Tail-stock Stand

I have a mini lathe and it came with a tail-stock. This is removable and I use the lathe without it quite often. It spends most of its time on a bench somewhere, or propped up against the back of the lathe. The design of the tail-stock means that it can't stand up in it's normal operating orientation and so has to lie on it's side or lean against something. This started to irritate me. I thought of a shelf, then decided to make this:

 The tail-stock rests in it like this:

I then mounted the stand on the side of the shelf unit I built around the lathe:

It's now in a space that I couldn't really use for anything else. We'll see how good an idea this was as I use the lathe for future projects.

Video of DRO Operating

Video of DRO Operating

I've made a little video of the DRO operating so you can see how fast the update rate is. It's several readings a second and easily fast enough for anything I do. The gauge data stream is pretty fast and all six channels are read by the main processor over I2C, only three are displayed.

The main TFT is quite slow with big updates, but just about responsive enough when I use the menus.


One thing I was worried about was the auto power-off that the gauges have. After a period of inactivity they shut down, but fortunately all they do is turn the display off. The data stream continues, which is perfect for a DRO like this. It also might explain why the batteries go flat so quickly...

Collets

I needed a holder for my ER32 collets on the lathe, so one piece of scrap plywood and some holes and he have a holder:

The lathe has grown from just the machine to a machine surrounded by a myriad of stands and tools...

Finally Got DRO Touchscreen Working

I rewired a few GPIOs to move them away from the JTAG interface and the
XPT2046 touchscreen is now working:

I now have all the hardware working and can start on fleshing out the firmware a bit. Then I'll put the DRO back on the lathe and try it for a bit.

Lathe DRO 

I've mounted the ARM based DRO on the wall and attached two gauges to the lathe. The Y axis isn't attached and the code mirrors the X axis, but apart from that it's working:

The gauges are here:

I've re-cased one PCB but left the other one with a display. I'm not sure what I'll do with the next ones, it depends on the space I have available. There's only two channels of gauge decoders plugged in at the moment, both decode the cheap Chinese gauge data streams (24 bit). For some reason I've not worked out I have a signal problem with the channel that attaches to the more expensive gauge that outputs the 2x24bit data stream. I need to build some more gauge channels and attach gauges to the mill and the third gauge to the lathe.

The TFT display isn't working at the moment, I have to get the SPI protocol working, I'm going to do that on a breadboard.

I'm going to try the DRO out as it is for a while and see how it goes.

Lathe Centre Height Finder

I got fed up with fiddling with tool heights on the mini lathe, so I cobbled together this

It's not hugely pretty, but it works and is adjustable. I like the base, as it's a bit of metal I picked up while walking somewhere, on the off chance I could use it, and I have, excellent. The brass and base are polished, but you can't see that in this picture very well, so there's some shiny bits.

DRO Display Running

The main display PCB has now got some firmware that does something. The code can talk to all three OLED displays and also to the three LED readouts.

It can also get pixels on the TFT, but the range of co-ordinates seems limited in some way. There's also some spurious pixels on the OLED displays, but it seems deterministic so I don't think it's noise.
I need to get the touch screen code in a fit state to register keypresses.

I've also routed a couple of gauge channel daughter boards:

The bottom one is milled using a 0.2mm bit as I have done with most of my PCBs so far. After the problems with shorts on the display PCB (which turned pout to be soldering problems, as there's no solder resist), I have tried a double stage milling process in the second PCB. The first stage is a mill with a 0.6mm bit, followed by one with a 0.2mm bit to cut away the final detail. This leaves a larger gap around most of the tracks, which I hope will act as a sort of solder resist.

Here's a populated gauge channel PCB:

The socket is for the PIC12F1822 which reads the gauge data stream. The transistors are used for level shifting the data to 5V and also for driving the data and clock lines in order to put some gauges in to fast mode.
There's also a 1V5 supply generated with a simple voltage divider.

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.

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.

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.

Mini Lathe DRO

I'm looking at building a DRO for the mini lathe and mini mill. The electronics isn't much of a problem, but the mechanical aspect of fixing gauges to the lathe and mill is another matter. I've decided to have a go with the cheap plastic digital calipers that you can get from China for a very cheap price. They have a data output that can be attached to a processor of some kind, which is very useful. The plan at the moment is to have a processor per gauge to handle the data stream and then have a larger master processor that handles the LED displays and does the keypad and clever stuff.

After hacksawing a caliper apart and 3D printing some parts I have the first version of a mounted caliper:

There's a couple of problems with the 3D printed parts, but it all seems to fit and work. It also doesn't seem to interfere with the operation of the compound. I need to put the PCB back on the gauge and wire up to the electronics, but it's looking hopeful. I'm not going to replace the LCD or buttons one the caliper PCB, I'll just use the data output.

From the data output it looks like there may be better resolution than the 0.1mm resolution that the caliper itself displays.