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materials – CNC Maker Zone

3D printing with wood-infused PLA filament

Working with real wood is always exciting, but not everyone has a CNC machine for cutting and carving. And given the limitations of small desktop CNC machines, generally with only three axes, there are many times we can find ourselves wanting to make something with wood that isn’t going to be possible. So, for times just like that, I was excited to go and buy some wood-infused 1.75mm PLA plastic filament to use with my 3D printer. Wood-infused filament promises to allow 3D printing of complicated shapes while ending up with a part that looks and feels like wood.

For anyone who hasn’t heard of it, wood-infused PLA is a mixture of normal PLA combined with finely-ground wood powder. Ratios vary but generally around two-thirds PLA to one-third wood. Colours also vary, but mostly you should be able to get at least light and dark varieties, sometimes even ones limited to a specific species. The version I bought was a light-wood shade no-brand Chinese filament I picked up on eBay for fifteen UK pounds for a kilogram reel, so quite inexpensive. It was described as PLA infused with recycled wood powder, making the material doubly environmentally friendly.

To test the filament I needed a 3D model to print that would be virtually impossible to produce with my 3-axis CNC machine. I decided on a 3D scan I did of an eagle carving I bought in the Philippines in the 1990s, which I scanned with an XYZPrinting hand scanner v1.0A. In case you’d like to try printing it yourself I’ve uploaded the STL file to Thingiverse (click here to go there). The filament instructions stated a temperature of 180-200°C so I was able to slice the model in Cura and produce G-Code using the same settings I use for generic PLA. The results, before and after removing support material, can be seen in the photo below.

The eagle carving 3D printed with and without support material
The eagle carving 3D printed before and after removing support material.

Probably the first thing you’ll have noticed is that the print is quite ‘stringy’ where the nozzle hops between different areas. Probably that means I should tweak the retraction settings when slicing, but actually (compared to generic PLA and especially TPU anyway) it was very easy to clean off using just a small metal nail file. In fact, this was the thing that struck me most when cleaning up the print: the wood-infused plastic is very easy to sand and file to a nice finish. If you’re used to hours of effort filing, sanding and priming PLA prints to get them smooth you’ll likely be overjoyed to sand wood-infused filament! However, I should caveat that by mentioning that this filament was also more brittle than ‘normal’ PLA: in fact one of the prints cracked across the legs (where infill, set at 25%, was probably too low to give enough strength) during sanding, so care in slicing and finishing is required.

As for the print being faux-wood, well it does have the look of a very fine-grained wood. And, after sanding the surface does feel a lot like you’re holding a soft wood. The layer-lines in the print do add a little of the look of wood, but for the eagle carving I think lots of parallel lines throughout the whole height is a giveaway that this isn’t ‘normal’ wood. But if you’re not inspecting it closely the print could blend in with other wooden items on a shelf. So I wondered, would using a wood-infused filament with an oiled or stained surface add to the effect. To find out I tried oiling an eagle using natural-colour Danish Oil and another with a Brown Mahogany water-based stain, as you can see in the photo below.

An eagle carving after finishing with Danish Oil (left) and water-based stain (right).
An eagle carving after finishing with Danish Oil (left) and after applying water-based wood stain (right).

Compared to my other tests using Danish Oil, I think the results were a little subdued. Because the wood particles are suspended in a larger amount of plastic I suppose I shouldn’t expect the oil to soak in very much or have much effect on colour. And the oil did seal the surface and give a little of the effect of an oiled wood. It even felt a little like handling wood afterwards too. The stain was also quite effective and looks quite good from a distance, but close up you can see the layer-lines where the stain has soaked in more. And the stain was difficult to apply evenly as it just runs off the surface, so some time in the future I’ll try this with an oil based stain too for comparison.

So, after the above do I think wood-infused PLA is a useful alternative to using real wood? Well, in retrospect I was a little disappointed, but only because the prints lack the look of wood grain and, because of that, lack the ability to be finished using normal woodworking techniques intended to bring out the grain. That’s more a reflection on my expectations though, rather than on the material itself. In fact, for making complex objects the filament did a good job of making the best of a very difficult job I wouldn’t be able to do any other way. It was very easy to clean-up and sand the surface to a smooth finish, and without looking closely it gives a nice ‘wood-esque’ effect. So, yes, I think wood-infused PLA is a very useful tool for some interesting projects, either on its own or as a part of larger wood-plastic composite objects 🙂

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Choosing a wood finish to enhance colour and grain

After all the love and care we put into our CNC projects their success often hinges on how well we finish the exposed wood surfaces. Sometimes we may just want to leave them plain, even unsanded, but usually we’ll be wanting to bring out the colour and grain structure to show off the beauty of the wood we’ve chosen. So what is the best way to do that? Should we just cheat and use clear-coat, or should we use traditional techniques like Danish Oil or Shellac sanding sealer? How much work is involved varies a lot depending on which we choose, so is the best way the one that involves the most perspiration, or can simple ways provide more inspiration?

To try to answer some of those questions I decided to do some tests with six of my favourite woods: Basswood, Oak, Cherry, Walnut, Mahogany and Birch plywood, as shown in the photo below. I then decided on four finishes: plain unsanded wood (A), Plasti-Kote aerosol clear-coat (B), Danish Oil (C) and Shellac sanding sealer (D). The last three were all done in two coats and after light sanding with 400 and 1000 grit sanding paper/pads. I think one of the most interesting things the photo shows is that all three surface finishes, even the simple spray-on clear-coat, enhanced colour and grain significantly.

