It can be quite fiddly fixing down a routing or LASER cutting project onto the bed of a CNC router. It’s even harder if you also want to align the material to the edge of the bed so you can align cuts with existing clean edges, or because you’re doing work over a number of sessions. So to help me quickly place lined-up sheets of plastic or wood onto my CNC bed I designed the small edge fence shown in the image below. It has to be 3D printed but takes up only a small amount of plastic and simply slides into the groove on the front or back edge of the bed-plate as the photo above shows. If you want to have a go at making some just click here to get the STL file (and OpenSCAD file in case you want to customise it).
Mahogany is a wonderful wood with fine, beautiful looking, grain. It’s ideal for any CNC routing project where you want to give your work a professional, and high-quality, look. So I thought it a good idea to write a short article about my experience of working with it on my cheap Chinese 1610 CNC machine. I decided I’d use a small (c. 50mm or 2″ long) fish design because it includes some shallow work for inlay, as well as a full-depth cut around the outside. The sheet was cut from a 1.5mm thick sustainably sourced plank and, according to my meter, had a water content around 9%. Below is a photo of the wood on the CNC during cutting.
As this was a small piece I chose to use a 1mm end-milling bit, so that the shallow details would look tidy. Bits/tools of that size are easily broken through overly deep or fast cutting. For that reason I cut in two passes for the shallow details and three for the outside cut-through, which equates to between 0.5mm and 0.6mm depth per pass. Also, I kept the feed rate down at 50 mm/min which, although a little slow to watch, usually keeps my small diameter bits in one piece. The spindle speed was the maximum of 1000 rpm which, together with the low feed rate, provides a nice clean cut in my experience.
As you can see in the photo below, after just a light sanding, including using a folded piece of sandpaper to run along the shallow grooves, the fish looked quite nice. The only issue I’ve found, if it can be called an ‘issue’, is that the cutting tolerance around the bit is a little more than I’d like: with a 1mm diameter bit I ended up with 1.5mm wide grooves. That’s a 50% overcut which, given the simplicity of the spindle system, and the amount of vibration, is probably technically not bad for a small tool, although it does cause some difficulties cutting thin grooves for things like hammered wire inlaying. Overall though, my experience is that Mahogany can give inspiring and impressive results.
One of the downsides of buying a cheap CNC router is that you’re left to your own devices when it comes to the best ways to hold down thin sheet materials like wood and plastic. Lucky then that there are plenty of designs online for hold-downs to secure your workpiece when cutting or engraving. On this page I thought I’d introduce you to two of my designs: one for edges and one for corners, both of which can be customised, if you have the need and knowledge, using OpenSCAD. Of course, making them means you’ll need your own 3D printer, an amenable Maker acauaintance, or a willingness to pay for 3D printing online.
Firstly, here’s a photo of my edge hold-downs. They have a small step-out at the bottom to hold the sheet above the CNC bed, so cuts can fall downwards and valuable cutting tools can be kept away from the underlying metal surface. They also have a sloped vertical face to help ensure the sheet doesn’t get pulled upwards. They also have holes and slots so they can be fixed to the bed using standard bed-bolts or some suitably sized bolts and wing-nuts. Click here to visit the Thingiverse page to download STL files for 3D printing and the OpenSCAD file.
While the edge versions are very useful, sometimes we’d rather hold down corners, either instead or as well. So below is my design for corner hold-downs. They’re very similar to the above design, but have a right-angle end to restrain the sheet on both the X and Y axes simultaneously. As for the edges, there’s a version for fixed corner positions (with a bolt hole) as well as one for adjustable corner positions (with a bolt slot) so they work with a wide range of sheet dimensions. To get the STL and OpenSCAD files for these you can click here.
If you’ve read my other Basswood LASER cutting tests you’ll already know that it’s a great material for use with a low-power CNC-mounted LASER. So I wanted to see how well I could cut 1mm thick Basswood with my 5W LASER. As the photo below of my single-pass cutting test shows, 1mm thickness provides little challenge for the LASER.
In fact, a single pass, at 200 mm/min feed rate, at around 70% power, is all it takes to cut through it. And it’s likely that the feed rate could even be sped up a little too. Plus, as the photo below shows, the cuts were quite clean and don’t require too much effort to clean up.
MDF (a.k.a. medium density fibreboard), just like plywood, is a very popular material in LASER cutting circles, largely due to it being a stable and relatively strong sheet material. Its stability comes from the use of wood fibres set in glue and means its less likely to bow or warp compared to plywood. So it’s likely any CNC user with a diode-LASER will want to cut a piece sometime. However, it’s important to note that burning glue, and released wood fibres, can be hazardous to your health. For that reason the MDF sheet I used here, with my 5W diode-LASER, is a LASER-safe version with less hazardous glue: although care is still needed to avoid inhaling anything nasty. Below is a photo of my cutting test.
