detailing plastic parts

[alwaysdrunk]

Hi!


i am new here. I am currently working on a plastic part and i am creating a pro/e drawing for it. Does anybody here has an idea about the guidelines in detailing plastic parts? i mean, the only things that needed to dimensioned (since plastic parts are complicated surface) thanks

 

[jlivengo]

Welcome!


If your part contains complex surfaces you are probably giving your model to the supplier to be to be used for the mold core and cavities. You will want on the drawing to have the dimensions that can verified by QC. Such as features that mate to other parts etc. Also overalls are good to have.


Hope that helps!

 

[alwaysdrunk]

thanks jlivengo .it gave me somehow an idea.But i want to have some "general rules" on plastic drawings if there is, or a good practice for plastic drawings. Thanks again...

 

[dgs]

We only dimension critical fits and inspection dims. We place a note like this on the drawing:
<BLOCKQUOTE dir=ltr style="MARGIN-RIGHT: 0px">


THIS PART WAS DEVELOPED AS A SOLID CAD MODEL. ALL TOOLING AND PROCESSING DEVELOPMENT SHOULD BE BASED ON THE CAD DATA. DIMENSIONS ON THIS DRAWING ARE FOR QUALITY CONTROL</BLOCKQUOTE>

 

[Mindripper]

I worked in this industry for several years, so I'll try to give you some advice and direction. dgs is on the right track: themodel itselfis a fundamentalcomponent of the part definition, unlike most machined parts. The function of the print is largely just for in-process inspection of critical or overall dimensions, not for completelt defining the part


We typically included the following notes on every drawing. Please excuse my use of all caps: you can copy and paste this way. I am not shouting.


NOTES: UNLESS OTHERWISE SPECIFIED


THISDRAWING IS BASED ON A SOLID MODEL, AND IS FURTHERDEFINED BY THE SOLID MODEL FILE (add your .prt filename here, including rev).


TOLERANCES ON ALL FEATURES ARE TO BE IN COMPLIANCE WITH THE REQTS OF THE SOCIETY OF PLASTICS INDUSTRY PUBLICATION 'STANDARDS AND PRACTICES OF THE PLASTICS INDUSTRY' FOR (add your generic material name here, or the name of an equivalentmaterial as agreed to by your molder).


SPI/SPE MOLD FINISH: (add appropriate mold finish designator here).


ALLOWABLE FLASH: (add appropriate limit here) MAX.


ALL EJECTOR PIN MARKS TO BE (within some value of flush, protruding or bElow flush).


ALL EJECTOR PIN LOCATIONS TO BE APPROVED BY (the customer's name here - probably your company).


TRIM GATE WITHIN (tolerance) OF FLUSH.





You can see there are two documents here you need to obtain: the Standards and Practices, and a set of mold finish samples. Mold-Tech is a good source for the mold finish standards: get a set of texturing standards while you're at it.


Additionally, specifying a gate location on the drawing is a great idea.


It's also acceptable to actually model the ejector pin locations, as slight depressions/projections or as colored surfaces in the model.


Coloring the surfaces of complex parting lines, side actions and slides in the model is usually appreciated by toolmakers, and aids in draft checking too.


If it's a multi-cavity tool, specify the location of a cavity marker (usually on an ejector pin).


Date wheels are also commonly used: specify a location.


And don't forget your recycling designator: the three-arrowed triangle with a number in the middle. Europe demands these: everybody should be using them, regardless of the material. The world is going green: get with the program.


Is this enough to confuse you? I'm sure there is more ....

 

[Mindripper]

P.S. Be sure to specify commercial or fine tolerances in the note regarding the material spec from the SPI (Society of Plastics Industry) publication.

 

[dgs]

In my experience, you cannot get the SPI finish samples from Mold Tech. You need to get them from SPI. Mold Tech has a great set of texture samples, though.

 

[magneplanar]

alwaysdrunk,

It might be useful for you to talk with your mold maker before you proceed. Some mold makers have special details they want you to specify. In my experience, I make a drawing for the tool maker with a variety of specifics added just for making the tool. I then make a release drawing for the production inspection that removes those details, and specifies things I want observed in the off tool part.

If your tooling drawing and part drawing are the same, then you should put all that you want for tooling and production into the details.

I suggest you talk to your coworkers as well in case there is a company standard.

In addition, or agreement, with some of what has already been posted...

Some basics:
expected plane or location for the parting line
preferred gate location and type
special limitations such as flash, parting line mismatch, gate trim tolerances
critical dimensions that affect form and/or function

Specific details that may only apply to the tool maker:
texture or polish of the mold steel to produce the part texture
special features you expect such as areas of interchangeable inserts, sliders, lifters etc
define areas that should be free of marks or mold features, if any
number of cavities expected and EAU
plastic material and the shrinkage ( I usually include the spec with each tool order)
appropriate dimensions to make the part and an understanding of the part tolerance for EDM and CNC set up.

a plastic part can have just a few dimensions or be fully dimensioned depending on your needs. Your company standard policy is the best starting point, look at your coworkers drawings and ask what they use. If you are the only designer then ask your mold maker for some examples so you can get a sense for what is needed.

cheers,

M

 

[alwaysdrunk]

Thanks a lot to all of you. I really had great infos from you guys.

Two thumbs up to all of you!!