3D sketch - spline issues

[pottersfriend]

So, I rarely use 3D sketches and splines but I've been trying to model something using lofts and it's been giving me issues. I'm using Dell M6600, Nvidia, Win7 Pro, and Alibre 2018.1.1 (19055).

When I create splines in a 3D sketch and either dimension to a control point or make the spline tangent to a line, or really just about anything to do with a spline, then hit CTRL-Z or the escape key the spline will switch to straight lines. I then have to start over and recreate the spline.

Is this some undocumented "feature" I'm unaware of? Sure seems like an issue with the program. I guess the only thing I can think of is possibly video driver. I don't think I've updated the drivers since I upgraded to 2018.

Anyway, if someone else can confirm that this happens to them, or if you have suggestions on how to solve this that would be great. Otherwise I guess I'll submit a support ticket.

Thanks.

 

[DavidJ]

Why hit Ctrl-Z (Undo), or did you want to cancel the previous action? I agree it does do odd things to the spline. Hitting Esc doesn't seem to cause any problem for me, it still looks fine.

Do you really need a 3D guide curve? won't a 2D curve work (tend to be easier to place).

 

[bigseb]

The solution is simple: do it a different way because 3D sketching don't work quite right.

In Solidworks you can draw a two point spline and then add a tangent tangent constraint. Simple. But in AD this simply doesn't work despite me having requested this feature many times over the years. Moving control points doesn't work right either.

 

[pottersfriend]

DavidJ - I might have been wrong about the Esc key. I was trying to recall from memory (big mistake for me). Anyway, yes, I was just trying to undo the previous step. For example, create 2 lines then a spline between them, then make them tangent. Create another line connected to one of the other lines. CTRL-Z to get rid of the last line. It will convert the spline to just lines. Yeah, I can probably do it using just 2D sketches, but I wish I didn't have to.

bigseb - Yeah, I assumed this was going to be the case but I was hoping. Though I don't use SolidWorks that much we have it at work and I was recreating the same thing in it the other day to see how it would work and it is so much easier. I really like being able to create a curve by projecting a sketch to another sketch. Constraining entities to other entities is much more robust as well.

I guess my biggest problem is the fact that I finally decided to pay the money to upgrade after years of being at 2014 and there are still issues like this. Well, time to put in a support ticket I guess. I also upgraded my video driver to the latest, but as I suspected it didn't help.

Thanks for the feedback.

 

[bigseb]

You'll find that AD often (not always) has an alternative method to achieve the same thing. Can you post an example of what you want?

 

[DavidJ]

I really like being able to create a curve by projecting a sketch to another sketch.

You can project sketches to sketches in Alibre.

 

[pottersfriend]

bigseb - So, this is what I'v come up with so far. Loft using 2 sketches for the ends and 6 3D sketches for guide paths. The circled areas are where I'm still having trouble. I need to create at least 1 more guide path in that area. This isn't anything that I'm actually going to build. Mostly just a guide for something I'm trying to build around it. Doesn't have to be that accurate so I'm not too worried about getting it too exact. I just wish it was a little easier to create. Mostly the compound curve 3D sketches are eyeballed over 2D sketches.

Seat Rail

• pottersfriend
• Nov 3, 2018

 

[pottersfriend]

You can project sketches to sketches in Alibre.

I'm not sure if we're talking the same thing. In SW you can take 2 sketches (just line/curve/spline entities) project them to create an intersection curve (which is also parametric). I don't think Alibre can do anything like that but if you don't mind sharing how to do it that would help me out a lot. Maybe Alibre can do it if you actually create a solid body from the sketches first?

 

[bigseb]

Lips like this are tricky to do in AD. If it were me I'd do this Moi.

 

[pottersfriend]

I've been playing around with booleans, and I think I'll just do it that way. It will get me close enough and a whole lot quicker than anything else.

 

[DavidJ]

Sorry I don't follow what you are describing....

 

[pottersfriend]

Sorry I don't follow what you are describing....

Not sure if this will help, but here's a basic example of what I'm talking about.

 

[Lew_Merrick]

Not sure if this will help, but here's a basic example of what I'm talking about.

How abput this approach?

 

[NateLiquidGravity]

Lew,
I think that video was simply an example of the way the "project curve" feature can be done in Solidworks.

pottersfriend,
You can project faces and edges to sketch in Alibre Design 3d sketches. Its not as elegant of a solution but can be very helpful. See this random example attached.

 

[Lew_Merrick]

Lew,
I think that video was simply an example of the way the "project curve" feature can be done in Solidworks.

pottersfriend, You can project faces and edges to sketch in Alibre Design 3d sketches. Its not as elegant of a solution but can be very helpful. See this random example attached.

Nate -- Could we define Reference Points usinng Equation Editor Variable it would be simpler yet. The only "issue" is deciding whether you want to define things in terms of OD/2, ID/2, or Median_Diameter/2.

 

[NateLiquidGravity]

Nate -- Could we define Reference Points usinng Equation Editor Variable it would be simpler yet. The only "issue" is deciding whether you want to define things in terms of OD/2, ID/2, or Median_Diameter/2.

Correct as usual, but not on topic with the original post.

 

[HaroldL]

I just wish it was a little easier to create.

I would break this into three features, a Loft for the main body (large U-shape) and two Sweeps for the return curve flanges. The Sweeps would use the edges of the U channel as their paths.

In Solidworks you can draw a two point spline and then add a tangent tangent constraint.

Alibre should not only have Tangent but also Perpendicular constraints to be applied to 2-Point Splines. That would get rid of trying to get a smooth perpendicular transition at the start of a loft using splines for guide curves. Now the only way is to place several aligned knots at the end of the spline.

It is interesting that SolidWorks added a Style Spline a couple of releases ago. It is the same as Alibre's spline by control points with more controls for constraining and placement.

 

[pottersfriend]

Seat Rail 002

• pottersfriend
• Nov 13, 2018

I know this topic was originally about the issues with 3D splines but I just wanted to finish up with my solution. I did go with booleans and this is the final result. It turned out pretty well and good enough for what I need it for. Thanks for the help and suggestions. I still need to report this to support. It is unfortunately too easy for me to put off that sort of thing.

 

[JST]

This part just did not work with splines, and had to be done a different way. With splines it bulged out in spots and was not acceptable

Splines seem to have issues, have had for years, I have complained about it going back probably 4 years, and CS admitted it was a problem.

 

[bigseb]

Seat Rail 002

• pottersfriend
• Nov 13, 2018

I know this topic was originally about the issues with 3D splines but I just wanted to finish up with my solution. I did go with booleans and this is the final result. It turned out pretty well and good enough for what I need it for. Thanks for the help and suggestions. I still need to report this to support. It is unfortunately too easy for me to put off that sort of thing.

Nicely done!