Tolerance Data 2011
Example of geometric dimensioning and tolerancingGeometric dimensioning and tolerancing (GD&T) is a system for defining and communicating. It uses a on and computer-generated three-dimensional solid models that explicitly describe nominal and its allowable variation. It tells the manufacturing staff and machines what degree of is needed on each controlled feature of the part. GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possible size of individual features, and to define the allowable variation between features. Dimensioning specifications define the nominal, as-modeled or as-intended geometry. One example is a basic dimension.
Tolerancing specifications define the allowable variation for the form and possibly the size of individual features, and the allowable variation in orientation and location between features. Two examples are and feature control frames using a (both shown above).There are several standards available worldwide that describe the symbols and define the rules used in GD&T. One such standard is (ASME). This article is based on that standard, but other standards, such as those from the (ISO), may vary slightly.
The Y14.5 standard has the advantage of providing a fairly complete set of standards for GD&T in one document. The ISO standards, in comparison, typically only address a single topic at a time.
There are separate standards that provide the details for each of the major symbols and topics below (e.g. Position, flatness, profile, etc.). Contents.Origin GD&T The origin of GD&T is credited to, who developed the concept of 'true position'. While little is known about Parker's life, it is known that he worked at the Royal Torpedo Factory in,.
His work increased production of naval weapons by new contractors.In 1940, Parker published Notes on Design and Inspection of Mass Production Engineering Work, the earliest work on geometric dimensioning and tolerancing. In 1956, Parker published Drawings and Dimensions, which became the basic reference in the field.
Dimensioning and tolerancing philosophy According to the ASME Y14.5-2009 standard, the purpose of geometric dimensioning and tolerancing (GD&T) is to describe the engineering intent of parts and assemblies. The datum reference frame can describe how the part fits or functions. GD&T can more accurately define the dimensional requirements for a part, allowing over 50% more tolerance zone than coordinate (or linear) dimensioning in some cases. Proper application of GD&T will ensure that the part defined on the drawing has the desired form, fit (within limits) and function with the largest possible tolerances.
GD&T can add quality and reduce cost at the same time through producibility.There are some fundamental rules that need to be applied (these can be found on page 7 of the 2009 edition of the standard):. All dimensions must have a tolerance. Every feature on every manufactured part is subject to variation, therefore, the limits of allowable variation must be specified. Plus and minus tolerances may be applied directly to dimensions or applied from a general tolerance block or general note. For basic dimensions, geometric tolerances are indirectly applied in a related Feature Control Frame. The only exceptions are for dimensions marked as minimum, maximum, stock or reference.
Dimensions define the nominal geometry and allowable variation. Measurement and scaling of the drawing is not allowed except in certain cases. Engineering drawings define the requirements of finished (complete) parts. Every dimension and tolerance required to define the finished part shall be shown on the drawing.
If additional dimensions would be helpful, but are not required, they may be marked as reference. Dimensions should be applied to features and arranged in such a way as to represent the function of the features. Additionally, dimensions should not be subject to more than one interpretation. Descriptions of manufacturing methods should be avoided.
The geometry should be described without explicitly defining the method of manufacture. If certain sizes are required during manufacturing but are not required in the final geometry (due to shrinkage or other causes) they should be marked as non-mandatory. All dimension and tolerance should be arranged for maximum readability and should be applied to visible lines in true profiles. When geometry is normally controlled by gage sizes or by code (e.g. Stock materials), the dimension(s) shall be included with the Gage or code number in parentheses following or below the dimension. Angles of 90° are assumed when lines (including center lines) are shown at right angles, but no angular dimension is explicitly shown.
(This also applies to other orthogonal angles of 0°, 180°, 270°, etc.). Dimensions and tolerances are valid at 20 °C (68 °F) and 101.3 kPa (14.69 psi) unless stated otherwise. Unless explicitly stated, all dimensions and tolerances are only valid when the item is in a free state. Dimensions and tolerances apply to the length, width, and depth of a feature including form variation.
Dimensions and tolerances only apply at the level of the drawing where they are specified. It is not mandatory that they apply at other drawing levels, unless the specifications are repeated on the higher level drawing(s).(Note: The rules above are not the exact rules stated in the ASME Y14.5-2009 standard.)Symbols Tolerances: Type of tolerances used with symbols in feature control frames can be 1) equal bilateral 2) unequal bilateral 3) unilateral 4) no particular distribution (a 'floating' zone)Tolerances for the profile symbols are equal bilateral unless otherwise specified, and for the position symbol tolerances are always equal bilateral.
