Thursday, 28 September 2017

Decommissioning the Micro Kossel

Micro Kossel
    After almost 18 months of heavy use the Micro Kossel was long overdue for maintenance and wear checking, so I decided to partly disassemble it last week, this unfortunately lead to the discovery of several fatal flaws that would have required basically replacing the frame to correct, so I decided that it was time to retire it.

Micro Kossel parts after disassembly
    Most of the flaws were wear and tear issues that some of the PLA parts hadn't stood up to well at all, specifically the AMZ3D transparent red carriages and green rails and corner/motor brackets. I don't have photos but the motor corners were warped badly enough that the motors were stuck pointing about 20 degrees up from the normal horizontal position, making any attempt to tighten the drive belts pointless, they'd just slip off the mounts or the plastic would just melt further and worsen the problem over time. 

Micro Kossel frame rail with cracked section

Micro Kossel frame rails with cracked sections
     As you can see, the Seacans green PLA fractured across the layers on these sections, a highly atypical failure for a printed part, normally you'd see fracturing along the layer lines with PLA, not this glass-like fracturing. It's worth noting that the Tinkerine Lavender PLA shows only minor damage where stuck nuts and bolts were removed, and that's mostly cosmetic, so I'll probably be reusing those parts in a future project. 

Carriage plate showing stress fractures
    The AMZ3D PLA carriages are by far the most alarming of the parts, two of them cracked at the hinge point (lower left of the image above), and all three where showing some alarming stress fractures that you can just see in the picture above, I've warped the contrast to make it a bit clearer, my camera has a hard time seeing them but they're very clear to the naked eye. Taken together, these issues mean that it was just a matter of when, not if, that the hot-end would come off axis during a print and make a complete mess at minimum, start a fire at worst, so I've dismantled the frame and salvaged the electronics for a new project, here's a preview, but more on that next time.

Mystery parts for next project

Monday, 18 September 2017

Stress Testing the Mega Kossel: Building C. Laimer's Tourbillon Watch

Tourbillon Clock
     After the painting project from last time, I decided to try building a more mechanically complex project, Christoph Laimer's Tourbillon Watch (thing:1249221). It's a very complicated model with very tight printing tolerances, all the parts need to be as close to perfect as possible or the clock won't work properly. 

Printing the mainspring pinion gear on the Mega Kossel
     Obviously the first step in this project was lots of printing, about 100-120 hours in total, perfect for shaking out any glitches in the printer. Aside from a couple of spaghetti incidents caused by the print bed shifting on it's mounts, actually printing the parts was the easiest part of the project, tracking down compatible screws was the hardest part, I ended up reaming most of the screw holes to accept M2 screws since those were the closest that I could find.

Clock parts organized for assembly with mainspring being assembled
Mainspring clamped for assembly with printed machine vise
    Actually building the clock took a few days, the virtual walkthrough and assembly videos were invaluable for this stage, always making it clear what part was installed next at every step of the process.

Mainspring fully installed with outer casing in place
Clock parts set out for assembly
   I ended up using some 14-gauge wire cut to length for the gearing axles, long needle nose pliers are crucial for installing them in the upper center plate. Other tools I used were a 3/64-inch drill bit for reaming the gears mounting holes and a Philips screwdriver for the M2 screws. After a couple of days work I had it assembled and mostly working, one of the gears is a bit sticky on its axis, but it's mostly complete.

Test fitting Clock face components
Completed Tourbillon Clock

Tuesday, 22 August 2017

Prop Replica Making: Building the Sidewinder pistol from Mass Effect: Andromeda

Mass Effect: Andromeda Sidewinder
     After upgrading my Mini Kossel to a Mega Kossel, I was browsing Thingiverse for something interesting to test it with, I was searching the names of some of my favorite games, and Rawrbomb's Mass Effect: Andromeda Sidewinder design looked like one of the best modeled props from the game available.

Sidewinder V1 parts waiting for painting
     Printing was fairly straightforward, most of the digital prep work was mostly just orienting the parts for printing with my Mega Kossel, the default orientations are optimized for a prusa i3 style machine, so I ended up sticking most of the parts on end with a large stack of support material. Final step before printing was choosing which parts to do in black or white, so most of the gun's frame is in white PLA with some of the details in black PLA. Total print time was 52 hours 41 minutes and used 369 grams of filament including the support material.

