The Complete Operating Guide for Bally Flexing Tester

What is bally flexing tester?

Bally Flexing Tester, or Bally Leather Flexing Tester, Bally Flexometer, is designed for testing the flexing resistance of leather, cloth, and other materials folded back and forth, is to use one side of the specimen as the inner side, the other side as the outer side, bend back and forth until the specimen is damaged or after bending a certain number of times to see the degree of damage to assess the tendency of the sample to crack. That’s also what flex resistance means.

The machine is applicable to all flexible materials, particular leathers, in particular leathers, artificial leather below a thickness of 3.0mm, and other coated fabrics, sheet materials, etc.

The structure of the bally flexing tester? (take Bally Flexing Tester TF116 as an example)

1. Angle identification
2. Upper clamp
3. Lower clamp
4. Foundation
5. Foot screw
6. Manual operation rotary
7. Controller and display

1. SV, show the preset value.
2. PV, show the actual value when
3. clear times button
4. Value changing button, 0 ~ 9
5. Cursor moving button,
6. Speed display: 100 cycles / min
7. Start button
8. Stop button
9. Power button
10. Set button, press this button to enter the speed setting page.

How to take samples before testing?

Sample in accordance with ISO 2418. From the sample, cut at least four pieces for the dry test and/or four pieces for the wet test by applying the sample cut template to the grain surface. Cut at least two test pieces with the long edge parallel to the backbone and two with the long edge perpendicular to the backbone.

If there is a requirement for more than two hides or skins to be tested in one batch, then only one test piece in each direction need be taken from each hide or skin, provided that the overall total is not less than three pieces in each direction.

For dry-flex testing, condition the test pieces in accordance with ISO 2419 and test in the conditioned atmosphere.

For wet-flex testing, place the test pieces in a glass dish, add sufficient distilled or deionized water to give a minimum depth of 10 mm, put the dish in the desiccator and reduce the pressure to below 4 kPa for 2 min.

Restore to normal atmospheric pressure and repeat the pressure reduction/restoration twice. Remove the test piece and remove excess water using blotting paper. Carry out wet flexing without delay.

NOTE: It may not be possible to clamp thick leathers in the upper clamp. In such cases, the thickness of the test piece can be reduced for a maximum length of 15 mm from one end only and that end inserted in the upper clamp. Even so, the leather may be too stiff to be tested by this method.

How to operate the Bally Flexing Tester? (testing procedure)

(1) Open the upper and lower clamps so that the gap is at least twice the thickness of the test piece.

(2) Turn the motor until the ledge EF on the upper clamp is parallel to the upper edge of the fixed lower clamp, as shown in Figure c).

(3) Fold the test piece in two with the surface to be tested inwards so that the two longer sides are brought together. Clamp the folded test piece as shown in Figure a) with the folded edge against the ledge and the end against the stop formed by the clamping screw.

(4) Draw the free corners of the test piece outward and downward around the clamp as shown in Figure b). Bring the inner surfaces together and clamp the free end in the lower clamp as shown in Figure c), keeping the part of the folded test piece in the clamps vertical and using no more force than is necessary to make the leather just taut.

(5) Run the machine for the required number of flex cycles selected from the following lists:

Dry flex: 500; 1 000; 5 000; 10 000; 20 000; 25 000; 50 000; 100 000; 150 000; 200 000; 250 000 cycles;

Wet flex: 500; 1 000; 2 500; 10 000; 20 000; 25 000; 50 000 cycles.
In addition to the above inspection points, remove the wet test pieces from the machine every 25,000 cycles and examine them for spue before re-wetting them and replacing them in the test machine.

The test pieces should flex without excessive bulging at the sides. If they do not flex in this mode, include this in the test report.

(6) Stop the test machine and remove the test piece. Fold it along the longitudinal axis and examine it visually in good light using the naked eye and with the magnifier). Record any damage in the flexed area, ignoring damage in the clamped area.

If required, to evaluate the intensity of the cracks, bend the test piece along the longitudinal axis around the mandrel. Stretch the test piece slightly with the fingers or using a clip. Use the following wording to describe the cracks:

• cracks: visible to the naked eye;
• fine cracks: visible with magnifier;
• microcracks: visible with microscope having a magnification of 25 times.

Cut through the flexed area, if necessary, to help identify any loose leather structure.

Cutting through the test piece damages it too severely to allow further testing and may therefore only be carried out after the final inspection.

The damage may include the following:

a) change of shade (greying) of the finish film without further damage;

b) cracking or crazing of the finish with the cracking extending through one or more finish layers. Thenumber of cracks may be reported if feasible;

c) loss of adhesion of finish to the leather;

d) loss of adhesion between finish coats;

e) powdering or flaking of the finish coats;

f) colour contrasts shown by finish cracking, powdering, or flaking.

(7) If required, replace the test piece in the clamps using the marks produced by the clamps as a guide to ensure that the test piece is returned to its original position in the clamps.

(8)Restart the machine and continue to the next required number of cycles. Repeat the inspection given in (6).

(9) Repeat steps (7) and (8) if required for other numbers of flex cycles.

NOTE: The actual number of cycles chosen will depend on the specification, the end use of the leather and the expected performance.

(10) If only one test piece shows slight damages in final inspection, repeat the test with a new set of at least four test pieces. If all of the additional test pieces pass the test without any damage, report the final result as “no damages”; otherwise, report the evaluation of the worst test piece.

The repair and maintenance of the bally flexing tester (take TESTEX-TF116 as an example)