Tag Archives: cnc

CNC sign from Plywood

My neighbor is starting to brew his own beer, which is a great boon to me.  In an attempt to curry additional favor I offered to make him a sign for his garage.  My intent was to do a trial run in plywood, then do a final in maple with walnut letters.  While doing a clearing operation the main portion of the sign, I got into a layer of plywood that had a very nice grain/color.  I am no real wood expert, so I don’t know what it is, but it was very pleasing overall.

Got off easy on this project, just routed the letters down into the next layer of lighter colored wood, and I was set.  Few coats of rubbed poly and off to the neighbors.

Lesson learned – look at the edges of plywood when routing, you may be able to use the various layers to your benefit!

HT Controller : Troubleshooting

So I had some issues when putting the final product into use.  Which is to be expected, but this bugger had me opening the case at least 6 seperate times..

Issue 1 : when the 5v relays would kick in, it my 7805 voltage regulators didn’t have the reserver to engage them both at the same time.  I needed to add a capacitor.  I did it the easy way, and just screwed it into the terminals.  The +5v is wired in parallel so both relays benefit.

Issue 2 : I used digital pins 0 and 1 on the arduino to control the relays.  Turns out those pins are used for serial communications.  So when updating the board the relays woudl clickclickclickclick like no tomorrow.  No good, had to use different pins.  Obviously I didn’t account for that on the board creation, so they got solder to the pins directly.  Picture is a little out of focus, but it is the orange/yellow leads in the foreground.

Issue 3 : In the external power strip where 6 seperate relays live and are controlled by the arduino here, I made a mistake in that I didn’t have any 10k pull-down resistors on the 6 control lines.  I should have put them in my original circuit, and instead I added them via a little ‘daughter’ board I added to my original circuit board.  Oh, and if you actually jump to read about the external power strip know I took the power supply and arduino out as they are replaced by this build.  All that is left is the transistors and relays.

Ribbon cable removed, and ‘riser’ pins installed:

Daughter board freshly machined:

And installed:

Lessions Learned :

* Patience.  I had to keep telling myself that there was no way I would get everything right on the first try.

* That a 7805 regulator needs a headsink in most cases.

* That a 7805 also needs filter capacitors.  You can’t just plop it in a circuit and expect clean output.

New sign for the workshop

Took a shot at making up a sign for the workplace.  Learned quite a bit in the process, and wanted to document a few of those learnings for the proverbial ‘next guy’.

I used 3/4″ mdf.. and a 1/4″ upcut spiral bit to do most of the cutting.  The circle logo and ‘aperture’ letters are .4″ above the surface, and the ‘laboratories’ letters are .2″.  I profiled the letters after the overall pocket was created with a 1/8″ bit to get more definition.  This all worked ok except for a few things:

  • An ‘R’ and an ‘I’ in laboratories popped off.  The MDF doesn’t hold well when the letters get small.
  • I re-routed those letters and then glued them on.  In that process I realized that NEXT time i would just route all the letters out of another (thinner sheet) and glue them on.  It would save many hours of pocketing work.
  • Glueing the letters would also allow for easier painting as you could paint everything seperate and then glue them on.
  • On the topic of paint, for $3 for a 1/2 quart home depot will create color matched ‘sample’ paints… awesome for this kind of work.
  • Be careful when shopvaccing around the machine while its working.  At the end I looks like a skipped a few stepper moter steps on the x axis, so i have some rough edges on the right side of my letters.  I vaguely recall the router pinching the hose against a letter while vaccuming.. that may have caused it.  If it didn’t.. well thats a problem for another day.

So I learned a lot, and have a fun sign for the garage – its about 36″ long for reference.

Isolation routing

I had very good success with my isolation routing endeavor.  After having to remember how to do things in eagleCAD, the actual manufacturing process was very straightforward.  To start with, I got the eagle files for an arduino board from adafruit.  I needed this to ensure the through-holes would line up so my board would end up being an arduino ‘shield’.  From there I laid out my components.  I won’t get into the actual circuit, but a few things to note:

  • You will be well served by increasing the trace width to .032″.  The smaller traces I have (seen below) will machine, but are a little small for comfort.
  • When you do the wire layout wizard tell it to put wires on the bottom of the board.  One-sided.
  • For optimal wiring I needed a few traces that ‘crossed’.  Normally you would bring them to the top of a two-sided board.  I wasn’t ready to mill two sides and try to get them to line up.  So I basically put in a 0-ohm resistor as a ‘jumper’ to cross over traces.

So this is my diagram:

From there to get the gcode to mill your board you need to run pcb-gcode.  This is a eagleCAD addon that does a wonderful job of creating gcode.  Installation is well documented on their site, so I won’t cover off on that.  There is no shortage of options to configure, but I didn’t change anything other than my machine type (mach3).  To run the setup options you type “run pcb-gcode-setup” in eagleCAD.

From there you can do your configuration.  Mine is included here, FWIW.

After you have everything configured, you have it work its’ magic by typing “run pcb-gcode”.  The output will e a file showing what the board output will look like.  Remember it will be ‘mirrored’ as its the bottom of your board.  You can close the preview, and the actual gcode will be in your eaglecad folder.  There will be two files, a boardname.bot.etch.tap and a boardname.bot.drill.tap file.

