Saturday, 7 April 2018

Prop Replica Building: Han Solo's DL-44 Blaster
DL-44 Blaster from Star Wars: A New Hope
     After installing the new magnetic bed surface on the Mega Kossel last time, I decided to test it out with another prop replica build. After some deliberation, I decided on Han Solo's DL-44 blaster pistol from Star Wars: A New Hope. Looking around Thingiverse quickly turned up a decent set of files for a static version, (thing:2230835) so that's the model I went with.
DL-44 flash suppressor
     As you can see, the parts printed quite nicely, so I decided to experiment with a couple alternate finishing and assembly techniques. Since the scope is setup to print in two parts with this model, I decided to try some friction welding to join them together instead of my usual 5-minute epoxy.

DL-44 Scope and Barrel after printing and sanding
     Friction welding is fairly straightforward to do, you just need some scrap filament of the type used in the parts and a Dremel with the optional collet kit or 3-jaw chuck add-ons. What you do is cut a small piece of filament, I found about 2 cm (1in) worked best, and stick it in the collet of the Dremel and use it as a sacrificial tool to weld the parts together. It does take some practice and patience to get a good joint but it worked fairly well. Afterwards there was a slight ridge of extra material on the part but some light sanding dealt with that in short order.

Glue-up of main parts
    For the bulk of the main parts I switched back to my normal go to solution of 5-minute epoxy and glued the main body sections together next. I've found that the Gorilla Glue brand stuff actually dries clear instead of slightly yellowed like the LePage stuff, makes it much better for builds like this.

Main Body after gluing with finished scope

    One thing that I did have issues with on the printed parts was the mounting screws for the scope clamps came out really badly, think it was just a slicing issue but looking at the reference images reminded me that I had some M3 cap screws that looked almost perfect in my spares bin, so I drilled out and tapped the parts to fit the screws and bolted things together.

M3 cap screws installed on scope brackets
    After gluing the remaining parts together, the next step is sanding any stray glue off prior to painting it. For this one I decided to layer the pain in 2 coats, a slightly blackened silver for the first one and then the cannon black overtop. This allows for some neat tricks with weathering the final piece since you can just lightly sand the areas that have wear to reveal the underlying paint instead of painting overtop.

DL-44 with first coat of paint applied
DL-44 half painted with initial weathering on muzzle
    After doing the rough coats on the main body and scope, it was time for some masking before painting the handle sides, this would probably have been easier if I'd left gluing them on for after they were painted, but some basic masking tape takes care of things quite nicely.

Masking applied to handle
Painted handle with masking in-place while drying.

DL-44 with basic paint scheme finished
      Once the basic paint was dry it was time to start weathering the prop, so I tried a couple of different techniques that I'd seen used online. I started off with some light sanding with 60-grit sandpaper to create some of the basic scuffing that is seen on the original prop. I followed up with some Scotch-Brite to dull finish to a slightly more matte effect overall and then got to doing some fine detail highlights with a silver marker.

DL-44 with wear marks partially applied
DL-44 Left side with wear marks
    After highlighting some of the surface details with the marker I gave the entire thing one final pass with the Scotch-Brite and then blasted the surface with my heat-gun to seal any residual damp spots. Overall, I'm fairly pleased with the result and I'll definitely be using some of these tricks for future builds.

Finished DL-44 Right Side
Finished DL-44 Left Side

Friday, 2 March 2018

Magnetic Print Bed Surface on a Budget

Mega Kossel with magnetic build plate
     When I rebuilt my Mini Kossel into the Mega Kossel last August, I installed upgraded rod-arms that allow for a maximum build diameter of 250mm (9.84 in), and I've been using a 190mm (7.5 in) piece of glass topped with Buildtak as my bed for the past 6 months, so I've really been using only 58% of my theoretical build diameter. I'd looked at upgrading the bed surface with the Buildtak Flexplate system in the past, but the only circular option currently available is a 300mm (12 in) set, far to large for my frame and 220mm heat-bed. Thus, I started looking at options for building my own custom version.

10-inch pizza lifter from the local dollar store
     Concept wise, the Flexplate system is fairly straightforward, an adhesive sheet with magnets in it that sticks to the printer's heat-bed or build plate, topped with a spring steel sheet with some Buildtak material on one side. For my version, I'm using some steel pizza lifters that I found at the local dollar store in the cooking supplies section of all things, $4 each and a bit of drilling to remove the riveted-on handle and I've got some fairly flat surface plates.

Adhesive backed magnets assortment from Lee Valley Tools
     For the magnetic part of things, I'm using some 6mm rare-earth magnets that I salvaged from an old toy building set that I had floating around, but Lee Valley sells some 1/4" ones that are a fairly close match. 

