Category Archives: 3D Printers

Designing for 3D Printing – Making useful things – Part 1

I’m starting a series of articles and accompanying videos on designing for 3D printing, using 123D Design as a starting point.  As I learn more about other software such as Solidworks, I’ll try to pass that info along.

Disclaimer:  I’m not an expert, I just figure things out and make notes here on my blog.  If those notes help you that’s great!  If I make mistakes or you know of shortcuts that I could benefit from, please leave me a comment!

This first article will discuss how to make a small simple part for a 3D printer project: A nut!  Yep, a simple nut, but this nut is for aluminum extrusion!

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A good 3D printer design emphasizes a solid frame as its foundation.  Some good inexpensive material for this is called Aluminum Extrusion.  A really good supplier for this material and many accessories is http://www.misumiusa.com. Another fine distributor is 80/20, Inc. http://www.8020.net

Metric_Catalog_17_Sections

 

As you can see in the above image there are slots on all four edges.  Special nuts are made to fit inside these slots.  But sometimes you need a few extra, or just want to do some quick and dirty prototyping.

In this article, I’m going to show you how to make a nut that will fit inside this profile.  Some extrusion profiles are small enough that you can just use a regular metric or SAE nut and slide it in and tighten it.  However, with the larger extrusions, the slot is too big and the nut won’t seat properly or you will have to use a really big bolt.  The nut we’re going to make is called a pre-assembly nut:

preassemnut

 

On Misumi’s website, they provide a great amount of details and dimensions to help us decide which part to pick.dimensions

It’s difficult to know which way is up with these things and our dimensions can get confusing.  The way the nut fits into the extrusion should help us:

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I’m going to call 6.3 the width, 15 the length, and 14 the height, because that is basically how it will load into 123D Design.

In the above image you can see the dimensions for our part.  I will note these here for reference later:

Width:  6.3 mm
Length: 15 mm
Height: 14 mm

You can use the product configuration tool to order parts and download 2D/3D cad drawings of certain parts.  However, for the nuts you can only download the 2D profiles.

Misumi Part Config Tool

nutconfig

Now that I’ve made my choices, I’m going to download the 2D cad file.  Here is the file that I downloaded if you want to follow along. Here is the part profile that I downloaded. It is for the HFS6 30×30 extrusion profile.

Inside the zip file are three .DXF files.  Each has a different profile design and I’m going to use the one that gives me enough room to insert a standard M4 nut into the back of the 3D printed part so that I can tighten the screw appropriately.  The three choices for this part are:

 

nutprofile1

 

nutprofile2

nutprofile3

I picked HNTT6 because of the wider bottom (which is pointing right).  This gives me room to create a nut capture hole for the M4 nut.

Opening the .DXF files in Inkscape allows me to edit them and remove all the stuff I do not need, so that I can save it as an SVG file.

Here is what it looks like after I cleaned it up:

nutsvg

 

I’ve selected all the parts (Control-A Windows). Then we have to click on Path, Stroke to Path then Object, Combine so that when we load it into 123D design we do not get an error message stating it could not find any valid paths.

Save the file as an .SVG on your desktop.

Now we’re ready to import it into 123D design.  Open 123D Design, the click the 123D Menu drop down to open the menu, and select Import SVG, then As Solid.

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Here is what it looks like after the import:

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Looks great!  However, you need to inspect this closely.  The file I have imported seems to have two faces.  So when I click on the top of the solid body, and move it over, this is what I see:

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You can see there is an outer shell.  So I drag the solid to the left to reveal the entire shell, then I select all of it except the solid and hit delete.  This is easier done from the TOP view:

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Now we’re going to do some measuring.  We want to measure the length, width, and height, and we’ll need to put these somewhere so we can recall them.  I use Google Docs/Spreadsheets for this so I can do the math there as well.

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Use the measuring tool and measure from one edge to the other being careful to select just the edge and not the face.  Make sure you select furthest parallel edges to get the overall size.

As you can tell, it is wayyy too big.    So we need to scale it.  But as far as I know, 123D is not a “Parametric” design tool like Solid works.  So I haven’t really figured out the easiest way to re-size something to specific dimensions, so I’ll show you “my way”

I measured all the dimensions, and put them into Google Sheets.

