Sunday, December 29, 2013

Delta Bot Build

The first time I saw video of a delta robot style 3D printer, I decided the next printer I built was going to be a delta. Based on everything I've learned from my MendelMax, I knew I wanted a printer that was as stout and stiff structurally as possible, with a GT2 belt drive. Some of the deltas use spectra fishing line, which to me seems like a troublesome way to drive the mechanism, particularly since the GT2 belts are so reliable. 

I decided to try using the Makerslide system for the linear bearings vs. the traditional Rostock bearing rods. This solution seems like a nice way to combine a linear slide with the vertical structural components at an affordable price. I sourced the Makerslide linear slide extrusions and related hardware from 

The Wolfstock style delta-bot seems like a good design. But, I wanted to run the drive belts through the inside of the Makerslide for a cleaner look. I couldn't find quite what I was looking for on Thingiverse, so I started to design my own version. 

All of the solid models are my design work, but they are almost all heavily based on the Wolfstock, Kossel, and Rostock printer designs. I'm putting the solid models and .stl files on Thingiverse if you'd like to download them: This being Minnesota in the winter- I decided to call it the "Snowstock Delta Bot."

The parts from Inventables arrived quickly and all seem to be top quality. I'll definitely keep this stuff in mind for future projects- maybe even some light-duty industrial automation. It certainly is much less expensive than traditional linear bearings.

Linear slide carriage components from Inventables
Laying out the parts for the V-grove rollers
Pressed in one bearing and a M5x20mm SHCS
Using washer to space bearings (so when tightened, compression load is transmitted through bearing hub)
Second bearing pressed in to place
Spacer washer in place

Linear slide carriage assembled
Carriage mounted to Makerslide extrusion

Eccentric spacer allows for adjusting preload of V-grove wheels against Makerslide rail

The overall design of the printer is intended to keep the structure as simple and solid as possible. Some of the other designs I've seen on Thingiverse have really large printed parts. I tried to keep the printed parts as small as possible, and utilize more 8020 style extruded pieces. Really large printed parts take excessive amounts of time to print, and I always have problems with part warp-age or other quality problems. Plus, if you can source the 8020 extrusions used from a industrial surplus source it's really pretty inexpensive.

I printed all of the big structural parts using a 0.5mm nozzle with a 0.5mm layer height. I think the thicker layers are stronger than thinner- fewer opportunities for layer separation.
Base components, one motor mounted to test hole alignment

Base components
Top corners, including idler pulley mount

M5x10mm SHCS, washers, & T-slot nuts ready for assembly
 The first two extrusions are easy to install- locate the screws & T-slot nuts in the printed corners, line everything up, and carefully slide the extrusion into place. The last extrusion is much tricker to install!

Upper Triangle Assembled

Lower Triangle Assembled

Motor & motor mount

Testing alignment between upper and lower triangles

Testing alignment between upper and lower triangles

All 3 Makerslide tower sections clamped together before a final trim to get all three lengths exactly the same

Frame Assembled!

The assembled frame seems pretty sturdy- I am considering installing diagonal corner braces just to really stiffen it up.

Carriages in place

Carriage detail

The is the whole reason for a new design- keeping the belt return path inside of the vertical extrusions- nice clean look

Motor mount, GT2 pulley detail

Next steps: 

  • design, print and try belt clamps
  • source some suitable tie rods & tie rod ends
As for the Tie (effector) Rods, initially I'm going to try using the same dimensions as the benchmark Rostock 3D printer design:

  • Rod Length: 250mm Eyelet to Eyelet (same as Rostock)
  • Traxxas 5347 Rod ends x12 (popular online choice for rod ends)
  • Thursday, December 26, 2013

    Improved Filament Guide

    More efforts to improve filament feeding into the printer- mostly to try and eliminate filament jams around the spool, but also to reduce the force required to pull filament off the spool. The files for this filament feeder can be found on thingiverse:

    Components printed and ready to go
    608 bearings pressed into place
    whole range of parts tried- no wheel version on the left, and various guide peg locations on the right. 


    And running!

    Saturday, November 16, 2013

    Terawatt Industries 00str00der Follow-up review

    After running the Terawatt Industries 00str00der for a few weeks, I had a few initial impressions:
    • belt drive extruders seem to be far superior to geared extruders - no backlash, smooth operation, and no wear. 
    • The 00str00der design didn't seem to be optimum, at least for my installation on a MendelMax 1.5 printer:
      • The mounting orientation perpendicular to the X-slides causes considerable flexing of the slide rods during prints, causing the nozzle to move in the "y" direction and thus adding print inaccuracies
      Photo showing stepper motor hanging over front edge of X-slide rods
      • Extruder design doesn't tie stepper mount to structure surrounding hobbed bolt, possibly allowing flex
      • Use of rubber discs for springs vs. wound steel springs does not create as much clamping force between the idler bearing and the hobbed bolt, causing filament feed problems
      • The slots that provide for belt tensioning don't have enough travel, making installation of the belt difficult.
    Since I'm trying to slowly increase the print quality and precision of the printer, I decided to re-design the printer to try and address the problems I noticed. I couldn't find Solidworks files of either the 00str00der or any of the Greg's Wade style extruders, I started this design from scratch, using a few of the existing components. (Idler being one)

