I saw an artical in EDN Magazine today called “So you want to build an H-bot?”. It describes a cool little light duty method to get XY motion. It is used in pick and place type machines. It uses two motors and one open belt. The belt is fixed at both ends to one end of an axis. The rest is run over idlers. By controlling the directions of the motors, you can move in 2D space. The article does a great job of explaining it. If you both motors in the same direction one axis moves. If they move in opposite directions, the other axis moves.
I thought it would be fun to try it in MakerSlide. This is a just a conceptual drawing with most of the parts free floating where they would be attached with brackets or plates. The two plates in the middle would be firmly bolted together.
This is a (4) axis stepper driver Arduino shield that is perfect for use with GRBL (garble) and other Arduino applications. The steppers drivers can be Pololu A4983, Pololu A4988 or open source StepStick drivers. These drivers can run steppers motors at up to 30V and 2 amp per coil. The resolution is jumper selectable per driver between full step,2x, 4x, 8x and 16x microstepping. Soon there will be relay driver board that is pin compatible with the stepper drivers that could be used to control spindle motors and coolant devices.
The plug in drivers are a great low cost solution for low power CNC devices. The drivers can easily be moved to other projects or replaced if they are damaged.
Features
Screw terminal blocks for all stepper motor connections
Screw terminal block for the motor power supply.
Arduino reset button for easy access to reset the Arduino.
Jumpers for resolution selection.
Motor enable wired to an Arduino pin. Default is set to enable motors.
Works with GRBL (see user guide for pin reassignments)
I have been using a ShuttlePro as a pendant for years on my router. A pendant is basically a hand held remote control for your CNC. It allows you to control a set of functions right at the machine. I typically use it to zero the machine on the part, tweak the feedrate, start/pause/restart the job and do an e-stop.
The router’s pendant is starting to die. It has been through hell. I have dropped it about 10 times on the concrete floor. It has also seen a lot of oil and fine dust. A couple buttons are getting intermittent. I have the functions to working buttons, but I was getting worried it would stop working completely. I could not live without it, so wanted to get a replacement on order. I found a good deal on eBay ($54) and since they had several, I decided to get one for the laser as well.
The ShuttlePro was designed for video editing. One thing you do a lot in video editing is jogging the video forward and backward. Typically you want to race forward until you get close then slow down and even go frame by frame until you get to the desired spot. Sounds like CNC doesn’t it? It has three dedicated functions for this. Full speed forward and back via buttons, variable speed via a spring loaded jog dial and a frame by frame little detented rotator wheel. It also has a lot of redefinable buttons. These buttons have clear snap on caps, so you can add labels to them. I have a Corel and PDF template at the end of the post. Someone at the Mach3 forum dicovered this product and within days there was a plugin for it.
Setting it up is easy.
Download the ShuttlePro plugin from the Mach3 downloads page. Place the ShuttlePro.m3p file you download in a convenient place like your desktop. Double click on it. That will launch a program that registers it with Mach3. Plug in the ShuttlePro into your computer. It uses the built in Human Interface Driverss (HID) so you do not need to install a driver. It comes with some software to test it, but you must uninstall it before using Mach3. Start Mach3.
Use the config Plugins menu pick to open the
Make sure the plugin is enabled with a green check. Now click on the word config to the right of the plugin name.
That will bring up the screen above. Each button can be associated with any of many functions. My config is shown above. You probably want some keys across the top to select the current axis. I like to have the two buttons to the outside of the central wheels be rapid movement buttons. It is also handy to be able to lock the pendant so accidental button pushes do not screw up a run. I used the second button from the lower right. The rest are up to you and how you use your laser.
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 a the new Laser Interface PCB. It adds a lot of new features including the stepper motor drivers. This board is designed to reduce the wiring requirement of a home build laser cutter/engraver. This should significantly reduce the cost of a laser cutter. If you use this with EMC2 (free) you should be controlling your laser for less than $100. There is a video at the end of the post.
Controller Connector
This is a standard 25 pin ‘D’ connector. The pinout is compatible with PC control (Mach3, EMC2) or the FSE Retina Engrave controller.
Stepper motor Drivers
The PCB provides three slots for Pololu stepper motors drivers. It can use the A4983 or the A4988 stepper drivers. The PCB provides the logic power so you use the cheaper versions of the boards. These drivers can provide up to 2amps of power at resolutions up to 1/16 step. The microstep mode is easily adjustable through rotary DIP switches. These are placed along the edge with the control connector so they can be made accessible through the enclosure wall. If you ever blow a driver, you can simply replace the broken one. There is a built in fan to cool the drivers that cools them to within a few degrees of the ambient temperature.
