Keeping shape integrity while using spline

[Sebastien Carreau]

Hello,

First post! I'm currently making parts for an instruments company, more precisely trombone custom tubing. So lots of sweeps using a spline and a circle to make the parts. To bend this tubing we will be machining a mold of the parts, and once both halves are assembled with the tubing roughly bent within it we pass ball bearings through the tubing to smooth it out. Tolerances on the shape in the mold is +/- 0.001'', and the wall thickness for the brass tubing is about 0.04''.

All that being said there is very little margin for error, and the sweep that I'm creating needs to be perfectly round all the way through, if not the ball bearing will not go through the shape. How do I ensure that the sweep is perfectly round all the way through?

NOTE: I am also using the spline handles to achieve the particular aesthetic my client is looking for. I noticed that when too extreme it creates a bump in the shape of the part.

NOTE II: I also used the spline curve line to try and smooth it out as much as possible but some shapes are just sharp to smooth out completely.

Any words of wisdom are appreciated.

 

[SBaugh]

Sometimes I will us Construction geometry to control the tangency of the ends of my spline. Maybe you can use line or arc construction geometry along with Tangent relationships to help control your spline? I have used "Fixed" relationship per points of my spline once I have them in the position I want.

Scott Baugh, CSWP
CAD Systems Manager
Evapar

http://www.evapar.com

"If it's not broke, Don't fix it!"

faq731-376

 

[Theophilus]

Also, when you toggle the "minimum twist" in a sweep that can help keep the swept form more consistent.



Jeff Mowry

http://www.industrialdesignhaus.com

A people governed by fear cannot value freedom.