There are a lot of misconceptions out there about compacting no bake foundry molds.
The longer I compact, the better the compaction. Many think that longer compaction cycles improve mold face density. Actually, compaction is complete as soon as the sand stops dropping in the box. Compacting any longer than that actually causes ram-off which is detrimental to casting dimensions and drastically affects lettering quality.
- Altering frequency is a good way to control the force of compaction. No. Frequency does not equal force. If you want to reduce the force of a compaction table, you have to affect the force output of the vibrator.
- Pneumatic vibrators work fine for compaction. Sometimes. Generally, pneumatic vibrators are highly susceptible to changes in air quality, pressure, and flow. Electric vibrators are far more consistent and generally require less maintenance.
- Do you need to compact? Yes, in most cases. There are some mold types where it does not help, but largely, compaction greatly reduces issues with burned in sand after pouring.
What do we recommend? Hit the mold hard for a short cycle. Use rotary electric vibrators for molds over 1000#. Compaction cycles should only be 2-3 seconds long. If you have multiple force levels required for your molding, use counter rotating electric vibrators to alter force, never frequency. We also strongly urge you to use high frequency vibrators. Why? So that you compact the sand rather than just bounce it around.
Lee White
President
Del Sol Industrial Services, Inc.
To learn more compaction of no bake molds or for any other foundry realted questions, contact Lee White.