Safety Loop
The board creates a safety loop of switches to protect the user and laser tube. The loop runs through the emergency stop button, the cover switch and the water flow switch. If any of these items are are not in the run position or if there is a break in the loop, the laser tube cannot be enabled.
Laser Power Control
The board allows two different laser power control modes. The default mode is via a remotely located manual potentiometer. This is usually mounted on the front panel. You can also use a switch to change to PWM mode. This allows an external controller to provide a digital PWM power level control. This switch would be located on the front panel. The PWM signal can be configured to use pin 14 or pin 15 on the 25 pin connector.
Dual Relay Drivers
The board has two high current MOSFETs that can be used to drive external relays. these are controlled via pins 1 and 8 on the 25 pin control connector. These are typically used to control assist air and exhaust blowers. They can easily be configured through Mach3 or EMC and G-Code as if they were mist and flood coolant devices.
Laser Power Supply Connector
There is a direct 1:1 connection to standard laser power supplies. The board takes car of connecting all the grounds and safety interlocks.
Water Switch
There is a three pin terminal block to connect to the water switch. The switch can be a simple mechanical switch, plus there is a 5V power source to use if you want to power a more complex water monitor.
Enclosure Connections
There is a connector dedicated to the enclosure connections for the limit switches and cover interlock. The board provides the pull up resistors for these items so they can be wired in a mode where a break in the wiring would trigger signal an open circuit. The pull up value can be either 5V or 3.3V.
The second generation open source laser cutter/engraver design from buildlog.net is complete. The new machine is called the Buildlog.net 2.x Laser. The name comes from the fact that this is the second generation machine and it is basically a 2 axis design. The third, vertical axis, is manually controlled with an optional upgrade to digital control. The 2.x Laser takes all the optimizations learned from the first laser and all the other lasers documented on buildlog.net forum.
The usable work envelope is just under 12” x 20” x 4”. The internal design has been optimized so the overall size of the machine is much smaller than the previous design and can easily fit on a small table. It is designed to work with 40W CO2 lasers sealed gas lasers. The frame is built from inexpensive 20mm aluminum T Slot extrusions and the skin is made from a painted aluminum and HDPE laminate.
The first major improvement is in the linear bearing system. The 2.x Laser uses Delrin V groove wheels running on V rails. The custom Delrin bearings are a lot cheaper and run smoother and quieter than the previous metal on metal system.
The next major improvement is in the electronics layout. All the primary electronic systems are contained in a simple electronics module. This has an interface PCB that makes wiring a simple 1:1 connection for each item. The module is removable so all assembly can be done outside the enclosure. The electronics are compatible with 3.3V or 5V control systems whether they are PC based like EMC2 or Mach3 or dedicated commercial or open source controllers.
The original laser attempted to be self replicating with regards to most of the fabricated parts. That limited the materials that could be used. The 2.x Laser drops that goal and concentrates on a more robust design with stronger metal parts. Shimming, drilling and tapping fragile parts is no longer required. The rest of the design was simplified wherever possible. There are less parts and many of the parts self align.
The design is completely open source with all drawings, schematics, BOMs (with sources and prices), 3D models, build instructions, software and Gerber files available. There are kits for anything that is not readily available for people who cannot fabricate their own. Due to the smaller size, the enclosure skins can now be fabricated on smaller home routers or can be purchased as a kit.
The design is supported by a robust community of laser builders and users at the buildlog.net forum.
After working like mad for several days to release the 2.x Laser, I decided to take a break and have some fun. I thought it would be fun to add some interior lighting to the laser. It is not really necessary if the room is at all bright because the top is so big and clear, but I thought it would be fun.
I searched around some PC case mod sites for a while, but was not sure what would work right. They fall into two categories: LED and Cold Cathode (CCFL) lights and virtually all of them run on 12V. I use 24V, so I had to deal with that.
I had few negative issues with CCLF. Most have a big power supply thing that is probably very noisy and I was not sure how happy they would be to run in series to deal with the 24V. I decided LED were very flexible and very clean.
I was not happy with the stuff I found on line, so I ran off to Micro Center. They only had one LED strip that was white. Frys is just down the road, so I went there. They did not have any white LED strips. I decided to check their lighting section and found what looked to be a perfect solution. It is made by Trend Sources Inc, but I could not find much on line about them. I paid about $19.
This is a two pack 12V flexible LED strip. It looks like a flex circuit with a molded silicone boot over it. It just so happens that it can be pushed into a 20mm Misumi extrusion. You need to gentry work it in, but it is not coming out on it’s own.
