Archive for the 'Laser Cut Stuff' Category

Next Project – Wooden Nickel Engraver

I started working on my next backpack scale CNC project. My backpack scale projects are tiny CNC machines that I can easy carry in a backpack to tech meetups and events. This machine is going to be a wooden nickel laser engraver.

Wooden nickels are small wooden discs. You can buy blanks from various places, including Amazon. You can usually get 100 for less than $10. The goal is to create a machine that loads them from a feed tube, engraves them, then ejects them.

Mechatronics

The basic drive will be an H-Bot. It will be similar to the midTbot, but the motors are at the ends of the X axis. It will be fully enclosed, but I not started work on that part yet.

Disc Feed System

I hope to be able to use a single hobby servo to handle the loading and unloading of the blanks. The servo will control a sliding device that has three positions.

  • In the first position it acts like a support shelf for the disc. The bed slides under the feed tube and a disk drops into the pocket.
  • The next position is the clamping position. This holds the disc still while engraving.
  • The final position retracts the shelf so the disc drops through.

Electronics

The goal is to use a low cost controller like an Arduino Nano.

  • (2) Stepper motors for the X,Y motion
  • (1) Hobby servo for the disc feed system (PWM)
  • (1) Laser power control (PWM)
  • (2) homing switches
  • (1) interlock switch loop if there is a door and/or cover

Status

The major new feature of this design is the disc feed system, so I am primarily working on that right now.


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Coasty Update

Here is a quick update on Coasty. Several people have asked if I am releasing the source files or selling a kit. I am adjusting the design to make that more viable.  The original version was made with parts I had laying about and not necessarily the best design choices for an open source project.

X Axis.

Originally I used an TR8-8 ACME thread lead screw. It was mounted to the motor by drilling a hole in the lead screw and epoxying it to the motor shaft. This worked well, but you needed a lathe to drill the hole and a special low backlash nut. The axis was also a little loud with and all metal design.

I changed to use a GT2 open belt cut to length.  Belts and pulley are really easy to get and don’t cost too much.

Electronics

Need to shorten some wires after testing.

There were some issues with the EleksMaker electronics that I did not like. The laser circuit did not appear to have a pull down on the signal and it tended to fire if the Arduino was not pulling it low. This would happen during reboot and other scary times. The wiring was also quite a pain. There were no connectors for the limit switches so you had to directly solder to the Arduino Nano.

I changed to use a custom PCB that is the entire rear panel. This contains all of the circuits including the limit switches. Building a Coasty was a little like building a ship in a bottle. Now the bottle has no bottom and there are less parts inside.

Front Door.

The front door now has a window. This makes the machine more fun to watch and no glasses are required.

Next Steps.

I have one build and am testing it for a while. If all goes well, I will release the source files and consider a kit.

 

DIY Solder Stencil on a DIY Laser

We use a lot of solder stencils where I work (during the day).  We usually buy stainless steel framed stencils for about $300 each.  For prototyping we usually hand paste each pad.  We have an semi-automated dispenser, but it is still tedious work.  I see several places like Pololu selling low cost mylar solder stencils.  I wondered if my Buildlog.net 2.x home made laser cutter could do it.

I researched a few blogs and pulled some information from Pololu.  Pololu sells 3mil and 4mil mylar stencils and recommended 3mil for fine pitch work.  I decided to buy the 3 mil mylar.  I picked it up on my way home from McMaster Carr.  It was a life time supply for about $15.

I found a bunch of old small SMT PCBs that I could play with.  I got the top side paste mask  gerber file for it.  I imported the file into a Gerber tool called ViewMate from Pentalogix.  This is a great program that I have be using for years.  A partially disabled version is free.  I have found that it has plenty of useful features.

 

Most PCB layout software has layers for the solder stencil.  There are industry standards (IPC) for the size of these pads, but they are generally a little smaller than the pad.  Often large pads, like thermal pads under big power ICs are divided into smaller windows or dots.  This prevents excess solder from causing problems.   With this in mind you probably need to shrink the pads even further to deal with the kerf of the laser.

ViewMate has a nice feature that allows you to shrink the apertures.   Apertures are a somewhat archaic term from when artworks were done optically on film.  They basically mean the shapes.  To use this feature select the Setup…D Codes menus.

 

Select all the shapes in the list and select the Operations…Swell menus.

Enter a negative value to shrink the shapes.

I then printed 1:1 to a PDF.

ViewMate has a lot of export options, but most of them are not available in the free version.  PDF is fine for what I needed to do.  I then imported the PDF into Corel.  I cleaned up a few extra lines and text in Corel and moved it over near the origin.

If you were always going to make your own stencils,  you could probably skip a few of these steps by defining your stencils layers with the right values.  Pololu actually shrinks it differently in X than Y for even better performance.  Many CAD programs could print straight to PDF or other formats then.

Corel is a front end for my DSP laser software, so I was ready to try making the stencil.  The PDF has vector information so you could cut it or engrave it.  Everyone seems to recommend engraving, so I gave that a try.