I then added a formula column to show me the scale factor.  This is determined by dividing my desired dimension with the measured dimension:

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Now, I can go back to 123D Design and select my object, then select Scale, Non-Uniform, then enter the values above.  However, 123D Design only allows 3 digits to the right of the decimal, so we have to round to 3 decimals, so I added that to the sheet:

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Now we can scale it properly.  Sometimes it’s hard to know where the X, Y and Z are relating to our dimensions, so just change one and observe how it shrinks, then you’ll know.

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After we’ve scaled it, we can re-measure each dimension to see how close we got.

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My end results were 6.322, 15.008 and 14.00.  These are totally acceptable!

Now we need to make a hole for our screw and a nut socket.

You should use some inexpensive digital calipers to do your measuring.  Here I am measuring the diameter of the nut.

PLEASE NOTE:  I didn’t have any M4 Nuts!!!  Argh, so I had to use an SAE nut that was approximately the same size.  The dimensions below should work as well for M4.

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We’ll need a cylinder about 4.2 mm in diameter for our M4 screw, so we’ll enter 2.1mm for the radius.  Note, we’re making the hole for the screw, not the nut.  Drag the cylinder around until it “snaps” to the center, and enter your dimension of 2.1 for the radius and 20 for the height:

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Next we need to position to make the face of our cylinder and the face of our shape to be flush:

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Now at this point we could “cut” the cylinder from the shape leaving a hole, but let’s add our polygon first.  Use the Draw Polygon tool:

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We want to “snap” the polygon to the center of the cylinder:

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The diameter of an M4 nut is 9.45 mm, so we need to divide that by 2 and give it a little extra, so we’ll go with 4.75 which will come out to 9.5mm.  We need 6 sides for our polygon.

Now let’s extrude our polygon into the object and that will create a 6 sided hole:

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The nut is 3.2 mm thick so we’ll enter that as our depth:

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Now we can delete the sketch that was left behind:

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And lastly, we can cut the cylinder from our shape and we’re done!

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Now let’s print it, and see how it fits!

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Perfect!

In my next post, I’ll show you how to take an STL file, and convert it to a 123D Design object that you can edit!  Stay tuned!

 

 

Finally getting some decent prints

After what seemed like endless hours of fine tuning, I’m finally getting decent prints.  I still have work to do, and learning to learn, but I’m happy with the results so far.

Here is a vase printed at .2mm layer.  That’s like a “medium” setting, and is my standard setting.  The nozzle in my printer is .4 mm.  This red plastic is called High Impact Poly Styrene.  It doesn’t warp like ABS and so far has been a real gem to print with.  It’s also harder than ABS.

vase1200

Here is a thing that someone tossed out as a challenge for RepRap machine owners.  mine printed it fairly.  I mean, it printed it.  Without failing.  But I wouldn’t call it amazing… yet.

epicdevicething

 

I decided to load up the PET+ that I bought a week ago at MicroCenter here in Dallas.  I had been reserved about printing this in my cheapo Jhead hot end because it has a PTFE liner inside.  If you run that hotend too hot, it will melt that liner.  Well, PET+ needs 250-260 degrees C to work properly.  Well, it printed nicely!  I’m so stoked by the results.  I’m quite amazed that this machine that I built out of random bits, fine tuned over about 150 hours of work is producing these results.  I’m not giving up on fine tuning because I’m sure there is more to do, but for now I’m a happy printer owner!

bluevase1600

2 inches tall by 3 inches across the top.

Madesolid Sapphire PET+ 1.75mm diameter

Printed in sprial mode, .2mm layer, 250-260 degrees hotend, 90 bed, probably around 40mm/s

Koch Tealight Vase on Thingiverse

Here is a sample of the layering consistency I’m getting at the moment.

x-axis-sample

Analysis of the Y Axis (Bed) on a Cartesian style printer

I’ve been observing the dynamics of the print bed on my 3D printer which is a Prusa i3 style Cartesian printer.  The bed has 3 linear bearings that rid along two smooth rods.  The bearings are arranged in a triangular pattern, with the drive belt down the center line.  I have noticed that with some bearings, that have play or are loose, I get wiggle in the bed.  I believe it is due to the following:

bed1

I’ve surmised that because the bearings have play, the motor applies a force on the bed which the single bearing receives as force across the horizontal axis in this picture, which is opposite (accros) the belt. This allows a “wobble” or slight rotation of the bed in the center point of the triangle.  Because of the unreliable specs of the bearings, each has a different tolerance and even the smooth bars may not be manufactured to any type of specification.  If the bearings aren’t fitting on the bar with minimal play, then you will get inconsistent layers, and your walls will not be smooth/straight.