Sidewinder right side initial paintwork
     For the painting, I started with the raw parts after removing the support material and gave some sections like the barrel and grip cages a coat of acrylic paint on all surfaces. Others sections got partially masked and painted in stages for the full effect, while others were left mostly untouched since the print was already the correct colour. For some of the detailing, I used coloured sharpies to prime the area, then 'weathered' the area, then recoloured with the sharpie again. 

Sidewinder left side initial paintwork
     This worked reasonably well, but after rewatching this YouTube video, I thought I could do better, especially as some of the weathering was only highlighting the layer lines in a few spots. So, after a quick trip to the local paint store to get some more colours and brushes, I repainted it to more closely follow the in-game texturing, with a little bit of rusting around the edges and seams. I've still got a bit of weathering to do at some point, but I'm very pleased with how it turned out.

Sidewinder left side final paintwork

Tuesday, 8 August 2017

Supersizing a Kossel Mini

Mini Kossel

     This time I'm upgrading the printer I started out with, a basic Mini Kossel kit, to a larger and taller frame. After replacing the original wheels with steel wheels last year, the aluminum towers finally wore down to the point that one of the carriages basically fell off the tower.

2020 Aluminum extrusion after running steel wheels for 14 months
     The obvious choice for replacing the damaged towers was OpenBuilds V-slot, same outer dimensions as the original extrusions allowing reuse of the printed frame parts. I also ended up swapping the steel wheels with the Delrin versions, don't want a repeat of what happened to the old towers.

Enlarged upper triangle

Enlarged lower triangle

     Since I was upping the size of the frame anyway, I cut the old towers down into new sides for the bottom triangle, the idea was to allow for mounting the power supply under the bed with the rest of the electronics, as well as allowing for upgrading the build plate in the future. Dimension wise, the side rails are now 30 cm long, allowing for anything up to a 25cm build plate. Reassembly was mostly the same as the original build process, just scaled up by a large margin.

Upgraded frame
     I did learn some new tricks to make assembly more precise, probably the most useful was using a spare section of extrusion to set the end-stop height to exactly below the upper triangle. All that's needed for this trick is a 3-inch C clamp, a spare or unused piece of the extrusion and the end-stop assembly.

The simple way to set endstop height

     Once the frame was rebuilt, the other parts that needed replacement were the rod-arms, the originals were both too short for the new size and one was cracked after a rather spectacular malfunction last fall. For the new rod-arms, the parts list is quite simple, 12 Traxxas 5347 joints (, 6 12" lengths of 8-32 threaded rod, an 8-32 tap and AndrewBCN's assembly tool (Thingiverse, thing:701248). The 8-32 tap is optional, it just makes assembly easier by pre-cutting the first couple turns of the thread in the Traxxas joints.

Parts for new rod-arms with completed arm
     With the new rod-arms done, the next step was reinstalling the electronics and print bed. Since I'm not replacing the current print bed, some new mounts were needed, along with a new mounting bracket for the Re-ARM/Ramps boards. After creating a Fusion 360 mock-up of the bottom triangle, it was fairly easy to design new mounting brackets for the print bed, the Re-ARM was even simpler since the manufacture provides a cad file of the boards physical layout. The resulting STLs are here for download.

Re-ARM and electronics installed
Power supply mounting bracket
Mounting bracket installed on power supply

     As you can see, the power supply ended up under the bottom triangle, just wasn't space for the control boards otherwise. The brackets I've designed for mounting the power supply are in with the other STLs above, you'll need to mirror file with your slicer program to get both the left and right versions. Only other parts needed for mounting are some M4x20mm screws and the power supply, I'm using this one, but the brackets should work for any similar module.

Print bed installed with dust covers
     One of the recent improvements for deltas that's been trending on the net lately is adding protective covers to the corners over the lower pulleys and electronics bay. I've been meaning to add them for a while and came up with a simple way to make them out of some spare foam core.

