[shotpeen]

Hello, I need a drawing (old fashioned, pencil-on graph paper) turned into a DXF file suitable for use with a water-jet cutting machine. My part will be a small (< 1 sq. ft.) 20 gage sheet metal item. Most aspecs of this item are easily rendered with AutoCAD. The problem is the most important shape within this configuration is a modified compound parabola. (The item will be a 'rib' component in a secondary solar reflector; it will hold the contour of the mirror sheet metal within the housing.) I cribbed the shape from a book, decreased the aperture, and tweaked the curve a bit. I do not have the math that generated the original curve.
Is there some scanning program that can look at a drawing and do this?
Is it something that can be done manually (create a curve by physically measuring and plotting thousands of points on X/Y axes ?)
I would really like to hear from someone who has some insights into the matter.
Thank you

[txcncman]

Without a digitizing pad to literally trace over the hard copy drawing (which will include human error) the only way to avoid re-drawing your part in a CAD program is to scan it into a raster image and then use some program that can convert raster images into vector graphics. If you already have it scanned into raster format, upload it and maybe someone will offer to help by converting it for you. Understand, that raster to vector conversions are not usually "clean" and have to be tweaked a little and even then may not be 100% "perfect" like a CAD drawing would be.

[jkhesch]

A digitizing tablet with software that will generate a "free form curve" from a series of discreetly digitized points is what you need. It is NOT recommended that you TRACE the shape as there is much "fuzziness" in a traced image. Rather, art-to-part software that allows one to digitize discrete points and that automatically generates a a mathematical curve that passes through those points is what is required. Then, mature software can export the curve as a series of primitive drawing entities, i.e., line segments, arcs, etc., into a CNC-ready dxf.

Kind regards,
Jim Hesch

[keebler303]

When drawing the profile of wood molding from a customer supplied piece, I have been known to get a drawing close, print it out at 100% scale and compare, then tweak and repeat.

Maybe this will work here? You could use a light table to compare your printed drawing with your hand drawing.

Matt

[Al_The_Man]

If you have access to CorelTrace?
Technical support for customers of Torchmate CNC Cutting Systems.
Al.

[zool]

You will be way happier if you take the pencil and paper drawing to someone who draw it with CAD with DXF output.

This way fewer steps, and fewer steps means less chance of errors.

[keebler303]

You will be way happier if you take the pencil and paper drawing to someone who draw it with CAD with DXF output.

This way fewer steps, and fewer steps means less chance of errors.

That is not the issue. He is asking how to get a complex curve transferred into CAD when he does not have the actual dimensions or the equation used to create it.

Take measurements to get close, then fine tune with trial and error as I described above.

Matt

[zool]

There are techniques in CAD that make replicating his "modified compound parabola" easy.

1. Bezier curves. Using a bezier curves the "modified compound parabola" can be replicated quickly. Adjustments can be made by moving the points that define the curves, or adding point to enhance a section of the curve.

2. A haptic device along with some two-sided tape and piano wire. First, apply two-sided tape over the "modified compound parabola", then adhere the piano wire to the two-sided tape so the piano wire is directly over the curve. Then trace along the curve with the stylus of the haptic device.


See this: Haptic technology - Wikipedia, the free encyclopedia

One manufacture of haptic devices: PHANTOM OMNI - Sensable

Also, the probe used on a three-axis CNC machine is a haptic device.

[BurrMan]

I do not have the math that generated the original curve.

Maybe the graph paper gives you this? Old fashioned conics were fashioned with the graph paper as the base. Can you post a pic of the hand drawing?