axCut moves home, AFRo comes alive

axCut + Man Cave

It's been a long summer, but the man cave is now virtually complete and last weekend, the laser cutter (axCut) got moved into its long-term home:

AFRo

Whilst I've spent most of the sun-lit hours building, the dark hours have recently been spent on a new project - building an assistive feeding robot (named AFRo) for the UK charity REMAP.  The goal is not dissimilar to the HelloSpoon project (see Indiegogo campaign), but with enough differences to require a new solution.

You can are welcome to read through my detailed Design Notes as the design progresses, but for instant gratification, here is the latest video:


The hardware/software are both open source and published on github - see links in the Design Notes document, or search for the AFRo repo.    Hardware is fully modelled in OpenSCAD and predominantly 3D printable.   Total parts cost is currently around £260.

Comments/ideas welcome, but please read the Design Notes first in case they're already answered.

AFRo mk2

Although the mk1 mechanical design is functional and meets the design parameters, it suffers from too much vibration at the spoon tip :(  No good having a robot that shakes your food off the spoon.  It's not serious enough to abandon mk1, but it does mean I'm already working on mk2 in parallel.  It'll re-use most of the software, as the axis configuration is logically unchanged.  Here's the design sketch:

Will put up a more detailed post reviewing the design changes/reasons when I have time.

Man Cave (aka axLab)

So... progress on the laser cutter, and a number of other projects, has stalled in recent months due to two major issues:

1. We have a 3rd baby on the way, so I need to evict myself from my office and the dining room :)
2. The dining table is not stable enough for the laser cutter, so it needs a strong trolley to stand on

The solution to number 1 is to finally get on and build a good size workshop (man cave) at the end of the garden.  Number 2 will be solved by building and installing a trolley in the new man cave.  Simples.

Latest progress:

Man Cave Requirements

My choices in design, materials and approach will probably make more sense if you know I've always been fascinated by architecture, nearly went into a career as an architect, am addicted to DIY and plan one day to build my own house.  As it happens, I've been sketching designs for a work-shop/garden studio for years (nearly 10), but the deadline imposed by point 1 above has forced me to finally settle on something.  This has also been the first year where we could actually afford to build it!

So, top-line requirements:

• As big as I can get away with - subject to permitted development, building regs and my wife
• Split into a "clean" area (home office, electronics) and a "dirty" area (everything else)
• As close to maintenance free as possible
• Visually appealing (inside and out)
• Solid concrete floor
• Fairly well insulated walls, whilst keeping the total wall thickness to <150mm and cost to minimum
• Include a decking area for patio set, bbq, etc
• Budget of £6k

Exterior Design

Given the dimensions of our garden (18m long x 9m wide), plus the substantial hedgerows down both sides, I settled on a width of 6.5m.  Permitted development caps the roof height at 2.5m.  Wife, building regs and convenient timber lengths set the depth at 2.5m.    Although I've tried to keep the design as simple as possible, I just couldn't bring myself to build a plain box - so I opted for a sloping and gently curved facade.

Quick specs (happy to provide more info if anyone is interested):

• Foundation: 250mm hardcore, 50mm sand blinding, DPM, 120mm concrete slab
• 2-course dwarf perimeter wall from concrete blocks
• Timber studwork walls (2"x4" framing, 16 inch centres) with 12mm OSB outer sheeting and 12mm plasterboard inner skin.  Insulated with 80mm rockwool.
• The whole building is wrapped in Tyvek building paper, then the roof, back and sides are clad in industrial steel siding (in a rather fetching Forest Green).
• Front cladding, window frames and stable door are handmade in oak.  
• Deck - There will be a 5.5m x 2m deck along the front of the building.  Am keeping it simple with a floating foundation (80mm of gravel), then pressure treated framing in 2"x2", covered in oak boards.

Oak

I have a minor obsession with oak...  it's an awesome material.  For this project, I managed to find a great source of 30mm kiln dried oak boards (100 - 200mm width, random lengths) for approx £850/m3.  Given the great price, I've elected to use this same material for cladding, windows, doors and decking.  However, this has meant profiling a LOT of boards to make the cladding - a table saw is pretty much essential for this job!  Fortunately, the money I saved in sourcing cheaper oak meant I could afford to buy a table saw (at last) - a tool that has been on my wish list for years.  

Interior

The interior will be divided into two areas, with a partition wall just to the right of the main door.  The smaller right hand space (1.5m x 2.3m) will be the clean office area.  The remaining space will be the workshop.  The surface of the concrete slab got a bit ruined by a downpour just as I was finishing laying the slab, so I added a thin screed to improve the floor finish.  Walls and ceiling will be plastered shortly, then I can start installing work benches, etc.  I've not yet settled on an interior layout - so more to come as that evolves.

Current Status

As of last night, I've finished the stable door, so the building is secure for the first time.  The double glazed units are due to arrive later this week, ready for me to finish the windows.  Jobs for the next week or so:

• Finish the cladding
• Build partition wall and pocket sliding door
• Build deck

Once the office space is functional, I can relocate from the house and then my old office needs to be converted to a bedroom for my son.  T-minus 16 wks to baby no. 3....   plenty still to do!

axCut Laser Cutter - cracked it! z axes working, honeycomb bed installed - lovely jubbly!

