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-TJ

Modeling a leadscrew - loft, sweep, extrude, helix - no luck.

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-TJ

I'm trying to model a 3d leadscrew. How can I extrude a 2d closed polyline in a straight line while at the same time twisting it (360° twist for every 1.5" along the path). I've tried loft, sweep, extrude all using the helix as a path. When I can get a result, it ends up being a corkscrew.

 

Thanks for any help,

-TJ

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GhostRider

Sounds like your on the right path, from your explaination it soulds like you need more twists in your helix..

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-TJ

"Never give up"

I abandoned the helix and realized that if I use "sweep" and only model one 360° twist over 1.5" along a straight path (the spec for the lead), I can then assemble 16 sections to make a 24" long leadscrew. If one was able to enter a twist value greater than 360°, like 5760°, then the entire 24" length could have been sweep'd at once.

 

If anyone has a better way, I'm all ears. Unfortunately, when the sections are union'd together, you can still see the joints.

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shift1313

there is a thread button in 09 if i remember correctly right, or no?

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nocturne00

Try out the Cut Threads or Twist and Shout Tutorial by JD Mather,

its very similar to making a leadscrew.

Check his profile, the link is on his Sig.

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-TJ
Try out the Cut Threads of Twist and Shout Tutorial by JD Mather,

its very similar to making a leadscrew.

Check his profile, the link is on his Sig.

 

Thanks, I'll read that & give it a try!

 

Thanks for the other replies as well. If there's a thread button in '09 I haven't found it yet!

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-TJ

Looks like I'll be trying again today - while my leadscrew looked good, aside from being comprised of 16 sections, today the file will not load - STRIKE THAT - the file seriously just took the better part of 10 minutes to load. It's just under 5mb, but apparently very taxing on a dual core 3Ghz machine with 4Gb of ram.

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SilverTiger

Possible solution. Here's a walkthrough of a bolt I created. (It's a step-by-step, I know, but I like to be thorough nonetheless.)

 

 

Create a circle and divide it 20 times.

1.jpg

 

Array your circle down the Z axis (or whatever axis runs perpendicular to center) 21 times and move your nodes to each circle accordingly; your first node (which should not have been moved) will be copied to the same exact postion on the 21st circle to restart the pattern.

2.jpg

 

Create another layer and offset you first circle whatever the width of your thread is going to be and divide it 20 times.

3.jpg

 

Repeat the same process and move the nodes to their respective positions on each circle, following up with your first node as your last on the 21st circle.

4.jpg

 

Erase all circles except the first two. (Use them as reference points, and then later on extrude the inner circle into a bolt or pipe.)

5.jpg

 

Create another layer and draw a spline on each set of nodes.

6.jpg

 

Set the surftab system variable to 64 -

Command: surftab1

Enter new value fo SURFTAB1 : 64

Now create a ruled surface using the splines as your edges

7.jpg

 

Now you can copy your thread end to end as many times as you want and make you pipe or your bolt or whatever. I hope this is what you were looking for.

8.jpg

 

But of course, this is only a 2d representation of the thead. To actually give another dimension, you have to copy the interior spline to both sides of the exterior spline. This is the top view. To the left is the original two splines. The larger is the outer, and the smaller is the inner. To the right, I have copied the inner spline .125 units in both directions on the Y axis.

9.jpg

 

Then I drew 3 ruled surfaces to connect all of my edges...

10.jpg

 

End Result:

12.jpg

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-TJ

SilverTiger, wow thanks! I'll have to try that out.

 

I had mild success modeling the leadscrew by drawing & extruding each lead (each along it's own helix) and then subtracting them all from a cylinder. The model still takes more than a couple minutes to load now, but once it's up all is well. Seemed like the harder way to go about it rather than my first effort where I simply had drawn a cross section of the lead & tried to extrude/twist it.

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shift1313

in acad 05 i modeled a thread just like silvertiger showed here. Its a very effective method. although i didnt use circles. i just drew a vertical line, did an array for the number of segments i wanted for my thread pitch for say 1". then i did a line back in the Z direction, re-oriented my ucs and did an array of this line. This line in the z will be the location of each line segment from the first part. the amount of lines you use will determine your resolution. I think i did an array of 30 lines in the first step and each variation back in the Z direction was like .01".(cant remember the exact numbers i used).

 

V4TimingSpline.jpg

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SilverTiger

I'll have to try that sometime. Anyway, I read TJ's post and figured I could give it a try - it was my first time modelling a screw, so I had to figure it out along the way.

 

Glad I could be of some help to you TJ.

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shift1313

here are a few screen shots i just made.

screw.jpg

screw2.jpg

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catfan

First, draw a helix with diameter equal to the OD of your leadscrew and a turn height of 1.5". Next, draw a rectangle whose length is the OD minus the diameter of the shaft and whose width is the desired material thickness.

Snap the midpoint of one of the short faces of the rectangle to an endpoint of the helix so that it extends toward the inside of the helix and is perpendicular to the spline at the snap point.

Sweep the rectangle along the helix, and (when prompted) select "Align" and choose "no".

 

That should do it.

 

I can draw one and attach it as a sample, if that would help.

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ReMark

Sure, why not. Post a sample.

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JD Mather
I can draw one and attach it as a sample, if that would help.

 

Help who? This thread is 4 years old. Surely the OP has figured out this problem.

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fuccaro

Post the sample, Catfan!

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catfan

Sorry, I din't pay attention to the age of the thread because I found it while searching for an answer to a question of my own. (How to draw realistic NPT threads. I still haven't figured that one out, because Sweep behave differently with a conical helix.)

 

Anyway, an easier way to do something is always useful, so my sample is attached, showing the setup and then the result of applying the Sweep.

LEAD SCREW EXAMPLE.dwg

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ReMark

Thanks for sharing. BTW...Welcome to the CADTutor forum.

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