I fired up one strip, then 2 in series. They worked perfectly and quite bright. I pushed them into the extrusion the is located right behind the cover hinge. I hid the wires using Misumi slot cover material and wired it over to the central 24V supply.
It looks great. The LEDs stick out about 1/8″, but you really don’t see the individual LEDs until you look at a low angle. The camera is actually held inside the laser, below the level of the cover here. This only shows one of the strips. I separated them by about 2.5 inches.
Cut2D is 2D CAM program from Vectric. It is designed to quickly and easily import DXF plus several other vector formats and create G Code for CNC cutting. It is primarily designed for traditional mills and routers. While I would not recommend purchasing it to only use on a laser, people who have both a CNC router and a DIY laser will find this to be a very capable and inexpensive product.
I have used Vectric products for years. I started with VCarve, then upgraded to Aspire. A forum member recently asked for help using Cut2D. Vectric was gracious enough to give me free evaluation copy. This is probably due to the fact that I already own their top of the line product. They did say that they are not really interested in selling it for laser use only because the program may be confusing to them and they only want 100% satisfied customers.
The Vectric products ship with 100+ pre-made post processors. There are several flavors of Mach3 post processors that will work right out of the box for most mills and routers. It is also very easy to customize your own post processor. I created one for Aspire last year and found that it worked perfectly for Cut2D as well. I wrote a blog post about it and the file is available here. All Z movement is removed from the post processor, so the actual Z values used below are not going to affect your machine while cutting.
I am not going to explain how to use Cut2d. Vectric does a great job of that. I will just explain the differences when using a laser cutter.
Creating a Laser Tool
The first step is to setup a “tool” in the tool library for the laser beam. The beam can be thought of as an end mill. It is basically a cutting cylinder with a fixed width. The major difference is that it has an “infinite” depth of cut. In reality most lasers are not going to cut anything thicker than an inch or so due to beam divergence.
Many values you set are just default values and can be changed when you use the tool for a cut.
Tool Name
I called my tool “Laser Beam 0.003″. If you want to go crazy, you could setup dozens of tools with default values that work well with certain materials. You could name the tools “1/8 Plywood laser cut” or “6mm Acrylic laser cut”, for example. This way you do not need to remember what speeds and feeds are needed for each material.
Tool Diameter
Cut2D will use this when calculating how much to offset the cut line from the geometry when cutting inside or outside features. An easy way to determine this is to cut out a 1 inch square on the geometry lines with no offsets. Measure the actual size of the part. The amount you are less than the inch will give you the beam diameter. If you want to be as accurate as possible, you could define multiple tools based on different materials and thicknesses.
Pass Depth.
You cannot realistically use Cut2D to control the depth of a laser cut. Therefore, this value is not important. You do want to make sure this value is larger than any value that you will use when specifying tool paths so the cut is always one pass. I suggest setting this to a value of 1 inch. This default value can always be changed when you are setting up a toolpath if you actually want to play games with multiple passes.
Stepover
This does not apply for lasers, because we will not be doing pocketing. Just set it for 45% to keep Cut2D happy.
Spindle Speed
This value is also not really important at this point. You could use it to control beam power if your laser supports that. If your laser can use this for beam power then set it for the number that would yield max power, otherwise a value of 1000 should be fine.
Feed Rate
Again, this is a default number that can be changed at each tool path, so pick number that is close to t typical number you might use.
Plunge Rate
This does not apply so just put in any reasonable value.
Here is what a typical laser might look like.
Usage
I will explain one cut using the wing_spar example file that comes with Cut2D. The cut will be the inside features of the wing spar.
Select all the inside features and then click the Create Profile Toolpath icon on the toolpaths flyout menu on the right.
Cutting Depths.
These values do not matter. You just want to make sure the cut depth is less than the pass depth set for the tool. This will insure that only one pass is done. Advanced user could of course use this to setup multiple passes.
Tool
This is where you select your laser tool. Use the edit button to set the actual cutting speed you want.
Machine Vectors.
Use this to tell Cut2D what side you want the tool offset to. The direction setting (climb or conventional) is primarily for spinning tools, like end mills, but if you care which way the cut goes around the loop, you can change this.
Ramp moves
Don’t use this.
Tabs.
Tabs are primarily used to keep parts in place with spinnig tools, but you might want to take advantage of it to keep light parts from blowing around, or if you want all the parts to stay on the material after cutting.
Outputting the G Code file.
The last step is to output the file using the custom laser post processor. A copy of the file is available here.
Good luck. You might want to try a few dry runs with the laser disabled and you hand on the e stop button to make sure it works for you.
