epicyclic curve
in [SolidWorks]
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From: Giorgis on 25 May 2005 08:44 I may have things confused. http://watchmaking.csparks.com/CycloidalGears/ Effectively I need a wheel withone tooth in it to cut a flat surface. G PS: I am having trouble using the macro you supplied. Could you give me some pointers ?
From: That70sTick on 25 May 2005 08:48 An involute (gear tooth) and an epicyclic curve are very similar. Picture the following for drawing an involute: ·A string wrapped around a spool with a pencil on the end. ·As the string unwraps with the string held tight, the traced path is an involute. I once needed to cut a true involute on CNC from SW geometry. I laid out a series of construction sketches (8 in total) equivalent to "unwrapping" string at 5° intervals. The endpoints of the 8 "strings" were used to anchor a spline. An additional aid was that the "strings" were instantaneously perpendicular to the involute path, making it possible to use tangent constraints to help form the spline.
From: TOP on 25 May 2005 09:03 1. Make a dummy macro by turning record on and then off. 2. Save the macro as epi or some other descriptive name. 3. Open the macro you just created in macro editor 4. In the editor window erase everything. 5. Paste in the macro I posted 6. Start a new part. 7. Make sure the name for the Front plane matches that in the macro. 8. Hit run. The macro should draw a close approximation of an four petal epicycloid.
From: rmchugh on 25 May 2005 19:43 TOP wrote: > 1. Make a dummy macro by turning record on and then off. > 2. Save the macro as epi or some other descriptive name. > 3. Open the macro you just created in macro editor > 4. In the editor window erase everything. > 5. Paste in the macro I posted > 6. Start a new part. > 7. Make sure the name for the Front plane matches that in the macro. > 8. Hit run. The macro should draw a close approximation of an four > petal epicycloid. > By the way, the units for the 'a' dimension is in meters. You may want to convert unless you need a 60+ foot epicyclic. I thought the macro wasn't working until I thought to zoom out. .... ->Try this. Just set a and m. a is the OD of the circle around which you ->want an epicycloid and m is the number of cusps. Start a part. This ->will draw a sketch on the Front plane. ->'****************************************************************************** ->' C:\DOCUME~1\kellnerp\LOCALS~1\Temp\swx2044\Macro1.swb - macro recorded on 05/24/05 by kellnerp ->'****************************************************************************** ->' a is the OD of the circle around which you want the epicycloid. m is ->the number of cusps. ->a = 20# ->m = 6# ....
From: TOP on 26 May 2005 00:09
Good point. SW works in metres. Well I just threw it together in 15 minutes. User friendly it ain't, but it works and it is layed out reasonably logically to the point that it can be tweaked. Any parametric functions can be inserted for x and y. Even z can be added if you want to open a 3D sketch. . You should also be aware that at the inflection points where the epicycloid touchs the base circle the spline does not come to a perfect point, so in that region it is inaccurate. To fix it play with the indices in the point generator to get just one petal. Then the spline should be pretty accurate. |