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project – CNC Maker Zone

Making miniature 1/12th scale fruit crates

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Sometimes it seems like there’s no end to the range of projects we can make with a CNC machine. And it’s quite amazing that even cheap versions are accurate enough to make miniature projects for model scenery and even dolls houses. So I thought it might be fun to try making some miniature fruit crates, as the photo above shows, and post the design here for anyone to have a go at making some too. At full size they would be around 450mm long, 300mm wide and about 200mm high but at 1/12th scale, commonly used for dolls houses, they’re much smaller: I’ve included a photo below with a one pound coin for comparison.

A photo of the miniature fruit crates with a one pound coin for scale

I’ve put an SVG file below for you to download, or you can click here to launch it in the GCoderCNC web-app. If you need to edit it, or make a DXF file for your CNC software, you can do that with Inkscape quite easily. The red box is there in case you need to get scale in your software, but doesn’t need to be cut: it should be 70mm wide by 65mm high for 1.5mm thick wood (or other materials such as plastic, or even cardboard, if you prefer). If you use thicker material you can scale it proportionately, such as 2x scale for 3mm thickness. The design works for LASER cutting but can be adjusted easily for routing by offsetting the lines through half the cutting width.The SVG file of the fruit crates for cutting or editing in InkscapeI LASER-cut a prototype in Oak (the one on top in the photo above) and the rest in Basswood, both from 1.5mm sheets. Once cut they are quite simple to put together. I started by putting the sides onto the bottom of the crate, then slipped the ends on one at a time. I also used glue at all the push-in joints: the base could be left floating but the glue helps prevent the thin pieces of wood at the joints breaking away when sanding. To finish the crates off I used 400 and 1000 grit sandpaper, including using a finger sander, followed by a couple of coats of Danish Oil to give the wood a nice look without too much of a shine. Personally I’m quite happy with the results and hopefully you’ll enjoy making some on your CNC machine too 🙂

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Cutting gaskets from EVA foam with a diode-LASER

One of the great things about having a CNC machine is that we can make very professional looking projects whenever we want to. So sometimes we’ll want to add those nice details that make a project stand out. Things like, for example, gaskets between parts. Recently I had a need to cut a couple of 50 mm square gaskets for a 3D printed extractor project, for which I chose to use commonly available EVA foam sheet. So I thought I’d write a quick post to let you know how that went with my diode-LASER and whether EVA foam is useful for low-power LASER-cutting on a CNC router.

As you can see from the photo above, my 5W diode-LASER module cut right through the sheet easily with the power set to 25% and a feed rate of 200 mm/min. I’ve cut EVA in the past with a 1500 mW LASER module too, so those settings sound quite comparable and show that low-power LASER’s cut EVA well. At those settings I didn’t find any burning of the foam, and the shape came out pretty much as planned with just a little shrinkage at the edges. Plus, as the photo below shows of the MDF sheet I cut the EVA foam on, the LASER energy left after it had passed through the sheet was small: although probably I could have used a lower LASER-power just as well.

A photo of the laser cut EVA foam gasket together with a photo of the limited damage to the underlying MDF sheet

If you decide to LASER-cut some EVA too, please remember to use lots of ventilation as the fumes are unpleasant: given the small amounts of fumes you’re likely to create you may be tempted to skip the ventilation, but be warned that there have been reports of some EVA foam containing chlorine, which could make the fumes quite hazardous. So please make sure the foam you use is safe for LASER-cutting and use plenty of ventilation just in case 🙂

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Finishing wood using Danish Oil

There are many choices for wood to use in CNC projects, and just as many ways to add a surface finish. But, whichever choices you make on materials and finishes the important thing is that we’re trying to bring out the beauty of the wood colour and grain structure. It’s perhaps one of the big joys of working with wood that it can start off looking really quite plain, even dull, but change completely with a little bit of loving care finishing it off. So, I thought I’d write a post about Danish Oil as I find it a very easy and effective way to bring out the traditional look of hardwoods.

A definition of Danish Oil is hard to pin down, as there’s no set recipe, but it’s usually around a third varnish and two thirds oil (click here to read more on Wikipedia). That means it needs to be mixed-well before use and dries hard, so can be used with or without a later clear-coat. It can also be bought with lighter and darker stains mixed in, to help give a variety of finish effects, so is very versatile. Personally I like to use the natural version, which has very little stain in it, to retain the natural beauty of individual bits of wood.

As an example, below is a photo of my routed Mahogany fish before and after finishing. After a light sanding (very important to open up the surface for a good oil finish) it had two coats of Danish Oil applied simply using a bit of cloth to rub it in. Once dry I added some gold enamel paint to the routed grooves to add detail and then the fish was very lightly sanded to remove over-paint and give a smooth finish. That’s all the finishing it had and hopefully you’ll agree that it looks a lot nicer than it did before.

