Are you able to make the pitch vary constantly or are you creating a "fixed" pitch coil a certain number of turns and then a second coil with a different fixed pitch?

I am refering to a coil that is constantly changing its pitch. In my case I have also got to make the coil od change at a constant rate as well.

I have managed to finaly complete a usable model of what I have explained above.

Cheers

can you post your model?



i'm trying to find a workaround for a variable pitch helix, and by variable i mean constantly changing, something like the feature in solid works.



Regards,

That i managed to do, i think the excel file i created is the same you wanted to post, but in this case, you will not be able to update your part if you change any parameter in the excel file. AFAIK, you'll have to re-import the whole file.

here is the model

Sorry JD, i don't have solid works, but i found the attached video while googling for variable pitch helix.



Thank you ravikmb5 for your part, but i was asking for a constantly changing pitch, and that we would use as a feeding screw at the infeed of packing machines, i.e. fillers, labellers... to feed the bottles with the correct pitch into the starwheel of the machines, so the pitch of the screw has to start as one bottle diameter and grow till being equal to the pitch of the starwheel of the machine.



Regards,

JD, thank you for your concern, i already explained what i want in the previous post.

i attached here a part (INV 2010) with constant pitch of 200mm.



i cannot share all information about the screw, all i can say is that i need the pitch to start at 200mm and end after 1m at 350mm, it must increase gradually, as smooth as possible.



I hope that helped,

how is that?



in my part i used coil, and the sketch is in the same plane of the coil axis. ain't that enough?



What i want is a part exactly like the one i posted in the post you lastly replied to, but the pitch must be varying.



My workaround (also described herebefore) is to put the equations of a helix in an excel sheet to calculate X, Y and Z with respect to radius and pitch for every angle, then import the cloud of points with an Spline passing through them all as a path, and sweep a profile on that path.

Ok, but how is that not good for me? and how to correct that?




I totally agree, i did this part in 5 seconds, only for visualization purposes.




Of Course you don't, please find attached the .zip and the link for the video herebelow



<!--[if gte mso 9]><xml>
Normal
0
false
false
false
EN-US
X-NONE
AR-SA
MicrosoftInternetExplorer4
</xml><![endif]--><!--[if gte mso 9]><xml>
</xml><![endif]-->
<!--[if gte mso 10]>
<style>
/* Style Definitions */
table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;}
</style>
<![endif]-->http://video.google.com/videoplay?docid=-6382369554824933261#




Regards,

Here's my attempt to do what you want. I suspect that what you're looking for is a groove cut into a cylinder or a cone, rather than the flight that I added to a cylinder, but the concept is the same, and this does start out at 350 pitch and ends at 200 over 1 m.

This is an IV2009 file, pull the EOP marker down step by step to see the process. Hope it's helpful.

Sam

How so? If you know your constraining conditions, you can generate the curve required. In this case, you gave the constraints of length, beginning pitch and ending pitch, and that was enough to nail down the curve, right? It's only an arc with tangent constraints at both ends.

Sam

Hey Sam,

I had a look at your part. Nice easy method to achieve the helix. I don't quite understand the principle / theory that led you down that method of modeling, could you perhaps explain the concept a little?

I wonder how this method would compare to the "mathematical method" mentioned before (importing calculated x,y,z, points from excel)?

Thanks,
Cheers

Hello JD, can you please show me your method? The best method i found so far was projecting a pline (line+circle) on a cylinder, the line creates the constant pitch and the arc creates the variating pitch, i am having trouble though in the tangencies. Should i create a fillet between the line and the arc? or just tangent? There is also the problem that you pointed out: the sweped sketch being not orthogonal to the profile. Can you please elaborate a bit more on this issue, i am sure it interests a lot of people.



Regards,

Howzit,

This method sounds the same / similar to sbixler's method. Have you had a look at the ipt. posted by sbixler? How does it compare to the method you are describing?

Could you perhaps post an example?

Thanks.

Hi JD

I understand the importance of the workplane being perp. to the sweep path. I was, however, refering to the method used to create the variable pitch helix used as the sweep path.

Thanks

Unfortunately this method will not work for infeed scrolls, because when you loft the bottle shape down the path, the profile banks to follow the path. This will make the bottle tip back.

here is an example of 3dsketch helical curve



can we do this with coil command

Spring with variable pitch