Welcoming 2013 this morning with a hearty breakfast, I realized that 2013 will be an exciting year. It will see the completion of both the Honda CX500 Cafe Racer project and the reprap based 3D printer build. Both will be great additions to my completed projects.
Wishing everyone all the best in 2013, let’s make it a great year!
As I near completion on my 3D printer build, I found myself needing a way to drive stepper motors to quickly test axis motion (watch the video at the end of this post). To that end I threw together this low cost stepper motor drive. It is based on a Pololu A4988 stepper motor driver being run by a 555 timer set up as an oscillator. I wanted something cheap that I could quickly throw together to test the motion on the axis as well as keep handy for future stepper motor projects. I spent a little more time on this project then it warranted but now I have a great little stepper motor drive for testing future projects.
The circuit diagram above shows the basic schematics for the stepper motor drive. Sorry about the chicken scratches on paper version, but all the info is there if you want to make one of these for yourself. As always if you have any questions shoot me an email at: zac AT projectsbyzac.com The 555 timer is run as an astabile oscillator to generate the step pulses to drive the Pololu A4988 stepper driver (A4988 data sheet is here) & (Pololu A4988 datasheet is here) . If you’ve read my previous post on building a cnc machine control box based on Pololu 4988’s you know I love these little stepper drive boards. They are similar to stepstiks (drop in pin for pin replacements in fact) which will eventually run the 3d printer on the RAMPS electronics which just arrived. There are newer drop in higher performance Pololu models available now but I had a A4988 green boards on hand. To allow for variable motor speed control I used a 10 turn 10K potentiometer inline in the 555 circuit. This allows the drive speed to be varied by turning the knob. The pot I used has a digital read out. When I find a speed that works well to test a particular motor/axis drive, I can easily set it in the same speed in the future. Thanks to Adam Perkins for these 10 turn pots. I traded him some parts a few years back for a few of these 10 turn pots with read outs. This is the first project on which I have used one of them. He has a very useful webpage with great info on electronics and is my electonic project mentor from my UNH Days.
The circuit is soldered up on a small board from Radio shack. I’ve housed the entire project in an old PC power supply case. I love using PC power supply cases for projects and always have a couple on hand in my parts inventory. They have good cross flow cooling, built in fan, switch and power cords making them the perfect project enclosure. The pololu A4988 can handle up to 2.0 A with a heat sink and air flow for cooling which the power supply case fan supplies. To power this project I initially used a spare 12v 2.0A wall wart installed. The supply was noisy and it was affecting the stepper motor drive output. Additionally when it was driving the motors I could hear the cooling fan speed decrease, so it wasn’t up to the current draw needs of the motors being tested. I changed over to an Astec LPS50-M Series 60 Watts power supply I had on my parts shelf. This supply could easily handle the motor load and would provide a clean 15 volts, the supply used was an Astec LPS54-M (datasheet for the LPS54M powersupply is here).
The above photo shows the finished product. I used my CNC machine to mill out the top of the case for the pot with the readout and drill holes for mounting the power supply and the 2 toggle switches. One switch controls the direction of the motor (dir pin #14 on the pololu) and the other interrupts the signal between the 555 oscillator and the step pin (pn #13 on the pololu) allowing to start and stop the stepper motor without powering down the controller.
The above video shows the driver being used to test the Z axis on the 3D printer. I have the current control way down so when raising the axis the motors struggle a bit (the sound you hear changes from the smooth driving on the way down). I thought some of you might enjoy the video clip. There will be more videos as the printer is further tested now that I made a youtube account to host them.
About a year ago I started building a 3D printer based on the RepRap 3D printer community. Progress essentially stopped with the arrival of spring (aka adventure season), but it is once again project season (aka winter). My 3D printer build is approaching the testing phase for axis motion, print head extrusion quality and laying down my first builds. This post will show the progress and provide some thoughts on the design of my 3D printer.
Last winter I had worked out a rough design for my own plastistruder 3D print head, I made a first go at my own design but felt I could do a better job. I had set the x axis such that it would mount a plate with 1.5″ on center bolts allowing me to experiment with different print head designs by having them be modular and easily swapped out. The above renderings show my current design for a 3mm filament plastic extruder. Based off the MK6 extruder from makerbot (that they apparently no longer support or sell), it was designed to use the same nozzles and 40W 12v cartridge heater.
Above you can see I’ve finished the x axis mounts. They are functional but had any weight reduction done to them yet. The mounting plate and heat break/hot end side are done. I plant to machine down a pc heat sink to mount to the body of the extruder opposite the NEMA 17 stepper that will drive the filament into the hot end and out the extrusion nozzle. I found online a great little 1.75mm extruder head that I purchased here at a company called QU-BD and have ordered one since they are so cheap. I will test out both of them and compare results in a future post.
The Z axis design in my printer is basically two steppers driving threaded shafts from the same stepper pulse signal. This seems to work well and has been done in other reprap 3d printer designs. I am doing basic motion testing of the axis with a 555 timer as a pulse generator to drive a pololu A4988 stepper driver board. These are great little boards for running steppers and I have used them in other projects like my cnc control box. It’s a crude set up but does not require having a computer dedicated to this thing yet.
What’s left to get this thing running? I need to order some new LX series timing belts the correct size for both the y and x axis. Build a y axis chassis that is lighter then the solid aluminum test plate you see in the above pictures and then mount my larger heated build surface. Then it will be another round of electronics headaches. Hopefully this time the supplier for my reprap electronics board doesn’t send me junk. See my earlier post for my problems with the first Gen 6 electronics I ordered. Then it will finally be time for testing and printing parts. I already have a list of things to print out a mile long. Several friends want me to print them out the standard rep rap parts. I plan to help them out. Everyone should have their own 3d printer at home.