Kossel on foam core for tracing
Kossel and Print bed outlines on foam core
     Yep, that's it, just stick the printer on the foam core and trace around the base with a marker. I also used an earlier version of the print bed supports to center it under the printer frame and then traced it out as well. After that it was just putting the printed parts in their approximate spots, trace the outlines and then cut out the section that's left. I did use a drill to put 3 holes in each for ventilation over the motors but that was basically it. last step was wrap the edges with electrical tape for safety and colour the top black for aesthetics.

Corner covers finished and installed

      Now, obviously the power supply is currently serving as the structural base for the entire frame, not the best idea for long term stability or noise. I found these tennis ball feet (thing:2158108) on Thingiverse, they're printable adaptors that let 3 standard tennis balls serve as vibration damping feet, so I used the Micro Kossel to print a set and installed them.
Tennis ball feet 2/3 installed
   And that was pretty much it, only things left to do were recalibration running a few test prints which turned out nicely.
Completed Mega Kossel

Tuesday, 18 July 2017

Summer Project: Upgrading the workshop

Workshop upgrades
     My workspace has been getting into a bit of a mess over the past year, so it was time for a cleanup this summer and I've ended up building a couple small projects to help with reorganizing. One's a cart for the spare that was piling up in one corner, the second is a small router table to help with the third which is a tool chest for storing all the small hand tools.

Wood Cart Concept
     The worst of the mess was, not surprisingly, the wood pile. After watching this YouTube video, I decided that building something like it would be the best solution for my own wood pile. Starting with Fusion 360, I drew up rough plans for a wood cart that could handle anything up to half a sheet of plywood, that's the largest piece of wood that I've got space to work with. After a trip to Home Depot to get some wood for the frame, I ended up building the final cart from a 2'x4' 1/4 sheet of plywood for the base, 4 8'x2"x2" composite posts cut to 5' and 3' sections, 4 casters, and a couple of old IKEA storage boxes that were in the shop. The Fusion 360 file is here.

Wood Cart as built with MPCNC in background
Router Table
    With the wood pile sorted, the next area that needed reorganizing was the hand tools. Previously I had them in the upper trays from some old tool boxes on a long shelf about 12 inches above one of the work benches, didn't work that great with the tools constantly getting mixed up and covered in sawdust. After seeing some YouTube videos of other tool organizing methods, I drew up a concept for a wooden tool chest in Fusion 360. (File)

Tool Chest Concept
     One issue with the design that was immediately apparent was that I'd need some form of jig or tool to cut the slots in the sides for the drawer bottoms, which double as the drawer slides, to run in. I've seen slots like this cut in a few ways on YouTube, a Dado blade set with a table saw or a router table are the most common options. I don't have a dado set but I did have a spare plunge router that was just gathering dust, so I made a simple table for it out of some stuff that was lying around the shop.

Router mounting system
Power management
     I used an old folding worktable for the legs, bolted a 2ft by 2ft square of sanded plywood on for a top. For mounting the router, I used a skill saw to cut a hole in the top that the plunge router would fit through, then used the MPCNC palm router to cut a shallow groove that would allow a 1/4" sheet of hardboard to sit flush with the top, then cut a piece to fit and screwed the router to one side after drilling a 2-inch hole for the bit to pass through. After that it was a simple matter of dropping the router through the hole, sanding the top completely flat, and dealing with the power wiring. Since the plunge router has its trigger mounted on one of the hand grips, I simply used its lock-on function to bypass it and zip-tied an old power bar to the side, plug the router into that and it functions as a on/off switch.

Tool Chest as built
     With the router table complete, it was a simple matter of firing up the table saw and cutting all the pieces of plywood and hardboard to size, using the router table to cut the slots for the drawers, and then screwing everything together. I did use a hole saw bit on the drill press to cut the notches for the drawer handles, but that was basically it for making the tool chest, and I'm very pleased with the result of both projects.

Tuesday, 27 June 2017

Design tutorial: Modeling a jar lid in Fusion 360

Old tea jar lid
    Remember this thing from last year's '3d Printing around the house'? Well, it's suffered a similar fate to the one it replaced, got dropped and the handle snapped off at a thin point near the base, so I've made a new one with a thicker base as a replacement.

