Wednesday, 24 October 2018

Thermal laser head for 3D printer? - and sonic screwdriver!!

It's easy (and cheap) to buy thermal lasers for DIY engravers these days. If you head over to AliExpress or Banggood, you can pick them up for peanuts.

I noticed Marco Reps' post on the matter, not long after I got the Cetus 3D printer and had a spot of bother with my finger when I was on Banggood and before I knew it, I had a 300mW blue / violet laser module on its way to me. Including the discount vouchers and the 10% off for using my iPhone, it worked out quite reasonably.

Here's what turned up about a week later, although the guts are only hanging out because I wasted no time getting inside it:

There's some sort of driver board which I guessed was a constant current regulator:

Strangely, it has a bridge rectifier on the input, so is capable of being driven from an AC source:

You can pretty much see what's there without getting too carried away. In fact, it's a 2 stage design: firstly a voltage regulator, then a constant current regulator. I'd been hoping to find some means of PWMing the output but there is none.

Couldn't help sketching out the schematic. Note that the voltage across the LED is about 6V at the rated current, so even without any external components, it would struggle to run at full power directly from a 5V source, which is how Marco Reps used it. Good enough for proof of concept I suppose.

Finally, another moment of profligate indulgence. The ES121 screwdriver is a rather bizarre invention that could only appeal to gadgetboys and armchair engineers. 

It's by e-design, who make some technically interesting stuff. Have a look.

It's not quite so ridiculous if you get it at a promotion price and combine that with vouchers and mobile app discount but it's still completely unnecessary and extravagant. So here it is:

It was the fault of that same bloody mad German, damn him! Take a look and see if YOU can resist.....

Seems to use an accelerometer and DSP (actually, it says it's an STM32) to sense when and how to spin the motor. There's also a tiny epicyclic reduction gearbox in there, presumably multistage. It says it uses "open source application layer" but nothing about the electronics. You can probably guess for yourself - accelerometer, microcontroller, simple H bridge and motor. There's a small display and a USB interface for flashing the firmware and recharging the battery.


Saturday, 20 October 2018

Retuning the DMM servos without handwheels

With 2 of the handwheels replaced, the Align power feed needs to come off. It came with its own special bracket and of course I kept the original bracket that came with the machine. So let's whop that back on. I'm planning on using the power feed unit on the knee soon...

Here's the power feed unit alongside the original bracket:

All done. And finally, after changing the PID settings in the DMM config software, I seem to have a much better response. Here's what it looks like:

For the next step, I plan to make up some simple, 3D printed handles so that I can still do some limited manual movement of the table and saddle. These can be small(er) diameter and being hollow plastic, should have much lower moments of inertia (MoI).

Need to model these up in Fusion 360 and get them flashed up...a

Sunday, 14 October 2018

Off with the hand wheels - make up some spacers

Right, having figured out how dumb I was to retain the handwheels on the Blidgeport conversion, let's do something about it.

Look how ginormous the damned things are. These are cast iron mothers....

Once these are removed, there will need to be something in their place - the bearings have to be clamped up tight and the motor / belt drive housing will have a bloody great hole in the front otherwise. That hole was to clear the back of the handwheel.

Here's a piece of mystery 'loominum - probably 6061, as I'm fairly certain it came from Canada. This will be for the LH end of the X axis ballscrew. Using a CCGT polished, uncoated tip gives a nice finish:

Fitted - seems to work. The bore is 16.5mm on a 16mm shaft due to the drill I had available, so there is a bit of slop. Just holding it in place here but at final assembly, it just took a bit of tightening and tapping to get it aligned:

Now for the Y axis. Another piece of mystery metal, slightly larger this time:

Getting there. The reduced shoulder is to make contact with the pulley and the larger diameter is to shield the opening.

Ready to part off, setting up the Iscar parting tool. This is their uncoated insert, specifically for 'loominum:

A bit of video of it in action. 500rpm, 5''' per rev (IIRC). Didn't complain:

Job done - nice finish:


Offer it up. Looks OK:

Here's the full complement of handwheels to be stashed in the cupboard:

Now to finally assemble them.....

Bantam CNC - sequence of events

 There's a right way to do this: Some of the critical machining work will need to be done on the lathe itself - stuff like modifying the...