I ran the etch file with a 60 degree 1/4″ v-carve bit.  I ran it on 1″ pink foam first to verify it wouldn’t crash, but then ran it on my copper circuit board.  The etch file was awesome, and everything went smoothly.

The drill file was a little weird though.  It kept going back to x0,y0.. I think maybe for bit changes?  Sometimes it would go back to x0,y0 with z0.. so it would drag the drill bit lightly along the surface.  So I ended up hand editing the gcode a bit.. removing all the tool changes.  I have never edited gcode before, and this was very easy to do.  Its basically just three steps that get repeated:

G00 Z0.1000 (raise bit)

G00 X-2.0000 Y1.4000  (move to new hole)

G01 Z-0.0320 F10  (drill new hole)

You just take anything extraneous out.  And then run it on your machine with the bit zeroed an inch up (air carve!) to verify everything looks good.  My drill/etch files are attached at the bottom of post so you can check them out.  Only other change was I must not have had the material thickness setup right in pcb-gcode, so the drill depth didn’t go all the way through.  Easy search/replace on the drill file to replace the depth with a new one.  That’s the (G01 Z-0.0320 F10) above.  Just change the -.0320 for example to whatever depth you want.

I used a .9mm drill bit for this task, and all my components fit well in that hole.  From resistors, to regulators.

BRIEF VIDEO

Snapshot of the board below.  You’ll see some scratches going to bottom-right (0,0) from the problem I noted above.  You will also see the size difference in the traces.  I will ensure I use all larger ones in the future.

Here is another photo after a light sanding to clean up the burrs.. pretty good!

Gcode:

motherShip_daughterboard.bot.drill.tap

motherShip_daughterboard.bot.etch.tap

Isolation routing

Working on a little project for the home theater cabinet, and wanted to make a small circuit board to remove what would otherwise have been a point-point wiring mess.  I am a rookie at eagle-cad, but can cobble together a schematic/board eventually.  In the past I have sent my boards off for manufacturing, but I wanted to try my hand at milling one.  There is a great plugin in called pcb-gcode that works well with eagle cad.  While it has tons of configuration options, don’t be daunted.. using the defaults and a 60 degree 1/8″ v-bit the results look as though they could be impressive.

I ran the trial on 1″ extruded foam to get a feel for the process.  PCB-gcode kicks out two files, one for routing, and the other for drilling.  The image above is just the routing, which includes  a small ‘dot’ on the pads which would be useful for centering a drill bit later.  I have not yet run this on copper, as I didn’t have any small enough drill bits.  I ordered up two #65 or .90mm bits from Midwest Circuit Technology.  As soon as those arrive I will route/drill the board.

After it is completed, I am sure I will recall a few things I left out of the schematic…

CNC Build

I have come to the conclusion that while I am moderately handy, I still frequently fall short of the goal line when it comes to execution.  I like to envision, plan, and design things and then get frustrated when I can’t make them physically turn out as I like.  I have been eyeing CNC machines for quite some time but have been put off by the price of entry, and the space they require.  I have recnetly moved my workshop from the basement to the 3rd stall of our garage to accomodate an office build out I recently completed – so that took care of one of the barriers.  The other was conveienty (somewhat) overcome as I came across a co-worker whom had a cnc machine.. so he could manufacture my wood parts for me.  I think the concept of self-replicating tools pretty fantastic!

I got a ‘kit’ of goodies from buildyourcnc which got me going.  The kit included the electronics, and the code required to cut out the wooden parts (called gcode).  It also came with all the nuts/bolts/chain/sprockets etc needed to assemble.  It took about 5 hours of milling to get the parts cut out of 3/4 plywood, but it was entrancing to watch!  Below is a pic of all the parts drying after having poly applied.  Probably wasn’t necessary, but as it will live in the garage I didn’t want the humidity cycles to affect it.

From the bottom up here is how those parts come together:

  • 2×4 frame on locking roller wheels from Lowes.  This was pretty basic, but I did do lap joints in all the corners for stability.
  • On top of that is a 2′ x 6′ torsion box made out of MDF.  There are lots of good guides on building torsion boxes, and it was suprisingly easy with just my portable tablesaw.  The advantage of the torsion box is it should stay dead flat over time.  I also put 2 coats of poly on this as MDF loves to suck up water!
  • On top of the torsion goes the actual bits that make up the CNC.  The X-axis rails go on the torsion, which the gantry rides on.  Y and Z axis are rails on the gantry.  Its a pretty amazing design, v-groove bearings ride on basic aluminum L rails.

 In the gantry are three stepper motors that are controlled by the electronics below.  Pretty basic wiring for the most part.  PC parallel port goes to the breakout board bottom-right.  This controls the 3 axis via the black boxes top right.  Power supply for the 36v needed on the top left.  Bottom left are two electrical boxes for outlets.  The left most one will have a circuit to turn the router on/off.. but that is a post for later, as I intend to mill the circuit board with the cnc.

There are a lot of steps not documented here, but you can see very detailed build videos on buildyourcnc.com if interested.  I just wanted to share my beginnings on this project, and will post more detail as I go off the beaten path and start to create my own parts.  Below you will see the first milling operations I completed – the manufacture of the sacrificial top for the machine.  This top is intended to be replaceable as it will get chewed up over time.  The T-Slots allow mounting of wood for milling out of parts.