I was not sure what to put the mylar on.   I decided to hang it in the air.  I taped inside a wooden frame.  I tried different power levels and speeds and looked for my best result.  I onlt tried about 3 settings combinations before I ran out room.  I looked closely and they all looked pretty good.  I think I got the best at 200mm/s and about 60% power.  The power was not too much of an issue.  It seemed better to cut it with more power than it need.  It tended not to heat the surrounding area.  The step over was 0.15mm.  That probably could have been smaller for more accuracy.   There was a slight smoky haze after cutting that I rinsed off with water.

It matched up perfectly with the PCB.

 

 

 

 

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.

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

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Full color 3-D viewing Stand For iPad

iPad 3D Viewer

Thomas Kumlehn of Pixel Partner sent me a nice email regarding the iPad Chair.  He did a roughly similar Instructable to mine on an iPad 3-D viewer.  This is another laser cut flat-pack iPad holder, but this holds the iPad in the perfect location for viewing stereoscopic 3D images and video.  He uses a readily available lens the redirects your vision to over under pairs.  The iPads portrait mode works very well for this.

I remember as a child, a friend had a vintage side by side stereo viewer with a bunch of black and white pictures for it.  I remember how amazed I was by them.

He has files available for cutting on his web site.

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The iPad Chair

iPad Chair

I am working on a fun, geeky project and I needed a little stand for an iPad.  I am not a real fan of the Apple company, but my wife got this though work and it will be perfect for my project.  I love this flat-pack style of construction and I was inspired by my recent post on SketchChair.  So I decided to make a little chair as my stand.

I started out by downloading the SketchChair software.  I was able to create a lot of cool chairs, but I could never get exactly what I wanted.  The software is a great concept, but it was not quite ready for what I needed.  I switched over to my 3D CAD package (Pro/E).  I stole a lot of the construction techniques in SketchChair, but modeled it in exact scale in Pro/E.  The design only uses four distinct pieces: 2 Sides, 2 Center Pieces, 6 Slats and 1 rear leg brace.

iPad Chair Mode

I exported the the drawing of the pieces via DXF (DXF Is here) to my Vectric Aspire CAM program.  Here I duplicated the parts to what I needed and used the nesting feature to fill the cardboard size I had.  Normally I would restrain the amount of rotation allowed to keep a consistent grain direction, but this time I let it rotate any any angle (screen says 45deg, but I actually used 5deg).  I wanted the finished product to look sort of cattywampus.

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Laser Cut Vinyl Record – Bad Idea?

Laser Cut Vinyl Record

Everywhere I look these days I see a blog article about someone laser cutting old vinyl LPs.  I think the first place I saw it was on the Make Magazine Blog.  It seems like a great idea, especially if you choose an image that fits the record you are cutting.  It also fits the recycle/upcycle trends.

I decided to give it a try.  I had an old Zydeco LP on the Alligator records label.  I found a simple alligator profile and decided to give it a try.  I don’t remember the exact speed and power settings, but the material cut like butter with a nice clean edge.  The only strange side effect was huge amounts of brown smoke.  I had a decent assist nozzle, but my old evacuation blower was not the greatest.

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Laser Cut Lamps

Laser Cut Lamp Curious Customs

I saw this over at Boing Boing.  They are by Curious Custom and are for sale in the Makers Market.  It is a really nice example of laser cut wood.  Unfortunately, I don’t think my laser is quite up to this thickness.  I live in a Bungalo with American Craftsman / Arts and Crafts style furnishings.  This would fit in just fine.  They are a good price at only about $30 USD.

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The Age of the Self Replicating Machine.

MC Escher - Drawing Hands

There is a saying amongst DIY CNC router builders that goes something like this… “You only need to build your first router good enough to build you second one“.  In my case that turned out to be true.

I built a wood, conduit and skate bearing Solsylva router.  I painstakingly layed out the various pieces using calipers, t-squares and compasses.  I cut them out using hand held tools like jigsaws and drills.  It worked remarkably well, but every time I routed out a perfect CAD drawn piece, I always thought “Gee, I wish I had this thing when I built the router“.

It wasn’t too long before I built my bigger, better, more accurate router.  I was able to use tougher materials, hold tighter tolerances and cut more exotic shapes.  It works much better.  A few months ago I finally pulled off all the good bits and Sawzall’ed the old one apart to get more room in the shop…a bitter sweet day.

Most of today’s designs develop inside a computer.  Resolution and accuracy are infinite in this realm.  We expect our fabrication machines to output similar accuracies, but how does one construct a machine with this accuracy with common (analog) tools.

Today’s open source machine are addressing this head on.  There is a big push towards self replication.  Struggle past the first one and the rest will be easy.  It is not just an accidental bonus it is initial design requirement.  It is a lot more work, but I think it builds the strong communities behind these projects that help insure their success.

Here are three examples of self replicating machines…

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