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.
I cut a lot of parts on my home built machines. These machines were never designed for production work, so I have developed strategies to get the most productivity out of my work. My goals are to get the best yield out of my material, have the shortest run times, spend the least time babysitting the machine, minimize tool breakage and get the highest quality parts. This post is primarily focused on routers, but some of it also applies to laser cutters and other machines.
Modern professional, production machines will have vacuum hold downs, tool changers and automated clamping, etc. This post is about optimizing basic machines. A lot of this is obvious to many people, but recently I have seen some videos where I saw poorer strategies and even examples where part quality is going to be hurt.
Don’t Break the Tools.
For me, as a hobbiest, my time is cheap compared tool costs. The first priority is preventing tool breakage. I usually run with a 1/16″ dia. 1/2″ cut length carbide bit. This minimizes material loss. These babies are brittle. One mistake and it will break. With that said I have cut continuously in Acrylic for 6-10 hours with one bit. When cutting out parts, my number one cause of breakage is getting caught on a loose part or scrap. I design my cutting to prevent pieces the might break the bit from flying around.
Analyze The Part.
The first thing I do is look over the part to see the issues I might face during while cutting. The first issue I see is the large oval internal piece. This piece will come loose and is big enough to cause problems. It might try to jump out of the hole and catch on the tool or it could land somewhere where the tool will come down later. The smaller circles won’t be a problem. The cooling blower on the spindle will whisk those away. The small slot could be a problem. Long aspect ratio, small cutouts often start to fly away, but get hung up if they tip on the way out. If a rapid move happens to cross this, it could break the bit. I would probably address this by choosing a rapid move height of about a material thickness above the surface. Maybe a little higher if the slot is longer. An excessively large rapid move gap will seriously waste time, so I want to choose this carefully.
Keeping things together.
There are several methods to keeps parts from flying around. One popular method, if your software supports it, are “tabs”. These are small uncut or partially cut areas that are left behind. Ramped tabs like I show above are a lot faster because they do not require the move to stop and retract at each tab. This method works well on parts like wood that will probably get cleaned up and sanded later. On some parts like aluminum or plastic, it may not give you the even finish you want. The second method I use when the cut will require multiple passes is to leave the final pass to later. All parts are cut, unattended, down to a small remaining amount. Then all parts are cut out with me there. This can often be done at very rapid rate if not much material is left. I usually use a soft wooden, hand held ”chicken stick” to hold the parts down during the cut.
Clamping
Clamping can be a challenge on large sheets. You can clamp from the edges but the center might bow up a little. This gets worse as the parts are removed and only a thin web of material remains. Bowing causes two problems, you can get chattering of the material which impacts cut quality and your zero Z point is not consistent. I use two strategies to deal with this. If all the cuts are through and a little Z variance is not a problem, I try to cut out parts from the center and work my way out. This keeps a stronger path of material to the clamps.
If I have blind pockets to cut and the depth is critical, the Z need to be accurate. In this case, I will usually run the though hole toolpath first, then add a few wood screws through the material and into the spoil board in the central areas of the material. Make sure your rapid Z will clear the screw heads or the rapid path avoids the screws.
Cut Order.
Obviously you want to cut all internal part holes and features before you cut out the part because the part needs to be held firmly in place. I chose to not cut any parts out until all internal features on all parts are done. This keeps the material ridged as long as possible. This applies to laser cutters as well. People are not as conscious of cut order because parts are less likely to move, but on really small parts on thin material the assist air or exhaust blower can move the parts a little. I see cutouts before internal cuts all the time on videos and I can see the parts move.
I optimize my cut order to minimize my babysitting time. I cut all large internal part features first and monitor that. I then combine a lot of unattended toolpaths. First is the cutout of all small internal feature. Next I cut any blind pockets. Next, I cutout all the parts almost through. This is generally the longest run. The machine will stop and wait for me. I then completely cutout all the parts working from the center our while watching the machine to prevent problems. I will use my “chicken stick” on parts I think might jump out.
Cut Speed.
Don’t be afraid to raise the cutting feedrates. Most tools are optimized for certain chip sizes and speeds. You are not doing the tool any favors by running it slowly. If the tool cannot make decent chips, it will run a lot hotter and will dull and fail sooner. You need to experiment with speeds to get the highest reliable speed. Home built machines are not perfect and things like runout (wobble on the tool) and tram (Z out of square) problems might come into effect before ideal speed is reached. With high speed router spindles consist single flute tools. Don’t be temped by cool looking 4+ flute tools. They are more expensive and will give you a worst cut and will fail faster.
