thermoplastic injection moulding

[Andrea Bozzi]

Good morning.
My name is Andrea and I recently went from mechanical designer to product specialist in an electrical material company.
I have a generic knowledge of the moulds in general and now that I look forward to the design of injection molded thermoplastic products I would like to confirm the legislation to follow...in particular I am interested in dimensional tolerances.
I found the din16901 that seems relevant, but I don't understand if it is related to the mold or the final model
thank you in advance to those who read my question and want to give me advice

 

[TECNOMODEL]

In reality there is no special norm, the customer provides a model/design with the tolerances it requires, the molder/printer will have to evaluate and possibly agree changes to make the particular printable, to reduce costs, to optimize the mold etc.
at the end it is interest both to find the best compromise between costs and achievement.
even because if a customer requires you a tolerance that is out of what the norm you do? you tell him it's not normal and so he has to change or value it if it's feasible and then, possibly, ask for a change?
if it is feasible it is realized and only, obviously making you pay the right price to do so.

 

[Andrea Bozzi]

thanks for the answer,
Now I try to explain myself better... My dilemma concerns the norm for quotas without tolerance to indicate in the chart of the model table that I must send to the molder. according to your experience would be good the uni en 22768-1 k?

 

[TECNOMODEL]

can be good, if that is what you need to your details.

I try to explain better:
you have a rectangular detail of 200x100 mm in which you indicate a general average tolerance (m).
as a standard for 200 +/-0.5, for 100 +/-0.3.
now you have to analyze your piece, mounting positions, encumbrances etc.
may require tighter tolerances, then they will be indicated in the quota.
or it may not even matter if the share was out of that range.
So, does it make sense to apply that rule?
there is no unique rule, everything depends on the functionality of the piece, exactly as it happens in all mechanical details.
the choice is to the designer.

 

[massit78]

Good morning.
My name is Andrea and I recently went from mechanical designer to product specialist in an electrical material company.
I have a generic knowledge of the moulds in general and now that I look forward to the design of injection molded thermoplastic products I would like to confirm the legislation to follow...in particular I am interested in dimensional tolerances.
I found the din16901 that seems relevant, but I don't understand if it is related to the mold or the final model
thank you in advance to those who read my question and want to give me advice

from the site cesap European center development plastic applications, if you refer to the printed pieces:

Regulations on the dimensional tolerances of printed parts (iso/ts 8062 and din 16742, which replaces din 16901)
http://cesap.com/corso/progettazion...lle-tolleranze-e-analisi-delle-difettosita-2/clearly on the mechanical parts that make up the mold, being worked with cnc, turning, electro-erosion is worth the uni en 22768-1

 

[Meteor02]

if you only design the plastic detail and not the equipment leaves the regulations, it indicates to design the tolerance you need in assembly es +/- 0.1 of the rest let you take care of who will make the mold and the printer. they will calculate the retreats according to the material chosen for the production. I recommend that you involve the printer from the early stages of design so as not to have to intervene 100 times to make the details "printable", I see that you use sw if you have the version with plastic helps you a lot me not replace the experience of a good printer.

 

[Andrea Bozzi]

hi, your answer seems to me the most pertinent and thank you
The problem is that I don't trust the molder...... .
I would like to know if there are dimensional tolerances based on various types of plastics

 

[TECNOMODEL]

And why shouldn't you trust the molder?
has all the interest in printing to the best so that you are happy, that way keeps that job and hopes to have others in the future.

 

[Andrea Bozzi]

I have been in this company since June 15 and I don't know well the injection molded plastic products, plus our suppliers are almost all extra European so if you don't understand right away, the times are stretching. .
I can add that in general I trust little and I tend to define as much as possible the product in such a way as to have less snare.. .

 

[Therapy?]

hi I did a proper course dedicated to the tolerances of thermoplastic artifacts to the cesap

the standard used so far is the din 16901 which differentiates tolerances depending on the material (particularly average withdrawal) and the fact that the share comes from a moving part on the mold or from a fixed part: if you look for I think you can find something also on the internet


However, we have been told that some industrial sectors (automotive in particular) where tolls are required. + narrow refer to iso it8-12 always linked to the collection of the material with tables from which the values are extracted

 

[Meteor02]

the percentages of withdrawal of the material read only in the technical sheet of the material you choose. each producer has different withdrawals and also the same producer will have for example a pa 6 that withdraws more than one other according to flute, if it is v0 eccecc. if the tolerances to which you go against are very restricted choose the material first specifying in the drawing the precise code with which it will be printed. then you can apply the withdrawal or medium or to be more precise the transverse and longitudinal retreats. Please note that depending on the geometries and the material of the piece you can have deformations both in molding (distribution of mold cooling channels) and post molding, here the simulations of molding help a lot to nche to evaluate any retreats. for the rest try to follow the guidelines of progetation, reforms, ribs etc.
However, I'm shocking you to take this path alone, the risk is to go wrong and not be able to attribute the blame to the trainee, however, having to pay a discarded mold.

 

[Andrea Bozzi]

Hi.
the din 16901 concerns the tolerances of the moulds, what I would need is precisely the tables with the withdrawal of the various plastic materials

 

[TECNOMODEL]

generic tables probably find them, but they are indicative.
consider that for each family of material there are various types, each with specific characteristics.
a complete table would be exterminated, you'd better create one by getting the data from the technical data sheets of the materials you use.
However I don't understand why you want to put the retreats at all costs, I would let anyone design/make the mold.
clearly indicates the size and tolerances of the finished piece, in that way in case of differences on the printed you will have the knife on the side of the handle and you can refuse the pieces.
if you provide an inclusive model of withdrawal and this is wrong how can you contest the final dimensions of the artifact?
In addition, how do you define the collection of the piece if you do not know how the mold is designed?
the withdrawal, in many materials, has a value in longitudinal direction to the flow and another in transversal direction to the same.
If you don't know where to inject, you won't know how to turn the flow, so...

 

[Andrea Bozzi]

As I have already explained, I have recently come to the world of prints, I come from light carpentry.. .
I probably also explained badly.. .
I would like to give an indication of dimensional tolerances and general form.
For example, where I worked first in the paper mill I used the following indication:
uni en 22768/1 m

 

[Therapy?]

the din 16901 concerns the dimensional tolerances of the plastic piece not of the moulds

the collection of plastics you see it from the technical board but it serves to those who design the mold to properly dimensional the equipment

 

[Meteor02]

Andrea, the technical boards of the material you need to ask the manufacturer of the chosen material bayer domo novalca or who it is as each producer has slightly different retreats. to get the cards often it is necessary to make request since online are not always available. regarding the regulations let alone indicates only tolerance +/-, in almost 30 years of work I have never seen specified the regulations, risk only to make confusion to those who will realize the mold. draws the piece as you want and leaves the calculations and beats to those who have sufficient experience to evaluate and possibly solve every little difficulty that can be presented.