Introduction: Arduino Controlled Finger Jonter
Creating finger tines with the table saw PTS10 using a motorized device.
The aim was to create a device that allows me to quickly and easily produce finger-tine connections on the table saw. The respective workpiece is moved on a slide by stepper motor to the respective position, in order to then carry out the cut. There are many such devices on the Internet, most of them manually operated (a well-known one is The Woodfather, which I've built before, but I wanted a bit more comfort, and most of all fun developing and building ;-).
Step 1: Construct and Draw
First of all, inspired by the many jigs that exist on the internet, I drew my model in Sketchup.
Step 2: Wood Parts
Next, I then sawed the various boards (all waste wood from my crate) of 18mm and 16mm plywood with the table saw, only straight cuts, nothing special, attention to angularity and accuracy
Step 3: Assembling
Then assembled according to drawing. Again, nothing special, just assemble and screw together. Again, pay attention to accuracy and angularity (especially in the slide and the guides), but otherwise it goes by itself.
Critical is the positioning and alignment of the bearings to the engine and to the threaded rod. If it is not aligned here, the engine has heavier when moving the slider and may jam.
The procedure of the slider is controlled by the stepper motor and the threaded rod. The threaded rod is guided on the left and right with bearings. I
opted for an M8 threaded rod instead of a ground spindle because the ground spindles are very expensive, and I do not need the accuracy of these here. I've taken a stainless steel threaded rod (M8), which is slightly more uniform cut than the simple of mild steel. The rotational movement of the threaded rod is transmitted via a simple drive nut in the block under the slider to this. The play between the threaded rod and the nut ("dead gear") is irrelevant in this case, since the positioning, where it depends on accuracy, always done in the same direction. The dead gear has only an effect on the free cuts, and it does not matter to half a mm. That first the two outer edges of a groove are cut, and then turned back to cut the groove in between. The device itself uses the sliding table of the PTS10 to make the sawing movement. I used a 10 mm hole in the PTS sliding carriage to position the device. In the base plate of the device, I have a piece of copper tube (diameter 10mm) used, which is inserted into the hole of the sliding carriage. Furthermore, I stuck a short piece of hardwood under the device, which comes into a groove. This positions the device
Step 4: Arduino
The controls are actually
quite simple: the Arduino Uno is connected to the LCD screen (2x16 characters), the two LEDs, the three buttons and the three lever switches as well. The stepper motor is connected to the Arduino via a stepper motor driver (for example, EasyDriver (€ 1.07 on Ebay), or a TB 6560 Driver (about € 4.00)). Power is supplied via an old laptop power supply (20V 2A). The 20V go directly to the stepper motor card. For the Arduino, the 20V is ramped down to about 7V via a voltage regulator module (e.g., LM2596) and fed to Vin.
Step 5: Programming
Now it was time to program the Arduino. The
operation should be done via push buttons and with an LCD screen, and be as universal as possible, so I have written a menu structure, through which you work through accordingly. There are currently two ways to cut the tines, as well as configuration items: - Finger 1: input of board width, tine width, groove width, minimum width of the side tines. The Arduino then calculates the appropriate configuration and moves the slider.
- Finger 2: input of board width and board thickness. The Arduino then calculates the standard distribution. (Formula: wood width / wood thickness = number of parts). You can then increase or decrease the number of parts. Then the shape is selected, so whether █▀█▀█▀█ or ▀█▀█▀█▀ should be cut. And then it starts
- Moving the table: Move the carriage to the left or right with the buttons
- Set zero point: Position the carriage on the edge of the saw blade so that the system knows where it is (only needs to be reset after the saw blade has been changed)
- Homing: Approach the carriage zero. Must be executed once at system startup, or when the stepper motor has "lost" steps
- Configure: Adjustment of saw blade thickness, overlap (of individual cuts), Correction factor (if the tines are too loose or too tight, can be corrected here), Home Offset (distance between Home and saw blade zero) - is actually set via the menu item "Zero point" but can also be entered "by hand".)
Step 6: Lets Go
After switching on, the system logs on with the version number, and then jumps into the "homing" routine. When homing the carriage moves to the right and "searches" the limit switch. The system now knows where the sled is. If you now, for example, "Finger 2" selects, the dimensions of the boards must still be entered: First, the width and thickness of the board are measured. These values must be communicated to the system. The best way to measure with a caliper, the input should be as accurate as possible. The system accepts tenths of a millimeter in width and thickness. (This is the display resolution, please do not dream that this is actually the accuracy of the system ;-)). Then the board (or boards) is clamped in the device, tightened with the reference edge against the stop and with the locking nuts. Then the measured values (width and thickness) are entered. After that, the system proposes the configuration of the finger tines: number of parts (one part is a groove or one tine, must always be an odd number) and the width of the tines or grooves. The formula used is: Wood width / wood thickness = number of parts. It must always be an odd number, so it will be rounded up or down accordingly. The part width should always be smaller than the material thickness. If this is not the case, the number of parts will be increased by 2. Use the "UP" and "DOWN" keys to increase or decrease the number of parts as desired. With "Ok" the selection is accepted. Then the shape to be sawed must be selected (█▀█▀█▀█ or ▀█▀█▀█▀). For a fit you always need both forms, which are inserted into each other. So one shape is cut and then the other, and hopefully it fits together. If not, the correction factor must be adjusted in the configuration menu.