WARNING – Those opposed to over-engineering should avoid reading this lot…

This project started as a challenge, rather than any need for a 3D printer. It has been almost a year and slowly it is starting to come alive – although I still find no need for a 3D printer…

Anyway, a challenge it is – Polar co-ordinate world to work in, with inverse kinematics and some fun math..And I don't leave it there – the Hot end is an induction heated one, the heat part is currently being worked on on the bench in an attempt to see how often I can blow it up in one day…

Also, the extruder drive train will ( hopefully..) be a brushless (RC) motor drive – so am also developing a Step/Direction input brushless motor servo drive. The reason for the induction heater and brushless motor drive is to try get the entire hot end / extruder below 150grams, 200grams max. I also want the extruder to be at the hot end, no Bowden tube, etc. So a lot of fun still to be had.

In the meantime, the actual SCARA arms, the drive servos/stepper, powers supplies, Nucleo brain, etc ias all together, and my good Wife is software-ing it – I have to fit a spring loaded pen to the hot-end end, so she can draw some calibration verification squares and circles to start.

Some photos – beware, the qty of pics matches the engineering effort..

The electrical/electronics box, ready for tig welding

Some tigging done..

Re-winding an old Amplifiers toroidal txfmr to suit my voltage needs:

All Wound:

Trial wiring before stripping and painting:

Ready to strip and paint:

Painted:

Starting to test things:

Electrical box wired – Extruder control and induction heater still to go in at lower right.

SCARA Arms servos:

Z Axis Stepper drive and leadscrew:

Next installment when the thing moves about and draws stuff…

Joe

Neil, a 'tad' is slightly understating, no?..

I am keen to be able to fit a laser head of sorts, but that is another field on its own. A fibre laser would be nice as the weight is remote, with only the fiber and lens at the end of the arms, but the fibre laser is rather limited in application with certain materials – wood and many plastics are a no go, pvc, acrylic, etc. I did try one of those chinese '5 watt' blue laser heads – absolute junk – if that was 200mW it was a lot…and the control electronics was useless – pulse control was very poor so raster engraving was mediocre. There are a lot of those type lasers from Ebay, Ali-xyz, etc, but the specs are impossible to believe..

So, any ideas for a good (light weight) engraving laser are welcome!

No idea what sort of laser is needed for SLS, but the idea is interesting – when the machine is sort of working I may try the SLS route.

Thanks for the good words chaps!

Joe

Please excuse if I am repeating old queries – I did try a search on the site and did not find much…

What Slicers are in 'popular' use by people on this forum? The firmware for my oddball SCARA printer is slowly coming to life – it can draw squares and circles to decent accuracy, all done by the firmware interpreting G_code.

Next step is to investigate what sort of G_code flavours are generated by the Slicer package, to ensure my firmware interprets it all. I have investigated Cura and Slic3r – Cura is sort of 'open' and free, but seems a few years ago it became an Ultimaker product, focused on the Ultimaker printers. Anyone using Cura?

Slic3R seems more appropriate for my use – reasonably simple for a beginner!

There are so many settings and controls in the slicers – hotend and hotbed fan speed controls – anyone here actually use those features?

Maybe Neil will chip in – Neil does do some 'real' stuff on his printer!

Joe

I have progressed a little on the Induction Heater for the printer Hot End. I tried various options, Class D switcher, Royeur, and a few others. The Royeur worked well, is simple, and was quite efficient, but failed as all these topologies did, because they are all 'low frequency' – that is, typically below 500Khz, and mostly around 80 to 200KHz. I am trying to heat an aluminium shaft, which holds the hot end nozzle ( non-magnetic stainless steel) and for that the frequency needs to go up – way up – to the 7 to 14MHz region.

So to test this theory , before starting on the RF source design, etc, I dragged out of the store room an old 50watt solid state CW transmit brick ( was used as a variable power output HF CW beacon, for NVIS tests, long, long ago..). I knocked up a test hotend, with the nozzle attached and a 6mm thin wall St/Steel tube as intended heat break.

The body is aluminium, with the heating coil of 16turns, diameter 10.5mm. This measured out at 3.5+j20 ohms.

The RF source was set to around 35 watts, and a 50ohm matching network kludged to match to the work coil.

The results were indeed very pleasing!

The hotend heats from 25degC ambient to 180deg in 15sec, to 295deg in 20sec and to 440degC in 50sec.

Some non-linearity there, mainly due to the heated material eddy currents behaving differently at the climbing temps.

Some pics :

Test setup – The hotend is the device sitting atop the pink ceramic thingy..The wire entering is the thermocouple

Top scale = 250watts FS – abt 38 or so watts in. (Reflected pwr = nil..)

Around 45watts in ( amp is class C so fairly efficient)

After 15sec

After 20sec

After 50sec

The RF signal source – Two amps in one – 7MHZ and 10MHz, latter changed to 13.5MHz for this test

The test Matching network.

Matching network, some copper coils used with the low-frequency inverters – just cooked the coils due to skin effect and high currents needed to heat aluminium or stainless – insulation burned.

The test hotend- Wire is silver, 0.35mm diameter, 16turns 10.5mm diameter.

uMetal shield for EMI mitigation..

The heat break end.

All in all a resounding success! Now to turn it all into a solid design..

Joe

Edited By Joseph Noci 1 on 22/07/2020 19:27:04

Got to stop feeding Swarf to this thing…else this happens…

Wiring and Coax cable to the induction heated hot-end, the fans, thermister, extruder stepper, etc.

Everything moves, drawing squares and circles with a pen in the hotend position looks very very good, hotend induction heating works fantastically well, extruder is a butchered Bondtech unit from a big creality printer.

Next step to fit the bed heater, bed leveling sensor, and a Nextion based control panel so the PC is not needed.

The leveling sensor to use the Texas LDC1101 – a very neat induction measuring device which will use a sliding ferrite rod ( 1mm diameter) that contacts the table and moves into the sense coil. The change in inductance ( a 24bit value) is easily converted to a distance measurement with 20um accuracy, with 5um resolution, from 40degC to 120degC

Just another over-done sensor excercise…

Joe