For beds arranged like this, the situation is different and maybe non-existent:

bed3

Three bearing designs are great for machines that have expensive, tight tolerance components.  For RepRap printers, four bearings are probably better over all.

The following approach would minimize the problem for three bearing designs:

bed2

The reason for this is that in three bearing designs, you typically have “leaders” and “followers”.  The Leaders are the drive bearings.  The follower is a supporting bearing.

These are my theories based only few hours of observation and non-scientific brain-storming.  I’m not an engineer, just a mechanically inquisitive person who was raised in a junk yard.

Hardening your Prusa i3 3D printer

I believe the current and original design of the Prusa i3 3D printer has a lot of areas that need improvement.  It seems the printer serves a great purpose of teaching you about Fluid Deposition Modelling (FDM) printers, but as a printer in itself, it leaves a lot to be desired.  They should have called it “The Trial and Error Printer.”

If you make the mistake, as I did, of building your printer out of lexan or acrylic, you’re going to have a lot of problems.  Additionally, if you buy some random set of printed parts off ebay for your printer’s structural members, you’re going to have even more problems.

All in all, it is a wonderful  stepping stone to the next printer project, but in itself, I would not call it a production class machine that you can rely on day in and day out.  No, sadly, those cost a few more bennies.

Here are some pictures of what I have done to harden my machine so it prints more precisely.  Note, I’m not calling it reliable, or precise, but “more precise” than a vanilla kit machine.

My first priority was to stabilize the platform and frame.  I made a bad choice in using the 6mm acrylic frame.  But I’m stuck with it for now.  So I am doing the best I can with it.

I dug out a piece of 18×24 MDF for the base.  I set the printer about in the middle and marked the places where the frame had zip tie holes and drilled through the board.  I ended up using zip ties for the time being, but reality is, a screw and nut will be a more permanent solution.

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Next on my list was the X axis carriage.  I reduced the bearing count from four to three, and re-arranged it so the two bearings are oriented on the top where the two belt ends connect to the carriage.  Though not scientific at all, my theory was that this was a better arrangement to control wobble on the X axis carriage.

 

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The next big area of improvement, especially when using printed bushings, is to constrain the bearing sleeves on the X axis.  The combination of ABS and HIPS here causes too much slip.  So I used M3x6 screws as a set screw.  I drilled a hole in the side of the X Motor carriage bearing sleeve using a 2.78 mm (7/64) drill bit.20150530_103421I then followed suit on the right side X Axis Idler.  Additionally, pictured above and below you can see a set screw that holds the Z axis nuts in place.  These are important because these nuts come unseated easily.

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Next thing I wanted to do, but didn’t get around to it until now, is to get rid of the silly zip ties on the bed that hold the bearings in place.  I finally got these half printed before something happened and oh well I used them anyway.  These greatly minimize the wobble of the bed that is caused by the zip bearings rotating in their seat.  The zip ties do not constrain it enough.

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Lastly, I used dry lube that you can get at a quality bike shop.  This is the lube we use on chains to keep dust from collecting on the chain.  Apply a thin coat with a foam brush to all your rods and move your axis all the way from one end to the other several times.

20150530_105020Now you should have a fairly stable and solid Prusa i3 printer.  There are still yet more tweaks to be done to this project-disguised-as-a-printer.

 

High resolution closeup of 3D Printer quality

Here are some high res photos of things I’ve printed, or attempted to print.

These were printed at .2mm layer height, green is ABS, red is HIPS.

Some of these are duds.  They either didn’t finish or didn’t make the cut.

