sam Bixler Eli Lilly and Company, Indianapolis "Scott Stubbington" wrote in message news:4177658f_2@newsprd01... > Hello, > Every sketch I start, I'll project something if there isn't something to > work from to begin with. Your first sketch, what do you project and why? > Me, well I always start with projecting the Centre point, however I'm > begining to question it, I'm thinking that the projection of both the X and > Y axis will be better as I'll then be able to use Colinear constraints to > nail it down as opposed to a Coincident constraint holding everything to the > Centre point. > > I've just had to move an entire sketch, the Coincident constraint applied to > the centre point has forced me to break the loop by removing more than two > constraints, I believe the centre point has also been consumed by the line, > hence removing the constraint and moving the entire sketch I've found to be > impossible, under the same circumstances using Colinear constraints I could > have removed two constraints, moved the sketch without having to rebuild the > loop during the process. > > Thanks and take it easy > > Scott > >

[Anonymous]

I also use another SoftWare that automatically projects the origin point to each new sketch - so I have gotten into the habit of projecting the origin in Inventor and use lots of construction lines (I avoid horizontal and vertical constraints between points in favor of horizontal and vertical construction lines that others will be able to decipher when they edit my models). Never had any problem with this method. I don't see why it should present a particular problem when moving sketches, but then I rarely have the need to move a sketch.
Actually now that I think about it I do move sketches. I often create a sketch first and then move (I should say drag, I think I have used the move command less than 3 times in 3 years) the sketch to the origin after it is done based on where I decide I want the datum to be.
J.D.

[Anonymous]

I always project the origin point, but I draw a diagonal construction line from the corners of my sketch & constrain to the center of that. Most of the parts I draw require center planes for constraining or measuring. If the part needs to be adaptive it's easy to delete the constraint. You're right, using a coincident constraint from the projected origin to the end point of a line can make things difficult. "Scott Stubbington" wrote in message news:4177658f_2@newsprd01... > Hello, > Every sketch I start, I'll project something if there isn't something to > work from to begin with. Your first sketch, what do you project and why? > Me, well I always start with projecting the Centre point, however I'm > begining to question it, I'm thinking that the projection of both the X and > Y axis will be better as I'll then be able to use Colinear constraints to > nail it down as opposed to a Coincident constraint holding everything to the > Centre point. > > I've just had to move an entire sketch, the Coincident constraint applied to > the centre point has forced me to break the loop by removing more than two > constraints, I believe the centre point has also been consumed by the line, > hence removing the constraint and moving the entire sketch I've found to be > impossible, under the same circumstances using Colinear constraints I could > have removed two constraints, moved the sketch without having to rebuild the > loop during the process. > > Thanks and take it easy > > Scott > >