HPGL shortcomings

Hi - On a previous post that I commented that small dia circles cut on my machine( Stepcraft 600 1) importing HPGL files were ALWAYS smaller than required.
.
I think I now know why! and its not a fault of the machine, or its software.

HPGL resolves all circle & arc commands to polygons, the edges of which are straight lines. Thus all circles are cut as straight lines, not curves. This means that any circle diameter is only contacted by a cutter at intervals.

Thus, say a 2mm dia circle would be resolved into, say 8 straight lines, only touching the proper diameter at 8 points & the straight lines cut are less than true diameter This means that ALL circles using HPGL - will be undersize. The problem is obviously worse for small diameters & reduces as the diameter increases.

However its still more convenient for me to just increase circle diameter marginally to allow for this -as I prefer to continue to export in HPGL format. I don't know how dxf files treat circles.

I use the full USB program supplied by Stepcraft & its excellent for my 2d applications, with its own tool offset feature & a host of extra features.