arc length to define sketch

[tmalinski]

When I develop a sheetmetal part with multiple tangent bend radii I often need to compensate for recoil or material spring-back when forming. A basic rule we follow is when altering a rad for recoil never change the arc length or your total flat blank length will not be acurate. So my question is..

How can I use the arc length as one element to define a sketch?

In concept I would construct a sketch of my form profile with tangent relations, lock all flat lengths and arc lengths. I would simply modify the radii dimensions for recoil and the entire sketch will adjust its shape accordingly but will always maintain the overall form profile length (flat blank length). We have a custom lisp routine in autocad that does this for us. It saves a lot of time when developing complex formed parts.

Can I possibly achieve this with table driven dimensions? can I control arc lengths in a table? if so then my problem is solved

Tom Malinski
Sr Design Engineer
OKay Industries
New Britain CT

 

[smcadman]

Have you tried modifying your k-factor to match your tooling? If your lisp routine is simply a .lsp file, open it up and read the coding. You might be able to find out what k-factor or formula is being used to derive the flat blanks.

Flores
SW06 SP4.1

 

[tmalinski]

In most cases, the K-factor is not changing when developing the recoil, just the rad value. If Solidworks could just make the rad and the arc length independent from each other I could define the sketch that way. Maybe I can use deg of arc and rad to define the recoil instead, and apply a formula in a table. I think that should work.
thanks for your reply

Tom Malinski
Sr Design Engineer
OKay Industries
New Britain CT

 

[TheTick]

Dimensioning arc length in sketches: with dimension tool active, select each end of the arc and then the arc segment.

 

[tmalinski]

Yes, that works well, but you cannot dimension the rad also without over defining the sketch. I want to change the rad but leave the arc length as is....

Tom Malinski
Sr Design Engineer
OKay Industries
New Britain CT

 

[BiPolarMoment]

In any given sketch I have no problem dimensioning the radius as well as the arc length, you must have a dimension somewhere else constraining it such that one or the other would suffice to fully define the sketch.

 

[tmalinski]

BiPolar
thanks for your input. I went back to my sketch and it would not let me dimension both. But thanks to your reply I looked a little closer and found another dimension that was causing the overdefined error. So I deleted it and now everything works as I thought it should.
Thanks so much.

Tom Malinski
Sr Design Engineer
OKay Industries
New Britain CT

 

[handleman]

You can dimension an arc with an arc length dimension. With the Smart Dimension tool active, first select the arc, then select its two end points. You'll get an arc length dimension that you can hold constant as you vary radius.