Last week I made a Line-us drawing robot clone. Unfortunately I had no good way to make it draw easily. I thought I would give the CNC toolpath a shot. My goal is to have a super portable thing to generate conversation at meetups. If I used Easel it would allow anyone with a web connection to easily make something.
The most compact machine controller is Grbl and I have a lot of experience with it. Grbl is designed to send step and direction signals to stepper motors. The draw ‘bot uses hobby servos. The nice thing about hobby servos is they don’t need to be homed. They have feedback to tell them where they are. They also don’t care about speed, acceleration or steps/mm. They just go wherever you tell them as fast as they can go. It occurred to me, the easiest way to hack this into Grbl was to not modify the Grbl code at all. I would let Grbl think it is using stepper motors. I would just add some extra code that runs on regular interval to tell the hobby servos where the stepper motors are in 3D space and they would be told to go there. I played around with some intervals and 8 times per second (8Hz) seemed to work pretty well. The ‘bot uses machine coordinates. The work coordinates are offset to the left because the ‘bot cannot draw at 0,0. The pen would crash into the frame.
I recently port Grbl to PSoC. I used (3) 16bit PWM components to control the hobby servos. See this blog post on how I did that. I then attached a 8Hz clock signal to an interrupt. The interrupt sets a flag when it is time to update the servos. When the main code sees this flag it does the calculations and and sets the PWM values. Keeping the code out of the interrupts gets Grbl happier.
Easel is already setup to use Grbl. You can either import gcode or create a design right in Easel. I started out with importing gcode because the Benchy design was not in a format I could import. I created a template that shows the allowable work area. This will allow anyone to quickly create a drawing.
I wanted to have a little fun with the first print. ”Hello World” was not good enough. 3D printers use benchmark prints, so I thought I would do a 2D version of the classic 3DBenchy. To get a 2D drawing of 3DBenchy, I traced over an image with the line tool in CorelDRAW. I then exported a DXF of that.
We build a lot of skateboards for fun at Inventables. Some of the guys even sell them at local craft fairs. They thought it would be cool to have a CNC router optimized for skateboards that was easily portable. I first thought about putting wheels at one end, then realized the machine itself could be a skateboard. We thought it would make a perfect Gonzo Build.
A Gonzo Build is something we came up with at Pumping Station OneCNC Build club. The concept is that we try to build an original, “one off”, CNC machine in one evening. They also tend to have a whimsical aspect to them, so we don’t take ourselves too seriously. We usually get about 8-12 people to help build. If parts need to be fabricated, they must be done that night on -site.
Building a stock Shapeoko 2 in one night is a challenge in itself, but we decided to up the challenge by totally tricking this out with every feature we could think of. We did have a few master CNC building ringers in the group, like Tait Leswing and David Ditzler.
Here are the stats of the machine.
1200mm x 250mm work area
Skateboard specific wasteboard supported by additional extrusions. It is narrower than a stock Shapeoko 2 and about 3 times as long.
Portable dual 24V/48V power supplies with master power switch.
Most of the Shapeoko parts came from reject area at Inventables, so there are a few dings and scratches.
The wasteboard was cut from 5/8″ particle board on the PS1 Shobot. It has a grid v carved into the work area. There are threaded inserts for clamps, primarily around the perimeter, but there is a truck bolt pattern strategically placed so a cut out board can be flipped or remounted accurately . It is supported below by 2 additional MakerSlide pieces and tied to the MakerSlide rails above. It is the bed turned out very rigid. It does deflect a little with heavy rider but pops right back. After the build, I added several coats of spar varnish to ward off the dusty footprints. Biggest guy to ride it so far tips in at about 230lbs.
We set our selves a goal of completing before midnight. Done or not, I was going to ride it at midnight. We thought we were finished about 20 minutes early. Everything worked fine except the Z axis was not moving correctly. It had the classic stutter and random motion of one coil wire not connected. We tried to find the problem, but over 2 meters of drag chain slowed us down. Midnight came some we dropped it to the floor and I rode it across the shop.
