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Torque Converter Wafer Bonding Tips
January 7, 2019

The following bonding tips are suggested as a guide for successful torque converter ring bonding. Raybestos Powertrain Torque Converter Rings are pre-coated with QuikR Bond adhesive. QuickR Bond Adhesive was developed for what the name suggests, a quicker successful bond. A successful bond is possible in as little as 2 minutes once the bond line temperature has reached 350°F. What does that mean? It is as simple as this; after placing the part in the pre-heated bonder and closing the platens, the part temperature will rise. The bond line is between the surface of the part the adhesive is going to adhere to and the surface of the torque converter ring the adhesive is going to adhere to. Once the bond line temperature has reached 350°F, this is not the platen temperature, then an additional 2 minutes is needed to achieve a successful bond.

STEP 1 | DETERMINING BOND LINE TEMPERATURE

For each assembly type, you should measure the bond line temperature. Most importantly, how long does the bond line take to reach 350°F? Each different assembly, due to its mass, can take different times to heat up the bond line to 350°F. Once you determine the amount of time the bond line takes to reach 350°F then add a minimum of 2 minutes and that is the minimum amount of time it takes to bond that part. The best way to determine bond line temperature is to measure it at the bond line. To measure bond line temperature, use a thermocouple connected to a monitoring device. This can be as simple as using a DVOM that has a thermocouple port, or a dedicated device that reads only temperature. There are other methods to calculate bond line temperature; however, it best to measure at the source.

STEP 2 | CALCULATING NET FACING PRESSURE

Make the calculations for Net Facing Pressure between 200 psi and 275 psi to determine the line pressure to the bonder piston ram. The formula can look complicated and daunting, but fear not, it is not that complicated. Let us look at the formula and then break it down. LPA = (NFP*SA)/((Pi*(BPD/2)2) LPA = Line Pressure Applied NFP = Net Facing Pressure SA = Surface Area (wafer) - Determined by subtracting the inside diameter’s area from the outside diameter’s area. ((Pi * (OD / 2)2) - ((Pi * (ID / 2)2) Pi = 3.141592654... - Pi is the mathematical constant used in calculating area of a circle. It is determined by dividing the circumference of a circle by its diameter. BPD = Bonder Piston Diameter (This is the diameter of the ram) 72.

Let us break this down; Say we have a GM 298MM converter ring. It measures 11.125” x 10.000”. Its surface area is 18.66547823 sq. in. We determine this by the following: OD = 11.125” divide by 2 = 5.5625”. Square it by doing this: 5.5625” * 5.5625” = 30.94140625 sq. in. Multiply it by Pi (3.141592654 * 30.94140625) = 97.20529458 sq. in. Total surface area of the circle (OD) with a diameter of 11.125” is 97.20529458 sq. in. ID = 10.000” divide by 2 = 5.00”. Square it by doing this: 5.00” * 5.00” = 25.00 sq. in. Multiply it by Pi (3.141592654 * 25.00) = 78.53981635 sq. in. Total surface area of the circle (ID) with a diameter of 10.000” is 78.53981635 sq. in. Subtract 78.53981635 sq. in. from 97.20529458 sq. in. = 18.66547823 sq. in. The total surface area of the Torque Converter ring is 18.66547823 sq. in. Now that we know the total surface area, let us fill in the formula with what we know. Let's say we want a net facing pressure of 250psi (NFP*SA) / ((Pi*(BPD) / 2)2) (250psi) * (18.66547823) / (3.141592654 * (10.00) / 2)2 = 59 psi of line pressure to the Bonder Piston Ram in the bonder. Bonding Pressure Calculator For assistance please use our torque converter bonding pressure calculator available at: torque.raybestospowertrain.com/bonding-pressure-calculator. The bonding calculator will give results of Min PSI 48 and Max PSI of 65. That is because it calculates using 200 psi as minimum and 275 psi as maximum. For more information on piston profile and calculations, visit https://www.youtube.com/watch?v=d3OyfL9VA-U.

STEP 3 | CLEANLINESS

Make sure your parts are clean of dust, debris, water, and oil. They should be dry and clean.

a. Wipe with a lint free cloth using a solvent such as MEK, Acetone or Rubbing Alcohol (90% or higher for better results).

Caution: Do not use a petroleum-based solvent to clean parts, as these leave an oily residue, which will interfere with the adhesive’s ability to adhere to the bonding surface.

b. Wipe again. This time using a dry lint free cloth.

STEP 4 | TACKING

a. Use a drop of solvent such as; MEK, Acetone, or Rubbing Alcohol (90% or higher for faster results) in at least 2 places on the adhesive side of the torque converter ring to soften and make tacky.
b. Position the ring on the part and hold for a few seconds to allow the adhesive to stick to the surface of the part.

STEP 5 | BONDING

a. Pre heat the bonder (we recommend, when you start out doing the time calculations, to set the bonder platens to min lower temperature of 425°F and min top platen temperature 425°F).
b. If equipped, set the timer on the bonder to the time calculated for a successful bond.
c. Set the pressure to the proper amount you calculated for Net Facing Pressure.
d. Insert the part, apply or close the platens and when time is up, remove the part and let cool.
Caution: The part will be extremely hot, use safety gloves rated for high temperatures. You should now have a successful bond. To view the full video on how to successfully complete a torque converter wafer bond, visit https://www.youtube.com/watch?v=o2r6P7BOhG8.

posted by: Nathan Truncone   comments: 0