Basics

dimstack.dim

Basic

A measurement is a single measurement of a part.

Parameters:
  • nom (float) –

    The nominal value of the measurement. Defaults to 0.

  • tol (Union[SymmetricBilateral, UnequalBilateral]) –

    The tolerance of the measurement. Defaults to SymmetricBilateral(0).

  • a (float, default: 1 ) –

    The sensitivity of the measurement. Defaults to 1. If the nominal value is negative, the sensitivity will be multiplied by a -1 and the nominal value will be made positive.

  • name (str, default: 'Dimension' ) –

    The name of the measurement. Defaults to "Dimension".

  • desc (str, default: 'Dimension' ) –

    The description of the measurement. Defaults to "Dimension".
abs_lower property

The minimum value of the measurement. AKA, absolute upper

abs_upper property

The maximum value of the measurement. AKA, absolute lower

abs_lower_tol property

The absolute minimum value of the tolerance.

abs_upper_tol property

The absolute maximum value of the tolerance.

Reviewed

Reviewed

Parameters:
  • target_process_sigma (float, default: 3 ) –

    The standard deviation of the process represented as ±σ. Defaults to ±3σ.

  • k (float) –

    The ratio of the amount the center of the distribution is shifted from the mean represented as a multiple of the process standard deviation. Defaults to 0σ.

  • distribution (str, default: None ) –

    The distribution of the measurement. Defaults to "Normal".
mean_eff property

effective mean

stdev_eff property

effective standard deviation "6 stdev" is the standard deviation of the distribution

process_sigma_eff property

calculated sigma (# of eff_stdevs away fromm USL and LSL)

yield_loss_probability property

Returns the probability of a part being out of spec.

assume_normal_dist()

Assume a normal distribution.

assume_normal_dist_skewed(skew)

Assume a normal distribution with a skew

Requirement

median property

median

yield_loss_probability property

Returns the probability of a part being out of spec.

R property

Return the yield loss probability in PPM

dimstack.tolerance

SymmetricBilateral

Bilateral tolerancing is a method of specifying a tolerance that is symmetrical about the nominal value. This is the most common type of tolerancing.

UnequalBilateral

Bilateral tolerancing is a method of specifying a tolerance that is asymmetrical about the nominal value. This can also be used for Unilateral tolerancing.

Bilateral(upper, lower=None)

Automatically determine the type of bilateral tolerance to use from the upper and lower inputs.

Parameters:
  • upper (float) –

    description

  • lower (float, default: None ) –

    description. Defaults to None.
Returns:

dimstack.dist

Uniform

Uniform distribution.

Parameters:
  • lower (float) –

    Lower limit.

  • upper (float) –

    Upper limit.

Normal

Normal distribution.

Parameters:
  • mean (float) –

    Mean.

  • stdev (float) –

    Standard deviation.

NormalScreened

Normal distribution which has been screened. e.g. Go-NoGo or Pass-Fail fixture.

Parameters:
  • mean (float) –

    Mean.

  • stdev (float) –

    Standard deviation.

  • lower (float) –

    Lower limit.

  • upper (float) –

    Upper limit.