As a skateboard, it is pretty much a joke. On the first ride, we didn’t even have long board trucks, so the turning radius was huge and you can easily scrap an edge. The front has a handle cut into the nose of the bed. The ideal way to move it around is to lift the front and drag it on the back wheels.
In a couple weeks we are going to do a CNC V Carving night at Pumping Station One. We hope to fabricate a number of designs on the CNC router. This blog post will serve as a basic introduction to the concept and will help people get artwork ready.
What Can V Carving Do?
V Carving uses a V shaped bit to to “carve” a design into the material. Because the bit has a v shape, you can cut narrow shapes with the tip or wider shapes near the bottom.
You can even cut shapes wider than the widest part of the bit by doing multiple passes of the bit. The depth of the cut is proportional to width of the cut, so you need to make sure your material is thick enough. If you have very wide areas, you can set a depth limit and you can make that area have a flat bottom with a second flat bit.
Normally routers cannot cut square inside corners because you are cutting with a round bit. V Carving can get around this limitation because the bit can rise up into the corners until it gets to the zero radius tip.
V Carvings can look great simply cut in the natural material, but they can really pop when you put a contrasting finish in the carved areas. This is a time consuming process and can be difficult to do well.
You can often shortcut this process by using masking materials. You start by applying a background finish to the work piece. This is then masked with tape or specialized masking material. The router then cuts through that as it is cutting the design. Now, only the cut area is exposed and you can simply spray paint the exposed area. If the design has multiple colors you can cut one color, paint, remask and repeat the process.
The files should in in DXf, DWG, AI, EPS or PDF format. Many programs like InkScape and CorelDRAW can output these formats. If you have hi resolution bitmap, some of these programs can convert to a vector format. Feel free to try that, but help with that will be beyond the scope of the session.
The quality of the masking material comes into play with very fine details. If your design will leave tiny isolated dots of masking, some materials may not stick well enough and break free during cutting. If that happens, you can manually touch up those areas later. I like to use Avery Paint Mask, but plain masking tape, adhesive shelving paper and materials for vinyl cutters also work.
What is good artwork to start with
Avoid very thin lines lines. The material needs to be needs to be perfectly flat and consistently thick for this.
Very large areas to cut will take a long time, so avoid them for this session.
Multiple colors. Multiple colors is OK, be each color needs to be separated from the other color so there is masked uncut area between them.
This logo would work. The red would be the base material and all other colors would be cut and colored.
This one would be very hard to do because of the adjacent colors.
How to bring the artwork to the session.
To save time, the artwork should be as ready to import as possible. Problem artworks will be pushed to the back of the queue and might not get cut.
The artwork needs to be in a digital, vector format. By digital I mean you can sent the file electronically. Vector files are created with actual geometry. Lines are lines and not a string of pixels. Scans and photographs are not usable. If you zoom in and the image gets pixelated, it is not ready to use. The shapes also need to be closed. If you have a square, for example, all the corners need to meet or the software cannot determine inside from outside. Tiny gaps can be closed in the CAM software, but if you can see them, close them.
Try not to be too complex or have large cut areas. These will take a long time and will limit how many people we can accommodate in one session. We can still create G-Code, but you many need to cut it at a later date.
If there is time I my cut small PS:One snowflakes for the people who did not bring any artwork.
The idea material is a smooth, pre-finished piece of wood. It needs to be as least as deep as 1/2 the width of your widest feature if you are not planning a flat bottom. The material should be as flat and consistently thick as possible or the results can be distorted, because the depth of the cut is so critical. Avoid oily or wet finishes because the mask material may not stick well. Plywood does not look well and often interior layers have voids.
The subject of skateboards came up about 2 weeks ago at meeting of local makers. One of the PS:One Hackerspace guys confessed he wanted to buy a longboard for getting around town. Longboards are more about basic transportation and carving smooth turns than doing tricks. The large size also encourages design and graphical creativity. I thought it was the perfect opportunity to get the creative juices flowing. It was a fun project that cost less than $50 to complete.
Once I get these ideas in my head I am totally obsessed with them. The only way to clear my brain is to actually build the thing whether I need it or not. I finally got some time between 2.x Lasers and ORD Bots orders on the CNC router last Sunday night.
