I'm working on some bottle concepts and I have a need to model standard plastic bottle threads. These threads are designated by a diameter in mm and how many threads are on the bottle. Example: 33-400 The 33 is the diameter and 400 refers to a single turn of the cap. Manufacturers like Aptar make bottle tops of various types to fit this spec. I happen to be looking at dispensing lids (think Heinz Ketchup bottle). While I've found specs for Major diameter, Minor diameter and TPI, I have found precious little that describes the thread shape itself. I've tried to reverse engineer a sample thread from... you guessed it.. a Heinz Ketchup bottle. I feel that my venier caliper and micrometer are not doing this effort justice.
Does anyone out there have a DWG file or Inventor model of the thread profile?
I'm using the coil command to create the thread on the bottle neck. It works okay. An issue arises with the thread termination. The threads on the bottle itself "chamfer" into the bottle neck. While I don't think I can do this with the coil command itself, I was interested if anyone has been able to create the "lead-in" for the plastic thread. I would be interested in any suggestions.
I hardly consider myself to be an Inventor expert. So, if you have discovered alternatives to modeling the thread I'm all ears.
Thanks for your consideration!
Solved! Go to Solution.
The lead in can be modeled with coil (enter a taper angle for the helix).
A while back someone posted a url for standard dimensions for these threads - a Google search might turn something up.
Experimenting with Taper angle on the thread design itself yielded a taper for the coil helix itself. Very interesting results... but not a thread lead-in. Again, I may be using the wrong options in the coil command itself. I am using Inventor Version 10.
I have attached what I've been able to Google regarding standard bottle threads. This is probably the best reference I've found and it comes from the Society of Plastics Engineers (??). However, it still doesn't actual detail the thread profile.
I may be picking a nit here, but I come from an Aerospace background and a fine thread and a "J" fine thread make a big difference in holding an aircraft engine together. The only difference being a radius condition on the "J" thread itself.
Many Thanks for your quick reply.
Experimenting with Taper angle on the thread design itself yielded a taper for the coil helix itself. Very interesting results... but not a thread lead-in.
Attach the ipt file here.
It actually takes 3 Coil features.
One for the main thread pitch and two for the lead-in and out.
That is perfect....
What did you use for the thread profile sketch itself?
As I understand, your response and images... You used a 400 series main ptich (1 turn). Afterwords, you projected the thread profiles to sketch planes used a taper angle with a partial pitch 1/8 turn to create a lead-in and lead out.
Great model of a Gatoraid bottle.
Oops, don't pay attention to those numbers in the browser.
That was an example a student did and it didn't look correct so I moved the top out of view (notice that you can't see the thread in that image - but he was trying to reproduce steps as I showed in right image on my example).
The bottle on the right and with the close-up is one that I did.
I can't read the numbers in the browser anyway.. Do you have a detail of the thread profile? or a look at the browser for the correct model?
I believe that this will do it. I did go to your web site at the college, but didn't find anything specific in the tutorials.
BTW: Great job with the tutorials and all the work your doing with the students. It looks impressive.
I've been pretty busy lately but I wanted to post an Inventor file that I was using to model Threads on a bottle neck per your suggestion. I have a pictue of the threads below.
I not sure that I have the thread profile right. I think that I didn't use the coil command correctly either. Any help is appreciated.
Well with help from JD and a little internet persistance, I've figured out threads. Technically this is referred to as "neck finishes" by SPI. Neck finishes are defined by SPI. While the thread profile itself is defined by ASTM standard (ASTM D 2911). ASTM D 2911 is available for purchase on the internet for about $40 USD.
I have attached a HTML file, found on the net, that defines the neck finishes. I have also included a pic of the 22-400 neck finish that I modeled in Inventor. I choose a "M-style" thread that is common to plastic bottles and is referred to as a "buttress thread". I'll leave it to the reader to tell us why it has this name. Hint: think Cathedral of Notre Dame.
As far as the operations for modeling in Inventor, it's pretty much a snap. You'll need 3 coil commands; main thread, lead-in, lead-out. It takes some experimentation, but use the "Pitch Revolution" option for the main thread. For the lead in and lead out use a negative taper and a fraction of a revolution. Inventor does the rest. (Thanks JD!) Remember...Rightee tightee, leftee loosey.
JD, I think that the thread profile used in your example isn't quite correct. The model itself is missing radii for the thread profile. I don't mean to be a stickler.. but as my first post indicated a missing radius makes a big difference in performance.