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 (Amazon.ca), 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.

Monday, 3 April 2017

Safety Upgrade: adding an air filtered enclosure to a 3D printer

Micro Kossel moving into new home
     After reading the 3Ders.org article on 3D printers with enclosures and filters reducing particle emissions, I decided to relocate and re-house my existing printers for safety's sake. I've moved the Mini Kossel out to my garage workspace for the moment, more on that another time, and the Micro Kossel got a new housing. 

Micro Kossel's new housing with intake fan installed
     Drawing inspiration from the method of refitting a plastic bin with air seals for storing moisture sensitive filament (example video), I went about tracking down a plastic bin deep enough for the Micro Kossel to fit inside. And since the original article mentions using a hepa filter that is rated for filtering hydrocarbons, I tracked down some normally meant for use on a workshop filter mask. 

Hepa Filters and 60mm fan
    Add to that a couple of 60mm fans, a roll of aluminum tape, some stick-on foam weather-stripping, and a couple of printed adaptors to complete the parts list. Tools are a drill with a 2.5inch pocket hole jig/blade, the aluminum tape, a 1/8th inch or 4mm drill bit, and a pair of scissors or cutters for trimming the foam striping to length.

Foam weather-stripping
One of the filters unboxed
     The first step was to put a strip of the foam tape along the rim of the bin, followed by using one of the fans to mark out where to drill the holes in the sides. After doing that, I measured the dimensions of the filter and designed a printable mounting bracket to interface it with the exhaust fan.

Foam seal installed on bin with spare parts in background
Filter mount on the exhaust fan
Filter retainer ring
    The STLs are available here, they will probably only work with that specific brand of filter, but should be a useful reference regardless. While that was printing, I used the pocket hole bit to make openings for both the input and output fans.

Fan mounting hole with points for screws drilled out.
    After the holes were drilled, it was a simple matter to bolt the fans into place with some spare #6 screws that I had leftover from building the MPCNC, although M4 screws would probably work just as well.

Filter installed and secured with aluminum tape
    For securing the fans, I had planned to use elastic bands to hold the retainers in place, but remembered that I had some Aluminum tape left over from another project, and since it's normally used for sealing holes in air ducts, I decided that wrapping the joints with some couldn't go amiss. 

Power lines for the fans
    Finally, it's just a matter of wiring up the power to the fans. I've got the Micro Kossel fitted with a 2.1mm barrel jack for power, so I just got a couple of spare connectors and created an in-line patch cable that basically just hooks the fans in parallel with the printer itself, turn the printer on and the fans come up automatically.

Sunday, 12 February 2017

Experiments with Flying Extruders and Deltas

Mini Kossel with flying extruder
     Not long after finishing the Re-ARM upgrade, my geared extruder suffered a failed bowden coupler, so rather than reprint the entire thing, I decided to switch to an alternate configuration that I'd read about called a 'flying extruder', basically suspending the extruder motor over the effector/hot-end, allowing for better print quality with a wider range of materials.

MK8 extruder with suspension bracket attached
     I started by replacing the failed extruder with a MK8 variant that was in my spare parts pile, then tracked down one of the designs for the suspension mounts from Thingiverse (thing:1295606). It's a fairly good starting point, but it is missing a couple of parts for mounting on a standard Kossel frame, so I had to design some custom parts for the pulley mounts, the files are here.

Moving extruder power cable to the effector wire harness
Heat-damaged PLA fan duct skirt
     One unexpected issue cropped up during the process of changing the Bowden tube, which on an E3D Lite6 requires a full stripdown and rebuild, so I had to remove the lower half of the effector I've been using (thing:1569106) and found that part of the hot-end had rotated and melted part of the lower half of the effector. My solution was to rework part of the design and add a small loop on one side to allow use of a zip-tie to secure the heater wires, thus locking the rotation and preventing a recurrence. The file for the reworked part is on Thingiverse (thing:2103488).

Remixed and improved ducting skirt, note the zip-tie on the right
    With that issue corrected, I designed some custom brackets to use a couple of spare 608zz bearings and the MK8's old idler bearing as pulleys. Other parts use were some old washers and pipe fittings from the workshop junk bin for a counter weight, a roughly 30cm piece of 1/4-inch steel rod for the main shaft across the top, a 1.5m length of thin rope/string, and about 30 zip-ties. I also added some temporary loops to the carriages allow using some zip-ties to hold the extruder in place while I installed the upper pulleys.

Pulley bearings, 1/4-inch shaft and part of the counterweight
Using the cable to loosely suspend the extruder during install
Temporary anchor for zip-ties
      Initially, I had thought to try running with just zip-ties holding the extruder block to each of the carriages, but that proved unworkable due to the zip-ties restricting the range of motion. The basic idea of suspending from the carriages would probably work if you used some form of elastic for the cables, but that still leaves a 400-gram weight sitting in the middle of the frame, so it would definitely lower the maximum attainable speed.

Initial configuration idea, doesn't work with rigid cables
Initial Z-tower pulley mount 
Upper pulleys 2/3 installed
    As you can see, I'd initially thought to use just the zip-ties to hold things in place, but that resulted in some strange glitches during homing, so I switched to the full counterweight option. After I'd installed the first couple of pulleys, I realized that the counterweight would hit the back of the z-tower carriage, so I designed a short arm with a 608zz on the end to act as a spacer. Other hardware used in the spacer arm was 3 M5x35mm bolts, 4 M5 nuts, and 1 M5x10mm bolt.

Spacer arm fully assembled
Spacer arm fully installed just below the top triangle
     As for the counterweight, I just used a small scale to measure the approximate weight of the extruder assembly, roughly 395 grams, then found a combination of old washers and stuff that was reasonably close to that weight to use for the counterweight, ended up at 405 grams, then tied the lot to the end of the string/rope. As for the print quality, I still need to retune the retraction settings, but it's a drastic improvement over the original configuration, with a much finer surface finish. Here's a couple of #3DBenchy prints for comparison, the Green one is from the filament comparison post with the original configuration, the gold one is done with the new configuration.

#3DBenchy 32-bit on the left, 8-bit on the right