Is anyone really good with curves functions ?
Is anyone really good with curves functions ?
(OP)
I'm trying to some angled curved cut outs on the cylindrical body. I have tried just about everything to make the cut work but I cannot get it, so I was wondering if there is any one who's really good with curves that might wanna help me out. It's kinda hard to explain in writting, if someone would like I can send a particle model to help describe what I am trying to do.






RE: Is anyone really good with curves functions ?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Is anyone really good with curves functions ?
http
here are some links to the image of what i have.
RE: Is anyone really good with curves functions ?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
But are you saying that it is actually not possible to make this cut accurately in solidworks?
RE: Is anyone really good with curves functions ?
HELICAL GROOVE thread559-41468
Helpful SW websites FAQ559-520
How to get answers to your SW questions FAQ559-1091
RE: Is anyone really good with curves functions ?
I did a machine with a full 180 degree barrel cam. actually 2 of them. It was a bitch. SW support essentially said I was on my own. I found that I could get 90 degrees around the barrel but the sweep would roll over itself if it would work at all. I finally projected points on the surface of the cam and created spline lines for a path that was adjustable. I then made the roller and in an assembly, rolled the roller along the created path and adjusted as required. It was another trick to get the roller to be tangent or to just stay in contact. I really used a narrow roller and then redid the path untill I got what I needed. It was a nightmare. As it turned out we couldn't make this thing in our CNC as we don't have a 4th axis so I then cut the cam into sections to fit material thickness available. This was another nightmare as for some reason I couldn't break the link between the original model and the save as copy new models I made for each section. I now have to be very carefull when making changes to the cams, as they can cause unexpected results in the other models. One of the sections was modified at assembly and I had to recreate this one. I used a digitized point cloud, again it was said it couldn't be done, and created a surface which I used to cut the blank so to speak. This was machined nicely by our cnc and it worked even better than the hand ground model. Fortunately the whole thing was in HDPE so machining was relatively easy. The machine is well past the 5 million cycle mark so it is working well.
There are cam software programs that do just this type of thing but we couldn't justify the cost since this was a 1 off machine. Camco and Stelron are two big users of barrel cams.
99 Dodge CTD dually.
RE: Is anyone really good with curves functions ?
As I said previously, if you can get the same size cutter as follower to follow the correct path at the cam outside surface then the cutter will get the sides right for you. Also, you may be able through trig to show that the difference from parallel on the cam sides is insignificant. It looks like your barrel is rather large, your groove rather small, your motion profile fairly small in slope, and the line of contact fairly short. All of those tend to minimize the "dovetail" effect on the groove.
RE: Is anyone really good with curves functions ?
1. handleman is making a lot of sense here. Understanding helix geometry is the key to this problem.
2. I would discourage anyone from using the loft method. It is a difficult way to get even a pretty model and it is not useful if you want an exact representation of this barrel cam.
3. Swept solid capability would make this easy to do exactly. Until then, I think that using surface modelling techniques is the easiest way to get an exact representation as follows:
a) make your base ring, cut two holes for your start and end positions, and then do a simple undersized helical sweep to join the holes
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b) Create a "surface-sweep" by sweeping a line that represents your cam follower axis along your helix path. Then create two "surface-offset" features by offsetting by the follower radius plus clearance.
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c) Now use these two surfaces to do two separate "Cut-with Surface" operations. Done.
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The key point is that the surface offset creates the cam walls exactly. Theoretical mathematical types can prove this using "envelope theory".
This is actually a relatively simple problem. It gets a lot more complicated if you have a track bottom where there is a complex fillet generated at the corners.
I hope this helps. Please share if anyone has a better way of doing this.
ERT
http://www.akeng.com
RE: Is anyone really good with curves functions ?
Ok, I've tried some of your suggestions and have had some
luck but i'm not completely convinced that this is the path i am looking for. In the link below I drew a stetch showing the mechanism, could anyone look at this and give there opinion on what the cam slot would look like ?
ERT in the model you created does that cam slot rotate away from being normal the surface of the barrel ?
http:/
RE: Is anyone really good with curves functions ?
Chris
Systems Analyst, I.S.
SolidWorks/PDMWorks 05
AutoCAD 06
ctopher's home site (updated 06-21-05)
FAQ559-1100
FAQ559-716
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
Simply sketch the geometry of the outside of the cut (on the surface)--you need the arclength. Dimension the vertical (axial) distance relative the cylinder appropriately. Use wrap to wrap the sketch onto the outside face (this is why you used the outside[final] dimensions) and select deboss. Pick an appropriate depth and voila. Keep in mind that it literally wraps the sketch not projects so the dimensions of the sketch are unchanged when put on the face of the cylinder.
Here's a picture of the result with the measurement to explain what I mean: htt
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
RE: Is anyone really good with curves functions ?
My example only makes sense if the follower axis and cam axis always intersect. I assumed that the follower translates parallel to the cam axis. A follower that swings on a lever would require a different approach.
I find your mechanism sketch confusing. Can you explain a bit further? Does the cam translate and rotate? What is the objective? I think you may have very poor pressure angles, but it is difficult to be sure until I understand the mechanism.
ERT
RE: Is anyone really good with curves functions ?