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Capping threads

sully

New member
I have modeled a thread form which will be made in plastic and therefore would like to cap each open end of the thead.At present I have used a swept blend to create the cap , if I try toapply tangency, the bottom of the cap lifts from the thread surface so insteadI have added rounds to smooth it out. This works okay but the trajectory of the cap does not follow the helical trajectory of the thread..........any better ways of capping threads out there?
 
I use another helical sweep to cap or blunt start a thread. I create an axis the radius distance I want from the end of the thread. That requires a plane also. (See the picture) I use the helix angle of the thread to figure the pitch required for the blunt start. The profile is on the minor dia surface and the section is the section of the end of the thread. Not sure if this is perfect but it works.


View attachment 2334


View attachment 2335
 
sip:



I just figured out what you show in
your captures. A student showed me over the weekend your
exact techniqe. Nice. I should pay closer attention.
 
The only problem I've had with that gradual tapering technique is getting the exact location of the thread start or end is a bit more difficult. The start will emerge a little farther up the cylinder from the sketchplane. Otherwise it works great. Someone actually just showed me this recently also. Before I was using Swept Blend with the End Section a point which is the best way imo
 
To All,

The picture that Sip made is a good idea. You can take that a step further. Instead of having an angled line you can add a radius between the two segments and get a nice transition. The thread will then come out of the shaft body, revolve helically, and then go back into it with no visible transition. A single feature to do it all. I offset my section sketch from this sweep profile.

View attachment 2861

Have good one...

Mag
 
Hey Guys,


I need to do a similar Blunt Start on a 1.625-.01 P Triple Start thread. I tried the revolve idea but I ended up gettting non-manifold edges. The model has to be accurate because a mold will be made from it. I'm still in college and I'm interning over the summer and this is a project my boss gave me. Can't send you the part or show you the whole thing... but here are some screen shots of the threads. Anyone have any ideas?


P.S. Can't do a protruded helical sweep because the thread cut has to stop dead in the Maj Dia. Must be a cut(s).
 
The revolve idea seems like it would create a thread that wouldn't work given the lack of slope.

You can achieve a gradual start and end to the thread using a variable section sweep (VSS) and a datum graph that would have the thread on the surface at the start and raise up in a curved fashion as the revolve option does.

If you create a Datum Graph feature called G1 Insert > Model Datum > Graph
You can create a graph 36 units long 1unit = 10degrees for the datum
graph and sketch a line at the thread height at it's highest and bring
it to zero with an arc of some type at the min and max point of your
graph. Datum graphs require a sketch csys.

You can drive your relations for a Variable Section Sweep using the following relations.
sdX = evalgraph( "G1" , trajpar*(L/N))sdY = Pitch * trajpar * N
/* L is the length of your datum graph from start to end (Range) and N is # threads. trajpar goes from 0 to 1 during the sweep.

Replace sdX with the dim symbol of a dimension from the trajectory to the flat surface of the thread.
replace sdY with the dim symbol from the trajectory to a point on the thread profile.

N=1 for 1 thread

THESE RELATIONS are for a single thread you can multiply by N for number of threads.
e86c046a.jpg


Michael


Edited by: mjcole_ptc
 

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