3/4″ baltic birch deck.
Logo inlay on top near the front in a contrasting wood type.
The inly would be 1/4″ thick so minor dings and chips would not wreck the inlay.
Pockets cuts on the back to look cool, reduce the weight and give the board a little flex.
Miter the edges of the pockets for a cool look, make it more comfortable to carry and make it less prone to chipping.
Round the perimeter edges.
I really like the drop style truck mounting, but I would stick with a conventional bottom mount to start with.
Drop through mounting – Image from Moose
I found a whole bunch of longboard PDF templates here at Silverfish Longboarding. I started with the ST11 version. I felt the exposed wheels would allow more wheel, truck and mounting options without the wheels “biting” the board. The outline had a few sharp corners that I smoothed out. I didn’t want the line that is produced when you round the edge with the sharp corner. I imported an SVG of the snowflake logo from the PS:One wiki and sketched in some pockets on the back that looked cool, but still preserved the strength off the board with hope for a little flex.
I bought a truck and wheel kit off eBay for about $35 (free shipping). I only did basic research into what made a good choice. I just bought something that fit the basic requirements and looked cool (wide, reverse kingpost, big red wheels).
The basic deck is 3/4″ thick Baltic birch plywood.. The local high end lumber yard, Owl Hardwood, had some really nice 13 ply material. The top side is perfect. The back side is really good with only a few small blemishes and all the inner layers are high quality with no voids. Most plywood has knots and voids on the inner layers. The exposed edge and the pockets would show the inner layers so I wanted them to look good.
Cut the inlay piece out of 1/4″ thick oak.
Mount the Baltic birch on the router and check for Z flatness in the inlay area. I mounted it on a sacrificial particle board. This board was clamped by itself, so unclamping the plywood would not affect the position of the sacrificial board.
Cut the pocket for the inlay slightly under sized. I then continued to profile the edges larger until it fit tightly.
Glued the inlay in place.
Cut the bolt holes for the trucks.
Cut the deck outline. I purposely cut extra deep into my sacrificial base so that I would have a clear outline of the board. This would allow me to flip it squarely to do the back side.
Cut the back pockets 1/4″ deep.
At the last minute I decided to add the the PS:One logo to the back as a 1/8″ deep pocket. It turned out to be my favorite detail.
Used a 1/2″ 90 Deg V bit to miter the edges of the pockets. I did a profile pass on the pocket lines set inside the line 0.02″ to make sure the tip was always inside the edge for a clean cut. The depth was set to leave 1/16″ of the original pocket wall.
Unclamp the deck.
I used a 3/8″ 1/4 round bit with guide bearing on the router table to round the edges.
Stained using Minwax Golden Oak stain. It is a light colored stain that varies quite a bit with the wood type.
Sealed. Minwax Satin Poly Urethane.
Design, research, ordering parts…about 1 hour.
Total time on the router…about 1 hour.
Sanding and Finishing…about 1.5 hours.
$10 worth of baltic birch
$5 1/4″ x 8″ oak for inlay
$35 trucks and wheels.
Already had all bits, stain and varnish
I want to laser cut a bunch of little PS:One snowflakes out of grip tape and sprinkle them on the deck.
I am not super happy with the way the baltic birch stained. Woods like that can look blotchy due to varying wood density. I might have done better pre treating with a wood conditioner the birch or going without stain.
There has been a ton of interest in camera slider applications for MakerSlide. A while ago I decided to make a very simple reference design for a motorized slider. This design only required fabrication of one part. The rest of the parts are existing components. The part can be made on a laser cutter, router or even by hand. There are no tight tolerances and you can use the MakerSlide carriage as a template for drilling some of the holes. I can sell a complete slider system including motor for less than $120 for a 1 meter setup. It would only be $10 for each addition meter. The longest I can ship is 2.5 meters, but I stock the material in 4.5 meter lengths if you can figure out how t0 get it.
