Update on the Never-Ending Printer Project

I installed the Y-axis screw drive in MegaMax using the old NEMA-23 stepper motor.  A couple really good things came from this:

1) I can now adjust the bed leveling screws from the underside of the bed using thumbwheels instead of a screw driver.  I know, I know, everyone else in the world has been able to do this from day 1…

Thumb screw for leveling print bed.   Screw is threaded into teflon block.

Thumb screw for leveling print bed. Screw is threaded into teflon block.

 

 

 

 

 

 

 

 

 

2) Unlike everyone else in the world, with fully supported linear guide rails, the print bed does not move in any direction but along the Y axis.  In the old scheme, with the end-supported round guide rails, the rails would flex and the bed would move up and down when applying pressure to it (sometimes even the screw driver pressure to adjust the bed leveling screws).  Now, if the bed moves at all in the vertical direction it’s because the bed plate (1/4″ aluminum) itself is flexing!

A couple bad things were also discovered:

1) The vibration and noise problem I was hoping to solve has not been solved.  It has been made worse, though the character of the noise is improved to musical tones instead of just harsh buzzing and rattling.

2) Several failed test prints at ever decreasing jerk, acceleration, and speed settings have demonstrated that the old motor simply doesn’t have enough torque to drive the screw reliably at reasonable printing speeds.

Shift occurred in Y-axis due to insufficient motor torque.

Shift occurred in Y-axis due to insufficient motor torque.

 

 

 

 

 

 

 

 

 

 

 

 

Further research into the first problem indicates that the vibration and noise are inherent in using steppers, and worse in MegaMax than in machines that use NEMA-17 motors because of the higher detent torque in the NEMA-23 size motors.  Detent torque is the little bump-bump you feel when you turn the motor shaft by hand.  The solution to the problem is to use a good driver for the motor and a higher voltage power supply.  The little A4988 chips in the Pololu drivers on the RAMPS board are very unintelligent- all they do is provide microstepping.  They work OK for NEMA-17 size motors because of the speeds and low detent torques in those motors.  When used with NEMA-23 motors the driver limitations become apparent – as they have in MegaMax- lots of noise and vibration.

Good stepper drivers are DSP based and automatically sense resonance and damp it electronically.  They use phase controlled sine wave currents to drive the motors smoothly.  Fortunately, DSP stepper drivers for NEMA-23 size motors are pretty cheap.   Here’s video of the DM542a driver pushing a NEMA-23 motor around.  I have ordered a DM542a driver.

The best power supply for stepper drivers is not a switcher, and running steppers from a switching supply will often result in a dead power supply.  I will be building a simple, unregulated transformer, rectifier, and filter cap supply to go with the new driver.

Next came the question of how to determine how much torque is needed to properly drive the Y-axis.  A bit of research took me here: Motor size calculator.  You just select the scheme for which you want to size the motor, enter the appropriate data, and it magically tells you how much torque you need to do the job.  When I ran the numbers on MegaMax, it told me that I need about 350 oz-in of torque (about double the torque of the motor I have).  I did a quick search and found a Chinese made (of course) 425 oz-in motor for $50.  Also on order…

The motor mount I am using is designed for a NEMA-34 size motor with which I use an adapter plate to allow the NEMA-23 motor to fit.  Since I’m buying a new motor anyway, why not just get a NEMA-34 motor?  It turns out that the best stepper for the job is generally the smallest motor that can provide the necessary torque.  A NEMA-34 motor could provide much more torque but the detent torque and rotor inertia would work against smooth and fast operation, and require a bigger power supply.

Back side of MegaMax showing motor mount, adapter plate, flexible coupler, and drive screw  in Y-axis.

Back side of MegaMax showing motor mount, adapter plate, flexible coupler, and drive screw in Y-axis.

 

 

 

 

 

 

 

 

 

 

 

The ATmega2560 and RAMPS boards will be replaced by a SmoothieBoard.  It has a much faster processor, much better connections for motors/external drivers, etc.  It currently lacks an easy way to add an LCD controller, so I may have to connect to a computer to start prints up (it has ethernet and a built in web server so it can be accessed from any computer on the network).  When a clean way to add an LCD controller becomes available, I’ll add it.  SmoothieBoard review

 

The never-ending 3D printer project

MegaMax has been and continues to be my main project for the last 2+ years.  I am currently working on some upgrades that will make him more Mega and even more Max.  The Y axis is being converted from belt drive to screw drive and the round guide rails are being replaced with linear guides and bearing blocks.  The X-axis will also get converted to linear guide and bearing block and change from 5mm pitch belt to 2 mm pitch belt drive.  I feel confident saying that once these modifications are complete the flaws/errors in prints will be due primarily to the nature of liquid plastic squirting through a nozzle, not positioning system errors.