A routed fish with and without finishing

Another example I can give is the photo below of my Walnut Darth Vader head routing project. The image on the left is before finishing and, even though the Walnut already looks good, it was rather plain. To get to the look shown in the right-hand image it had two coats of Danish Oil, and a light sanding when dry, to bring out the grain and the beautiful colours. The gold enamel paint was then added to the grooves, as doing it before the oil can make the gold look duller because of the small amount of stain in the oil (which sometimes can be a nice effect, but not for this project). I then gave it three coats of Plasti-Kote spray on clear-coat as I wanted a shiny finish. Then, a couple of red Swarovski crystals added a bit of sparkly bling to the eyes.

A Darth Vader project with and without finish

Hopefully you’ll have enjoyed seeing the hardwood projects above come to life using simple finishing techniques. If so, perhaps you’ll think Danish Oil something worth trying out on one of your projects too 🙂

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Routing Darth Vader from Walnut 1.5mm sheet

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Recently I bought some 1.5mm thick Walnut sheet as I wanted to try it out with my CNC router and see how good the results would be. Walnut is quite a dark wood with a nice dense grain, so it seemed like an excellent opportunity to take my CNC intergallactic by making a small inlayed Darth Vader from Star Wars. Hopefully George Lucas will approve if he happens by, so below is my completed Darth Vader head (at around 10% water content, in case you’d like to know).

The finished Darth Vader router project

I was quite pleased with the results, the details being routed to 0.75 mm deep in two passes, and the edge being cut in three passes, using the 1.2mm diameter end-cutting bit shown above (which gave finished grooves almost 2 mm wide). As the image at the top of this page shows, the Walnut sheet cut quite well and cleanly with the spindle at 1000 rpm and a feed rate of 50 mm/min to minimise potential breakage of the bit. The above photo is then after I’d given it some sanding with a fine grit paper, which took little work. Even sanding out the recesses with folded over sandpaper was quite easy, with a little patience. So overall I’m looking forward to some more small projects using this lovely wood.

If you fancy making your own Darth Vader head, whether in Walnut or some other material, the SVG file is below for you to download, or click here to launch it in the GCoderCNC web-app. And, click here if you’d like to see how this project turned out after some Danish Oil finishing.

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Holder for 12mm diameter LASER-diode module

I have a couple of 12mm diameter 1500mW laser modules and heatsinks, plus a cheap Chinese CNC router. However, fitting the lasers is difficult as the heatsinks don’t fit properly into the spindle motor holder. Also, the laser modules are 5V, whereas my CNC only provides a 12V PWM laser output. So, I designed this 3D printing project to hold the laser module and a small power step-down circuit that would fit properly in place of the spindle motor.

You can download the 3D printing files by clicking here, including the OpenSCAD file for customisation as modules, heatsinks and mounting holes may differ for your laser. Also, it can be modified to add a small fan if necessary, to cool the laser when used continuously for a long time. For anyone interested: the step-down circuit is just a 7805 voltage regulator with a 10uF electrolytic capacitor on the 5V side, because the laser module has its own driver circuitry. You can see it in the photo below. Surprisingly for a simple circuit, it seems to work very well so far with GRBL control, but please use that circuit at your own risk.

Inside the LASER holder

Finally, a couple of construction notes in case they help:

  1. I tied a knot in the cable under the lid for strain relief. As the knot is bigger than the hole in the lid, if the cable is accidentally pulled the knot stops it breaking off the circuit board.
  2. The disc part with cutouts is a spacer that sits on the rim above the laser module. It allowed me to keep the circuit, which I glued onto it, away from the module.
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Simple CNC fence for manual work

CNC routers are wonderful machines for cutting and shaping wood and other materials but sometimes there’s no choice but to use a router without computer control. For example, when trimming the edges of wood to size, or for using the router as a finisher with sanding drums. When that kind of work is needed I don’t want another machine: rather I want to use my CNC router for occasional manual feeding. To do that a fence is very useful, as it allows pieces of feedstock to be pushed past the tool/sander in a straight line. Not only can that help ensure edges are kept parallel, but it also allows creation of small mouldings with edge-shaping bits.

This 3D printing project is my attempt at creating a very simple fence system for my cheap Chinese CNC. The fence part simply slides into the groove along the top of the CNC bed, after light sanding to get a good fit that doesn’t wobble. However, for manual feeding we don’t want the fence to be able to move along the bed groove, so a part is included for a simple stop that can be used to prevent that happening. The stop connects to the side of the bed using a winged hold-down nut as shown in the photo below. You can download the 3D printing files by clicking here, including the OpenSCAD file for any adjustments you’d like to make.

The CNC fence in use

Hopefully you won’t mind if I finish with a word of caution. But, using a CNC router for manual feeding of materials brings risks you may not be experienced with. Probably two of the main ones are the dangers of having hands near your tool/cutter (which can be avoided using a proper push/feed stick) and extra dangers of pieces of tools and feedstock breaking and flying away (which can be largely avoided by feeding slowly and wearing sensible clothes and eye protection).

