Tuesday, March 7, 2017

Post 3: Core X-Y Musings...

It's been 4 months since my last update Post 2: Improved Z Screw Bearing Blocks so time for an update. Things were going a little (ok, a lot) slow because I was getting caught up in analysis paralysis and over design-itis - primarily because of the hgh cost in both materials and time for the aluminum parts I planned to make. But recently I discovered Atomic Filament PETG-carbon fiber. This stuff is really nice, it prints beautifully, has great dimensional stability and print accuracy and is quite stiff. So, my new plan is to print all of the parts in this PETG-CF and get the printer operational. I can always come back and replace with machined parts if needed. This allwos me to do fast design and test print iterations (with PLA) and then a final print for the machine.

I also have a home for the printer so it is up off the floor–where it was really difficult to work on.
There it is squeezed between RazMaTazz (my Taz 4) and a Terk (a mini Kossel).

This makes working on it much easier. And the new plan is working. Here are some of the parts in PETG CF:

X and Y stepper mounts

Bearing mounts for ballscrews with angular contact bearings

Monday, March 6, 2017

Segment-less Delta Movement

This post comes from a post I originally made on the SeeMeCNC forum in December, 2015. I find myself referring to that post often and repeating it in multiple places so I'm adding it here where I can keep it updated.
updated 3/6/2017

Segment-less Delta Movement
A little know secret to most delta (and Cartesian) printer owners is that path movement for all firmware except David Crocker's dc42 RepRapFirmware is actually broken up into short straight segments. In other-words, a curve is actually "drawn" as a series of short lines and not a smooth arc like you might expect.

These other firmwares are interpolating movements into short line segments so, in theory, there is a negative impact on print quality. There are other factors at play too though - hence the reason for "in theory". By it's very nature, 3D printing starting with an STL file sacrifices some resolution depending on how the original CAD model was converted into an STL (most profound is the # of triangles in the final model). Here is an example of how this works...

Imagine you have a CAD drawing of a 20mm diameter sphere. The CAD tool uses sophisticated math to calculate the geometry and display it. It looks like a perfect sphere on screen. Now, let's run that perfect sphere through the meshing process to create STL versions. To demonstrate I am using 5 different resolutions that generate a low number of triangles to a high number of triangles. When you download an STL from Thingiverse, you have no control over this, the original author made the resolution choice for you. And frankly, most of the folks uploading to the shared services really don't know how to create high quality meshes. Anyway, back to the example - here I've meshed to create a "sphere" with 48, 224, 960, 16128 and 99856 triangles (from left to right). You can see that the far left sphere is course and the one on the far right is reasonably smooth.

Now to take this one step further, imagine your slicer creating g-code from these STL models. To illustrate, I created an imaginary slicing plane 12mm above the base that is .02mm thick and took a cross section of the model at that plane. This is the red line you see inside each model. I projected these slices up above the models so you can see them clearer (black). The 48 triangle model has a slice with 8 sides - pretty low resolution. You can see as you move left to right, each slice has more line segments. These will result in a finer/higher resolution print all things being equal. But they are not! In addition to the slicer converting curves into short line segments, the firmware also imposes its own line segmentation on top of that - that is all of them EXCEPT dc42 RepRapFirmware. dc42 draws each point along the way completely tracing the original path it was given. Smoothie, Repetier, Marlin and the others actually break the path up into short line segments and draw those. This does not always match the original path exactly.

As you can see, if the STL had a low triangle count, you are going to get a course print whether or not your firmware does segment-less movements. Increasing the triangle count will improve the print quality until you reach the segmentation threshold of the firmware, at which point, increased # of triangles won't have an effect and might actually make things worse. That is except dc42, which will faithfully trace each of the tiny line segments exactly point by point.

But, there are other factors that come into play like stepper resolution (1.8° vs 0.9° steppers) and a host of others. Will segment-less moves make all your prints look fantastic? No. But if you design your own parts and optimize output for high quality meshes, I assert you will be able to see the difference. This difference is minute and impossible to photograph, I've tried for over a year. But, parts in hand 10 out of 10 test subjects will pick the part printed with segment-less moves as the best quality part.

I posted Musings on Impact of STL Triangle Count in Jan, 2016 if you'd like to get more info.

