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Ask the Search Engineer

Ask the Search Engineer

Dear Search Engineer: How do I calculate and simulate G-forces for FEA? -S.M., Lombard, IL

Dear S.M.: In ANSYS, you apply an acceleration load with a vector direction opposite of the desired G-force. The value of the acceleration load determines the amount of G-force. So, if you want a vertical down G-force of 2Gs, you apply a vertical up acceleration vector equal to twice the acceleration of gravity, in whatever units you're working with. You have to use units consistently, so you have to be careful that the value of the acceleration is in the same units of L/T 2. Try it without any other applied loads at first and checking the total reaction (value and direction) to confirm that you've applied the acceleration correctly.

Dear Search Engineer: I'm looking for a clear adhesive to bond sheets of Perspex (acrylic) together. The idea is to put several 6-mm sheets together to make a thicker section in my design. -E.H., Wiltshire, U.K.

Cheerio E.H.: We put on the old thinking cap and came up with several suggestions that may work for you.

  • Weld-On #16 is an excellent adhesive. It is a clear, thickened cement that allows a little adjustment before it bonds. You must clamp the pieces securely to squeeze out air bubbles, but when dry, it is as clear as glass. Check it out at: .

  • You can bond also acrylic with chloroform, which is known as solvent welding. The chloroform will melt the acrylic slightly so that the two pieces are molecularly joined. The joint will be optically clear.

  • Thicker acrylic is also available on the marketplace, if you would like to avoid bonding all together.

  • Try MEK (methyl-ethyl-ketone) to bond edges of Plexiglas/Perspex together so you don't see the seam. It would be worth a shot to try it for laminating pieces. Make sure you use the proper personal protective equipment (rubber gloves, respirator, etc.) though!

Dear Search Engineer: We are currently running small plastic molded parts where the tooling is owned by the customer. As such, we can't modify it. We are looking for a sprue picker robot that feeds into a cutting jig of some kind. However, as we are a fairly small company, we don't have the capital to commit to purchasing a robot. Initially, I assumed that this would be common equipment and readily available. To date, all my searching has come up empty. -T.N., PA

Dear T.N.: The equipment you referred to, robotic sprue picker and cutting jig, is the equipment that is common and readily available. I suggest you look at a used equipment web site-for instance,, for a less expensive robot. A local integrator could then assist you in installing and maintaining the robot and cutting jig. As with any capital purchase, cost justification is a critical aspect. You may find that the return on investment will be well worth the effort to pursue this project.

TAGS: Materials
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