Comparison images of the six woods before and after applying surface finishes

The unsanded woods (A) were obviously a little plain and dull, but still nice for many uses. The simple clear-coat (B), however, was much more interesting as it’s a very simple finishing process yet brought out the colour and grain structure very well. The main comment in comparison to the other finishes is that it gave a slightly darker look to the wood, although not in an unpleasant way. In comparison, I think the Danish Oil (C) gave a slightly nicer look to the grain, as well as bringing out the colour of the wood beautifully. Probably that’s due to it being mostly oil (see my post here) and so likely soaked deeper into the wood surface before hardening.

The sanding sealer (D) also gave a nice finish, although it was slightly duller. That’s not surprising though as its’ purpose is mostly to provide a sealed surface that can be lightly sanded smooth before applying other coatings. In the past I’ve used it with a finish of wax polish for a traditional look, and I think that would work well with the results here. The only other thing to note is, for me anyway, that the finishes improved the plain colours and grains of the Basswood and Birch plywood, even giving them some of the look of pine which could be useful for many projects. However, for a more exciting look they may benefit from a little wood stain/dye: in the case of the Danish Oil that can include darker oils that are commonly available.

Overall, I think the main conclusion from my tests is that simply applying a synthetic clear-coat to a carefully sanded wood surface is just as effective as more traditional techniques. Certainly it enhanced the colour and grain of all of the woods as well as giving an extra level of darkness if that’s what you want. Of course, using the other, more traditional, techniques gives subtly different effects so they still have a role to play and can be used with a final clear-coat too for some nice effects. Really it’s all down to our judgement, but without any need to feel guilty that using a cheap and simple clear-coat is cheating: in fact it’s a useful technique that compliments traditional finishes very nicely.

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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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Cutting 1.5mm Cherry wood with a 5W diode-LASER

Cherry is one of those woods we all recognise, mostly by the distinctive colour and beautiful grain. We’re likely to find many uses for it in CNC projects, so I decided I wanted to try cutting some 1.5 mm Cherry sheet with my 5W diode-LASER to see how easy it would be. As you can see from the photo above, the Cherry sheet (with a water content around 9%) was actually quite easy to cut through with a LASER, on a par with similar tests I’ve done with Basswood, Walnut and Oak. The photo below shows the back of the cuts and it’s obvious that too much power, either from a high LASER-power or multiple passes, leads to considerable charring. However, for my use one pass at 75% power, and a feed rate of 100 mm/min, seem to give quite acceptable LASER-cutting results.

The back of the cherry sheet after laser cutting

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Cutting 1.5mm Oak with a 5W diode-LASER

Oak is a widely used wood that crops up time and again in things like furniture and traditional building techniques. It has a distinctive look and feel, making it something that we’re likely to want to use in a CNC machine sometime. So I decided to try cutting a 1.5mm sheet of it with my 5W diode-LASER mounted on my CNC. The results are in the photo above and you’ll notice that it was relatively easy to cut (much easier than, say, Mahogany), with one pass at 75% LASER-power and a feed rate of 100 mm/min being useful settings for future cutting work. As you can see in the photo below, using a higher power, or multiple passes, can result in more charring around the edges. The Oak had a water content around 11%, after being kept indoors for a few weeks, so wasn’t overly dry or damp.

The back of the laser cut oak sheet

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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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Cutting 1.5mm Walnut with a 5W diode-LASER

Walnut is a beautiful and widely used wood that should enhance any CNC project. For that reason I was quite keen to see how well my 5W diode-LASER can cut through a 1.5mm sheet of it. Obviously thicker sheets are available but for small projects I find thin sheets are very useful. Besides, cutting thin sheets gives a good idea of how well we can cut thicker ones too. The sheet I used here had a water content of around 10%, according to my small meter, so the results were likely not too affected by the wood being overly dry.

So, above is a photo of my cutting test at a feed rate of 100 mm/min, which I find a sensible speed for a low-power LASER on a small CNC machine. I was quite surprised as it was much easier to cut through 1.5mm of Walnut than for the same thickness of Mahogany. In fact, it was cut cleanly through at 80% power in just a single pass. It also didn’t burn excessively or flame, which was a bonus making it easy to work with. And, as the photo below of the back shows, it cut with fairly minor cleanup work required.

The back of the walnut laser cutting test

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Measuring water content in wood

The water content of wood we use in CNC work is obviously important for many reasons. One is that the quality of router cuts, and the depth of LASER cuts, will be adversely affected if the wood is wet. Also, and maybe more important, is that wood will change length as the water content changes, and as different woods shrink and expand at different rates that can lead to a nicely finished project coming apart over time (or even a lovely finish cracking). And it can have some bad effects on some finishes causing slow drying or cloudy clear-coats. For those reasons I decided to invest in a moisture-content meter so I can get an idea of how dry my wood is before using it, as well as to let me monitor changes as the wood acclimatises to indoor life before I cut it.

The one I got was only a few pounds on eBay so I’m not expecting really accurate readings, but testing some thin wood sheets at home I’ve been getting sensible readings between around 7% and 12% so hopefully it’ll be useful. Using it is very easy once set to the wood mode: the two metal pins are pushed into a non-vital area (end-grain is a good place too) like in the photo below and, after a moment, the reading appears on the small LCD display. Personally I’m quite happy with it and with a little luck it’ll provide me with a good idea whether my wood is too damp to want to use and let me monitor it to make sure I know when it’s ready for a project.

Measuring water content in wood with a moisture meter

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