Workbench, part 3

Workbench progress.

Pocket hole screwing + gluing the table saw box on.

Those are Wen 4" pocket hole clamps. They just barely fit 2x4 pocket holes edge on like that. They help keep the 2x4s aligned while driving in the pocket hole screws. 

Adding edge banding to the shelves. Tiny $12 palm-sized iron works perfectly.

Needed some edge band trimmers, so printing those while I put the edge banding on

The edge band trimmers use M3 melt in inserts

Also did some of the M3 melt in inserts for CubeXY. Yes, that's still going to be a thing...eventually. Got to use one of the melt in insert soldering iron tips I turned awhile back. 

These work great. Found them on thingiverse.

Edge banding done, time to stain:

Factory edge=bad

I sanded them with 220 grit, wiped the dust off, cleaned them with mineral spirits, and then sealed them with stain primer. I stained the edges (banding) of the table saw shelf golden oak, but didn't bother staining the rest of it since it won't be visible. I stained the router shelf "golden pecan", however, it came out a lot redder than I was expecting. Lessons learned: The Varathane "premium" stain colors are NOT the same as the "classic" stain colors. The classic golden pecan doesn't have much red in it and is what I used for the base shelves. The premium golden pecan is actually very close to the classic "Ipswich Pine". Meh, luckily it's a workbench, and I'm already mixing a ton of wood tones, so it doesn't really matter. The edge banding didn't take the stain as much as the plywood. Also, factory edges, while straight, need to be cleaned up because the stain will accent the underlying grain.

While I had the printer going, I decided to use up some old shitty (Eryone brand, bleh) filament I had and print some wood working tools. 

♫ Part of a marking gauge, two mini sanding blocks,
and a set of center finding of guides ♫ (3rd day of Xmas)

Right angle clamp blocks, printed two sets ~800g

Time to install the table saw shelf:

Screwed on the table saw vacuum adapter

Clamped, then screwed down the shelf.

Looks good, very rigid

I won't be able to see the top surface, so I didn't bother filling in the screw holes. I installed the router shelf next: 

Left side of shelf. Center: The Mini-Motivator 

This was tricky. I drilled (normal sized, not the "HD" ones) pocket holes in the bottom of the left side of the shelf to screw to the left vertical 2x4s. There's a 3/16" thick spacer that has to go on the right side between the shelf and the horizontal 2x4, which I made by gluing together strips of 1/8" and 1/16" plywood. That shim is necessary because the left bandsaw pivot bearings mount to the top of that horizontal 2x4, and they need to be at a specific height. I used glue in all of the joints and used a ton of clamps to hold everything in place while I drove in the pocket hole screws. Leveling the shelf required a lot of unclamp-shift something-clamp-check level operations. Weirdly, while I was doing that, I realized that the shelf couldn't be clamped flush to the horizontal 2x4 in order to be level. 

Uh-oh...the shim needed shims.

The shelf ended up needing to be spaced about 1/16" lower at the back than the front. It was then that I checked level of the top of the horizontal 2x4: it was slanted. Hmm... re-measuring the back vertical 2x4 it was resting on showed that it was about 1/32" too long. Then I checked the CAD. Ugh, that same 2x4 was 1/32" too long. Didn't notice because it was such a small interference. 1/32+1/32 ... there's my extra 1/16". By this time, it was too late to fix because I'd already screwed it all together and the glue had partially set. So I used the handheld belt sander to sand down the top of the horizontal 2x4. 

Now it reads level. 

I also screwed on a few more horizontal 2x4s. These required a bit of fancy clamping, but all the joints came out good. 

A bunch of the horizontal 2x4s need notches cut in them. Some need to be re-sawn, which I'll need the table saw for, so I'm going to start refurbing that soon. 

3D printer updates

Tried printing something on the i3. The X axis was reversed because I had the belt tensioner flipped over. I can't flip it the other way because the extruder motor's connector interferes because I rotated it so it wouldn't rub on the top frame on tall prints. So I can't use the belt tensioner. That's the third or fourth x axis belt tensioner I've tried...may just have to design my own. I went back to screws + zip ties.

Did some more work on the CubeX, mainly taking it apart. I found more examples of decent engineering and terrible engineering.

Nice little rubber + plastic grommets around the screws to protect the acrylic. 

