DRO Electronics

I have breadboarded the DRO electronics now. I've settled on three 8digit LED displays for axis position and three 0.96" OLED displays as labels for the axes. These will show whether the axis is X,Y, Z or whatever, plus summed axes and any other information for the axes that may be needed.

I'm also having a 2.4" TFT touchscreen LCD as the main keypad instead of separate keys. This means I can change the layout of the keys and have firmware controlled keypads as required. I've added one hardware key per axis though as an axis zero button.

The TFT LCD can also be used to display various more complicated modes like centre finding and so on.

This is a couple of the displays breadboarded as I tried to get the TFT displays to work. This is a bit of a nightmare as I've had boards that look identical to each other but which seem to have completely different controller chips on them. The touch screen functionality isn';t the most advanced int he world either, requiring voltages to be set up with GPIO lines and then and ADC reading to determine each axis position. Finally got it working though. The OLED display was easy, I just ported the OLED watch code...

The PIC at the moment is a 16F18875. I think I may end up running out of flash space, well, maybe, but that's not a huge problem as there are PICs with the same pinout and more flash space. I'll move to one of them if I need to.
I'm in the middle of routing a PCB with the main displays and big PIC on it. The circuits for each gauge I've decided to put on separate daughter boards. It means I have to lay out just one PCB and I can also adjust the gauge circuit to match any future gauges I find that have slightly different interfaces. Each of these interfaces has it's own PIC12F1822 which captures the gauge digital output and acts as an I2C slave which the main processor then polls. I have done most of that code already. This means that there are seven processors in total and an idle loop for polling each gauge, the main processor doesn't then have to worry about polling six data streams. It should all work...

The main display PCB being routed:

Well, the start of it anyway.

Spindle Camera

While trying to drill very small holes in punches I thought it would be easier to align the drill bit with the centre of the punch if I had a camera that could be used to do the alignment. There's quite a few spindle camera designs on the web, and I found one that used a particular webcam, so I bought one. I then dismantled it:

The PCB had its microphone removed and also the LEDs that could be used for illumination. The problem with them was that the didn't fit in the case I found on Thingiverse, and also that the LEDs were not pointing at the subject when looking at very small items.

I then printed the Thingiverse spindle cam case I found, after I'd modified it for the smaller collet nut I have on the engraver.

The PCB is held by the two halves of the case which are bolted together.

The collet nut slides into the back of the case and there's enough friction there to hold it while adjusting the alignment.

This is the camera on the spindle:

I used some dots on a white background and the trails feature of the camera script that was on Thingiverse. It seemed to work well once I had printed a holder that was a tighter fit on the collett nut.

It was then fairly easy to align the spindle on the end of a punch, then put a 0.1mm drill bit in and have a go at drilling a hole:

You can see some chips at the base of the drill there. The first attempt snapped the drill bit on removal just as it was nearly done. Not sure why, maybe too fast an extraction speed on the peck cycle.

I had another go and all worked well that time. This is a video of the camera output while drilling another punch hole.

These pictures were taken with the camera out of the spindle and held in a marking base I recently bought:

Dragonfly Hairclip

 I've been working on this on and off for a while now. It's a dragonfly hairclip decoration made from acrylic and aluminium.

 The acrylic is turned and polished just like a pen would be, with two parts, one for the body and one for the head.

The wings are engraved aluminium sheet, each pair of wings took about two hours to engrave and cut out, admittedly this is mainly due to the resolution of the input file.

The parts are screwed together and then screwed to the hair clip.

Bergeon Platax Punches

Bergeon Platax Punches

I've been gathering watchmaking tools for a while as they are useful for making small things, and especially useful for fiddling with watches. I have a project watch that I want to work on and having the right tools is always a good idea. One tool I recently bought is a Bergeon Platax tool which is used for dismantling balances.

Unfortunately one of the punches that it came with was broken, so I decided to make some more. These are not easy things to make, as they have various holes in the end of 0.1mm, 0.15mm and 0.20mm.

I used 3mm silver steel for the punch body, and some EN1A rod to make the stop rings. I'm using the CNC engraver/mill to drill the holes in the end of the punches using carbide drills. I created a tcl script that writes gcode with appropriate feed speeds and pecking cycles. It took a few attempts to find something that works, but I seem to have that now. And a pot of broken drills... The results are pretty good:

That's mine on the right and the original on the left. This is the broken 0.20mm punch on the left. The hole is about 1mm deep, I've no real idea if that's the correct depth, but it seemed to work on the balance I had a go at dismantling. The silver steel isn't particularly hard, but then, if it wears out I can make another punch...

One problem is the accurate positioning of the hole in the end of the punch. I think I may have to build some sort of something that I can use for positioning the CNC spindle when making small things. Trying to do it manually by poking me head round the spindle just doesn't work very well.

You can see the hole here, and the fact it's a bit off centre:

I've also ground a used D bit down and used it to create the rounded edge to the hole that the original Platax has on its punches. I may have to do something more accurate for that too. Somehow.

Second DRO Gauge

The second gauge has been fitted to the lathe. This one was a cut down 'hardened stainless' gauge I got off ebay:

I'm not sure what was hardened or stainless, this machined like butter on the mill. I'm not complaining, it made my job easier.

The mounts are 3d printed, the gauge display unit fits neatly into the metalwork, I added a copper shim to remove the last 0.1mm of movement, now there's no measurable movement.

This metal gauge works better than the plastic 0.1mm resolution one I put on the compound. Even though you can get 0.01mm resolution on the data output, it doesn't stay very stable.  I think I may use one on the compound as well, if I can buy one. I'm going to experiment with other calipers, I need another 4 for the mill and the gauge on the lathe ways.

Box

A pen and box seemed appropriate for an upcoming birthday, as I always think it does. I turned a blue ballpoint pen and made a box from some pine.

The person the box was for is musical, so I added some engraving on the top of the box.

The notes are the first few from 'Happy Birthday'. I engraved it from a bitmap. I converted the bitmap to gcode with a utility that was slightly tailored for this engraving job. It looks like I finally have a set of tools that will allow arbitrary image engraving. The depth is set by the greyscale value in the bitmap. These notes were engraved at a single level.

DRO Displays

The displays for the axes of the DRO are going to be LED digits. I have some modules that use the MAX7219 chip and have 8 seven segment digits plus decimal points. One Arduino UNO and some code and we have a trial display:

So now I have a display and a gauge attached to the lathe. I thought it would be a good  idea to check the DRO gauge and see if it would be useful. It's not worth going through the hassle of building all the gauge channels if it doesn't work very well.

The first attempt was OK, but the gauge didn't slide very freely. Some adjustment of the gauge mounts might be a good idea. After some gentle filing the gauge freed up and all worked quite well.

I set the lathe dials to zero and the gauge to zero as well to check the calibration between the two measurement systems.



After moving a distance from the zero, I noticed that the gauge didn't match the scale. I finally found that when the gauge read a round number of millimetres:

The scale on the handwheel isn't at zero. I was about to give up on the DRO until I noticed that the ball on the handwheel was in the zero position.



So the dial had slipped when moving the handwheel. It looks like the DRO was more reliable than the dials in this case. Looks like it is worth continuing.