Is it designed based on KKD (experience, intuition and courage) alone? Explain the advantages and necessary knowledge of tolerance design concisely and easily!
What is tolerance/design?
Reality at the design site / changes in the manufacturing site
Advantages of tolerance design / calculation examples
The advantages of tolerance design learning
Recently, tolerance design has attracted attention again. Next, the advantages of this tolerance design are explained.
1. Possess tolerance calculation theory and judgment standards to make correct designs.
Even for designers who have implemented tolerance calculations, if you investigate the actual situation, you
will find that most of the answers are “Teached by my predecessors (OJT)” and “self-taught”. Many designers “always feel uneasy”. In fact Many people got it wrong.
※ About 15,000 designers were asked, about 80% of them answered that no tolerance calculation was implemented. (Survey
by Planer Co.) By systematically learning tolerance design theory, tolerance calculations can be carried out “confidently”, and they can be passed on to younger generations.
In fact, the most difficult part in tolerance design is “judgment” and “processing”.
Basically, five tolerance calculations, Cp, Cpk (process capability index), defect rate, etc. are calculated correctly, and the numerical value is used for discussion (judgment and processing) , This is crucial.
2. Companies that did not implement tolerance design before can get a great cost advantage. (30-50%)
If the cost reduction rate exceeds 20%, it cannot be achieved by force.
On-site improvement and financing efforts are limited, and unless the designer carries out a “design reform”, it will not be possible to achieve it.
The design leader or senior management noticed this and promoted the company-wide tolerance design, which ultimately reduced the cost by at least 30%.
There are at least 500 themes (PLANER performance), and some companies have disclosed some of them.(Please refer to tolerance design and achievement examples)
3. Theoretically solve the design quality problem and take precautions.
It is impossible to have a design that must be made to understand. Everything is determined by design.
If you look at the design drawing, if you manufacture and assemble all parts according to this drawing, you can simply calculate the probability (defect rate) of what problems (faults, non-matches) occur.
This is FMEA (failure mode impact analysis), and the work of deriving the probability of occurrence of each content and seeking improvement is “tolerance design”.
4. Able to make correct assessments of others’ designs. (Check the picture)
If it is the person in charge of design, he must immediately evaluate and guide the subordinate (or the externally commissioned designer) to design whether the design drawings are correct. (= Checking the drawing)
As the person in charge, pay attention to important design positions and perform tolerance calculations (manual calculation level). If there is a dangerous place,
call the designer to confirm the tolerance calculation book implemented by the designer. If you make a mistake If it is, we must carefully point it out and guide it to make the correct design.
At least 90% of the work of the inspector should be used to check the tolerance design.
As the person in charge of design, if you can’t do this, you don’t have to say about checking the drawings, and you can’t even guide and train your subordinates.
Tolerance calculation example
Next, an example of tolerance calculation will be explained. For example, consider this device.
The gap f is a very important value. Consider the case where the design standard 0.5±0.3 must be realized.
This gap f is composed of all parts from A to H.
Even if all the parts from A to H have large tolerances, the point is whether they can meet the design standards.
Therefore, how to set the tolerances of each part becomes very important.
Here, let’s think about it a little bit with a simple model.
In the state of the figure below, the gap of χ must be designed within the range of 0.5±0.4. When the conditions are given and the size of part A is specified to be 9.5±0.3, calculate the size and size of the parts B, C, and D as the same part In the case of tolerance, what would you do?