For example, the position of a hole has a tolerance of.020 inches. This means the hole can move +/-.010 inches, which is an equal bilateral tolerance. It does not mean the hole can move +.015/.005 inches, which is an unequal bilateral tolerance. ^ MacMillan, David M.; Krandall, Rollande (2014).
Circuitous Root. From the original on 27 March 2019.
Retrieved October 24, 2018. Dimensioning and Tolerancing, ASME y14.5-2009. NY: American Society of Mechanical Engineers.
2009.Further reading. McCale, Michael R. Journal of Research of the National Institute of Standards and Technology.
104 (4): 349–400. Archived from (PDF) on 2011-10-18.
Retrieved 2011-09-13. Henzold, Georg (2006).
Geometrical Dimensioning and Tolerancing for Design, Manufacturing and Inspection (2nd ed.). Oxford, UK: Elsevier. Srinivasan, Vijay (2008). 'Standardizing the specification, verification, and exchange of product geometry: Research, status and trends'. Computer-Aided Design.
40 (7): 738–49. Drake, Jr., Paul J.
Dimensioning and Tolerancing Handbook. New York: McGraw-Hill.
Neumann, Scott; Neumann, Al (2009). GeoTol Pro: A Practical Guide to Geometric Tolerancing per ASME Y14.5-2009. Dearborn, MI: Society of Manufacturing Engineers. Bramble, Kelly L. Geometric Boundaries II, Practical Guide to Interpretation and Application ASME Y14.5-2009. Engineers Edge. Wilson, Bruce A.
Tolerance Data Free Download
Design Dimensioning and Tolerancing. US: Goodheart-Wilcox. P. 275.External links Wikimedia Commons has media related to. Tests implementations of GD&T in CAD software. Analyze GD&T in a STEP file.
The dose to critical structures plays a very important role in treatment plan evaluation and forms a major challenging parameter in radiotherapy treatment planning. In this study, a simple index, Plan Normal tissue complication Index (PNI) has been proposed for treatment plan evaluation based on the dose to surrounding critical structures. To demonstrate the proposed index, four different critical treatment sites that include the prostate, upper abdominal cancer, lung, and head and neck were selected for this study.
A software progam (PNIcalc) has been developed to compute the PNI from the exported dose-volume histogram data and from the tissue tolerance data published by Emami et al. And Kehwar et al.
The software also shows the parameters that exceed the threshold limits of dose-volume parameters presented in the QUANTEC recommendations (2010). In all the studied cases, PNI gave an overall picture of the dose received by the critical structures and also indicate the fractional volume exceeding the tolerance limit.
The proposed index, PNI gives a quick comparison and selection of treatment plans that result in reduced dose to the critical structures. It can be used as an additional tool for routine treatment plan evaluation in external beam radiotherapy. IntroductionThe main aim of radiotherapy is to maximize the tumor control probability with less complication to the surrounding critical structures. A treatment plan is generated based on this simple rule and several methods of treatment delivery techniques, including 3D conformal radiotherapy, intensity modulated radiation therapy (IMRT), stereotactic radiosurgery/radiotherapy, image-guided radiotherapy, brachytherapy are currently available in radiotherapy.
Each of the above techniques has its own advantages and disadvantages in achieving the goal. In fractionated radiotherapy, the biological factors that affect response of normal and tumor tissues are repair, repopulation, reoxygenation, redistribution, and radiosensitivity (5R's of radiobiology). In reality, it is difficult to quantify the individual effect these factors have on normal tissues and tumor tissues for a routine clinical case. Based on previous clinical experience, the radiation oncologists prescribe the dose to the tumor after critical evaluation of the dose to critical structures.
In external beam radiotherapy, dose-volume histograms (DVH) play a key role in selecting the optimal plan for treatment delivery and it is presented in the form of cumulative DVH– and differential DVH. Indices such as conformality index (CI) and dose homogeneity index have been proposed to assess the target coverage and dose uniformity inside the target volume. In addition to these, slice-based plan evaluation methods were also proposed for treatment plan evaluation., The dose to critical structures plays a key role in treatment plan evaluation and presents a major challenging parameter in radiotherapy treatment planning. The dose to critical structure is analyzed based on the information available from the DVH.
