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Movable Bed CNC machine 15

Test leveling of waste board of thin plywood

Test leveling of waste board of thin plywood. The plywood warped in the center.

After my first cut, I knew I had to fix a backing spoilboard on the machine movable bed so that I can protect the latter from being damaged when the tool cut deeper than the thickness of the work piece. At the same time, I would take this opportunity to adjust the spoil board to be level with the movement of the cutting tool.

Previous, I had some success using sheets of paper with overlapping cut sections to make gradual transitions of thickness in order to present some gradual gradient from one point to another. I intended to do that again with the spoil board.

Result of test leveling of waste board of thick plywood

Result of test leveling of waste board of thick plywood. Test pattern covered the entire space of the tool movement limit.

But first, I needed to find out which areas on the movable bed were high and which were low. So I drew a test pattern consisting of lines that connected across the whole area where the tool would move. The idea was to paste a blank sheet of paper on top of the spoil board and let the machine move a pen over the whole area. Those areas which were touched by the pen would be the high areas, while those not touch would be the low areas. With the spindle already in place, it would be a simple matter to install the pen into the arbor and operate the machine as a plotter.

Testing second cut of text using cylinder milling bit and conical bit

Testing second cut of text using cylinder milling bit and conical bit

At that time, the only waste piece of board that I had was a 3 mm thick piece of plywood. I thought it would be ideal. However, after I tried a few times with it, I found that it tended to warp and showed up being higher at the center. Later, I found another piece of thicker 10 mm plywood, smaller in size, but just sufficient to cover the limits of the tool travel. I used that as my spoil board. Because it was thicker, the distortion was not too bad and I managed to adjust the level against the tool to an acceptable level.

Closeup of 2nd cut of text.

Closeup of 2nd cut of text

With the confidence gained with regards to clamping of the work piece, running the tool for cutting, supplying electric power and operating the spindle and programming the movement of the tool which were successfully executed, I did another test with the same soft wood work piece since there were some empty spaces available. This time, I was able to clamp the work piece in place on top of the spoil board.

I did a text cut to see what happened. Using the straight bit, I found that the tool was too large for the designed text. What came out was more like a pocket. The text letters was not recognizable. Not giving up on this, I changed the tool to an engraving bit, adjusted the depth to the newly surface and did another cut over the same locations. The text letters were legible and fine this time.

So, I had successfully tried out all the bits that I had. I particularly liked the engraving bits with their cone-shaped cutting edges. My next target will be to engrave on plastic.

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