Bed mounting bracket with magnets installed
Other side of bed mount with magnets
I've designed a variation of the mounting brackets for my heat-bed that puts 36 of them in a ring around the entire bed, massive overkill when it comes to this type of magnet but having the bed surface start drifting loose is the last thing you want on a 3D printer of any type.

Corner brackets waiting for magnets
Brackets mounted on Mega Kossel
     After printing the brackets, I used some 5-minute epoxy to fix the magnets in place, I've found that it does an excellent job of holding parts to PLA prints under most conditions.

Magnetic bed fully installed on the Mega Kossel
     I've been using this bed configuration for the past 2 weeks already and it works quite well. This particular implementation is specific to the Mega Kossel, but if I was going to install something like this on an i3 style machine, I'd make custom brackets that put the magnets in a line along the front and back edges of the bed, then use a slightly oversize sheet of steel for the bed topping plate.

Saturday, 3 February 2018

Household 3D Prints Roundup 2

LED candle shrouds
     Been a while since I covered prints that I've put around the house, so here's some of the stuff that's been made over the past year. Starting with the above, those are simple spiral vase prints that have a small LED tea light inside for decoration. Design wise, they're really simple, just a faceted cylinder with lots of extra horizontal rings twisted along it's vertical axis, I used Wings 3D 2.1.5 as my design program of choice here. Filament is MG Chemicals Gold PLA, prints look like natural beeswax in colour, really nice for making decorative shades and such.

Toothbrush Holders
     Not the kind of thing you'd expect to use transparent PLA vase-mode prints for, but the faceted spiraling makes them surprisingly sturdy for this kind of use. Again, custom designs done in Wings 3D, using 3D Solutech Natural PLA this time, all printed on the Mega Kossel.

Birdseed filter in use
Birdseed filter clean
Birdseed filtering funnel
     Next up is something bird related, I've got a couple of budgies that are rather picky eaters, they don't like large sunflower seeds and keep emptying the food dish onto the floor if the find them. My solution to the problem is to design a funnel with a removable filter grate that strains the largest seeds out but lets all of the smaller stuff through. It's a simple design, just a cone with a 2 cm cylinder stuck on the point and hollowed out to about 3mm thick walls, the real trick is that rather than modeling the final grill in the CAD software, I just modeled the outer dimensions for it and used the infill settings in my slicer software to create the grid. I'm using Slic3r for my slicing program and the filter grid is the result of using 10% rectangular infill with zero top and bottom layers.

Towel hook on bathroom door
    And finally, this is the current iteration of the Customisable U-Hook from Thingiverse that's being used as a towel hook on the bathroom door. It's printed in MG Chemicals PETG for strength, the previous ones were in PLA and both snapped after about 6-9 months of daily use, this one is currently at 5 months and counting, be interesting to see how it holds up after a year of use. And in closing, I redid the oven knob from last time, the original part wasn't thick enough on the walls for the adaptor plug and failed after about a year of use. the current one was made in one piece with a thicker walled plug and is still going strong after about 9 months of regular use.

Oven knob V2

Thursday, 4 January 2018

3D printing and Musical instruments

3D Printed Electric Violin and Cello
    Over the Christmas season my family discovered some of The Piano Guys music videos and I remembered coming across the O'Cello & Mina Violin files, so I got some transparent PLA and started printing the parts. The designers intended for the parts of both projects to be printed on a standard i3-type printer, but I ended up using the Mega Kossel instead. 

Mina Violin neck freshly printed
Printing the Mina Violin body on the Mega Kossel
   As you can see, printing some of the parts needed some creative positioning of the parts, the lower body of the violin was particularly tricky, I ended up standing it on end, rotated by 30° onto one side and tilted back by 10° to get it to fit. After printing, some cleanup was needed, mostly stripping support material and stringing off, but on the violin the fingerboard came out a bit rough, so I sanded it down smooth then removed the heat induced scarring, as sanding PLA tends to mess up the finish.

Sanded PLA fidget cube
     The solution to the scarring issue is to take a heat-gun and run it lightly over the surface, don't pause in one place or you'll melt the print, and after a few passes the colour will reset and be indistinguishable from a freshly printed surface in colour. I'm using a light-duty 'art & craft' gun, but for the more industrial models you'll want to stick to the low setting, the higher one's will just wreck the print.

Heat-gun from Opus Art Supplies

Heat-treating before (bottom of cube) and after (top of cube)
Finished cube, note the distortion on the thin sections from overheating
    With the printing finished, the next step was sourcing the non-printed parts, I ended up using these piezo pickups from instead of the default ones on both the violin and cello because the original ones are only available on and don't ship to Canada. The tuning pegs were these ones for the violin, and these for the cello. The strings are D'Addario Prelude for the cello and Thomastik Dominant for the violin, both bough from the local music store. All the fasteners were easily found at the local hardware store along with the structural threaded rods, 5/16" for the Violin and 7/16" for the Cello.

