CAD CAM tutorial

CAD CAM tutorial
by D.  Scott Williamson

This tutorial will show you how to use Computer Aided Design and Computer Aided Manufacturing or CAD CAM tools to create and preview a Gcode file of the Workshop 88 logo that can be run in a 3 axis CNC Mill.


There are 5 main types of machine operations

  1. Engrave (follow path): The tool tip will follow the 3D path provided.
  2. Profile: The tool edge will follow either the inside or outside contour of a path down to the specified depth.
  3. Pocket: The tool will remove all the material within a contour down to the specified depth.
  4. Drill: A drill routine will be executed at each point location.  Drill routines come in 2 flavors:
    1. “Peck” used with drill bits, drills to successively deeper depths liftig the bit out of the work regularly to clear chips from the flutes.
    2. “Spiral” used with endmills that are a smaller diameter than the finished hole.
  5. 3D relief: The tool tip will remove material above a 3D surface usually specified in a 3D model or a 2D height map image.  There are two main modes:
    1. “Waterline” similar to inverted pocket operations where bulk material is efficiently removed outside the 3D model to a number of stepped depths resembling waterline in a topological map.  Typically used in a first pass with a large roughing bit to remove the bulk of the material.
    2. “Raster” moves the tip of the bit smoothly over the model in a raster pattern.

Gcode is a “numerically controlled programming language” which is why a Gcode file extension is typically .nc.  It is a human and machine readable text file.  You will rarely if ever need to look at or edit the Gcode.


This tutorial will demonstrate Engrave, Profile, and Pocket operations, which are the most popular.

There are 4 steps to this tutorial:

  1. Create a .svg file containing paths needed for machine operations
  2. Create machine operations
  3. Export Gcode
  4. Simulate, visualize and validate

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T-Kit 1380 Kit Build: Part 2

Today, I’ll be continuing my 80m transceiver build that I started in T-Kit 1380 Kit Build: Part 1.

At the end of the last post, the board looked like this:

The full board

The full board

Today I’ll be moving on to the VFO section of the board.  A VFO, or variable frequency oscillator, is the circuit that allows you to tune a radio.  This particular VFO is based on a Collpits oscillator, and can tune over a 50-70 kHz range centered on a frequency determined by the component values.  The frequency range shown in the image may seem a bit strange.  This transceiver can be built to cover that 50-70 kHz range somewhere near 3.5 MHz to about 3.75 MHz.  The short explanation is that the frequency we’re interested in is shifted by the frequency of the VFO to an intermediate frequency of 8 MHz, where we can do filtering and amplification at a single fixed frequency.  Since a lot of circuit characteristics are frequency-dependent, performance is much better if the components can be selected for just one frequency.


The majority of the components are supplied with the kit, so their values are fixed.  One of them, an inductor, I had to wind myself.  Since this phase required quite a few components, I decided I’d lay them out before I started.


Rather than start building immediately, I decided to wind the inductor first, so I could get that out of the way.  The instructions specified 28 turns of the green #28 enameled wire on the red toroid core.  I had to count the turns several times to be sure.


The inductance of the coil is dependent on a lot of things, including the material the core is made of, the diameter of the core, the number of windings, and the spacing between the windings.  Later on in the build, I tweak the range covered by the transceiver by adjusting the coil spacing.


From this point on, it was simply a matter of stuffing the board and soldering, as per the instructions.  The one thing I would have changed was the process for doing initial testing of the inductor.  They have you tack a couple leads to the pads you’re going to use, and then tack the inductor to those.  Unless your inductor is wildly off, you’re not going to be rewinding it, so I would have skipped that step and just soldered it in directly at the beginning.

The testing of phase 2 was relatively simple, because I’m using a frequency counter.  I just hooked up the frequency counter, and adjusted the spacing of the turns on the coil I mentioned before until the VFO covered the range between 4.470 MHz and 4.391 MHz.

I’ll talk more about it in the next post about the transmit mixer and filter, but that provides an actual range of 3.530 MHz to 3.609 MHz.  This includes the QRP CW calling frequency at 3.560 as well as W1AW’s code practice sessions transmitted on 3.5815.  It does not include the main CW DX window between 3.500 and 3.525 MHz, but I’m still working on getting my Amateur Extra license, so I’m not authorized for that part of the band anyway.


T-Kit 1380 Kit Build: Part 1

I won a T-Kit 1380 80m 3 watt CW transceiver kit at the WCRA Hamfest back in 2014, and it’s been sitting on my bench unopened since then.  I didn’t have my license at the time, but I got my General license about a week later. I decided that this summer was a good time to start building it. Here’s a link to one you can pick up if you’re interested :

I have quite a lot of kit-building experience, but most of it is digital electronics, so this is probably the most complex kit I’ve ever built, both in number of components and circuit complexity.