I don’t know much at all about this type of camera work so I did not see all this interest coming. Several people approached me about buying my prototypes and I have sold several of them. Most of them asked me how to control the motor. I come from a CNC background so most of my demonstrations were done using CNC software like Mach3, EMC2 or even GRBL. This has few issues. The first is many photographers have no knowledge of CNC or G-Code. The second is the solution is way overkill in cost and complexity for a single axis machine. The third issue is portability. This will probably be used in the field where a PC is impractical and power may be unavailable.
I decided to make an Arduino based controller. Arduinos are good because they are cheap, small and easy to program. They also use very little power. I wrote a similar controller for the PIC processor a long time ago and borrowed the basic algorithm from that. The method used could work for multi-axis machines if you want to steal the code. The Arduino is. using my Stepper Shield. I have just one driver installed and in another “slot” I have a bread boarded switch. The stepper shield is nice because it can act as a mother board for many future features.
MakerSlide: Camera Slider Control Program 2011 CC-A-SA
0 = Set Current Location as 0
S = Stop now!
D = Disable Motor
E = Enable Motor
H = Home (Move to 0)
M = Move to ..(M Dest Speed Accel)
J = Jog until stopped ('J 1' for forward, 'J -1' for reverse, 'J' to stop )
I = Info (show current parameters)
G = Go (start program)
P = Show Program
C = Clear Program
L = Edit Line. Format: L Line# Dest Speed Accel) Ex: L 0 2000 3000 1500
Use 0 for destination and speed to indicate end of program
Use 0 for speed to indicate a pause. Dest is pause in milliseconds
R = Set Max Speed
A = Set Max Accel
V = SaVe to EEPROM
? = Redisplay this menu
The controller uses a menu driven interface via the USB connection. The easiest way to talk to it is though the Arduino IDE serial monitor. That allows a free, common interface between PC, Apple and Linux, but most serial terminals would work. The commands currently work in the unit of stepper motors steps. It could be easily converted to a real world unit, but at this time it is just easier to use the same unit that the motors use. My system has 4000 steps per inch. That makes for a very smooth system. Extremely slow rates are possible. It can go 1 step per second at 4000 steps per inch, so it could take well over and hour to go an inch. You could hack the code to easily drop this by many orders of magnitude. Each move can have its own speed and acceleration to fine turn the affect you want.
It has several commands to interactively move the carriage around. This would probably be done to setup the system before the actual “shot”. These include Move, Home (go to zero), Jog and Zero (define current location as zero). You can also create a move program. This allows you to define a couple dozen moves that run sequentially. These can either be moves or dwells (pauses). Once the program is entered it can be saved. This allows you to pre-program the device before you take it in the field.
At power up the motor disables. This allows you to slide the carriage by hand. This is handy if you don’t have a PC to do it in the field. As soon as you make any move or run a program the motors enable.
How it works (programmers only)
The controller uses a timer to run an interrupt function at a regular interval. The default is 40,000 times per second, but that be be tweaked by changing one program line. The interrupt function determines if a step should be taken. If you want to move at 20 steps per second, you allow the interrupt to run (40000/20) or 2000 times before the step is taken. A counter in the interrupt counts up until it is time to step. By varying the count on the fly you can create smooth acceleration. All the math required to smoothly accelerate could limit the interrupt rate, so the calculation are done once, before the move occurs. Inside the interrupt is all simple integer counting and a few tests.
Stepper motors draw a lot of power. I was running my NEMA 17 at 11V and 0.1 amps. You need a decent battery of 2000-3000 mAH to do a multi-hour run. Steppers are also notoriously loud. The camera will pick up the noise if the mic is close the the motor like on the camera itself. The motors I have are way over kill and running at less than 10% of their rated current. I have some NEMA 14 motors on order. Servo (not hobby servo) motors would be a lot quieter but and lower power, but are more complicated and might require gearing down.