I recently updated my web site with a sort of historical look at the project, including all the mistakes I’ve made along the way and the often failed attempts at correcting them.  Here is the page that shows how it all started, how it has ended up, and where it is going.  http://mark.rehorst.com/MegaMax_3D_Printer/index.html

Don’t ask me why I do this-  I have no choice.

MegaMax beginning

From this…

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MegaMax present state...

To this…

MegaMax is Too Noisy

As part of my effort to reduce the noise and vibration in the Y axis, I am going to try using a screw drive instead of the 5mm pitch belt.  I rescued a screw drive assembly from a big XY table but it uses a 200W servomotor for which I have neither power supply nor drive electronics.  Never fear!  The motor was a NEMA-34 size, so I designed an adapter to mount the NEMA-23 stepper that MegaMax uses in the NEMA-34 motor mount.  Next I needed a shaft coupler- the screw has a 9mm diameter attachment and the NEMA-23 motor has a 1/4″ shaft.

Adapter plate on NEMA-23 motor

Adapter plate on NEMA-23 motor

 

 

 

 

 

 

 

 

 

 

 

 

 

I used DesignSpark Mechanical to design the motor mount adapter and  flexible shaft coupler.  I uploaded the motor adapter to Thingiverse (http://www.thingiverse.com/thing:526424) and it proved surprisingly popular so I designed another that adapts a NEMA-23 mount for a NEMA-17 motor (http://www.thingiverse.com/thing:526443).  I had to make two attempts at the flexible shaft coupler- the first design proved a little too springy and flexible, so I tried again with a more beefy design.  It turns out it is pretty easy to design this sort of thing in DSM.  I probably spent 30 minutes on the first one and about 10 minutes on the second one.

I sliced in Cura because Slic3r was having some problems.  The prints look a little rough because of all the support material required to print the springs, but they work fine.

Flexible shaft couplers

Flexible shaft couplers- not-so-springy and super-springy.

 

 

 

 

 

 

 

 

 

 

 

 

Adapter and shaft coupler on motor

Adapter and shaft coupler on motor

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Motor mounted on screw assembly

Motor mounted on screw assembly

 

 

 

 

 

 

 

 

 

 

 

 

I’ll post an update when I get the screw mounted on the machine.

 

 

A phone with a frickin’ laser!

My recent acquisition of a Meade ETX-90 telescope with computer go-to system for locating objects in the sky got me thinking that it would be nice to have a system to locate objects in the sky when you’re looking through binoculars or a telescope that doesn’t have a computer and motors to drive it.  To that end I came up with the idea of mounting a green laser pointer, commonly used by astronomy nutz to point out objects in the sky to noobs, on a cell phone or tablet running a program such as Google SkyMap or Skeye.

sky laser all parts

CAD rendering of the parts

After much thought and a few prototypes I came up with a system that allows a laser to mount on a phone and that assembly to mount on a tripod, a handle, or a telescope.  The tube that holds the laser has adjustment screws to allow the laser to be aligned with the SkyMap on the phone.  It also has to slots that fit over standard gun sight rails.  On one side I have a phone/tablet bracket that has a gunsight rail and slides into the laser tube, and the other side can be used for a rail that mounts on a tripod or a handle.  Extra rails can be mounted on telescope tubes.  I haven’t yet designed a binocular mount, but will soon.

 

IMG_0388

Parts printing on MegaMax

I printed the parts on MegaMax with Octave fluorescent red filament (that’s why the colors vary in the photos- the flash apparently excites the fluorescence in the picture with the handle).   All the parts fit VERY tightly together but I included screw holes for extra security.  The phone/tablet mounts on the bracket using velcro tape.  I think it may be better to print or buy a cheap case to fit the phone than screw it to the phone/tablet bracket.  I’ll be posting the design files to Thingiverse shortly.

IMG_0409

Phone and laser mounted on handle

IMG_0404

Phone and laser on a tripod

 

 

Crafting for the Workplace

There seems to be a phenomenon in the workplace – in all workplaces – when you’ve just finished Doing the Thing you’re supposed to do.  The moment you lean back for one second, sure enough, the Boss walks by and says, “Why aren’t you Doing the Thing?!?”  In honor of this widespread misfortune, my fellow store managers and I developed:

The Barrister Free Mulligan Token

IMG_2536

 

You see, I work at a board game & toy store.  In the world of collectible card games, taking a mulligan essentially means putting back the hand you were dealt and drawing a new one.  We figured our staff could use a second chance if they were ever caught in the wrong place at the wrong time.  With plenty of help from Shane, I was able to laser-cut a bunch of wooden tokens.