Many of the corner holes were cracked like this. 

Shell off

Feet screw off. Didn't end up needing to remove these.

Some parts are fancy expensive CNC milled, some, like these
belt clamps, are just pieces of laser cut acrylic stacked. 

Removed those dumb stainless steel cylinders. 

These acrylic clips were nice. Removed the filament tubes.

Why are these shaped like that? $$

These were the little filament tube ends. Turned and threaded. $$ 

Got the X-Y portion off

Getting there... 

The single linear bearing on one of the X axis rails was shot. The wider one is ok, but it's far too wide for a single extruder. I'll replace both with nicer bearings + holders. The Y-axis bearings seem ok. 

To do: 

• Replace X axis bearing blocks with more standard ones with new, nicer bearings
• Design and make a new single extruder X axis carriage plate.
• Select extruder + hot end. Might use stock extruder + e3d v6 hot end
• Replace bed plate with a square one (still aluminum). May not need this depending on how I mount the build surface.
• Add a large AC heated bed + glass build surface.
• Replace the flimsy lexan Z axis plate thing
• Replace the reed switches with mechanical switches.
• Add a standard control board. Put the screen/control interface where the old one was. Will need a relay for the AC bed. May need something fancy to drive the big Z axis stepper.
• New x axis belt tensioner
• Design and laser cut top cover and side covers. Maybe use magnets to hold them on

Pretty cool thread: https://reprap.org/forum/read.php?1,707941,page=2

3D printing more things

I've been printing stuff for work and fun recently.

Sharkenbear, or "Bark" as I like to call it. I tried Cura's adaptive layer method with these settings: 0.175 primary layer thickness, with a max variation of 0.075, results in a min of 0.1 and max of 0.25. This causes some off-nominal layer blobs because the coast and extra prime settings for pressure compensation don't change, but not too much. You can tell where it switched layer thicknesses by the shiney-ness changes. Managed to resolve the teeth, which is pretty cool. I had to print some extra fins from another shark model and glue them on because three fins came off with the support removal. Removing the supports from inside the mouths and under the toes was a huge pain, too.

I designed and printed some horseshoe name plates for a horse barn. First time (successfully) switching filaments mid print. The cura plugin for pause at height or filament change don't seem to work well with the i3, so I followed the instructions in this post: https://3dprinterwiki.info/duplicatori3/pause-at-layer-height/ . It was pretty simple to modify the gcode.

I designed and printed this for work, can't really say what it is. Made from three pieces glued together. Too much extra prime on the long bit, so I had to sand the seam down.

I'm currently printing a new x-axis belt tensioner. Hopefully this one works better than the previous ones I've tried. The previous ones all had little nubs that the belt wrapped around; the problem is that those nubs always shear off, even if printed at 100% infill. They just aren't large enough to handle the belt tension. This one has a much larger nub/hub thing. I'm not too sure that the tightening ratchet thing will work, but I can always use zip ties if it doesn't.
UPDATE (Jan 2020): It works much better. I tried using a button head screw + locknut for the ratching knob first, but the hex stripped. Tried to use a screw extractor to get the screw out, but then the hex holding the locknut in stripped. I had to drill a couple holes near the hex nut in order to hold it with pliers, then use the screw extractor to get the screw out. I used a socket head cap screw (bigger hex) after that, worked much better. The belt seemed to be held in place fine without zip ties, but I added them anyways. I then re-leveled the Z axis and lubed all the bearings and lead screws. I haven't printed anything yet, but it should have less X axis ghosting now.

Been busy...

Back stateside again. Still very limited on room, though, so hobby progress has been limited.

Got the 3D printer recalibrated and set up on a shelf in the garage.

Wanhao i3 V2.1

Moved the filament spool off the top to the side. Bought a 16x16" tile for it to sit on, perfect size. Smoke alarm taped to the underside of the next shelf up (top left of picture). The filament dryer is the same one I had in England, so I have a 110V-220V power adapter sitting behind it. I found the same one in the US but for 110V power on eBay for $39 ("Rosewill" brand here), and I bought it so I can ditch the giant power adapter. The clear plastic cylinder parts should be the same, so I can extend it to hold 3-4 spools, which is nice. Printed an XYZ calibration cube and benchy first, then a new spool holder since the green one was on its last legs. Currently printing some wall mount holders for remotes for new ceiling fans we bought my mother in law for Christmas (guess who gets to install them...). 3D printer to-do: replace X belt and add belt tensioner.