    Main features of this new extruder:
    • orients all components directly over X-slide rods to minimize twisting
    • long slots for belt tension adjustment and easy belt installation
    • super-beefy construction to minimize flex within part during prints
    I've uploaded the .stl files and solidworks models to thingiverse, located here

    Belt Drive Extruder, assembled

    Extruder, Mounted

    Note stepper mount is directly attached to extruder body, no gaps
    So far is seems to work well. I did switch the rubber elastomer pucks in the idler tension mechanism for some coil springs. The pucks wouldn't supply consistent pressure on the idler wheel. 

    Saturday, October 19, 2013

    Wolftooth Chainring Install & First Impressions

    After last week's Fatbike Adventure ride, my 9:zero:7 needed some serious love. The bike was still covered in mud, and the bottom bracket was making some serious grinding noises. I had some time tonight to attack it, and I decided as long as I had everything apart, it was time to install the Wolftooth components 30T 104BCD chainring.

    These chainrings have the wide/narrow/wide profile to prevent chain drop even without a front deraileur or chain guide. Also, they have a cool chainring design that allows installation of a 30T chainring in the middle position- normally a 32T is the smallest you can go. Not only are these rings cool, they are also made in the USA- specifically Minneapolis. I rarely if ever use the granny, and going to a single small front chainring should work just fine, along with simplifying the bike and saving weight.

    With the cranks off- I could directly inspect the bearings. The non-drive side bearing seemed OK, but the drive side bearing sounded like it was filled with rocks and felt about as smooth. I don't have any spare 6806-2RS bearings laying around. Rather than waiting for new bearings to arrive, I popped the seal off with a X-acto knife, sprayed it out with some degreaser, let it dry, and packed as much Park Tools grease into the bearings as I could. I kept on rotating the bearing and applying more grease until the grease coming out looked mostly clean. Even after the grease packing they still feel a bit rough. I'll order another set of bearings and install when these start grinding again.

    After the bearings and cups were back into place, I could swap out chainrings, put everything back together, and remove the now-unneeded front deraileur and cables. The chainring install actually turned out to be a big weight savings:

    +41g: Wolftooth 30T 104BCD chainring & 4 chainring bolts

    -163g: Shimano XT Front deraileur
    -71g: 32T Chainring, 22T chainring, chainring bolts
    -165g: SRAM X7 front shifter, cables & housing

    Total: 358g weight savings (0.78 pounds)

    It looks great on the bike. Hopefully it works as well on the trails as it looks.


    Nice clean look

    Lots of chain clearance- ~ 13mm

    Friday, October 18, 2013

    Magicshine Light + GoPro Mounts

    I've been experimenting with various 3D printed mounts for my Magicshine lights. The stock mount uses a thick O-ring to wrap around the bar- and during rough off-road rides it tends to rotate around the bar. I've prototyped several clamp designs. None of them worked as well as I'd like- once I have a design that works well I'll post it online. 

    In the mean time, after doing last weekend's Fatbike Adventure Ride III, I realized that there are already some really nice helmet mounts for GoPro cameras. Since I wanted to also create an improved helmet mount, it seemed like a great shortcut to making a better mount. It was easy to put together a couple adapters to mount my MagicShine MJ-808 to a GoPro helmet cleat. The adapter uses the LED light's stock 4mm screw to hold it to the light, and the standard GoPro thumbscrews to attach to any standard GoPro mounts.

    MagicShine GoPro adapter, Handlebar / High-Rise

    "High Rise" Adapter with LED light & GoPro helmet cleat

    Side View

    High Rise Mounted On Helmet

    Zoomed View
    My initial mount worked well, but it put the light well above the top of the helmet- sure to get smashed on a low-hanging branch. This mount should work to mount a Magicshine to the GoPro handlebar mount.

    "Low Rise" Mount

    "Low Rise" Mount

    "Low Rise" Mount

    I hope to test the new helmet mount this coming week if the weather cooperates. If it works well, I'll probably post the mount on Thingiverse.