If you’re not familiar with amateur radio, this kit will let you transmit and receive on the 80m band (between 3.5 and 3.75 MHz) using CW (morse code).

1380 Manual

The schematics in the manual are a bit low-res, but the instructions for assembly are very good.  My biggest complaint with the manual so far is that errata are supplied as a stack of papers inside the manual.  Some of them referenced parts this kit doesn’t use, so it was a bit of a chore to go through and update the instructions and update the steps by hand.

The assembly process is documented in phases, with testing procedures at the end of each phase.

Phase 1 is construction of the DC input circuitry as well as the keying circuit.  The keying circuit is connected to the code key, and disables the receive circuitry while transmitting.  Here’s the diagram for phase 1.

Phase 1 schematic

Phase 1 schematic

Here’s the board as assembled:

Phase 1 assembled

Phase 1 assembled

This is a pretty densely packed board, and the silkscreen suffers for it.  The manual gives pretty decent drawings of the section of the board each phase is concerned with, and this helps quite a lot.  You can usually locate a component by finding a nearby component you’ve already installed, or one whose silkscreen isn’t broken up by a pad.

Once this phase was assembled, there was a short test procedure to verify that it is operating correctly.  Essentially, I had to apply 12v to the 12v input, and then verify that R13 (the resistor in the center of the board, just between the two beige ceramic capacitors) read 0v while the key wires were disconnected (the white and black wires just under ‘J1’), and 12v while they were touched together.

I misread the directions and it took me a while to figure out what I was doing wrong (I was measuring voltage drop across the resistor, not between the resistor terminal and ground), but in the end, everything checked out.

The full board

The full board

As you can see, there’s quite a lot of work still to do, so come back next time, when I move on to assembly and testing of the VFO section!

Surface-Mounted LEDs for LEGO & LED Inventing Camp

PlacingParts0270Rachel and Jim made up some very skinny surface mount LED/resistor strips that fit between Lego posts for a STEM camp Rachel is running.

A simple pattern was etched on flexible copperclad Kapton film, using vinyl from the vinyl cutter as resist.  Solder paste blobs and the tiny 0805 components were hand placed, ReadyToSlice0273then reflow soldered on the hot plate.  Here are some ready to be sliced apart.  The resulting glowing Gummi bears were a big hit with the kids!

EllaHead180514Campers beta-tested Rachel’s Conducty Inventing Kit during a week-long Spring Break camp at Moore Toys and Gadgets in Wheaton. They built circuits Cooper134906581directly on LEGO baseplates using conductive tape and components designed to fit between the LEGO studs. Kids lit up everything from Minecraft torches to outdoor campfires made of LEGO. Here, Cooper and Ella show off their creations.  The Conducty LED Inventing Kit will be launching on Kickstarter later this Spring.

Minecraft Extravaganza

IMG_20151023_002406We’ve mapped out a wiring diagram and rough layout for an Arduino-controlled Minecraft landscape. Bill has graciously agreed to write the code. Rachel roped in a bunch of newcomers to build part of the set and brainstorm Minecraft “events.”

We settled on a line of light-up Redstone dust (red LEDs in perforated boxes) leading up to a tree which catches on fire (LEGO flames IMG_20151023_012142657will stick out of the tree). Then a second tree will catch on fire. We’ll be working on it at Workshop 88 the next couple of Thursday evenings if you’d like to stop by and contribute your Minecraft, LEGO, and/or Arduino expertise.  Come play!

We’re gearing up to display this at the Barnes & Noble Mini Maker Faire, along with some other projects.  Scott Wojton from the Naperville store has been out to the space a couple of times and has been very helpful to us,so we’re happy to be showing stuff at his Faire Nov 6-8.

Book #2


I couldn’t find an empty notebook this morning, so I made threw one together from printer paper and the remnants of the box my Amazon Echo came in.


This one is a quarto with two quires, simply sewn together with waxed linen thread and no glue.

The top stitch on the cover is a bit strange, but topology wouldn’t allow the initial pattern I was planning on. I might use a small ring or a bar to secure the top stitch the next time I try this format so I can avoid the strange fifth hole in the spine.

It fits nicely in a pocket, and the cover feels pretty sturdy. I could probably have creased the spine a bit more heavily to make it close better, but I’m okay with that.

First Try at Bookbinding

I’ve always been interested in bookbinding, but haven’t given it a shot until now. I followed these excellent tutorials by Sea Lemon on YouTube, and I think my book came out okay.