I've been mentoring FloridaTech's Base11 space challenge team (Florida Tech Rocketry, FTR). The goal is to be the first university team to launch a liquid bipropellant rocket to space. I've been teaching them fluid systems analysis, fluid systems component selection, CFD, structural analysis, thermal analysis, basic design process, etc etc etc. They have a pretty solid preliminary rocket design and detailed engine and test stand design now. FIT promised to fund the whole thing, but you know how that goes...so currently looking at other funding options.

I've also been spending a lot of time over the past couple years working research contracts for various aerospace companies, most of them slosh CFD or slosh testing related. FIT has a large linear stage capable of shaking full scale spacecraft tanks, and we've designed and are fabricating a second one now. We got about half way through a NASA spacecraft tank test program before realizing we'd need a linear stage capable of much higher frequency excitation than the current one , or anyone has as far as I know...I mean, I guess there are vibration tables, but the excitation amplitude on those is tiny. The new linear stage should be capable of shaking 8000lb tanks at 6 Hz over ~4mm, which is kinda terrifying. Currently finishing fabrication on 1/5 scale upper stage propellant tank simulators. Slosh testing will start in about a month on those. My advisor and I wrote (so basically I wrote...) a proposal for another NASA slosh research project that got approved, so that's probably coming March-ish. I'm leading about 3 grad students and 4 undergrads working on these and some other aerospace/propulsion related projects.

Busy busy. So even though most of this blog is about my hobbies and not-rocket stuff, I am doing a lot of "rocket science", though I should have foreseen I wouldn't be at "MIT" for ever. Kinda dumb naming the blog that, oh well...live and learn.

As I tell the FTR team: "Skip all your classes, build rockets".

Wanhao i3 V2.1: more upgrades and maintenance

I did some maintenance on and upgrades to the Wanhao i3 V2.1 today.

Some cheap Chinese printers suffer from under-spec'd power connectors on their main boards. Over time, these can heat up, char, and eventually fail, causing fire. While none of my connectors have shown any sign of discoloration or impending failure after 75 days of printing time (6.8 km of filament), I decided to do a common preventative upgrade. Since the heated bed is the primary power consuming device, it makes sense to offload the heated bed's power. Since the heated bed is PWM'd to achieve different average power, you can add a MOSFET between the signal, power, and heated bed power wires, where the signal comes from the original heated bed connections on the controller board, power comes directly from the DC power supply, and the heated bed power wires are the original. Before doing this, I printed this thing, which is a nice holder for the MOSFET board. That gets installed on two standoffs under the Melzi, and the MOSFET board screws to it.

Upper right: MOSFET board installed

I used ~10AWG wire for the connection from the PSU, but it was pretty unwieldy. I'd suggest using 14AWG wire. Anyways, instead of just jamming the wires under the terminals, I soldered forked spade connectors to the ends and heat shrunk them. I did the same for the heated bed wires.

While in the safety mood, I installed a smoke detector on the ceiling of the room with the printer. 

The wires to the hot end heater cartridge come crimped from the factory. I found it annoying to have to work on the hot end with it attached to the carriage, so I replaced the crimps with micro-Deans (micro T) connectors. These are rated up to 10A, but the Chinese knock-offs are probably not able to handle that much current. Since the heater cartridge only uses ~40/12=~3.3A, it should be fine. 

I also re-built the hot-end again. In a previous post, I detailed all the things I tried to get back to how it would print previously (no blobs, no initial under extrusion, etc.). All of that failed, and I ended up applying software band-aids, but the last physical thing I tried was spacing the nozzle off the heated block and using the original PTFE tube, which was too short. This time I rebuilt it with a new nozzle, hex edge flush against the heated block and using a proper-length PTFE tube. I made sure everything was tight to prevent leaks, then put the whole hot end back together. 

I then oiled the bearings and greased the z-axis threaded rods.

I also printed a new Diii Cooler, this time out of PETG, which has a higher temperature limit than PLA. Before doing that, I printed a temperature test tower, with increments of 5 degrees from 250-200C (+10 from markings on tower). These are great for finding the optimal print temperature for a filament. 

