kencaz Posted December 16, 2009 Share Posted December 16, 2009 this is what i did according to kencaz approched see the gap? Well, If you make your sweep profile larger so that the swept helix ID is slightly smaller then the shaft OD then you can use the shaft to slice the helix the exact diameter of the shaft, thus no gaps. Use subtract. KC Quote Link to comment Share on other sites More sharing options...
orex Posted December 16, 2009 Author Share Posted December 16, 2009 i`ve already done the overlapping through the core thing that kencaz mention earlier (see my earlier post) then comes another problem 1) the front of the worm fin hold different thickness than the ending as it has the attachment so i have to do 3 types of fin (fin with no attachment, fin for base of attachment and attachment fin) the result.. they wont fit.. 2)as the front of the worm is thinner (not shorter or smaller in size, just thinnner) than the back of the worm so I`m not sure how am i going to slice em for them to fit.. 3) also the lenght of each fin is different so I end up making 7 helix and now trying to join them together like a jigsaw puzzle.. and the problem of doing that is that I dont know why, when I was sweeping the fin there will be a different angle although I do it in the same view.. (see pic) fortunately all the other fin fit in nicely.. but on the bright sight my wormscrew exercise is nearly finish... just a coulple more problem solving and its done... Quote Link to comment Share on other sites More sharing options...
SEANT Posted December 17, 2009 Share Posted December 17, 2009 With the variable pitch, this is a complex solid. It is not something I’d be eager to model – except it made a good test subject for some custom routines I’ve been developing. The attached matches the 2d Layout pretty well, though I was unsure about several details. Specifically, my grasp of the situation regarding the attachment fin is a bit tenuous. So much so, I didn’t bother dealing with any of the attaching hardware details. In any event, here is my take on the wormscrew and attachments. Worm.zip WormAttachments.zip Quote Link to comment Share on other sites More sharing options...
orex Posted December 17, 2009 Author Share Posted December 17, 2009 wow although the attachment does not quite fit so I will try to do some modification on it.. but you really did the whole thing perfectly SEANT can you explain how you did it? Quote Link to comment Share on other sites More sharing options...
SEANT Posted December 17, 2009 Share Posted December 17, 2009 A quick look through the earlier posts reminded me that this is a homework assignment. I, as well as the rest of the group, don’t usually offer more than suggestions on specific details to schoolwork. I suppose it is just as well, then, that the model I posted previously is not exactly as it should be. It still would require effort on your part to make it presentable. I have to wonder, though, if this is a sensible assignment for students. It sounds like the dimensions were measured from an actual part: Was the professor aware that the fins changed pitch? As previously mentioned, straight AutoCAD is not ideal for this type of modeling. I only attempted the project because I had a tool, not commonly available, that helped the effort. In light of that fact I’m not sure how helpful it would be if I gave a full explanation. Quote Link to comment Share on other sites More sharing options...
orex Posted December 17, 2009 Author Share Posted December 17, 2009 yep I did measure the worm my self.. the assignment is 'to measure and put it in autocad 2009 in 3D and 2D with annotation..' I`ve donwnloaded your file and did some modification is some areas once its finish I`ll upload it although its not a good one.. what tools did you use can you tell? I think my lec is no prof he just know how to use autocad and the collegge hire him i think he did know about the fin lenght differential and he did warning us about it to be extra carefull.. I`m not sure even he can do this assignment lol! Any way I think it would be very usefull if you could share your idea on this assignment SEANT.. since I really would like to know other stuff that can be usefull than just autocad... Quote Link to comment Share on other sites More sharing options...
SEANT Posted December 17, 2009 Share Posted December 17, 2009 I don’t have time right now (I will be away from the office for the remainder of the day) but will collect the various steps into a drawing and post it sometime tomorrow. Quote Link to comment Share on other sites More sharing options...
fuccaro Posted December 17, 2009 Share Posted December 17, 2009 Years ago I wrote a Lisp for variable pitch helix: http://www.cadtutor.net/forum/showthread.php?t=78 Scroll down to post #23 and see if you can get some help from... Quote Link to comment Share on other sites More sharing options...
SEANT Posted December 18, 2009 Share Posted December 18, 2009 As I see it, the most challenging issue with the assignment was the variable pitch aspect to the helix. AutoCAD does not have anything ready to go for that type of entity but does provide several methods of custom processing. One way would be to setup an Excel spreadsheet to do the Math, and then import the data for entity creation. Another way to automate the process is with one of the available programming languages. Fucarro’s link shows his excellent example written in Lisp. I used the .NET routine posted here (warning: routine is still in testing/tweaking phase). http://www.cadtutor.net/forum/showthread.php?t=41260 Whether or not you teacher allows for the use of custom routines may be something to investigate. The attached only processes the upper screw portion; the remainders would process similarly. A. The screw helix fits within a 310 dia cylinder X 617 tall. I used the CPM portion of UVVectorMapping routine to unwrap that cylinder. The helix makes three turns, so I copied the map 3 times in the circumference direction. I placed level indicators at the appropriate points of those three maps. Created a spline based on the level points. B. Used the CVP portion of UVVectorMapping to remap to cylinder. C. Copied the mapped helix up 35, connected endpoints with two lines, and lofted those lines with the helices as guides. D. Thickened (100) the lofted surface to create solid. The 100, instead of 99, the extends the screw beyond shaft solid, thus allowing a better Boolean operation. I then sliced of the top most section of the screw solid to match the 16 dimension. WormScrewExpl.dwg Quote Link to comment Share on other sites More sharing options...
orex Posted December 21, 2009 Author Share Posted December 21, 2009 as your solution is nearly completing the assignment I havent ask my lec if he allowed custom routines I`ve already submit the assignment today (mon 21 dec 09) cause we have a public holiday on last friday.. supposed the dateline of the assignment is on that day but i think my lec miscalculate the holiday and were force to extend the dateline lol! any way my internet connection have a little problem ad I only manage to upload some image of my finish assignment and I will try to upload the dwg file here as I have some other question regarding the screw hole Quote Link to comment Share on other sites More sharing options...
orex Posted December 22, 2009 Author Share Posted December 22, 2009 the file for the worm screw is 13mb.. can it be lowered down? my connection is not that good so it takes ages to upload.. regarding the screw hole as you can see in the attachment and my file attached in earlier post it is about 45degree for both side from the middle.. the cylinder is r12 and the polygon hole is circumscribed r17 with 6 faces.. the problem is that I have no idea how to make it fit at the screw and attachment and because of that I end up sending my assignment with kinda crooked screw hole I just hope that the lec doesnt realise it.. Quote Link to comment Share on other sites More sharing options...
SuperCAD Posted December 22, 2009 Share Posted December 22, 2009 X-ref the screw into the drawing. It will reduce the file size. Quote Link to comment Share on other sites More sharing options...
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