The concept of minimal (TD 5/5) and maximal (TD 50/5) tissue tolerance dose was introduced by Rubin and Casserett in 1972 and applied to whole or partial organ volume receiving daily fractionations of 1.8-2 Gy. The tolerance dose TD 5/5 represents the radiation dose that would result in 5% risk of severe complications within 5 years after irradiation and TD 50/5 represents the dose that would result in 50% probability of developing severe complications within 5 years after irradiation. A landmark publication by Emami et al. compiled the normal tissue tolerance doses for various critical structures in terms of TD 5/5 and TD 50/5 and it is widely used in radiotherapy treatment planning. These normal tissue tolerance data are defined for uniformly irradiated 1/3, 2/3, and 3/3 partial volumes of the normal tissues and organs and are applicable for conventional fractionation schedules of 1.8-2 Gy per fraction, 5 fractions a week. The missing TD 5/5 and TD 50/5 values in the Emami et al. publication were fitted by Kehwar using an empirical model.
Even though, many other researchers have also reported the tolerance doses for individual organs, but the data are scattered in the literature and the tolerance doses for same organ differ among different investigators. Recently, a new set of recommendations known as the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) has been published based on evidence-based guidelines.– The tolerance data published by Emami et al. represents the DVH in the form of 1/3 rd, 2/3 rd, and 3/3 of a critical structure and it is much simpler to compare two plans. In this study, a simple index, PNI has been proposed for treatment plan evaluation, based on the doses to surrounding critical structures and on correlating these dose values with the tolerance dose compiled by Emami et al., and Kehwar. Materials and MethodsTo demonstrate the proposed index, four different critical treatment sites that include prostate, upper abdominal cancer (UAC), lung, and head and neck were selected for this study. All the patients were planned on Eclipse ™ treatment planning system. In case of prostate, five different treatment plans: (1) three fields with open anterior and two lateral wedged fields (3F), (2) three fields with open anterior and two lateral wedged fields (3F-M) fitted with mulitleaf collimator (MLC), (3) four field box technique fitted with MLC (4F-M), (4) six fields fitted with MLC (6F-M), and (5) seven field intensity modulated radiotherapy technique (IMRT) were generated in the treatment planning system.
For plan comparison, the dose prescription was kept as 74 Gy uniformly in all the treatment plans. The DVH for the bladder, rectum, right femur, and left femur were exported to a software (PNIcalc) developed in Visual Basic.net 2008 (Microsoft Corporation ™) that computes PNI. Shows the screen shot of PNIcalc comparing the DVH of two rival plans. The software has the provision for importing the DVH data from the treatment planning system and the user can select the critical structures to be included for PNI computation. In addition to this, the PNIcalc can also compute the ratio of near-maximum to near-minimum doses (D2/D98) to the target volume, volume of planning target volume (PTV) receiving greater than 107% (D 107%) and less than 95% (D.
Software module for comparing two rival plans based on PNIThe plan normal tissue complication index is derived from the knowledge of the tolerance doses for different critical structures and the dose received by 1/3 rd, 2/3 rd, and 3/3 of the critical structure.PNI = f ( n, j/3, TD)wheren = critical structuresj/3; where j = 1,2,3TD = tolerance dose and it can be either TD 5/5 or TD 50/5.The PNIcalc computes the PNI for the plan based on the tolerance data given in adopted from Emami et al. And Kehwar.,. In case of upper abdominal cancer, two plans were generated (1) a simple three fields with anterior open and two lateral 45° wedged fields (3F-MLC) fitted with multileaf collimator (MLC) and (2) a seven-field IMRT plan with 6 MV beams. The prescription dose to the PTV was kept as 45 Gy in 25 fractions for comparing the 3F-MLC and IMRT plans.
Global Social Tolerance Index
The DVH data of the right kidney, left kidney, liver, and spinal cord were exported to the PNIcalc program. The spinal cord is a serial structure and the concept of 1/3 rd, 2/3 rd, and 3/3 does not apply and moreover the DVH does not contain the information about the length of the spinal cord. Hence, for computing PNI, the tolerance dose TD 5/5 was kept as 47 Gy uniformly for 1/3, 2/3, and 3/3 and the software reads the maximum dose received by spinal cord from the exported DVH data.The third case was a lung cancer, planned for 3D conformal radiotherapy (3D-CRT) and IMRT. The 3D-CRT was planned by three fields that include an anterior open and two wedged lateral MLC fields. The IMRT planning was performed with five 6 MV fields.