The main thing the photo shows is that cutting fully through 2mm of MDF is possible with two passes, at a feed rate of 100 mm/min, on full power. However, a second thing to notice is that the MDF burned heavily (with a small flame) especially after the first pass had blackened the surface. That’s likely due to the glue and the slow feed rate needed for a low-power LASER. So care is needed to avoid fires and multiple passes will require a lot of work to clean up. Most likely cuts will need to be offset slightly when designing, so that the edges can be filed or sanded back to clean material, although back faces were cleaner as the photo below shows. Overall then, MDF may be useful for some larger, low detail, pieces, or for faster feed rate engraving, but on the whole it’s not something I’ll risk too often.
Basswood, like Balsa, is a go-to material for many Maker projects. Unlike Balsa, Basswood is a little lighter and denser and so has many uses in structural and non-structural parts of scenery and model making. So LASER cutting 1.5mm sheet Basswood is likely a common need. For that reason the photo below shows the results of a cutting test with my 5W diode-LASER attached to my CNC machine, with the wood having a water content around 8%.
All of the cuts are for one pass, so you can see that there are various options for quick cutting. personally I prefer to cut quicker to save time and slightly reduce surface burning, so a single pass at a feed rate of 200 mm/min, at a power between 80% and 100%, seems the best option for me. Also, as the photo below shows, the back is quite cleanly cut and not in need of a lot of cleaning up and sanding.
If you’ve searched the internet about laserable materials you might have decided that plywood is the most popular sheet material out there. And, you might be right which is no surprise given that it’s a very versatile material due to its strength and the solid-wood look of its surface. However, the glue used to bond the layers (i.e. the plys) together can give off noxious and toxic fumes when burned, and is also difficult for a laser to cut. Also, the glue and its thickness can vary around the sheet, making cutting potentially inconsistent.
That’s why using a LASER mounted on a CNC machine means we really need to make sure the plywood we use is LASER-safe. LASER-safe plywood has a special glue that reduces the fume problems and is easier and more consistent to cut. So, to see how useful it can be with my 5W diode-LASER I tested cutting a piece of 3mm thick LASER-safe Birch plywood. The results are shown in the photo above. I found that two passes, at 100 mm/min, around 100% power was successful at cutting right through.
However, probably due to variations in glue thickness, and some curving of the sheet (and maybe water content variations: my meter said 8% although it’s hard to be sure with plywood) for some cutting I find I really need three passes. Below is a photo of the back of the test sheet, which showed that cleaning up the burn marks isn’t a small job, but nonetheless isn’t so bad that it’s not worthwhile.
Sometimes it’s nice to push the boat out and work with a nice (but obviously sustainably produced) hardwood on a special project. Once the staple of work and school desks, and plenty of furniture, Mahogany is an obvious choice for that, having a lovely dense feel and beautiful grain. So I decided that I should test some 1.5mm thick Mahogany to see just how easy it would be to cut it with a 5W diode-LASER. You can see the results in the photo above.
As the photo shows, the LASER has no real chance of cutting through in one pass, but at a feed rate of 100 mm/min, at approaching 100% power, two passes did the job. According to my meter that was with a water content of 12%. However, it does leave quite a bit of charring to clean away, although, as the photo below shows, it wasn’t so bad that it could be considered a game-stopper.
So, as with many other materials, cutting a mirrored version, so that the back becomes the finished front face, could be a good option. But, to give a good idea of how well you can cut quite detailed items out of Mahogany sheet, here’s a photo of a 30mm high Santa figure I cut at 100% power, 100 mm/min feed rate and two passes. Personally I was quite happy with the results.
Basswood is one of the most versatile woods I’ve found for CNC routing and low-power LASER cutting. And, when starting out in the world of CNC Making, I think it’s one of the most exciting too. The reason I say that is that you get a ‘real wood’ feel and ease of cutting more than just thin sheet. Why bother wasting time trying to cut through a couple of millimetres of plywood, which really doesn’t want to be cut, when you can cut shapes out of 6mm Basswood instead!
So why do I praise it so highly? Well, for one thing it lets you use thick and thin wood to make whole structures quickly. Also, it allows for easy cutting out of routed designs. Mostly though it’s because it significantly extends what you can do with a low-power diode-LASER setup on a cheap CNC machine. And above there’s a photo of my cutting test to show what’s possible with this wood which, according to my meter, had a water content of 11%.
Obviously it takes quite a bit of work to cut through a whole 6mm, but as the photo shows it is possible with three passes at 100% power on my 5W LASER. Also, the quality of the cuts was much better than I’d expected, meaning it’s possible to make some nice, fairly detailed, parts from fairly thick wood. Below is a photo of the back of the cutouts and, as you’ll see if you look closely, the back should be ready to clean up without too much effort sanding, which is a nice bonus.