This is a set of bushings I was printing.  These are duds because I had the wrong infill setting and you can see the dimples on the middle one’s side…

BushingsHD

Some more bushings that didn’t survive.  Not the printer’s fault, I just had to tweak yet another setting…

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This dragon was printing very nicely, albeit a few holes that I haven’t quite figured out, but then in the end, this green filament is very blobby and caused the print to fail. I’ve given up on this filament because of this issue.  It was Shaxon from Fry’s Electronics.

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Here is a hollow block I printed by accident.  I had left the infill set to zero for a previous print, and this is what I came out with.

The interesting part is the excellent bridging.  Look into the hollow block and you can see the bottom of the top, where it bridged. Also, you can see the layering on the sides and how nice and even they were.  I don’t see any banding either…

 

 

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3D Printing Bed Adhesion challenges

The difficulty with printing plastics using an FDM 3D printer is getting them to stick to the bed for the entire duration of the print.  There a lot of different common wisdoms that you will read about on the internet, and here is one more!

I’ve used ABS Juice for ABS, Blue tape for PLA, Glue stick, etc.  But Now I’ve found the ONE SIZE FITS ALL sticky stuff!  It’s Elmers Carpenter’s Wood Glue!

I diluted it in a mason jar, I didn’t really measure it, so you can just wing it.  Make it runny is all I can say.  Then apply it with a sponge brush.  Now all of my different filament materials including Nylon, PLA, ABS and HIPS stick to the bed!  They grip the glue very well, and I have no warping!  Check the pics!

glue

AdhesianSample
In fact, it stuck so well, it pulled the lettering off the blue painter’s tape 🙂

The line you see in the plastic is where the two parts of painter’s tape joined together on the bed.

 

3D Printing Aria the Dragon

My most challenging print so far.

Up to now I’ve been printing parts for additional printers.  Thought I would tackle something majestic.

I love dragons.  Here is Aria The Dragon from thingiverse.com

But So far she doesn’t look that great.

dragon1dragon2I’m trying to figure out the right settings for her.  I’d like to print at .1 or .2 mm layer height.

The above was printed with Repetier Host using Cura slicing.

So, I figured out why it was so bad… Printing too fast.

Rectangular infill, 50% speed, .3mm layer.

Retraction enabled, 2mm
1.6mm shell (4 shells @.4mm nozzle size)
.8 top/bottom
15 % infill – grid

I cancelled the print because something snagged and the Y axis skipped.

After several attempts, I decided to slow the print way down using the Feedrate setting in Repetier host.  I set this down to 25% in a desperate attempt to get a quality print out.  I was pleasantly amazed when I woke up this morning to find this on my printer….

aria3

While not perfect, it is definitely getting close!

Settings so far:

.3mm layer
No raft or brim
Shell thickness: 1.6mm (4 shells @ .4 mm nozzle)
Top/Bottom thickness:  .8mm
Infill overlap: 5%
Infill type: Concentric lines
Solid Top/Bottom
Retraction @ 40mm/s 2mm distance
Temps: 230/90
Material: Bright green ABS

The interesting thing about this ABS, I had terrible luck with it before. It would warp and banana like crazy, and I pretty much labelled it “junk.”

But after I modified my el-cheapo Jhead hot end, everything I print now prints great!

3D Printer build – it’s a lot harder than you think…

Anyone thinking about building a 3D printer from scratch should come to their senses quickly and just buy a ready-built printer or a high-quality kit. The prices are falling like a heavy rain and you can get a high quality printer for the same money, and less frustration, than building one will accomplish.

The problem is in the general design of the current crop of “open source” 3D printers.  There are just too many nuts, bolts, wires, haphazard software settings, firmware settings, mix-matched hardware and electronics issues to make it a user friendly experience.

First off, the motors.  Most people wanting to build a printer will rush to Ebay and buy the cheapest lot of 5 NEMA 17 sized motors.  These are the same people who don’t even know what NEMA 17 means.  Here’s a hint:  It is a form factor, not an electrical specification.  This means that NEMA 17 specifies the physical form of the motor’s case.  It does not dictate anything about the electrical current requirements, stepping angle, steps per revolution, etc.  All of these are “parameters” that affect the overall system, and they must be “plugged into” the software that runs on the controller board (aka firmware).