A dose of 60 Gy in 30 fractions was prescribed in both of the treatment plans. In this case, the right lung, left lung, liver, and spinal cord were the critical structures included for PNI computation.The head and neck was a case of cancer of vallecula (T3N0M0) for which a 3D-CRT and an IMRT plan was generated. The 3D-CRT plan included 50 Gy prophylactic planned by parallel opposed fields with spine sparing after 40 Gy and posterior bilateral neck on either side were boosted with 9 MeV electron fields to reduce the dose to the spinal cord. The lower neck was planned with 50 Gy anterior fields with mid-line shielding. The prophylactic irradiation was followed by a 20 Gy boost to the gross tumor volume. The IMRT plan includes a uniform seven fields planned with 6 MV beams. In this case, right and left parotid and spinal cord were the critical structures included for PNI calculation as both the right and left parotid were closer to the PTV.
Resultscompares the DVH generated for the IMRT and six-field 3D-CRT prostate plans. It clearly illustrates the dose received by 1/3 rd, 2/3 rd, and 3/3 volume of bladder, rectum, right femur, and left femur and its corresponding computed PNI. It also shows the tolerance doses for the user selected critical structures and the PNI for the whole plan.
In addition to PNI computation, it also shows a comparison of dosimetric parameters, such as D2/D98, D 107%, D. DiscussionThe PNI is a function of critical structures and 1/3 rd, 2/3 rd, 3/3 fraction of the critical structure and which can also be used for evaluating the treatment plans for a given fraction of the structure volume. The 1/3 rd, 2/3 rd, and 3/3 of the DVH curve represent the overall DVH for the critical structure and by incorporating these parameters for computing the PNI gives an overall trend of the DVH.
The tolerance doses compiled by Emami et al. are used in many clinics for assessing the normal tissue complications and form the basis of the decision-making process conducted by the radiation oncologist. The proposed index is applicable to treatment plans with conventional fractionation schedule of 1.8-2 Gy per fraction. The tissue tolerance data are stored in the software and it has the flexibility for the user to add any new tolerance data to the existing tissue tolerance table. The PNI should be as low as possible for a given plan and if it reaches 3 then all/most of the critical structures have exceeded the tolerance dose. It is clearly evident from that the PNI with 3D-CRT has exceeded 3, thus indicating that both of the parotids are receiving higher than the acceptable tolerance doses predicting possible xerostomia. If the PNI for a partial/whole organ of an individual structure exceeds 1, then the plan has resulted in a dose higher than the tolerance dose.
The treatment plan, 3F-O in shows that rectum and right and left femur have exceeded the tolerance dose. Similarly in, with 3D-CRT both of the parotids have exceeded their tolerance dose. Except for the lung cancer treatment plan, all other plans showed that IMRT considerably reduced the overall dose to surrounding critical structures.
In the case of lung cancer, five beams were employed resulting in a good CI as compared to 3D-CRT with three fields. Moreover the orientation of the treatment fields with 3D-CRT resulted in less dose to the spinal cord. In all the test cases, IMRT resulted in a very good CI. The PNI defined in Eq. 1 incorporates the minimal tolerance dose (TD 5/5) and can also be used for computing PNI for maximal tolerance dose (TD 50/5) by substituting TD 5/5 with TD50/5.
Tolerance Data 2011 Pl Download
Even though the tolerance data published by Emami et al. are applicable to a uniform dose distribution, they are frequently used in radiotherapy in most situations for assessing the normal tissue complications, and moreover the proposed PNI is essentially used for comparing treatment plans. The comparison of the overall PNI can be used for comparing rival plans, and their subsets can be used for analyzing the plan selected for treatment. The proposed index, PNI provides a quick comparison of the treatment plans for the radiation oncologist and also for the physicist to assess their treatment plans. The comparison of treatment plans based on QUANTEC recommendations helps in identifying those structures that exceed the threshold limit as set by the QUANTEC guidelines.