New tea jar lid with old lid handle on lower right
     Size wise, it's about 17 cm across at the rim, so normally I'd have just printed it on my Mini Kossel, but I'm currently in the middle of rebuilding it, so I designed this lid for printing on the Micro Kossel's 10 cm build plate instead. The Fusion 360 source file can be found here, and the STLs are on Thingiverse.

Fusion 360 design file
     After measuring the diameter of the existing lid, both the opening and lip, I sketched up a couple of circles that size in F360, then traced some 10 cm circles to determine the maximum size of an individual section of the lid, this worked out to 6 sections with one small part in the center for the handle. Second step was to draw a cross-section profile and revolve it to create the basic sections, one with a 60 degree angle for the outer sections and a simple full revolve for the handle. Last step of the design process was to add some angled holes for the screws that hold the sections together.

Partially assembled lid with M3x15mm screws
     After the design was finished, it was just the standard slice and print process, it takes about 2 hours for each arc section and about 1.5 hours for the handle section, so about 13.5 hours in total. After printing, final assembly took about 15 minutes to screw everything together.
Finished lid in use

Saturday, 13 May 2017

Project: Proteus Delta, part 8

Proteus Delta with Prometheus System installed
     Last time with the Proteus Delta I'd just installed the heat-bed, then left it sitting for a few months while waiting on delivery of the Prometheus System by Distech Automation, which is a dual extruder/single hot-end printing system that allows for the use of 2 different materials or different colours of the same material in a single print.

Prometheus System half assembled with parts of effector platform
     After receiving the parts for the Prometheus system at the beginning of April, assembly took a week or so of evenings working on assembly, partially because I got the parts for both the original design and the revisions that occurred after the 'early-bird/beta' system feedback was received. So, since I had the original PEEK feed pipe, the splitter fork got assembled as per the original design instructions, and the extruders are using the revised design with the reinforced Bowden clamps.

Prometheus hot-end installed in effector
     For actually mounting the Prometheus system on the Proteus, I'd designed a custom raised effector shell back in November, after giving it a final polishing pass, the parts got printed and bolted together. I'm still working on the part-cooling fan ducting but the rest of the parts are here.

Effector installed on Proteus for initial testing
     After installing the completed effector on the Proteus, I started moving the motion system around by hand to check for any issues, and it immediately became apparent that the clamps that were holding the print-bed in place where going to cause issues with the effector since the hot-end tip is only slightly below the effector ring. 

Proteus print-bed with new mounts
      After some revising, reprinting and reassembly, the problem was mostly solved by switching to a new mounting bracket design for the print-bed, the STL is here, it's designed to grip the glass along the side and recess the mounting screw flush with the upper surface, allowing for a 28cm maximum printing diameter, although I would recommend printing it in a high-temperature resistant plastic, otherwise the bed will start drifting when you go past the glass-transition temperature.

Effector mounting plate and spool holder hardware waiting for assembly
     Originally, I was planning to mount the ProStruders in a flying configuration, but after February's experiments, I've decided to put them on an independent pylon, roughly 46 cm down from the top, mostly level with the effector when it's homed. For holding the spools, I'm using one of the leftover sections of 1/2inch EMT from building the towers, it's the perfect length for sticking a pair of spools on, one on each side above the extruders. Add some printed caps and a clamp to keep things in place, and that finishes the assembly process.

Extruders mounted to Proteus with spool holder above
Proteus Delta ready to print
     With all that finished, the next step was calibration and a couple of test prints. Leveling the bed was mostly the same as I've covered previously, only real change was initial setup of the SD card for the Duet 0.8.5, most of the files are linked through the Duet wiki, but one really useful tool is the Reprap Firmware Configurator, it has a couple of quirks, specifically the default thermistor for heatbeds is wrong, but makes most of the configuration process fairly painless overall. I'm still getting the hang of using it, but the few prints I've done so far are fairly good for PLA without a part cooling fan. Overall, a fun build and I'm looking forward to trying some dual colour prints in the near future.