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2012/02/23 6:43 PM CST

This site is about a DRO (digital read out for a milling machine) prototype I have been working on in C# along with an interface board developed on an LPCXpresso with an LPC1343 (Info - Manual).

The idea is to be able to show your part from a DXF file and the tool position relative to it.

I have it working on a friend's Bridgeport. He reports that is is working well (even when he finds an occasional bug).

If you download it ( PC_DRO_20_2A.zip ) and check it out send me your thoughts at rlstrand @ yahoo.com.

Version 0.20

- Added five user defined tool select buttons so you can quickly change tool sizes. Can enter fractions or decimals.

No installer yet, just download, unzip and run from a folder. It requires .NET 3.5 to be installed. Should run on Win7 and XP.

I am looking at ports to WinCE, and maybe Mono compiler for Linux.

With a bit of code massaging to port it to Java for Android.

This is what Guided Mode looks like to cut the an ear on the par.

The arc was selected (in red), the pink circles are guide points that the program calculated for a roughing

clearance 0f 0.0200 a maximum bump of 0.0050 between guide points.

The display shows that the tool is -0.0305, -0.0355 away from the closest guide point (red center).

When exactly over a guide point the display will show 0.0000, 0.0000.

You can either plunge mill or carefully walk the tool to the next guide point while cutting.

Guided mode for a rec1angle, move tool to one corner or edge, move to next corner, when tool gets just over half way

nearest guide point will move, crank to 0,0 error and change directions.

Here is the setup screen, you can run DRO only, load DXF for a complex part, manually enter parameters for Bolt Hole Circle, Bolt Hole Array or a Rectangle and set custom display colors for the drawing area.

With the proto you can use the Sim Scales check box to pop up a little control panel to check it out on a PC without hooking it to a mill. I have prototype hardware based on an LPCXpresso board that will interface to A-R/5 linear scales. It sends scale data via RS232, RS485 or USB to the PC.

If you want to roll your own interface. The WinDRO program reads characters from the comport at 9600 baud, 8 bits, no parity, 1 stop bit. Message format is ten bytes XXXXYYYY CR LF, where XXXX and YYYY are unsigned 16 bit hex values of pulse counts for the X and Y scales. FFFF over flows to 0000 and 0000 under flows to FFFF. The program detects this and counts correctly.

How it works:

The ABS button switches between ABS/INC like a normal DRO can be used this way without a DXF file.

Clear the X and Y values by double clicking them.

The Guide button turn on guided mode. Guide point(s) are calculated and displayed on the drawing as tool locations for the selected part feature. The X and Y display shows distance from nearest guide point. For arcs, circles and slanted lines it determine the needed points base on tool diameter and Finish Tolerance. For lines on an X or Y axis only one point is shown, it will move with the tool. Guide points also offset the cutter based on the Roughing Clearance.

There is also a trace mode where there is only one guide point. The point is recalculated as the X and Y are moved. This mode allows the operator to adjust smoothness on the fly.

The Sim Scales controls tool position via a small control panel to demo without connecting to a mill. Click a button to move 0.0005. Hold it down and it will start to slew. It gets progressively fast as it is held.

There are pop up tool tips on most UI items.

Here is what a $26.25 LPCXpresso board looks like. The left half is the attached JTAG programmer/debugger.

The right side is the LPC1343 chip, oscillator and one LED.

When you are done developing you can cut the left side off if you want.

Here is the "complicated" USB connection for the LPC1343, three resistors and an old A plug cable.

When plugged into a PC it shows up as a new com port.

This is the type of touch screen I might eventually use:

rlstrand