Have finished installing the z-axes drives along with the honeycomb bed, and it has made such a difference.  I've been able to run some test cuts and finely calibrate the focal point (to within 0.1mm).  The host comms also seems to be behaving better (I'm convinced it's my windows laptop causing issues).

So... here's a video of it all working together - and it is working extremely well.  The test cut in the video is based on a friends wedding invite, and has converted into just 2223 lines of gcode - nice and compact thanks to the bezier curves!

The finished cut is very, very good - comparing it to the commercial reference (from same design file) it's as good, if not better (less wobble to the edges).  The low feedrate I've used may also be a contributing factor, but I'm still feeling rather smug.

Still lots to do on the hardware side (enclosure, cable chain for air assist, a rigid trolley), but for now, I think I'll take some time to play with cutting stuff!

axCut Laser Cutter - first cuts; not quite epic fail

We have cutting!  and a lot of smoke - really must order the cladding and setup some extraction!  This is a proper "Tomorrows World" video, it doesn't quite go to plan, but nonetheless - there's definite progress:


The cutting paths were generated from SVG via a little converter program I wrote using the paper.js library.  The arduino/Marlin combo is processing the bezier curves (as demo'd in previous video), but now with the addition of laser on/off commands around each path.  Air assist working nicely, except when the airline is being burnt by the laser :(

Laser control and watercooling all working well - the watercooling pump runs continuously, but the radiator fans only kick in when the laser outlet water temp rises above 22 degrees C.  The watercooling system is very quiet, thanks to the excellent little pump (Phobya DC12-260).  The fans are also extremely quiet when they are running, but the water temps haven't gotten above 19 degrees as yet (ambient temp during testing was just under 18, thanks to doors/windows being open for the smoke).

Laser control commands include arm/disarm of the laser PSU, control of laser power (0-100%), laser on/off and a diagnostic output.  The laser power control is via high speed PWM (62KHz, using timer4).
Air assist will soon be integrated into the relay module, so it can controlled by the arduino (via a couple of G-codes).

Air assist clearly plays a big role in:
 - stopping fires!  (without the air assist, there's a persistent flame about the cutting point)
 - keeping crap away from the lens

I'm assuming cut quality will get much better once the honeycomb bed is installed (so smoke/heat isn't being contained under the work) and once the focal point is properly calibrated.  I did go on to adjust the bed and do some power/feedrate tests, some of which you can see in the video below.  After bed adjustment, the cutting kerf at optimal power/feedrate is approx 0.2mm... should still be able to get better than that.  There is also quite a bit of scorching around the cut line, hoping the honeycomb+air will dramatically reduce that.


TODO:
 - Order cladding
 - Install honeycomb bed
 - Finish wiring z axis
 - Calibrate focal point
 - Solve raft of pronsole errors when sending complex jobs - presumably some errors in my firmware extensions
 - Integrate air assist line into axes (i.e. an x-axis cable chain)
 - Design/order/build decent trolley

laser cutter references

other than BuildLog and Lasersaur main sites.... I've also borrowed/been inspired by several items from Daniel's blog: http://danielbauen.com/make/index.php/laser-cutter/

In particular, I've borrowed the design of my laser tube mounts and plan to implement something along these lines for the diode laser:

http://danielbauen.com/make/index.php/laser-cutter/laser-inline-red-laser-pointer-solution-without-using-an-extra-m/

I like the passive design (dropped into the beam by the lid opening), but I'd also like to be able to use the visible pointer with the lid closed - so I'm thinking a little servo to lower the diode and a s/w interlock to ensure the laser can't activate if the diode is down (maybe not the safest arrangement, but hopefully good enough).

axCut Laser Cutter - Y dual stepper homing and z axis drives

Have uploaded a quick overview video of the completed homing system for the dual Y stepper arrangement:


It uses a normal microswitch on one side (the Y2 side) and a linear hall effect sensor on the other (Y side).  Have updated my fork of the Marlin firmware to support this homing technique.  Calibration parameter is modified using M666 command (and M667 to read), values stored in EEPROM.

Homing algorithm:

1. Home Y as per normal
2. Disable Y2 stepper, disable endstops
3. Measure hall reading and compare to calibration target
4. If error big, move Y one step towards correct position and goto 3
5. Enable Y2 stepper, enable endstops

I'm currently using 32x oversampling on the hall reading, with 5ms delay between reads, but there's still a load of sensor noise.  Doesn't help that the sensor is next to two stepper motors!  Works ok, just takes a few iterations to converge.  Will do for now.

Z axis drives fitted (uses Mendel90 z-couplings) and ready for wiring tonight.

axCut Laser Cutter - X/Y axes working, laser calibrated

Now have both the X and Y axes working and have calibrated the optics using a mock tube to hold a visible laser diode.  The laser calibration technique may be of interest to others building laser cutters, as it means I can carefully calibrate the optics with the visible laser, then drop in the CO2 laser and be fairly confident the beam will follow the same path - will found how well this works in a few days when I fit and fire the CO2 laser!


and a quick demo of high feedrate with a lissajous pattern:


Up next:

• Finish the water cooling system
• Integrate the laser power supply
• Fit and test fire the CO2 laser
• Finish the z-axes (waiting for stepper motors to arrive)
• Add RPI host controller and touch screen
• Order cladding