Determining flatness and parallelism rapidly

[greg123]

During our grinding operation of steel we are looking for a method to determine flatness and parallelism on a 100x50x 300/400/500mm long parts.
Our goal .005mm. This is a bit tricky and time consuming to do on a surface plate. I've been looking into laser levels and white light interferometry but thought I might ask around. Anyone have any ideas?
Thanks

[Kingsld1]

First Stab at this;

For flatness use a Surface Plate with a hole in the center to mount a LVDT indicator? Surface Plate would need to be twice as large as your part. Slide the part over the LVDT indicator looking for total range.

Mount another LVDT above the surface plate, opposite the first, so that it can touch the opposing surface to measure parallelism.

Downside is the surface plate may wear rapidly.

[beanat]

If you are still looking for a solution interferometry can provide extremely accurate results very fast (less than 30s) depending on the type of interferometer loading and unloading of the parts is also very simple. For large pieces in my opinon the systems produced by Tropel are the fastest and easiest to use and can measure parts from rough grind to mirror polished.