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Info Letter No. 138 - March / April 2013

by Fritz Ruoss

FED1+ Quick 4

A new Quick4 View with even more information, drawings, diagrams and tables has been added to FED1+. Results of the Quick3 view have been completed with bending diagram and load spectrum (if a load spectrum was defined).

Quick4 View is framed by an A3 drawing panel. Form of drawing header can be configured at "File->Settings->Drawing": DIN 6771 small, ISO 7200 fig.1, ISO 7200 fig.2, and DIN 6771 large.

FED1+ Production Drawing Quick 3

New output form of FED1+ is an A4 drawing frame with all informations, drawings and tables known from Quick3 view. Coiling direction, setting length and bedding coefficient have been added in Quick3 view (and Quick3 production drawing).

Drawing header can be configured: DIN 6771 min (Standard), ISO 7200 fig.1, ISO 7200 fig.2, DIN 6771 (large). ISO headers are drawn without list of modifications, only revision index is drawn as letter (A = without modifications).

FED1+, FED7: tau-s Diagram

A new tau-s diagram shows shear stress as function of spring travel. For dynamic application, stress between spring length L1 and L2 is multiplied with stress coefficient k.

This diagram gives the answer of an often asked question: How can shear stress tauk2 be higher than taun or even tauc? Because dynamic coefficient k applies between s1 and s2 only.

FED5, FED6 - tau-s-Diagram

FED5 and FED6 already provieded View-> tau-s diagram, but dynamic coefficient k was considered over the complete spring travel. This was modified now, dynamic area is between s1 and s2 only.

FED2+: tau-s and sigma-s Diagram

tau-s diagram shows maximum shear stress in the active coils . Dynamic factor k applies between s1 and s2. This consideration is sufficient for extension springs with hooks screwed in only. The most-stressed area of extension springs with loops, however, is the transition of the active coil into the hook. The stress correction coefficient q has to be considered always, because spring is stressed on bending in opening sense at the loop .

In FED2+, spring travel snq and spring length Lnq are calculated now, this means the position where loop stress reaches permissible bending stress. See load-extension curve and Sigma-s diagram of the loop stress.

FED1+: Diagrams

New in FED1+: View->Diagrams with 12 essential diagrams on one page.

FED2+, FED6, FED3+, FED8 for hollow wire

As known from FED1+, you can now also use FED2+, FED3+, FED6 and FED8 to calculate springs made of hollow wire.

FED6 - Calculate Dimensions from Load-Deflection Curve F-s

After input of the load-deflection positions, you will be asked about assembly lengths L1, L2, Lx. Now, you can also set "spring length L1,L2,Lx arbitrary", then FED6 calculates suitable values. This avoids annoying error messages in planning state, if you entered spring lengths smaller than Lc or larger than L0.

FED6 - Dimensioning for any Wire Section

Until now, calculation of coil sections from load-deflection curve was done for springs of round wire only. New release of FED6 supports also dimensioning of springs from square, rectangular, elliptic and hollow wire.

And natural frequency will be calculated for springs of any wire section now.

FED6 - usable Length Ln

Until now, usable length in FED6 was calculated Ln = Lc + Sa, with "Sa" as safety distance until block, using the Sa formula in EN 13906. However, on progressive springs, adjacent coils should not be considered. Calculation was modified now, so that Sa calculation includes only coils that are free before the spring goes on block.

FED6 - Quick3

In Quick3 View, spring is drawn in position L0, L1, and L2 now.

Table with coil sections was extended by coil distance aw.

Ln, sn, Fn and taun have been added to the table with spring travel, length, load and stress.

FED3+, FED5, FED6: S-N Diagram

SN diagram for fatigue stress (like in FED1+) is now also available in FED3+, FED5 and FED6

FED1+, FED2+, FED3+, FED5, FED6, FED7, FED8, FED11: Preferred Database Materials

A short time ago, material selection in the spring programs was improved so that red-marked materials no longer could be selected (see info 135). Now we made another modification, so that you can choose between preferred materials (priority database) and all materials (complete database). In database menu, you (or administrator on network versions) can red-mark materials that should not be used. Then, users should select materials from priority database (without red-marked records).

LG2 - Printout

Drawing name and drawing number have been added in Quick View.

In Printout, moving angle ß, relative transition eccentricity and transition Sommerfeld number have been added.

ZARXP - Edit Dimensions

Tooth height coefficients of the finished teeth instead of tooth height factors of the tool are now input values, because tooth height factors of the tool are valid for completely milled tooth only (kmn=0). Input haP0 becomes hf, hfP0 becomes ha, and rhoaP0 becomes rhof. In earlier versions, tooth height factors had been exchanged when input was repeated, this bug has been fixed.

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