What is the proper drawing for FRPs?
I want to write about the drawing of the FRP product in today’s column.
The drawing which all the requirements of the product are included, and has the highest authority in every technical document. This principle does not change even if materials were FRP.
I have a good chance to work with the companies which are designing and selling FRP products in addition to materials (resin, prepregs, fiber matrix), molding processing recently. Their products are well-considered about “concept” from engineering view point.
As I have written in this column a few of times, it is the concept that is the origin to be important to manufacture of the FRP.
The business model such as the sales price grows well, and the model expected me that the company will gain good sales and profit. I did not listen to a story to the details of a way of thinking and the distribution of the profit rate, the total concept is well-grown in a word for sure.
But, on the other hand, there is a predominantly insufficient thing.
It is;,
"Product drawing".
For details, I could not mention it, but in this situation the possibility that malfunction appeared would be thought about enough.
And it is the case which a story comes to to me that want to have the cause investigation and the suggestion of the measures method because it occurred in a final just before the product sale will be started.
There is not the story with the case which a big problem was given to after having appeared in the market, and it may be said that it is fortunate that measures suggestion of the malfunction that appeared before sale is started.
If this kind of problem happened after sale, become the issue of so-called market, and do not finally disappear in the brand damage against the company.
I want to speak the problems of the drawing of the FRP product which is apt to be today's column and the minimum refinement for it.
There are not dimension tolerance information
It may seem unexpectedly, but most of FRP-related drawings do not have any tolerance information.
There is a few of cases that public standards about the tolerance such as JIS B 0405.
And it may be said that there are a great many cases which the designers (drawers), so-called designers cannot answer definitely even if they hear a story to be why the tolerance information is not included in their drawings.
A problem that the high tolerance variation leads to the risk of the contact with other parts after they are assembled because it is not to be able to manage it without tolerance information. Sometimes it may be difficult to fill out all tolerance information, but key areas of the interface should be controlled by the tolerance information of the drawings.
There are the designers who issue the drawings only with 3D shape without the tolerance by using the software such as CATIA, but it may be the starting point to understand that there include many future problems/risks.
There is not Non Destructive Inspection requirement
Of course I do not have any problem if designers have an intention not to be necessary.
However, the people must not forget to be materials of the special constitution with the risk that an internal defect becomes the starting point to the fatal failure.
The special configuration here points at having the form that fiber and resin piled up by a layer form. Therefore, the cracks or delamination progress interlaminar layer along with it.
When I have such a talk,
"Let's put Non Destructive Inspection requirements" (first of all)
Or
"It is not necessary" (there are not the clear backgrounds)
There is only 2 patterns of the answer from designers.
As for the designer who can do it by an argument of Non Destructive Inspection with a clear intention, it is an impression that there is very little.
As a matter of course, in the case of a mass production, it is not easy to perform Non Destructive Inspection every part on the entire surface from the viewpoint of production schedule. Even if it is a development product, the thorough support of the expert with high knowledge about Non Destructive Inspection is essential to design the requirements of the inspection and the inspection technique.
It may be said that it is proper and realistic to push forward examination to inspect it around the place that seems to become a shape of the place where stress concentration happens while considering the structure of materials.
There is not materials spec (standard)
The FRP is the materials whose public material spec does not exist unlike metal.
Therefore the designers shall create a material spec to use, and it is necessary to clarify requirements.
When I say in this way,
"Strength and coefficient of elasticity"
There seem to be many people have the image as the requirement of material properties requirements like;,
"Strength and modulus".
But they are just a part of the spec requirements..
The material spec requirements cover the total quality control system including delivery, storage and recording requirements etc.
In other words the designers cannot define the proper materials without material specs.
There is the designer writing the commercial product number of the materials supplier in the drawing.
The material equivalence of ○○.
Of course a requirement (I do not say until a sufficient condition) that the materials completely meet product requirements should be okey. But when I notice the customization characteristics of FRPs, it should be normal that the designers would like to add these requirements or to change a part of the material properties.
It feels danger a little to use the word "equivalence" as the materials designation in the drawings.
It is for sure that the FRP products can not be produced safety without understanding regarding material requirement.
You may notice that the important point may be forgotten before you think about the productivity and cost.
It may be said that it is not so easy to make the business model to make a product because the customer requests have diversities.
On the other hand, it would be more reasonable that the designers create the drawing in accordance with the various customer demands by the different drawings which include the customized requirement.
I hope today’s column is meaningful for you.
Thank you for reading.