Standing up to your boss can be difficult.  But there are times when it’s appropriate, and now each employee is well-armed against fickle fortune.  Shane called our idea “very forward-thinking.”  My favorite part was at last week’s staff meeting, where everyone got do decorate their own personal token:

IMG_2558

 

To expend a token, we simply drop it through the slot in the top of the pencil case, which is bolted to the backplate.  Once you take your Mulligan, the boss owes you a second chance, an apology, and (for good measure) a sandwich.  Expended tokens may be reclaimed by attending a staff meeting.  Who knows how much use they’ll see?  Even as just a symbol, it gave us a way to talk about the elephant in the room.

And play with the glitter glue.

MARRIED TO A MAKERSPACE GEEK

logo

 

I’ve known since I met my Makerspace Geek husband that he could fix ANYTHING. It didn’t always look pretty but it would work. I’m reminded DAILY just how talented he is. Unfortunately, over the years, being somewhat of a minimalist, I ran out of things to put on his Honey-Do List. I would find myself, at times, racking my brain trying to think of something he could fix or make. Because after completing a task and joyfully erasing it from the fix-it/make-it board, he was happy, contented and fulfilled. Lo and Behold he discovered Makerspace. I should celebrate the day as one would a major holiday. It has transformed my little geek into a big geek. He LOVES Makerspace and I love that he has a place to go where he can share, with other like-minded individuals, all the geeky thoughts spinning in his head. He still shares some of that with me but I know that oftentimes my head kind of goes on blank mode and I find myself just looking at him, trying not to nod off and listen. After his joining and I got over his starting every sentence with something about Makerspace, or his approaching total strangers and handing out a Makerspace card, or striking up conversations with family and friends and droning on for, what seemed like hours, about Makerspace, I surrendered. Why??? Because it makes him darn happy, that’s why. And who doesn’t want to see someone they love being happy??

 

So now when we’re eating dinner and I see him chomping at the bit because he wants to be at the club, I wish him well on his merry way and sit back to a quiet evening. If I’m awake when he gets home I get to hear all about the goings-on. I admit to crashing, often before he gets home because when he does he’s often so jazzed that I then have trouble falling to sleep .
Thanks, Makerspace, for making a space for him

3D Printable shock mount for PCM-M10 digital recorder

PCM-M10 Shock Mount

PCM-M10 Shock Mount

Several years ago I played with a lot of audio stuff including making binaural recordings of things like cicadas, train rides, and festivals in Japan, and the singing of tree frogs in my back yard when I lived in a forest in Missouri.  Those recordings were done on a MiniDisc recorder because it was the best available audio quality recorder for people on a budget (i.e. cheapskates) like me.   Time and technology wait for no one, and I’ve been getting the itch to do some recording again, so I recently picked up a Sony PCM-M10 recorder.   This little machine records in many different formats up to and including 24 bit/96 ksps (though self-noise really limits the machine to about 15 actual bits).  The audio is recorded onto micro SD cards so unlike the MiniDisc, you get access to the raw digital data without any compression or associated quality degradation.

My previous recordings were done using a DIY binaural microphone that used a roughly matched pair of electret condenser mic capsules mounted on a wire bail that held the capsules inside my ears.  Even though those mic capsules were pretty noisy, the recordings came out pretty good.  When you listen to them with headphones you get a real “you-are-there”, surround-sound experience that can be quite startling.  You can hear those recordings here: http://mark.rehorst.com/Binaural_Recordings/index.html   Soon, I’ll be starting a new binaural mic project to go with the new recorder, this time using much higher quality mic capsules.

In the meantime I was looking for a shock mount to use when making recordings using the built in mics.  The shock mount prevents low frequency noise from handling, bumping the table the recorder sits on, etc., from being coupled to the mics through the body of the recorder.  I did a web search and found only a couple unsatisfactory designs so I did what any maker would do- I made!

One of the flaws in the few designs I saw was that some of the numerous switches and I/O jacks on the recorder would not be accessible when it was bolted to the shock mount.  They also didn’t look very nice.  After a lot of sketching possible designs on a whiteboard and paring the thing down to a minimal implementation, and spending much too much time making a 3D model of the recorder, I came up with a printable 3-finger design that holds the recorder either on a tabletop or a tripod and keeps ALL the switches and I/Os available.  The only thing you can’t do while the recorder is mounted is swap batteries (but with 40 hours record time on a set of two AAs, that shouldn’t be a problem).