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The same situation applies to heating elements, hot ends (the part the hot plastic comes out), temperature sensors, fans, end-stops (the little switches that tell the controller that your motor has moved the carriage into the 0 position).

Each and everyone of these are elements that must be hard coded into the device firmware.  There is no user-friendly machine-mounted menu option for these parameters.  In fact, depending on your other choices, you might not get an LCD screen at all (which is where the machine-mounted menu system is displayed).

I’m building this printer as a means to and end.  I need to experience it the “hard way” sothat I can design the “easy way”..

Here are some of my observations so far:

  • Nuts, Bolts, Screws – there are too many.
  • Settings buried in firmware – they should be easily accessible via software.
  • Wires – need to manage the vast pile of wires.  This means better end to end connectivity.  Perhaps using 4, 6 and 8 wire RJ-45 style connectors would make this a lot nicer to build.
  • There should be a “setup wizard” software that guides you through configuring the firmware for the first time. It should auto-detect that the printer has not been configured and guide the user through the process.  This could be a desktop application or available in the printer’s LCD controller (but not all have LCDs…)

 

 

RepRap 3D printer project is not for the faint at heart

So I launched my “RepRap” 3D printer project a few weeks ago.  I am building the Prusa i3 printer using 6mm acryllic for the front and side support wings.  A picture of it is shown below:

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Although I decided to scribe my nickname “Thetazzbot” in the printer’s frame, it should not be confused with “Taz” by lulzbot.  I’ve been using “thetazzzbot” since the 1990’s, and I’m not going to stop using the name now just because some company decides to use “Taz” as their product name.  Maybe I should trademark my name…

There are numerous “RepRap” printer designs available for the do it yourselfer.  The concept is theoretically good:  Build a bare bones printer, then use it to build the parts for a better printer.

The original design, aka Prusa Mendel, was built using threaded rods, a lot of washers and nuts, and even though I’ve never built this specific printer, I can tell you it will be a pain to build.  The critical part of the printer’s construction is alignment.  And all those threaded rods will be difficult to get the intersections aligned where the angles aligned and the whole thing squared up.

The other downside of the current generation of RepRap printers is the number of unique parts involved.  This includes threaded rods, screws, nuts, bolts and printed parts.  If you look at the bill of materials, it is quite staggering.  To picture it even better, take a look at this photo:

Mendel-reprap-entry-level-3d-printer-diy-kit

Let me reiterate, there are a LOT of parts that go into building your own RepRap Prusa Mendal or i3 printer.

Depending on the model you decide to build, you could also be facing “printed parts fatigue”:

Mendel90_plastic_parts01

Or, Nuts-And-Bolts-Hell:

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There are even MORE if you decide to build a Makerbot or Ultimaker clone.

I also have a great deal of heartburn with the “wires hanging everywhere” approach that the DIY community seems to be in love with.  This haphazard appearance makes the machine seem unapproachable by non-techies.  Exactly the opposite of what we need for mass adoption of the technology.

Assembled-prusa-mendel

The DIY community needs to try to reverse this trend.  I vote for Less is More.  Not every printer needs to have an 8″x8″x8″ build volume.  What if we started building task-specific printers that didn’t need the height (simplifying the Z axis), or a heated build platform (negating the need for big beefy power supply), or maybe use smaller, cheaper stepper motors, DC motors.

My goal is to build a platform that doesn’t require screws, or tools.  It shall have a wide platform (12×12 inch or 12×14 inch), with lower vertical build space requirements for printing small, flat parts.  The goal of this project is to reduce parts count drastically, and reduce construction complexity such that anyone can assemble it.

My bare minimum design includes:

  • Single board controller + stepper drivers
  • Hotend for PLA, Nylon, etc.  Experimentation here..
  • X/Y Nema17 or smaller steppers
  • Z with 4″ or less of travel
  • Little or no bolts/nuts/hardware (expensive)
  • Utilize inexpensive aluminum square tubing
  • Stationary build platform
  • Bowden style extruder

I’ve just finished designing and printing the plastic parts and cut the frame and test fitted everything.  So far very good results.  Now I have to put together the wiring and controller and then run some motion tests.

The long term goal of the project is to build a low profile, highly stable platform that is inexpensive to reproduce and simple for the end user to assemble and get printing.