Friday, March 3, 2017

The "Tusk Fan Shroud"

I don't understand why many people feel they must blast their part, hotend and heated bed with lots of air. Consider this: blasting a large area with a lot of air can create more problems than it solves - problems like part warping, hot end temperature fluctuations, beds that can't reach and maintain higher temperatures and a host of others. A much better approach - particularly for common filaments like PLA, ABS, PETG, etc - is to direct the minimal amount of air as precisely as possible with laser focus.
I started experimenting and writing about this a few years ago. See Strategy #12 Be a Fanboy here: A Strategy for Successful (and Great) Prints for more details and examples of part warping due to too much air cooling. Here's a photo of an extreme warping example due to too much air:
Part on the left was cooled with a typical 25mm fan blasted at the part.
Part on the right cooled with my "soda straw" air duct (note the straws look far away, that is an illusion!)
This early soda straw air duct concept gave way to a slightly more sophisticated version using several soda straws - one on either side - and ultimately to a 3D printed or machined ring (Re: BerdAir coming soon...). I used this concept on all my deltas (8) until Berd-Air produced their bent aluminum tubing cooling ring. It precisely puts air where it's needed and it is also very low mass on the effector and very low profile so it solves multiple problems. But the air pump is noisy and large.
Recently I've refined my design to address the loudness issue by leveraging a normal 25mm fan or squirrel cage fan. I call this new version "the tusk" for obvious reasons (see photos below). The aluminum tusks allow positioning closer to the heater block for more precise air flow control.The photos below show it mounted on the effector of a SeeMeCNC Rostock MAX V3 with a soon-to-be released new Bondtech mini extruder I'm testing. 

The "air shell" is low profile and can be located up and out of the way or even designed into an effector or platform if necessary. I'm showing a version with a squirrel cage fan but a standard fan tilted at a slight angle also works well. The tusks are 4mm OD aluminum tubes with 1mm holes. I have a printable jig that is used to align and space the holes for drilling. Then you crimp off the end of the tube. This has the additional benefit of allowing the crimp to be used as a sight to align the holes. With this arrangement, I have 100% clearance, something the three "hovercraft fans" of the stock V3 don't allow.
The middle hole on each tusk is centered with the nozzle tip. The air is directed 1mm below the nozzle and can be aimed as necessary with the sight crimps. With this precise air flow, you will not introduce thermal stress in your part (see link above), nor will you inadvertently cool your heated bed (especially important at higher bed temperatures), nor will it cool your hot end - especially if you use the E3D V6 sock (which I highly recommend for this and other reasons).
I have done smoke tests with this to study the air flow and can verify that it precisely streams air as claimed. The best part is, even with a 25mm fan I rarely ned to run more than 50% fan speed. The even better thing is, with this form of directed air flow, you can print longer bridges in PLA and ABS since the cooling air is in the right place to "freeze" the filament as its being drawn across the bridge. And part warpage is non-existent. And thin walls and posts/pillars like those in my fly fishing reel prints that are very difficult to print without distortion using the nuclear blast cooling method print perfectly every time.

If you'd like to try the idea, I've put STL and STP files for the Tusk Fan Shroud and STL for the Tusk Drill Jig on my Google drive: https://drive.google.com/drive/folders/0BxntGMCn8PVKOTFwU3F4NzNvNG8

Thursday, February 9, 2017

New "FSR Plate" mounting system

I've posted quite a bit about FSR probing along with my previous mounting system. I've been using FSRs for probing for coming up on 3 years. They are 100% reliable, very precise and result in excellent calibration results. I originally designed this system for a Max Metal delta printer but it worked so well that I used it on my Rostock MAX V3 and I'm going to retrofit my other deltas with it over the coming year. There are 2 significant aspects to this new mount.

1. The FSRs are now positioned outside the build plate perimeter as you can see in the renderings below. This minimizes the "teeter totter" effect when probing 1/2 way between FSRs. Moving the probing points out significantly decreases this effect.

2. The second improvement comes in the way the FSRs are mounted and how they are triggered. In my previous mounting system, a printed plunger moved inside a printed cylinder. This led to one of the two reasons folks had problems with FSRs (the other was that their bed is not stiff enough - this mostly applies to the Kossel Krowd™ that simply used glass with a Kaptan heater). The plunger system works reliably but only if you use high quality prints and prepare and lubricate them properly as I've described on multiple forums and here. Otherwise, they can bind ever so slightly, leading to inconsistent triggering. The good news is, this issue is easy to identify and correct. The better news is, this new system eliminates the problem altogether! Here's what it looks like:
With this new system I simply adhere the FSRs and rubber plungers with sticky tape so they are constrained in X-Y but free to move in Z. The FSR has a sticky back, just peal off the protective film and stick it to the top surface of the printer. The plungers that come with the Ultibots FSR kit also have a sticky back, so peal that and stick it to the top of the FSR sensor itself. Now you put a small dab of silicone seal on the top of the 3 rubber plungers (a SMALL dab) and press the FSR Plate onto them and allow to cure.

I actually don't bother with the silicone, I just have my plate resting on top of the plungers. I've never had an issue with the plate moving. I am working on a simple printable locator that will attach to the top printer plate that will keep the bed from shifting but since this has been working so well, I have not bothered.