I made the case using black Tyvek for the cover, and 1/4″ masonite for the spine and front and back boards. I think it worked pretty well, and I like the way it looks.


I sewed the signatures together using upholstery thread, and the book opens up really well.


This is the view of the cover with the book open on the table. I cut the board for the spine about twice as wide as I should have, and I’m not entirely happy with that. I got a bit impatient once the text block was done, and just charged ahead…


Another issue with rushing ahead was that I used a bit too much glue on the endpapers, and they wrinkled a bit as they dried.


All things considered, I’m very happy with the way the book turned out, and I’ve got some different techniques to try next time.


Audible Donation Box

Our local library recently asked us to help them out with their summer reading program, which is raising funds to support the Willowbrook Wildlife Center.

Here’s what I came up with:Glen Ellyn Public Library Token Box


When a patron turns in a book they’ve read for the summer reading program, they get a token to drop into the box.  Since the Willowbrook Wildlife Center rehabilitates native animals that have been injured, I thought that playing local native animal sounds would help create a connection between the program and the organization it is supporting.

Here’s what the box looks like inside.

Glen Ellyn Public Library Token Box Electrionics


The speakers are driven by an Adafruit Music Maker Shield run off of an Arduino Uno, using the Adafruit VS1053 library.  The token detection mechanism uses a high-intensity LED and a voltage divider, consisting of an 180 ohm resistor and a CdS photocell, to create an optical detector.  The voltage across the small resistor is checked with an analogRead() in a tight loop to detect a token falling through the slot.  Volume control is done through software on the VS1053, so I just hooked the sweeper on a 10K linear potentiometer up to a second analog input.  When a token is detected, I play a random sound from the SD card in the background while continuing to check the volume control.

Here’s the schematic and a breadboard layout.  I’ve just shown the control circuitry, as the Music Maker shield should be pretty easy to hook up.Coindrop SchematicCoindrop_Breadboard

All of the code, these schematics, and a Fritzing file are available on Github. Pay particular attention to the pin assignments at the top of the sketch if you’re using the Adafruit Music Maker board.  They are hard-wired on the shield, but Adafruit’s tutorial is based on their breakout board, which you have to wire to an Arduino yourself.

One thing I had to consider with this build was power.  I initially powered the box off of 4 AA batteries, and it looked like it worked great.  After a few days of testing, it started to act a bit flaky.  After being on for about 10 minutes, the speakers would just play static.  After some testing, I found that the supply voltage was too low, so I swapped in a USB power supply for the batteries, and it worked much better.  Since this has to run all day long for a couple months, USB is a better solution anyway.

We’re teaching a couple audio classes this summer, make sure to check back for scheduling details if you’re interested in doing something like this project yourself!


THOTCON 0x5 Badge Revealed


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THOTCON  is the annual, small venue, hacking conference based in Chicago IL, USA. THOTCON is a non-profit, non-commercial event looking to provide the best conference possible on a very limited budget.

For the past 2 years Workshop 88 has been honored to design and produce the electronic attendee badges for the conference as a service to the local community.  The badge crew this year consisted of: Paul Reich, Bill Paulson, Karl Knutson, Zach Cassity, Russell Lankenau, and Rudy Ristich

This year’s badge was inspired by portable gaming systems from the past and featured  102 x 64 pixel graphic LCD screen and a push button interface. Once again, the badge features an Atmel AVR based microcontroller. The badge used nearly every byte of the 32k available SRAM on its Atmega32u4 chip.  The software consisted of a Break-out style game which participants could play to passtime, a complete schedule of talks and labs for the day long conference,  and the ability to patch into arcade panels hosted in the Hacker Village, and a few surprises for discovering inside.

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Just like the THOTCON 0x4 Badge, the 0x5 Badge is compatible with the Arduino open hardware programming environment and can accept standard Arduino shields. This means the badge can be easily reused and repurposed to power any sort of project. An improvement from last year’s badge is that no additional parts need to be added; conference goers can simply plug the badge into their laptop once burning a bootloader to reprogram it, encouraging easier exploration and badge hacking.


The badge is designed to be completely open hardware and software.  Workshop 88 would like to thank the open source hardware and software community especially: Arduino, Oliver Kraus and other contributors to the U8glib graphics library, Dean Camera for the LUFA Project, and last, but far from least: Twisted Traces, our local assembly partner in Elk Grove, IL.

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Workshop 88 will be holding a badge hacking contest throughout the month of May.  Judging will consist of a panel from Workshop 88 and the THOTCON crew.  Interested contestants can register on the badge website:

Full details on the badge specifications and firmware will be released on May 1st in conjunction with the opening of the badge hacking contest.