AUTODESK AUTOCAD INVENTOR 2012 DESIGN ACCELERATOR: LIMITS/FITS MECHANICAL CALCULATOR

Transcription

1 AUTODESK AUTOCAD INVENTOR 2012 DESIGN ACCELERATOR: LIMITS/FITS MECHANICAL CALCULATOR Designers ften calculate and design a shaft-hle fit. This prblem influences the prperties f the final prduct and its price f manufacturing. Use the adaptable interface in Design Acceleratr t design the ideal fit. Limits and Fits are used t define tlerances fr mating parts. Limits are mst cmmnly used fr cylindrical hles and shafts, but they can be used fr any parts that fit tgether regardless f the gemetry. A limit is the upper and lwer tlerance fr a shaft r hle. A fit cnsists f a pair f limits. There are three categries: clearance, transitinal, and interference. Clearance The largest shaft is smaller than the smallest hle. Large clearances are fr relative mtin. A shaft in a bushing Small clearances are fr a precise fit that can be assembled withut tls. A shaft in a bushing Transitinal Tlerance znes verlap. The largest shaft is larger than the smallest hle (interference). The smallest shaft is smaller than the largest hle (clearance). Precise lcatin that may require tls t assemble. Dwel pins in tling t lcate parts Interference The smallest shaft is larger than the largest hle. Precise lcatin that requires tls t assemble. Parts d nt cme apart r mve during use. May require heating r cling t assemble parts. A gear n a shaft

2 T access the Limits and Fits Mechanical Calculatr, In the Assembly, click n the Design Tab: Click the Black Dwn Arrw n the Pwer Transmissin Panel: Click the Black Dwn Arrw Next T Tlerance Calculatr, and Click n the Limits/Fits Calculatr: This pens the Limits and Fits Mechanical Calculatr Dialgue Bx:

3 Sectin 1, Cnditins: Determine the fit type fr the Hle-basis system r the Shaft-basis system f fits. A similar fit is calculated autmatically if the ptin is checked in the Mre Optins area when the fit calculatin system is changed. Select the type f fits. This ptin prvides an easy way t keep hle r shaft tlerance class n "H" ("h" symbl). Yu can define any custm fit, if needed. Basic-hle allws the use f standard tling t bre the hle. Enter r measure the nminal size f the hle and the shaft. Set up the nminal diameter as a basic size. Fr ANSI active prfiles, the diameter value is in inches. Fr ISO active prfiles, the diameter value is in millimeters.

4 Sectin 2, Tlerances: Displays the selected tlerance image. The displayed image depends n the specified ptin in Mre Optins (Tlerance Image pull-dwn list). The image and dimensins dynamically update t reflect changes made in the Cnditins and Tlerance Znes grup bxes. The upper half f the image represents the hle and the lwer half f the image represents the shaft. Basic size value is indicated by a bld circle. The tlerance zne is indicated by a yellw, hatched area. The tlerance zne area is defined by tw arcs where the arcs represent the upper and lwer values f the limit. The arcs are tangent t the basic size circle n the left side. The dimensins display basic size, maximum clearance r interference, minimum clearance r interference, and distance between midpints f tlerances. Sectin 3, Tlerance Znes: Specify the limits and fits. Selected fit is displayed in a graphic frm. Sectin 4, Results: T display the Results area n the right side f the Calculatin tab, duble-click the duble line n the right r click the chevrn. The area displays numerical values fr the tlerances. Click Calculate t calculate the values. The fllwing items are displayed in the Results pane: Hle Minimum diameter f the hle (Hle min ) Maximum diameter f the hle (Hle max ) Upper tlerance f the hle (Hle upper ) Lwer tlerance f the hle (Hle lwer ) Shaft Minimum diameter f the shaft (Shaft min ) Maximum diameter f the shaft (Shaft max ) Upper tlerance f the shaft (Shaft upper ) Lwer tlerance f the shaft (Shaft lwer ) Fr Clearance Fits Minimum clearance diametric value f the fit (Clearance min )

5 Maximum clearance diametric value f the fit (Clearance max ) Fr Transitin Fits Maximum interference diametric value f the fit (Interference max ) Midpint Distance between midpints f tlerance znes (Midpint) Sectin 5, Mre Tab: Find equivalent fit when changing between Hlebasis and Shaft-basis Change fit system accrding t selectins in fit chart Standard Tlerance znes that are utside the specified range Tlerance znes that are within the specified range Tlerance Image When yu select a shaft fit symbl In the Tlerance Znes area (fit symbls are in a graphic frm), the Hle-basis fit system and 'H' fit symbl is set autmatically. The same behavir ccurs fr the Shaft-basis fit system. A crrespnding fit is calculated autmatically, if the bx is checked, when the fit calculatin system is changed. Use the pull-dwn menu t select the standard fr the calculatin. Change the clr f the tlerance znes. Change the clr f the tlerance znes. Use the pull-dwn list t select the type f picture t display in the Tlerances grup bx f the Calculatin tab.

6 Example: Shaft-basis system, ISO 30mm Diameter, Max Clearance.08mm, Min. Clearance.03mm. Fit Type is set t Clearance, Preferred Fit/Limits Will be set t a H7/g6 Standard fit, Tlerance Image set t Hle and Shaft: By Clicking n any f the Limits in the Tlerance Zne will shw Varius Results fr that Fit:

7 Here, the F7/k6 is shwn. Ntice the Different Results and als the Tlerance Picture: Changing the Tlerance Image t ISO Tlerance Range Image will nw shw: The Use f the Limits/Fit Mechanical Calculatr can save the end user valuable time by having the crrect values calculated autmatically accrding t inputted data! N need t lk up the values in Reference Bks, thereby pssibly chsing the incrrect values!