Settings were 0.2mm layer height, 40 mm/s (20 mm/s outer wall), 0.1 extra prime, 0.15 coast, 0.4mm nozzle, 0.5mm line width, 1mm walls, 10% infill, 100% fan after 1st layer, 70C bed temp, etc. I forgot to use a brim, so the little side bridge part popped off, and I had to pause the print to tape it down. Ignore the lower 3 bridges because of that. I started to hear some skips at 225C, and I had to stop the print at 205C. The best combination of strength and quality seemed to be about 245C. I could probably print at 230-240C if I cared more about quality than strength. Using less fan would probably let me print at a lower temperature, too, but since the DiiiCooler has huge overhangs that can't be supported, I need the fan. I then printed an XYZ calibration cube using those settings, 245C, and a layer height of 0.25mm.

It came out great. The first layer was smashed too much, so I lowered the bed slightly. Small warping at the downward facing points of the X and Y, but that was almost always present with PLA. Good layer adhesion. Might be slightly overextruding because the X and Y were ~20.2mm instead of 20. It popped right off the bed, so I increased the bed temp to 75C. Interestingly, the PLA DiiiCooler has had no problem with the high extruder temps...no signs of warping or melting. The PID controller isn't as steady at the higher temps, ~-2/+1C instead of +/-1C. But I figured that was good enough. Then I printed the DiiiCooler:

Sporting some CA on the side

The extruder was skipping on the long path inner walls (40 mm/s), so I turned speed down to ~65% to stop the skipping. I guess flow rate is more limited with PETG than for PLA. The slower speed throws off the extra prime and coast settings, i.e. you need less of both. This caused the blobs and inconsistent extrusion near the right side of the fan opening, which is where I set the Z change location. I think the layer thickness was too high...only two layers on top and bottom, and it was clearly not air tight on the top (CA to the rescue). If I were to print it again, I'd use 0.2 mm layer height or lower and go slightly faster (~30 mm/s).

Summary of PETG-specific settings:

• Same speed settings as PLA
• Use PLA prime and coast values
• Only use fan if printing overhangs/bridges, otherwise don't need it
• Strong temp: 245C (maybe lower if 0 fan?)
• Good quality temp: 235C
• 75C bed
• Max flow: 40 mm/s @ 0.2 mm layer height, 0.5mm line width. For long continuous extrusions, that will probably cause skips, so turn down to ~30 mm/s. Needs about 25 mm/s max for 0.25 mm layer heights. When reducing speed, reduce prime and coast approximately proportionally.

I'm using PLA next, so I'll need to heat the extruder to ~225C, remove the PETG, insert the PLA, and extrude a bunch to get all of the PETG out so it doesn't clog. 

One of the last things I need to do to this printer is replace the worn X-axis belt and install the belt tensioner. However, the belt is tight and still functional, so I'm going to wait on it to wear out more before doing that.

Making more things

I made some things recently.

My partner likes pink, so I painted the desktop "candy pink". They've been running astrophysics-y python codes, and their laptop just isn't cutting it anymore.

I also printed out the sugar glider decal.
Paint and decals make things faster, yes?

I modeled and 3D printed a Delta II rocket fairing for a downloadable 3D model of the Kepler Space Telescope, which I also 3D printed.

I put it on Thingiverse (see here for more info).

A few more successful prints

I designed and printed a couple things.

1. A better filament guide for the Wanhao i3.

It's shorter, so it aligns the filament with the extruder better. First attempt interfered with the spool holder, but I was able to modify it. The thingiverse model has been corrected. I made it so it would fit the teflon tube holder that fixes the coiling problem I mentioned earlier.

2. A SSD adapter for a Supermicro drive tray. I needed this for the homelab cluster.

This one is a bit tricky. Ideally, I'd have plastic on both sides and/or the bottom of the drive, but the way HDD's fit in the trays and the lack of space in the tray bays prevent this. Thus, the SSD is only held in by two side screws. Some support at the back helps keep it in place while being loaded. It works well, and is easy to adjust for thicker SFF drives. I thought about printing and selling them on eBay for less than the SM equivalent (MCP-220-00043-0N), but I'd barely break even.

My Phi adapters are selling ok on eBay. It's a small market, but I think my design is superior to all of the alternatives, so I should be able to make a tiny amount of money and hopefully partially pay off this printer.