    Tuesday, September 24, 2013

    Terawatt Industries 00str00der Build Instructions & Preliminary Review

    In the never ending quest to try and improve print quality on my RepRap MendelMax 1.5 3D printer, I decided to try a belt-driven extruder. I recently replaced my original extruder's straight-cut gears with helical gears which caused a noticeable improvement to part quality. The next step would be to move to either a direct drive extruder or a belt / gear drive system. The direct drive extruders I've seen use 1.75mm filament, but I'm set up for 3mm filament and have many spools on hand. So, it's either a gear drive or belt drive. Gear drive systems still have some backlash- and a GT2 belt drive system will have almost none.

    One choice that looked interesting was Terawatt Industries' 00str00der belt-driven extruder kit. It was a drop-in replacement for my Wade's gear drive extruder, and their kit seemed to include everything for an easy build. I considered printing the parts myself, (models found on thingiverse here) and sourcing all of the parts from the various sources. But, after taking into account parts costs and shipping, it wasn't a bad deal to buy the complete kit directly from Terawatt Industries. I also upgraded the motor at the same time- replacing my original small Nema 17 stepper I bought from the industrial surplus house and moved to a larger "standard" size Nema 17 stepper.

    Unfortunately, the kit didn't come with any instructions, and those found online either on or Terawatt's site were not very complete. I took photos and notes during assembly of my kit, hopefully they'll be helpful to someone.

    Kit, as received from Terawatt Industries
     The belt-drive extruder kit arrived nicely packaged from Terawatt industries. The various "vitamins" were individually packaged from the printed parts.

    Extruder body
     The part quality of the printed parts was acceptable, but not spectacular. One nice plus was they included two copies of the idler body- something that (in my experience) tends to fail over time.

    Kit Printed Parts
     The "vitamins" included in the kit seemed to be decent quality, and complete.

    Extruder Belt Drive Kit "Vitamins"
     Step 1: clean out filament hole in extruder body. I used a #28 0.140" drill

    Cleaning out filament hole
    Step 2: Attach stepper (not included) to extruder body with M3x10 SHCS and M3 washers. (not included). M3x12 SHCS might be better, but I didn't have any available. Don't fully tighten screws, you'll be removing the stepper later.

    Stepper Bolted on
     Step 3: Attach pulley to stepper.

    Pulley in place
     Step 4: Get Hobbed bolt properly aligned. The bolt head should be on the "left" or non-drive side. 4x 8mm washers under the bolt head, and 2x 608 bearings aligned the hobbed portion of the bolt perfectly with the filament path in the extruder body.

    Hobbed Bolt in position- note hobbing is directly aligned with filament path
     Step 5: Attach 608 bearing and large pulley to hobbed bolt on the "right" side of the hobbed bolt.

    Step 6: Attach belt. To get the belt on, I removed the small pulley, put the belt on the large pulley, and carefully slid the small pulley back into position with the belt in place.
    Belt attached
     Step 7: Tighten stepper bolts. This step isn't really necessary, as you'll be removing the stepper later to install it on the mounting plate and X-axis slide.

    Step 8: Assembly Idler. Insert 8mm threaded stud into remaining 608 bearing, and press into idler. The idler required some cleanup with a x-acto knife for the 8mm threaded stud to fit. Press captive nut into idler body.

    Idler, Assembled

    Other hardware for idler

    Captive nut in place
     Step 9: Install Idler. Attach to extruder body and insert fastening screw and tighten.

    Idler attached
     Step 10: Clean out 4 mm nut traps for idler tensioner with X-acto & install 4mm nuts. The part quality of the printed extruder body was a bit dodgy here, and one wall of the nut trap ended up breaking when I was cleaning it out. So far it seems to work fine, but I might have to print a new body myself.

    Cleaning out nut traps

    M4 nuts in nut traps

     Step 11: Install 4mm tensioner screws, washers, and rubber "springs"
    Idler tension screws installed
     Step 12: At this point, I realized that I wasn't going to be able to install the assembled extruder head on my printer without doing some dis-assembly. The minimum amount of dis-assembly is to remove the belt and stepper motor. I stripped it all the way down for easier access to all of the hardware during mounting on the printer. Pre-assembling everything on the work bench is the way to go, though, as it's easier to trim edges and test fit parts before the extruder is on the printer.

    Extruder, dis-assembled

    Extruder body attached to mounting plate

    M4 screw detail
     Step 13: Install on printer
    Old extruder

    Old extruder removed, tail end of hot-end visible

    New extruder bolted into position with stepper installed

    Mounting bolt detail

    Idler & hobbed bolt install

    Pulleys and belt re-installed

    Belt Detail

    Extruder backside detail
    So far I've done the initial tuning and printed a few small sample parts. After limited tuning my steps per mm setting was 535.3524.

    Overall, the belt-drive 00str00der was an easy build and upgrade. My initial prints have looked pretty good, but I don't have enough data to say whether it improves part quality in a big way. At the very least it should be a more durable option, eliminating the need for extruder gear replacements. More details and a final opinion to follow.