CAD Modeling Question

[billywight]

Does anyone have any idea how to model a 4th axis type groove in a cylider in SolidWorks 2007? I'm trying to model a selector Barrel from a sequential transmission and can't figure out how to model the groove. The wrap feature doesn't give me the proper geometry. Any ideas?

(grooves like these in the picture)
http://www.chronic50s.com/ebay/shiftdrum.jpg

[billywight]

One more thing - I made a spreadsheet that gives me cartesian and cylindrical coordinates of the groove positions, but can't figure out how to link it to SW to drive sketch points in the model. If I could do this I could just use spline on surface usning these sketch points and sweep a groove cross-section through the spline.

Oh, and the curve through XYZ points doesn't work either because the curve does not lie on the surface except at the points defined by the spreadsheet. (it would only work if I had an infinite amount of points)

[FryGuy]

Sweep Cut? You could do a 3-d sketch along the outside and cut the groove.

Better question is how would you machine it? Cast maybe, but i would imagine the grooves need to be pretty precise.

[rjwoods77]

Fry Guy,

Live tooling on a cnc lathe would do it easy.

http://www.haascnc.com/news/new_files/LATHE/TL-15.wmv

[FryGuy]

damn, cool video. I wasn't thinking live tooling. The chuck change on that machine is just crazy.

Our cnc lathe is ancient, i have enough of a time trying to cut threads.

[billywight]

Sweep Cut? You could do a 3-d sketch along the outside and cut the groove.

Better question is how would you machine it? Cast maybe, but i would imagine the grooves need to be pretty precise.

Yeah, a sweep cut will work, but how can I link the dimensions of the 3D sketch to the points defined in my spreadsheet? If I could just insert a bunch of refrence points using xyz coordinates (and link it to a design table or excel sheet) it would make this pretty easy, but I can't figure out how to do that.

Machining this is pretty easy with a 4th axis in the mill.

[Jersey Tom]

Ahhh. I tried doing this a while ago. Its a bitch. As far as I'm concerned it aint really possible. Mapping the path to a cylinder and following the paths you want..

I'd do it on a 4-axis mill myself. In MasterCAM doing the geometry for such a thing is super easy. Draw a flat pattern of the shift grooves and wrap it around an axis.

[Anday]

I don't know where your origin is, but you could offset planes normal to the axis of the part at the different z-coordinates. That way when you sketch on those planes you only have to dimension an X and Y. Still a lot of work and i would really suggest re-naming the planes for easy reference to your distances.
After plotting those points you should be able to connect the dots pretty much with a 3D sketch to be used as your sweep path.
I'm really not sure if this is the best way but it makes the most sense to me with the data you seem to have.

[repeatoffender]

could you not create a design table for the points?

spline away and then input the values from your spreadsheet. i.e. one point per set of co-ordinates. splines the points?

[Jersey Tom]

I still say the best option is not to waste your time on CAD and spend it on CAM instead, where making that part is really easy. Does the solid model *need* to exist?

[Dr Claw]

so.....i did a VERY NICE write up on how to do this using surfacing, but IE crashed..so im going to try to recapture what i wrote 5 minutes ago...

create a sheet of surface that bisects your barrel's OD at desired location of the centerline of where you want the track made (this is just a properly dimensioned sketch line, then extruded as a surface).

the next step is to work a semi-circle into the newly created sheet. this isnt as easy as it sounds though, because its a couple step process.

-first, make a semi circle sketch wherever your design requires it to be (could be on some weird angle). extrude one way, making sure it passes through your barrel's OD entirely.

-second, your going to make a "clearance surface" that will make it easy to stich this mess together

this clearance surface is just a circle with a slightly smaller radius than your existing barrel's OD, and also extruded so it passes through BOTH the semi circle and the sheet. use this surface to trim -towards the inside- BOTH of the previous two surfaces.

third, use the semi circle surface to trim the sheet surface towards the inside yet again, and stich these two surfaces together. dont forget to add a fillet both sides either!

this next part, your going to have to do some hunting because solid workds dosnt include this in the standard buttons. in the tool bar customize menue, look for INTERSECTION CURVE in the sketch category. drag and drop this into your toolbar space.

providing you have a good stiched surface from above, click the intersection curve button. next click the OD of your barrel. then click your flat sheet, then one filleted surface, then the semi circle, then the other filleted surface. you will see a sketch drawn on the barrel OD to the shape of the surface.

use that as your sweept cut profile and hide all the other silly surface bits so you dont scare yourself or teamates http://fsae.com/groupee_common/emoticons/icon_smile.gif. Rinse and repeat for other tracks.

dont get discouraged either, there is a learning curve to surfaces so just try this - it will work. only takes 3 minutes to do too

[ad]

Originally posted by Rob Woods:
Fry Guy,

Live tooling on a cnc lathe would do it easy.

http://www.haascnc.com/news/new_files/LATHE/TL-15.wmv

hey rob,

do you have the main link to more of these videos?

[billywight]

I still say the best option is not to waste your time on CAD and spend it on CAM instead, where making that part is really easy. Does the solid model *need* to exist?

Yeah, I'm starting to think the same way. I just used the wrap function to get a representation of the grooves and can program the NC off the sketch I used to wrap.

http://img123.imageshack.us/img123/482/selectorsq1.jpg

Dr Claw - your approach seems like it might work, but I didn't quite follow what you were describing. Can you post a screenshot?

Thanks for all the suggestions guys.

[Francesco Esposito]

Hi i'm new, i'm from the University of Palermo (Italy).
I'm tryng to start the FSAE project here, and believe me it's very very difficult :-)

So i need your help, i need the CAD models of the entire transmission gears and shafts of a cbr600 engine. Either if it's not Honda and if you have other transimissions it's useful for me
Also dwg is useful, because i need measurements.

If you have something that could help me, send me an e-mail at: expcic@hotmail.com.

Thanks to all

[exFSAE]

Ok.. in my few years of FSAE we never once needed CAD models of engine internals. That was with an established team.

What on earth are you planning on doing that involves all this, as a startup organization?