Mostly assembled O'Cello
Stringed O'Cello with Viola bow for scale
     After all that, the actual assembly was fairly straightforward, and they both sound surprisingly good, the O'Cello actually producing a decent level of sound even without the amplifier. The Mina violin turned out to produce a decent level of sound when played with a viola bow, I'm guessing the extra weight compared to a violin bow helps produce more volume of sound? Regardless I'm happy with how both turned out.

Completed Mina violin with pickup

Thursday, 30 November 2017

Flying extruders and Deltas, Round 2

Mini Kossel and Mega Kossel with Flying Extruders
     Back in February, I tried installing a flying extruder on my Mini Kossel, didn't work out very well because one of the carriages would randomly slip during the first few layers of a print and suddenly it was air-printing and making a complete mess. So I switched back to the normal extruder configuration and kept it that way until I built the Mega Kossel

Mega Kossel Flying extruder V2
    For this version I decided to use elastic bands to hold everything in place, worked a bit better but still hit the same issue of random carriage slips. After watching it do this a couple of times I realised that the root cause was the extruder assembly's inertia damping the carriage movement and overwhelming the motor on the tower, causing the drive belt to slip on the pulley and produce the effect I'd been seeing. At that point I was just trying to get the new printer working, so I striped the flying extruder components off and set things up for a conventional long Bowden system. Further research into Kossel design was obviously needed to sort out what the solution to the issue was.

34mm (left) & 48mm (right) NEMA 17 stepper motors
    It was while building the Sculptor that I finally figured out the issue, it was the NEMA17/34mm steppers that were originally part of my Mini Kossel kit that were the root cause of the problem. Like most ~$300 kits, it had fairly light stepper motors for powering the motion mechanics, and while they were sufficient for normal use, I'd found some old forum posts that recommended longer NEMA17/48mm steppers for use on delta printers, and indeed I'd followed that advice when building the Micro Kossel in the first place, so I did a motor transplant and installed the 48mm motors on the Mega Kossel. The difference was quite noticeable once I powered it up and homed the effector. With the original motors it was possible to shake the effector about 3mm sideways even with the motors powered up, with the new ones the effector felt like it was glued in place, zero wobble or shake that I could detect. 
Mega Kossel Flying Extruder V2
    I used the Mega in that state until early November, then decided to try the flying configuration again. Surprisingly, it worked perfectly even without the counterweight that I'd used in the previous versions so I decided to stay with this version for the foreseeable future. 
Mega Kossel with flying extruder

Saturday, 28 October 2017

Building a Prusa i3 MK2 from Scratch

Prusa i3MK2 'Sculptor"
    So, time to reveal what the mystery replacement for the Micro Kossel is, I've repurposed the electrical harness into a Prusa i3MK2 clone build. Sourcing the parts was a bit of a nuisance, but most of it had close matches at my local hardware store or was stuff I had on hand.
Imperial equivalents of the M8 (5/16") and M10(3/8")
 with 1/4" threaded rod for the z-axis screws
Idler arm for the extruder with a 625 bearing from OpenBuilds
     Now, some of the parts for this machine do require CNC cutting normally, but following some of the tricks used by Tom's 3D build from march, I printed the frame template on paper, glued it onto and cut it out from some 3/4" plywood for the frame and 1/4" plywood for the y-carriage.
3/4" plywood frame with template attached
Frame and y-carriage ready for painting
     After cutting out the wooden parts, the next step was to paint and seal them, otherwise they'd change size with the ambient humidity. I used some black acrylic for the first coat, then followed up with a coat of Varathane to seal them.

Main frame waiting for paint to dry
Y-axis parts and tools
     While waiting for the paint to dry I moved on to assembling the y-axis/base frame. Assembly is fairly straightforward, only major thing that you need to watch is that the frame is completely square and flat. Squaring the frame is fairly simple with an old woodworking trick, just take a tape measure and check that both diagonals are the same length, if they match the frame is square in that plane. As for making sure it was flat, I used the one surface in the workshop guaranteed to be perfectly flat, the top of the table saw.

Checking the diagonals for squareness
Checking the other diagonal
     Once that was assembled, the next step was adding the vertical frame, then installing the x/z-axis assembly followed by the extruder carriage to complete the primary frame assembly.

Main frame assembled
Extruder ready for installation
    With the Extruder installed, it was time to sort out where to mount the main control boards. The normal place for them is on the back left of the main frame, but the cables on the LCD module I'm using are only 10cm long, so I've mounted the Ramps package on the front left side with the power block on the back.

Installing the Ramps casing (Thing:761806)
Power brick with custom brackets
Raspberry Pi Zero W for Octoprint host
    I designed a couple custom L-brackets for mounting the power supply and Pi camera, with those installed, it was time to sort out the firmware and calibrate the z-height. For the print-bed, I'm just using a sheet of Buildtak stuck to some 3/8" plywood, basic but workable.

Completed i3MK2