Creo Community Challenge March 2024: Twisted Pairs

Written by: Dave Martin
5/3/2024

The March Creo Community Challenge focused on designing with curves and sweeps:

• Using part modeling features, design a twisted wire pair that passes through at least three non-planar points.
• (Bonus) Using Flat-to-Screen 3D Annotations, create parametric notes so that a user can modify the twisted pair. For example, the diameter of the wires or rate of twist (similar to the pitch of a helical sweep). Is your modeling robust enough to handle dimension changes?
• (Extra) Model two, three, or four twisted pairs that travel along the same trajectory, like a CAT6 cable.
• (Super Challenge) Can you make two twisted pairs that twist around each other?

The submissions

User KDirth submitted multiple models. KDirth’s first model had a few curves created by sketches, equations, and through points. These curves make an interesting shape where the wire passes through some points, and then at each end form a loop with the wire twisted around itself like a twist tie. These curves were consolidated into a single trajectory using copy and paste. Then they created a variable section sweep. The sketch consisted of three tangent circles centered on the spine (main trajectory). The sketch contained an angular dimension that controlled the clocking of the three circles about the spine. Then a relation using the trajpar parameter changed that clocking angle along the length of the trajectory. Straightforward and elegant.

I really like Kdirth’s second model. It looks like a CAT6 cable, with four pairs of twisted wires in a sheath. This is a good model to step through using the Model Player to understand the Design Intent. There’s quite a bit of construction geometry in this technique, including coordinate systems, points, curves, copies, and surface variable section sweeps. Interestingly, the wires themselves and the sheath/insulation are constant section sweeps. The net result is an extremely realistic-looking cable.

The third model was a braid of four wires that twisted around each other. It used constant section sweeps only. The twisting was achieved by four equation-driven curves. Interesting. I had not considered an approach that didn’t use a variable section sweep.

KDirth’s fourth submission had another novel approach. The 3D trajectory for the sweeps were created by intersecting two sine-wave shaped spline sketches. Four sweeps were based on this trajectory, and each sketch was offset a linear distance from the main trajectory.

Fiddix created a model with several parameters to control the aspects of the twisted cable. The model started with an array of datum points offset from datum planes. Then a curve was created through the points. A parameter for the curve length was created using a Datum Analysis Feature. The first variable section sweep created a flat ribbon that revolved around the trajectory. The locating angular dimension for this sweep was patterned, with the number of instances and increment driven by one of the parameters for the number of filaments in a bunch.

The outer edge of the ribbon becomes the main trajectory for each bundle of filaments. Once again, the curve length was captured by a Datum Analysis Feature. A second flat ribbon is created and patterned like the first one, and this pattern is then repeated to form the multiple bundles. An individual wire is created using a constant section sweep. The wire is reference patterned, using both the feature and group patterns.

The model was complimented by a Flat to Screen parametric note with dimensions like the diameter, pitch, number of wires in each bunch, and number of bunches. This is a fun model to play around with by modifying the values in the 3D annotation.

I highly recommend checking out this model. It would make a great teaching tool in an advanced part design class.

Bogdan submitted three different part models. The first depicted a twisted pair cable, including the copper conductor, its colored insulation, and outer sheath. A curve was created through multiple points. This was used as the main trajectory for a variable section sweep that twisted along the length. The sketch was a line symmetric about the trajectory. This enabled the edges of the resulting surface to be the trajectories of each wire. The insulation and outer sheath were offset from the end of the trajectory, to enable you to see the structure of the cable. They applied colors to each element of the cable, including a striped red and white wire.

Their second model depicted two twisted pairs in an outer sheath. The approach basically “doubled up” on the first model. The edges of the first sweep were used as the trajectories for a second sweep. In this way, each twisted pair twisted around the other.

Bogdan’s third model used a center rectangle as the section for the first sweep. This resulted in four edges as the basis for four additional sweeps. This provided four twisted pairs that twisted around each other.

Several users submitted images of their approaches without attaching models. These helped foster the discussion among the community members. These people include users Patriot 1776, Constantin, and Bart Brejcha. Their pictures show quite a lot of capability with curves and sweeps in Creo.

What’s next

Once again, we had a fun challenge where users got to show their creativity and ingenuity in a deceptively complex problem. If you have not checked out the submissions, I highly encourage you to do so. Reflecting that this is indeed a community activity, the next challenge is being managed from a widely known Creo user and Community contributor. Check it out now!

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