A big part of making myself a Curious George The Man in the Yellow Hat Halloween Costume was making the big yellow hat. I devoted most of my energy towards making one that was a perfect replica of the hat worn by Curious George’s friend, The Man in the Yellow Hat. As you can see in the picture above, my big yellow hat came out pretty well. This post explains how to make a felt hat for your Halloween costume.
The first step toward making a felt hat for a Halloween costume is to decide on what type of felt hat you want to make. Find some photos online, look at period correct movies, etc. This was easy for me as The Man in the Yellow Hat from Curious George only wears one type of hat, a big wide rimmed round yellow hat. I found about 2 dozen different images online and in the Curious George books to help me conceptualize the size and shape of the felt hat I would make for my Halloween costume. I want to state here that real felt hats are made differently then the process we are going to use. Real felting of a wool hat is more work, wool felt the appropriate color was not readily available and it costs significantly more.
I started by buying about 2 yards of basic craft store acrylic felt fabric from my local Jo-Anne Fabrics. The fabric was only $2.99/yard and was in the perfect shade of bright yellow to match my shirt, tie, and previously dyed pants (check out my earlier post). I did some rough measurements of the hat brim size to shoulder width ratio on photos of Curious George’s Man in the Yellow Hat. I then scaled up based on my shoulder width to get an approximate size. I made a quick beam compass to lay out the circular pattern on the felt. A beam compass can quickly be made from cardboard taped and folded over by punching holes at appropriate radii for your needs. The disposable beam compass is a useful trick for woodworking, crafts, fabric, and any other time you need to layout a large diameter circle or arc segment. Folding the fabric over results in two patterns being cut out at the same time.
I used the cardboard beam compass to layout an inner circle as well. The inner circle is a radius 2 inches shorter then the average radius of my head as measured above the ears. I used a fabric tape measure and mirror to get that measurement. Some quick math calculations gave me the radius I needed for the inner circle. Using some quality fabric shears I cut out my patterns for the brim of the hat.
The next step required a plastic covered piece of flat cardboard and a piece of circular foam cut to that previously measured and calculated average diameter of my head. Wrap the foam carefully with seran wrap and clear tape to ensure your felt does not stick to it during this next step. This next bit I learned back in my theater days working in the costume shop. It is the magic trick to making a felt hat with cheap craft store acrylic felt. Be sure to have lots of white craft glue on hand. Add about 25% water to the white glue and mix it in well. Next take your two cut out felt patterns and run them under hot water until they are well saturated. The felt goes limp and softens. Wring out as much water as you can from the felt. Then take the first pattern and carefully stretch it over the foam buck working slowly until you have it stretched nicely over the foam and flat on your plastic covered cardboard. Paint on the watered down white glue with a brush until you have saturated the felt with the watered down glue solution. Next stretch your second cut out pattern over the first being careful to smooth out any wrinkles or bumps in the felting. Again paint on a liberal coating of the watered down white glue onto this second felt layer. After saturating with glue rub your hands over the felt from the center outwards to smooth any small bumps, wrinkles etc. Let this dry for a long, long time. This part is what killed me, it took about 48 hours for the felt to dry and I was running out of time. I added a fan to help speed the drying. You can also use an iron when it is mostly dry to help it along and settle out any wrinkles/fold marks on the flat part.
Using a similar process, repeat the previous steps but stretch the felt over a styrofoam ball for the shaped upper part of your hat. If you are making a different shaped hat, say a fedora you would simply use a different shaped buck (foam or wood pattern to shape the felt over). Wetting and carefully stretching/shrinking the felt till it is smooth takes some time but is not complicated or difficult. Use elastics and push pins to hold the wet felt onto the buck until the watered down glue solution dries completely. Trim off the extra after its dry and you are left with a nice stiff felt hat. For a shorter hat this step would be the end of the felting. However Man in the Yellow Hat has a tall hat. I felt I could not stretch the felt as a single piece that length. I made a felt cone for the added height of his hat.
As this post is running long, I will simply say I calculated the arc segments and radii needed to make a cone the perfect size for the felt hat being made. I promise to do a short post on the trick behind making a flat pattern for a cone in a day or two. It’s not complicated but relies on a good understanding of trigonometry. After cutting out the arc segment, roll it up and sew the seam to make the cone section. Then stitched your cone onto the top “ball” section made earlier, ensuring it dried completely before removing it from the foam buck.
Stitch on the top cone/ball section to the lower brim section and you have your felt hat. Use a piece of heavy ribbon to hide the seam where you attached the two sections of the hat together. The ribbon serves the additional purpose of keeping the felt hat from stretching out while being worn. You will want to run a stitch around the outer rim of the hat. This keeps the two stiffened brim sections from separating. If you want to go hog wild with your felt hat you can stitch in millinery wire around the rim and cover it with millinery grosgrain ribbon as you will see done on fine felt hats. For my man in the yellow hat costume I kept it simple and ran a running stitch around the edge to keep the two layers of felt together. The glue dries in the felt and keeps the rim stiff but it does not necessarily glue the two pieces of felt together adequately.
Another shot of me in The Man in the Yellow Hat Halloween Costume.
2013 Note: I’ve gotten tons of great notes emails and comments on this page. I would love to see some pics of the hats you all are making. send em to me at Zac at projectsbyzac.com and if it’s ok to let me share them on this page please say so in the email. I love hearing that people find my posts helpful. It really motivates me to take the time to write more posts.