Finally, you can see in rendering below a recent modification - the FSR Plate now has three ears. In my V3 photo at the start of this post I'm using big binding clips. I needed to add 3 additional rubber plungers under the FSRs to make room for those. But, by tweaking the FSR Plate with the ears I can remove those and use the ears to attach the Onyx/glass with the little blue (or other) holddowns. I do one other thing on my printer, I adhere the Onyx to the top of the FSR Plate with a disk of the 3M 468MP tape we use to attach PEI. This holds the Onyx perfectly flat while allowing it to expand and contract in the X-Y plane without buckling. It works quite well.

2 Drawer Cabinet for SeeMeCNC Rostock MAX V3

My friend Chris Androsoff came up with a great idea to replace a Rostock MAX V3 base panel with a drawer. I saw it when I visited him in Calgary a few weeks ago. I liked the idea but wanted a drawer to organize my nozzles and small tools so I revised it with two drawers as shown here. I've posted the STLs on my Thingiverse account.

Wednesday, February 8, 2017

Coming up Roses!

I posted this Valentine's Box on thingiverse 3 years ago. A couple of weeks ago ProtoPasta announced a new limited edition Aromatic Rose HTPLA that I just had to have! There are only 36 spools of this stuff and it is made with real rose petals. It is really attractive too, kind of a soft rose/heather color. Here is the box in Aromatic Rose, how sweet it is!

This filament prints beautifully. I did have to raise the temperature up to 205°C from my standard 195°C for most PLAs.

Sunday, January 8, 2017

Presenting my all-new V6 3D printed fly fishing reel

It's been two years since I first went public (and mini-viral) with the world's first, fully 3D printed fly fishing reel. Field & Stream Magazine fly fishing editor Joe Cermele first blogged about my reels and then asked me for one to test. He put together this awesome video.
A few months later I made some major (and innovative) updates to the design - I called this the V5 design.
I make the STL files and detailed instructions freely available but I do ask you to agree to a few simple terms. Over 2500 fly fisherman and 3D printing enthusiasts from all across the globe have downloaded the files. In the summer of 2015, following publication of my article A 3D-Printed Fly-Fishing Reel with Click Check in their Journal,  I was asked to present at the American Museum of Fly Fishing in Manchester, Vt. I donated my very first "alpha" reel and the first V5 reel to the museum to be part of their permanent collection. They also bestowed the titles "world's lightest 4 weight fly reel" and "first 3D printed fly reel" on my work.

Over the last year I've learned a lot about the reel from all of my great users and even more about "design to 3D print". Although the V5 reel is quite robust there were a few areas that I wanted to improve to allow the reel to handle larger fish and be more robust. I've completed the iteration, design and testing work and now I'm ready to publish my new V6 3D Printed Fly Reel. It has quite a few changes and innovations that distinguish it from its predecessor as you can see.
I'll walk through the major changes but there are dozens of little tweaks to dimensions, etc to improve printability.

Ovalized Pillars - this modification not only makes the pillars (specifically the pillar to backplate junction) much stronger but also really improves printability. The pillars also have a small fillet at their base to improve strength. My informal break tests lead me to conclude that this new design is at least 3-4 times stronger than the V5 design. That's a major improvement.

Conical Spindle Base - this design change improves strength of the spindle-to-backplate junction, greatly improves printability and allows the spool to rotate more freely. 

Square Handle Spindle Attachment - the handle spindle attachment to the spool plate was a weak link in the V5 design. I struggled with this one and tested a lot of ideas. This simple square boss and hole did the trick!

Improved Foot Index - this positions the foot accurately on the reel. The earlier V5 design did not allow the foot to seat accurately or firmly. In addition, a small fillet at the base of the boot pillar significantly improves strength.

Asymmetric Click Check - I developed this innovation for my aluminum fly reel kits but it works just as well on the 3D printed reel. There will be three versions of the backplate - one for left hand retrieve, one for right hand retrieve and a simple symmetrical version like the V5.

Not shown in the diagram is a Friction Pad opposite the click check. This element supports the spool opposite the click check pawl to prevent the spool from binding when retrieving a large fish. My daughter's boy friend Brian actually came up with the idea when I had him beta test assembling one of my aluminum reel kits last autumn. Smart guy!

Along with these enhancements there will be a few other surprises mostly around design elements like porting. Stay tuned for the release sometime in the next week or so (I need to finish the Assembly Guide for the V6 design).

I'd like to thank the many supporters for their kind donations to help continue funding my work. After some consideration, I've decided to offer the STEP files for the complete V6 reel for a $10 donation. This will allow users to customize the reel, tesselate it (mesh) themselves, as well as learn a little about design for 3D printing