This is the new buildlog.net open source rotational adapter for laser engraving. This allows you to engrave on a round surface. This design uses a friction drive method to rotate the workpiece. This has the advantage of keeping a consistent surface resolution regardless of diameter. This was designed to be 1000 steps/inch resolution. The length was sized to fit the 2.x laser, but you could easily scale it up to much longer or shorter. One design goal was absolute minimum height. This allows Z challenged engravers to be able to do some rotational engraving
The main feature of the design is the the two drive wheels. These serve several functions. They hold the rubber o-rings used to provide traction on the work piece. They have built in MXL drive pulleys and they have a spacer to ride directly on the bearings. These were 3D printed at Ponoko. With 3D printing, complexity is free. This encourages you to make the part do as many jobs as possible. I was initially concerned about the strength of these, but they turned out to be quite strong. I can probably reduce the material to take some cost out. I used the basic, cheapest, white flexible material. I was impressed with the detail level the material was able to hold. The belt fit perfectly.
I started the design using convensional design techniques and off the shelf parts because I was concerned about the 3D printed part cost. I soon realized that it was going to take 3-4 separate parts to do the job of one 3D printed part. The cost was quickly getting close to even. The convensional parts were also starting to look a little mismatched. While I am a form follows function, type of designer, I am a big fan of a clean design.
Once I started playing with the 3D printed part approach, I quickly decided that was the route to take. It was fun knowing that increaing the details on the part has no affect on the cost and in some cases actually reduces the cost. The spokes and radiuses retain the strength, reduce the material and I think add a retro mechanical design asthetic. Dealing with a single supplier, with a fast turn around and no minimum order, was very nice.
I have done 3D printing from other vendors, but decided to give Ponoko a try on this part. Since this is an open source project, their online tools would allow others to easily order parts.
At the other end of the assembly are the idler wheels. These also are Ponoko 3D printed items. They have bearings that press on each side. This allows them to roll freely with virtually no wobble. One idler has a flange on it. This acts as an end stop to the workpiece. It prevents it from “walking” while it is spinning. The stepper motor pulley serves the same function on the other end. This end is highly adjustable. There are three positions the wheels can be placed in. The plate can slide on the extrusions and you can flip it over. While all the adjustments are manual, they only take a few seconds to do.
Below is a video of some testing I did. I was trying to test a variety of shapes to see how they performed. In actual use the speed is very slow, because the the laser is primarily rastering along the length of the workpiece and this adapter just advances it a faction of millimeter at a time.
They all performed quite well. The only item that did not test well was a roll of duct tape (not shown). It was not very round so it wobbled a bit. It also has a sticky edge so it did not ride against the stops real well. The screwdriver at the end is an interesting example. While it did spin smoothly, it shows that if the image is not going to be at the same diameter as the drive area, some image scaling will be required before engraving. The bit is only 1/8″ diameter!
The design will be open source. There are a few tweaks to make before I release the drawings and 3D files. I may sell a complete kit for this. I estimate it will cost less than $100 with motor and extrusions included. I have not tested it in my laser yet. I don’t have the time right now, so I am going to have another 2.x laser owner do that for me….stay tuned for part 2.
This little product from egg-bot.com has been showing up all over the web lately. It is primarily designed for coloring eggs and other small sphere-ish items. For the simplicity of it, it does a fantastic job and produces some amazing results.
With the recent discussion thread on the buildlog.net DIY laser forum about making an open source rotarty attachment for lasers, this has a whole new appeal. There are even some discussions on the eggBot FAQ about using this for lasers.
On the Egg-bot website, they down play the suitability of it and mention safety issues. To be fair, it is not really too suitable to laser use because of the size limits (1.25-4.25″ Dia and 6.25 max. long) and the special interface. The cost of $195 is also a little high, but that is due to the included controller and pen motors, etc. But lets get past all that and assume we have one and we want to hack it for lasers.
The first thing that comes to mind is dumbing it down to a simple rotary attachment to run inside the laser. This would be rather simple. Lets say you want to engrave a 1 inch square logo on a little 1.5″ diameter anodized flashlight. First you would strip it down to just the basic mechanism and the rotary stepper motor. The controller and pen controls are not used. You would then plug the stepper motor directly into your Y axis stepper driver. Be sure to dail down the current to what the Egg-bot stepper can handle. You now need to create your logo image. The image will be 1 inch tall, but the width needs to be stretched/squashed to fit the work piece. Since linear surface motion is dependant on the diameter of the item, a little calculation needs to be done.
