权利要求：
1. A method for optimizing one or more process parameters of an additive manufacturing process, comprising, prior to the step of manufacturing at least one AM part, preferably a metal AM part, the steps of : a. generating, on a computing device, a 3D digital model of at least one calibration sample, preferably a set of calibration samples, to be manufactured by the additive manufacturing process; b. manufacturing the calibration sample (ci), preferably the set of calibration samples (c1...ci...cn) on a build platform (P) of an additive manufacturing system, the calibration sample (ci) or each calibration sample (c1...ci...cn) being monitored by at least one electromagnetic sensor as it is being manufactured according to the 3D digital model, wherein the calibration sample (ci) or each calibration sample is made up of two or more test coupons (ci,1...ci,j...ci,m), preferably on top of each other, for obtaining at least one optimized set of process parameters (pi,opt), and c. storing the at least one optimized set of process parameters (pi,opt) for subsequent use during the building process of said at least one AM part, which is representative of the test coupon (ci,m), wherein said at least one optimized set of process parameters (pi,opt) is obtained by carrying out the following steps: i. manufacturing a first test coupon (ci,1) of the calibration sample (ci) with a first set of process parameters (pi,1) or a first test coupon (c1,1...ci,1...cn,1) of respective calibration samples (c1...ci,...cn) with respective set of process parameters (p1,1...pi,1...pn,1), ii. sensing the first test coupon (ci,1) of the calibration sample or each first test coupon (c1,1...ci,1...cn,1) of respective calibration samples (c1...ci,...cn) with said at least one electromagnetic sensor, iii. changing at least one process parameter of the first set of process parameters (pi,1) or of said respective set of process parameters (p1,1...pi,1...pn,1) as a function of the data sensed by said at least one electromagnetic sensor to obtain an improved set of process parameter (pi,2) for the calibration sample (ci) or respective improved set of process parameters (p1,2...pi,2...pn,2) for respective calibration samples (c1...ci,...cn), iv. manufacturing an additional test coupon (ci,2) of the calibration sample (ci) with the improved set of process parameters (pi,2), or an additional test coupon (c1,2...ci,2...cn,2) of respective calibration samples (c1...ci,...cn) with respective improved set of process parameters (p1,2...pi,2...pn,2) v. sensing the additional test coupon (ci,2) of the calibration sample (ci) or each additional test coupon (c1,2...ci,2...cn,2) of respective calibration samples (c1...ci,...cn) with said at least one electromagnetic sensor, and vi. if the data sensed during step v. do not correspond to a test coupon of an acceptable quality level, iterating steps iv. and v. until the data sensed for the additional test coupon (ci,j) or each additional test coupon correspond to an acceptable quality level of the coupon to obtain said at least one optimized set of process parameter (pi,opt) for the calibration sample (ci) or each calibration sample.
2. The method of claim 1, wherein each calibration sample (c1, c2...ci...cn) comprises at least three test coupons (ci,1, ci,2, ci,3), preferably at least five test coupons (ci,1, ci,2, ci,3, ci,4, ci,5) arranged on top of each other.
3. The method of claim 1 or 2, wherein each test coupon (ci,1...ci,j....ci,m), is made up of at least five layers, preferably at least ten layers such that the thickness of the coupon is larger than the penetration depth of the electromagnetic field generated by said at least one electromagnetic sensor.
4. The method of any preceding claim, comprising manufacturing on the build platform (P) a first calibration sample (ci) comprising a plurality of test coupons (ci,1, ci,2, ci,3..... ci,m) of different shapes arranged next to each other and at least one additional calibration sample having a corresponding plurality of test coupons (ci,1, ci,2, ci,3..... ci,m) of shapes identical to the shapes of respective plurality of test coupons of the first calibration sample, wherein step b. of claim 1 comprises: i. manufacturing the plurality of test coupons (ci,1, ci,2, ci,3 ci,m) of a first calibration sample with a unique set of process parameters (pi,j) per test coupon; ii. sensing each test coupon (ci,1, ci,2, ci,3 ci,m) of said first calibration sample with said at least one electromagnetic sensor; iii. changing at least one process parameter of each unique set of process parameters (pi,j+1) per coupon as a function of the data sensed for the corresponding test coupon to obtain an improved set of process parameters (p2) for each test coupon, iv. manufacturing the additional calibration sample with the plurality of test coupons (ci,1, ci,2, ci,3,.... ci,m) with the corresponding improved set of process parameters (p2) for each test coupon of identical shape to the shape of respective test coupons of the first calibration sample, v. sensing each test coupon (ci,1, ci,2, ci,3..... ci,m) of said additional calibration sample with said at least one electromagnetic sensor, and vi. if the data sensed during step v. for at least one test coupon do not correspond to a test coupon of an acceptable quality level, iterating steps iv. and v. until the data sensed for at least one additional test coupon (ci,m) correspond to an acceptable quality level of the coupon to obtain said least one optimized set of process parameter (pi,opt)
5. The method of any preceding claim, wherein several optimized sets of process parameters (pi,opt) are obtained during a single build cycle of the set of calibration samples (c1, c2...ci...cn), each optimized set of process parameters being assigned to a specific geometry and stored for subsequent use for building a corresponding part of said at least one AM part.