Another rookie error is to feed material with the rotation of the tool, which means it could unexpectedly get pulled through and shoot out like a javelin (I did that on a router table years ago and it’s amazing how fast the expelled material can be). Not only is that dangerous: it can even ruin your work. You may also want to wear ear protection as the sound level will be higher working close to the motor and tool. Basically, please be very careful and don’t take chances using the 3D models provided here 🙂

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Mounting a GoPro camera on a CNC machine

Sometimes it’s nice to make a video, even a timelapse one, of a project coming to fruition on a CNC machine. Maybe just as a keepsake, or to share, or even to make some educational Maker instructions. So being able to add a GoPro camera, or other camera that uses GoPro mounts, is something you may want. I did anyway, so the project shown above is a simple 3D printed mount that clips onto a 20mm-extrusion on the front frame of my CNC, which can be positioned right in-line with the work-bed centre.

It’s a very simple 3D printing project that doesn’t even need any support material, so shouldn’t be a challenge if you have access to a 3D printer. The files you can download from Thingiverse by clicking here, which include the OpenSCAD file in case you need to customise or adjust it. Once made you use it to fix on a sticky mount base like in the photo, for your camera arm to fit onto. And below is a photo of my GoPro session mounted on my CNC so you can get a better idea of how it works.

A GoPro camera mounted to a CNC frame

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Add Bluetooth to make your CNC wireless

Most cheap CNC machines come with a GRBL controller board that communicates with a computer using a wired USB connection. There’s no problem with that if you want a computer near your CNC, but a much more convenient way to communicate with it is over a wireless connection. That way you can keep your valuable PC well away from potential hazards or even use an Android tablet or smartphone instead. And the easiest way to do that is add a Bluetooth module to the GRBL board if it has serial connections available.

So a bit of manual reading, and looking at the boards’ circuit diagram, are necessary. You’ll be looking for connections for connecting wires to its positive (e.g. 3.3V or 5V) and negative (a.k.a. ground or earth), transmit (Tx) and receive (Rx) headers. Normally they’ll be on pins soldered into the board. Then you need a Bluetooth-serial module which are a few pounds/dollars on eBay or Amazon: I used a HC-05 which is commonly available. The module will need its name and communications speed set up first and I’ve put some tips on that at the bottom of this post.

Then the Bluetooth module needs a connection from positive to Vcc and from ground to GND, to power it. The Tx on the GRBL board goes to Rx on the Bluetooth module and, similarly, Rx goes to Tx. I’ve put a diagram below that shows how I wired my HC-05 to my Woodpecker 3.1 GRBL controller board, which is quite common on cheap Chinese CNC machines. Sometimes Tx and Rx connections are reversed on the Bluetooth modules, so if you have problems you can try swapping them over. And to make it easy to get started consider using female-female jumper wires (i.e. sockets both ends) for the connections, like I used in the photo above, before committing yourself.

Circuit diagram for an example Bluetooth wireless connection
Hopefully now your Bluetooth module will flash an LED when the CNC is powered, to tell you it’s waiting for a connection. If not, check everything carefully, especially your positive and ground wiring. If that’s OK you should be ready to pair with your PC or Android device and have fun doing wireless CNC’ing.

Setting up a HC-05 Bluetooth module with an Arduino

If you know nothing about microcontrollers then now is probably a good time to find a friend who does, or even try to talk an online supplier into doing the setup when you buy. However, it isn’t really very difficult if you have an Arduino as you just need to wire the HC-05 to it as described for the GRBL board above (see www.arduino.cc for help on your particular board). The code below can then be used to set the Bluetooth module to be called ‘CNC’ (which you can change) with a speed of 115200 bits/second. Most modern GRBL boards communicate at that speed but if yours is quite old, and uses 9600 bits/second, you can change ‘BAUD8’ to ‘BAUD4’ or simply remove that line. And then, hopefully, your HC-05 module is good to go.

void setup()
{
  Serial.begin(9600);
  delay(1000);
  Serial.print("AT+NAMECNC");
  delay(1000);
  Serial.print("AT+BAUD8");
}

void loop(){}

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Cutting white paper with a 1500mW diode-LASER

1500mW LASER diode modules are a very inexpensive accessory for cheap CNC machines, and are ideal for things like burning images and text onto wood. However, with a little care they can also be used for cutting thin materials. One of those materials that is likely to be widely used, especially when crafting or carding, is white paper. So I decided to see if I could cut some white paper, which was around 80 gsm (grams per square-meter) and came from a notebook.

Being white and fairly smooth it’s actually quite difficult to cut as it reflects a lot of the LASER energy. But with some care focussing the laser dot to be as small as possible, and adjusting the height of the LASER (as they often have short focal lengths so shouldn’t be too high), I was able to do quite a nice cut as shown in the picture above (100% power and 100 mm/min). Fortunately, the dot on the 1500mW LASER is quite small so I thought it could be fun to see how small I could cut out my dragon and the result is in the photo below: at less than 20mm wide the cut quality was still quite good.

A 20mm wide LASER cut white paper dragon

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