Say you have a 200step/rev stepper, a 10 microstep driver and a 1000dpi laser controller. Your new resolution will be (Motor Res * Driver Res) / (Dia * PI). In this case (200 * 10) / (1.5 * 3.14159) = 424.4 dpi. Your laser thinks 1000 steps will go an inch, but in reality it is going to go (1000/424.4 = 2.36) inches. The solution is to make squash the image narrower by that amount, so your image is 1000 pixels high by 424.4 wide. That is it. 424.4 dpi is probably a decent enough resolution for a logo, but that is going to drop quickly with as the diameter gets bigger. If your stepper driver can increase the resolution, that will help.
image credit: http://dnashopper.com
The second hack the comes to mind is letting the EggBot control things. It has a controller capable of running two small steppers. Hook the laser’s X axis up to the EggBot controller and let it do the work. That might work, but it would require some serious hacking to get the laser enable to work right. The pen control is probably the candidate to do this. You might even be able to just hook up a push button that clicks when the pen is in the drawing position. I think a really low power level on the laser would be needed.
The third hack might ditch the whole rotarty thing and keep just the controller. Actually you can buy the controller on it’s own from Evil Mad Science (out of stock for a while). I’ll bet you could hack the open source software to make it become the complete laser controller. It has two built in stepper drivers, a USB connection, a voltage regulator and a whole lot of other useful things. I am sure you could get it to be a cutter controller and you might be able to get it to do some simple engraving. The data transfer of the image data might be tricky with limited memory, but it is probably doable. It has hobby servo drivers which might be a good source for PWM power control.
I would love to get one for the pure hacking fun of the project, but I don’t have the time right now. If someone has a laser, has the hacking cred to tackle a project like this, I might consider a donation to the project.
Slicer3 is a new plugin for Google Sketchup from TIG. It allows you to slice an object into pieces that can be cut and re-assembled into the part drawn in Sketchup. This would be great for a laser cutter.
In high school I did several architectural models and cutting the terrain was fun (for a while), but always very time consuming. This tool would have saved me many hours of cutting and one nasty cut to my index finger.
Here are some images from the Google Sketchup blog that show some terrain being sliced in 3 different ways.
I decided to try a simpler example. This is a little project box, that I might cut out of Acrylic or foam board. If you subtract the time spend on screen shots and writing the steps, it probably took about 3 minutes to do. Here was my process. Continue reading ‘Slicer – Google Sketchup Plugin’
I play a lot of sand volleyball in the summer. I used to have a plastic winder for my volleyball boundary lines. It was in really bad shape because I tried to use it as a water ski rope and handle a while back. Anyway, someone was sort of laughing at the condition of it a few weeks back. On my bike ride home I decided it would be fun to make an over the top complicated one out of wood.
The next week I displayed my new creation and someone said, “Wow, look at Bart’s cool hand crafted line winder”. I accepted the compliment, but wondered about that term: hand crafted. I, of course designed it in CAD, cut it out on my CNC router and cleaned it up with a bunch of other power tools. Was it really hand crafted? What does that term mean these days? Continue reading ‘Hand Made?’
I saw couple of thing on various blogs regarding PVC lately. I think every general purpose maker has made something out of PVC at some point. It has a lot of desirable qualities. It is cheap, easy to find, and very easy to work with. It is relatively strong and can hold a lot of pressure. I have made a plastic bottle launcher, a paper rocket launcher and even a crude trebuchet for a scouting contest.
The first new PVC item I saw was these FORMUFIT PVC fittings. They are aimed squarely at the maker side of PVC usage. All of the parts are smooth, glossy, tapered, high quality parts without any of the annoying printing. labels or bumps. Some of the nice features are interior detents so you have a consistent stop point so your project will come out square. There are also slip tees. The tee section on these are not a tight fit to the pipe so it creates hinge. (This would have been real handy on the trebuchet). The other part that fit in this category are the table cap (attaches legs to table), caster base and internal pipe coupling.
They also have pre-made Google Sketchup and MS Visio parts ready to design with.