I used DesignSpark Mechanical to make the recorder model and design the shock mount.  DesignSpark makes rounding corners of complex 3D objects easy (nearly impossible in Sketchup), but I did run into some of its limitations that I hadn’t previously considered.  One huge limitation is that there is no way to put any form of text into a drawing without some special work-arounds (use Sketchup to make text, then import into DesignSpark).

CAD drawing of shock mount

CAD drawing of shock mount

PCM-M10 on shock mount- CAD

PCM-M10 on shock mount- CAD

This shock mount design is available here:  http://www.thingi

verse.com/thing:384567

 

I printed the shock mount on MegaMax using Coex3D Aqua ABS filament.

 

CNC Mogul Introduction

A few weeks ago Mike Stone of CNCMogul.com visited the Milwaukee Makerspace.

Mike donated one of his machines to the space for testing and feedback as well as to use for the membership. It should also be mentioned that Mike is local and has his shop and distribution in Wales, Wisconsin.

Joe Rodriguez built one machine and I also put one together at our shop at home. So here are some thoughts on the process as well as some pictures. It isn’t a review as these machines haven’t really been put to the test as of yet. Time will tell.

The CNC Mogul is a general purpose 3 axis CNC kit that is relatively easy to put together and can be used for anything that you like. I’ll be using ours for routing and Joe wants to make a CNC plasma cutter with the one in the space. The basic kit is affordable and it uses the Makerslide as it’s building blocks. The stepper motors are run with a rack and pinion setup on aluminum tracks and gearing as well.

The controller is a Chinese Tb6560 Stepper Motor Driver Controller that is controlled via parallel port.

The power supply is a 24V 14.6 AMP 350W Max Power Supply.

The whole kit can be ordered online from 2ft X 3ft up to 4ft X 8ft. Custom dimensions are also available.

So here is the kit before assembly. This is a 3ft x 3ft kit that I will be building and using with a router.

This is the kit right before opening.

This is the kit right before opening.

Inside the kit there are a bunch of baggies with tons of little parts. You can look at the manual here

I’m assembling the quad rail kit. Once I start pulling things out of the box there is an amazing array of parts that explodes out of it. Fortunately each bag and part are well marked.

Everything that you need to build your own CNC controlled machine.

Everything that you need to build your own CNC controlled machine.

cncmogul03

Everything is labeled really well.

Everything is labeled really well.

Everything is labeled really well.

Everything is labeled really well.

The kit took approximately 3+ hours to put together. The documentation in the manual is hit or miss. The pictures are extremely good and really help in putting this together. The accompanying text is also great for the first 1/3 of the manual and then you’re left to interpret pictures from there. There are a few questions that came up while building this but fortunately I was able to figure it out.

Little by little the parts are being built.

Little by little the parts are being built.

After the gantry gets built and all of the wires are connected it’s time to test. CNC Mogul recommends using Mach 3 for your machine control. And even has a few pointers on how to setup Mach 3 on their site.

I decided to go with LinuxCNC because it’s open source, I’m comfortable with Linux and it’s low cost (free). I loaded it up on a spare computer and after running through the instructions I was able to control the stepper motors on the Mogul.

What I had difficulty with is that the CNC Mogul uses an “A” axis and “Y” axis slaved together. LinuxCNC can do that but you can NOT test for that in the setting up process. You essentially tell the “A” axis to use the same step and direction pulses as the “Y” axis. I also inverted the “A” axis so they would turn the same direction when they are facing each other.

One of the other difficulties I had was figuring out the leadscrew pitch to enter into LinuxCNC. After some experimentation 1.27 inches per revolution seems about right but some more testing is needed.

Once you’re finished building the whole thing you need to mount it to something. I picked up a Craigslist find and the Mogul fit perfectly.

I generated some G-code from Vectric’s Vcarve Pro Zeroed each axis and started to cut.

I still need to put a waste board down and face it off flat and put some type of work hold-down system in place.

After the unit gets setup in the Makerspace the members will have access to the machine and we’ll see how durable it is.

The CNC Mogul with router mounted and ready to cut.

The CNC Mogul with router mounted and ready to cut.

Total time to build, test, and implement the whole system has been approximately 6 hours. There is still some testing and tweaking to be done as well as putting in a dust collection system.

If there are any questions feel free to ask me either on this post or in person. I’ll be putting this through it’s paces as well.

My 2nd test using the CNC Mogul with 2 types of router bits.

My 2nd test using the CNC Mogul with 2 types of router bits.