6. The method of any preceding claim, wherein the test coupon of an acceptable quality level comprises a bulk density of at least 99%, and wherein said at least one electromagnetic sensor is an Eddy-current sensor, the optimized set of process parameters (pi,opt) is obtained by finding the extremum of the signal acquired by Eddy-current sensor.
7. The method of the preceding claim, wherein an optimization algorithm is used to find said extremum, such as the steepest descent algorithm, the conjugate gradient algorithm or the Monte-Carlo algorithm.
8. The method according to any preceding claim, wherein a threshold of quality of the test coupon is determined, for example a given value of porosity, and wherein the process parameters among layer thickness, hatch distance and scanning speed are optimized to reduce the time to build the test coupon without exceeding said threshold.
9. The method according to any preceding claim, wherein the selected set of process parameters are maintained during additively manufacturing each test coupon as long as the quality factor inferred from the signal measured by said at least one electromagnetic sensor is within the range of the acceptable quality level.
10. The method according to any preceding claim, wherein once said at least one optimized set of process parameters (popt) has been obtained, a mapping of the build platform (P) is generated as a function of a specific quality for a multitude of areas on the build platform corresponding to the specific position of each calibration sample (c1...ci...cn) on the build platform.
11. The method according to the preceding claim, wherein said mapping is used to design a build platform layout excluding zones, on the build platform which have shown to produce test coupons of lesser quality in comparison with other test coupons, for additive manufacturing of said at least one AM part.
12. The method according to claim 10, wherein said mapping is used to correct one or more process parameters of respective optimized set of process parameters (pi,opt), such as laser scan speed, as a function of the position on the build platform, the corrected optimized set of process parameters being transferred in an electronic format to a machine controller of the additive manufacturing system so that real AM parts are built with the corrected optimized set of process parameters corresponding to their X-Y position of the build plate (P) to reach a uniform quality for all positions on the build platform.
13. The method according to the preceding claim, wherein the step b. of claim 1 is carried out on different additive manufacturing machines, and wherein the differences in quality between the calibration samples are used to classify the different machines as a function of the quality of the metal pieces that are machined in said machines.
14. The method according to any preceding claim, wherein the explored sets of process parameters (pi,j) and the corresponding measured quality factors on corresponding test coupons (ci,j), as well as, in particular, the optimized set of process parameters (pi,opt) for the calibration sample (ci) or each calibration sample, are used to compute a multidimensional process parameters' window yielding an acceptable quality level for said at least one AM part, and wherein a constrained optimization is performed on at least one process parameter of said optimized set of process parameters (pi,opt), for example the laser scanning speed, such that the new optimized set of process parameters is constrained within said process parameter window.
15. The method according to any of claim 1 to 13, wherein the explored sets of process parameters (pi,j) and the corresponding measured quality factors on corresponding test coupons (ci,j), as well as, in particular, the optimized set of process parameters (pi,opt) for the calibration sample (ci) or each calibration sample, are used to compute a multidimensional process parameters' window yielding an acceptable quality level for said at least one AM part, and wherein said process parameters' window is transferred in an electronic format to a quality optimization algorithm used during the building process of said at least one AM part, so that said quality optimization algorithm constrains its search for optimum to the process parameters window to ensure that AM parts produced are compliant for AM part certification which ensures AM parts meet the strict quality requirements demanded by the industry.