Archive for the 'Laser' Category

Hacking the EggBot for Lasers?

Egg-bot

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.

Eggbot-Objects

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.
Laser Cut Egg

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.
EiBotBoard
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.

Production Strategies on a Home Built Machine

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.

Feel free to comment below or join the discussion in the forum.

Slicer – Google Sketchup Plugin

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’

Laser Cutter Gas Containment Chamber

Fume Containment Box

I saw this post over at the Make Magazine Blog.  This is an interesting method of containing the exhaust gas on a particularly nasty material.  It basically puts the work in a box with an IR transparent window.  The box has a fitting to suck out the fumes.  It uses a polished silicon wafer as the laser window that was bought off eBay.

I probably would have put it in a Tupperware box, because the seal might be better and it is probably more resistant to the nasty fumes.  I could have used this when I tried my vinyl record cutting.

RepRap Controlling Laser – RepZap?

RepZap

I recently got my laser to do 3D printing via RepRap electronics.  I thought a fun exercise in hacking would be to get the ReplicatorG program and the RepRap controllers to control the laser.  Is this practical?  It is probably not the ideal solution, but if you are trying to make a dual purpose machine with the ultimate lowest cost it might work.  The biggest drawback is that RepRap does not do acceleration (yet).  This means there is a limit to how fast you can go before you loose steps or shake the crap out of your machine.  Also, there are not any fail safe features, like if you stop the machine in the middle of a run, does it turn the laser off.   This would be added to the ReplicatorG configuration, but was not done for this experiment.  Bottom line – no snarky, comments please, this was done for fun and learning only at this time.

I already had RepRap controlling the 3 axes for 3D printing, so that was done.  The next part was to figure out how to turn the laser on and off.  I needed to find something in RepRap flavored G-Code that would do this.  In G-code, there are  Gxx codes and Mxx codes.  The Gxx codes generally control motion and geometry setup and the Mxx codes control things like spindles and coolant devices.

Replicat.org has a partial list of the M-Code here.  The fan on/off M106 and M107 commands looked promising.  I wrote some quick G-Code to test this.  BTW: You can just type in G-Code in ReplicatorG and click the Build button to run it.

M106 (Fan on)

G4 P1000 (dwell .. Wait 1000ms)

M107 (Fan off)

Continue reading ‘RepRap Controlling Laser – RepZap?’

Laser Cutter Adds 3D Printing Capability

3D Printing Laser Cutter

The Buildlog.net Open Source Laser cutter/engraver just added 3D printing to it’s capabilities.   The printer system uses the existing CNC motion system of the laser cutter along with standard RepRap electronics.  A quick release plastic extruder carriage is added to the existing gantry.

The upgrade project is called the Chimera Project because this is a hybrid of two self replicating machines.  The parentage of the parts gets a little blurred.  A Chimera is a animal descended from two genetically different animals.  The laser is  self replicating by making all its non off the shelf parts.  Adding 3D printing takes that another step forward.  The electronics were packaged outside the enclosure for development, but will be moved inside soon.

Changing modes is quick and simple.  Swap the control cable, attach the extruder carriage and you are ready to print.  You can even leave the printer carriage in place if you don’t need to use the full width machine when laser cutting.  The total upgrade cost is less than $200.

The RepRap electronics can actually control the laser cutter with no modifications to the hardware or software, but the lack of acceleration parameters in the RepRap control system limits the speed the laser carriage can move before it becomes to jerky.

Already in the works are a tangential knife cutting head, Pen plotter and Dremel tool head.   The entire system is open source and well documented.  Starter kits for the laser are available and the 3D printing parts are coming soon.

Also see a build log for a project going the other way:  a MakerBot printing a laser cutter.

Extruder Carriage

Extruder Carriage - (X Motion via duct Tape!)

Chimera Project

First 3D Print

On It's Raft

Reciprocating Laser Cutter

Reciprocating Laser Cutter.

I saw this while checking up on the progress of his selective laser sintering (SLS) project.  Basically his idea was smaller power lasers might be able to cut through thicker material by “sawing” through it.  The required power density might only be high enough at the exact focal point of the laser.  Therefore, if you move the focal point through the material vertically, you might be able to cut it.  He did it using a reciprocating motion, but you could also simply run the same outline at multiple levels, which is what us mill and router people have done for years.

Reciprocating Laser Cutter

The machine is actually a beautiful work of hacker art.  He build it out of CD/DVD drives.  He only gets about 1.5″ of travel on each axis, but that is all he needed.

Reciprocating Laser Cutter.

small piece cut from CD case

Continue reading ‘Reciprocating Laser Cutter’

Negatively Laser Etched Metal

Negative Laser Etch

James Williamson posted this on his REDTOROPE blog.  It sounds like he was looking for an alternative to the really expensive  TherMark laser marking ink.

Basically he used some spray paint intended for use on wood stoves.  He did a lot of preparation to make sure the paint was perfectly adhered to the matal.  He then created an image by laser etching away paint to reveal a negative image.  I looks quite good with fine detail.  I do not know how well the metal will hold up to corrosion though.

I often wondered what would happen if you painted ceramic glaze on metal and hit it with a laser.  Would it cure to the metal.

Negative Laser Etch

New Laser Engraver Controller

Retna Engave Controller

Full Spectrum Engineering is about to release it’s new Retna Engrave laser engraving controller.  It is initially targeted at the hobby and DIY market.  There are Chinese controllers available, but most people are quickly underwhelmed by the software that comes with them.  The Moshisoft and Newlydraw interfaces are quite quirky.  Note: The image above is probably an old version.

Henry Liu, the head of Full Spectrum, and I have been chatting back and forth since the beginning of my laser project.  He is very sharp and seems to have good pulse on the low end laser and DIY laser community.  We hashed out most of the controller options out there from DSP to FPGA and both decided that the XMOS chip might be the perfect device for the job.  Once he decided to go full force with the XMOS, I stopped working on mine, knowing that he could do a better job.  He is sending me one of his controllers to try out next week.

Currently the controller runs as a printer driver for Windows.  This means that basically any program can use it to cut or engrave.  He also has a Mach3 plug-in coming soon and eventually an  open API where others can create new applications for it.  It falls short of full open source, but it is a good option for many of us.  The controller hangs off an existing DB25 parallel connector, so it is an easy upgrade for anyone currently using Mach3 or EMC2.  The firmware is also upgradeable over the USB connection.

Continue reading ‘New Laser Engraver Controller’

MakerScanner

Laser Scanner Assembly

Engineer Andy Barry has created a new budget open source 3D scanner.  He calls it the MakerScanner and hopes to sell it through the MakerBot web site for around $200.  It uses the same laser line, offset webcam than many other systems use.  He does a good job of explaining on the MakerScanner.com web site.  There are even more details on his web site and Thingiverse.

The system uses galvanometers to move a mirror which moves the laser line.  A sine wave is output to one galvanometer so it creates a line from the laser diode.  The other scans it across the model.  All of the parts appear to be printed with a Makerbot.

Galvanometers

Galvanometers

Continue reading ‘MakerScanner’