This post is for users of RD CAM, the software that typically comes with unbranded Chinese laser cutters.
When I laser cut 4mm birch ply, I use a jig to hold the sheet flat. I found this to be necessary as ply less than 12mm thick isn’t guaranteed to be flat, and the 4mm birch ply I have bought is particularly wobbly.
My cutting jig holds the ply clear of the table which means it is important to make the cuts in the correct order. If the cutter attempted to cut a hole in a part after cutting the part, the part may have dropped and so the laser would be out of focus. So it’s important to cut the holes first.
In theory, RD CAM is able to work out which parts to cut first. In practice I have found it can be easily confused and so I order the cuts manually. I use different colour lines for the cuts to be made first and order the colours in RD CAM.
It is necessary to configure RD CAM to use the coloured layer ordering. By trial and error (as the software’s manual is dreadful), I have arrived at a strategy that appears to work. First, click the “Cut optimise” tool bar button:
This opens the dialog:
Make sure the “Order of layer” check box is ticked and click “Ok”. In the main window move the layer colours up and down the list so the cuts to be made first are at the top.
If you’re just getting started with a laser cutter, you may be wondering what materials to buy. There are so many to choose from, it’s bewildering, and if you aren’t careful, you’ll spend a fortune. I’ve tried more different materials than I can remember and I’ve narrowed it down to what I think are the best three to begin with.
I’m assuming you want to do something more interesting with the laser cutter than engrave names and photographs on chopping boards. If that’s what you want to do, that’s fine, and I doubt you will be needing my help.
If you want to stretch a little to see how creative you can get, read on for my three top materials.
I’m assuming you have access to a typical school, college and small workshop cutter. Perhaps the machine takes sheets up to 600x400mm and the laser is 50W or so. Some (like mine) claim to be 85W which is an exaggeration. The lower power cutters of 35W or less may only be useful for engraving, lacking the power to cut anything thicker than cardboard.
MDF is cheap, stable, and the sheets will be flat if they are stored properly (which won’t be the case for plywood). MDF is available in a range of thicknesses. I think 4mm is the best choice. I found 3mm a bit too thin for finished products to have enough “heft” to them. Thicker MDF will ask a lot of your cutter unless you have serious power available.
MDF isn’t pretty. For purely functional items like jigs, that’s fine. For more decorative items, MDF can be painted. I have had excellent results using clay paint protected with furniture wax.
Wherever possible, buy laser quality MDF.
4mm birch ply
Birch ply has beautiful grain which is enhanced by polishing with furniture wax, Danish oil, Osmo Polyx or something similar. The ply is more difficult to work with than MDF as the sheets probably won’t be flat, even if thay are stored carefully. I cut 4mm birch ply on a special jig I made to hold if flat in the cutter. An easier ‘though less successful strategy is to tape the ply down to the cutter’s honeycomb bed. When making something like a box, choose the area of ply for the lid carefully. Find the area of the sheet which is flattest and has the most beautiful grain.
I have found 4mm ply works well for boxes up to 20cm wide. For larger boxes, I use 6mm poplar.
3mm birch ply is also available. As with 3mm MDF, I find this too thin for anything but the smallest projects. Thicker birch ply such as 5mm and 6mm is usually significantly more expensive than 4mm, and often difficult to source. I use 5mm birch ply to make hinges for 6mm poplar ply boxes as it is much stronger. My cutter can barely handle 6mm and I haven’t had good results. 5mm birch ply is usually more expensive than 6mm. Strange but true.
Laser quality ply is essential as it is made with a clean burning glue. Conventional ply will have blackened, sooty edges after cutting.
6mm poplar ply
Poplar ply isn’t as strong as birch, yet it is plenty strong enough for a large jewellery box. It doesn’t have the beautiful grain of birch. It stains very well. I have found the sheets to be flatter than 4mm birch and easier to work with. I don’t bother with my cutting jig for poplar, I lay the sheets on the cutter’s honeycomb bed.
You probably won’t need any more power to cut 6mm poplar than you need for 4mm birch.
For the light stain in this box, I mixed a small amount of purple stain with Osmo Polix oil. Used neat, the stain is very strong and dark.
The clip idea isn’t mine, this design using it is. These boxes are 10x20x6cm and are laser cut from 4mm MDF. I use them to hold small parts when I’m making lanterns etc. The clip mechanism is very satisfying. The box is ready for use immediately — no waiting for glue to dry.
Update: If you have access to a laser cutter, you can make these boxes/trays using the download project in my Etsy shop.
I made a series of tiny birch ply houses for an art project. I wanted the roof pitch to be 30 degrees and I wanted a nice join where the two roof parts meet. This meant cutting at an angle other than 90 degrees. I achieved this using a custom made jig.
I got side tracked by the Tiny Lantern project, but today I finally finished the key rings I made using my Engrave Both Sides technique. I’ll put these in my on-line shop next week. They will be £7 each. As you can see, there are several styles and colours to choose from.
Have you ever wanted to laser engrave both sides of an item? I was asked if I could cut some key rings and engrave both sides. My first thought was that it wouldn’t be possible. If your laser cutter is anything like mine, you won’t have any way to accurately position an item for cutting. My cutter has a LED cross hair projector which would get me to within about 6mm (roughly 1/4″) but no closer. Less than a millimetre out and the key ring would look terrible.
Then I had some inspiration: If I could cut two mirror image items, and engrave one side, I could use the cut outs to accurately position the items if I could keep the blank in exactly the same position. I think you could adapt this idea to laser cutting and engraving pretty well anything.
I got the idea of working with jigs in the laser cutter while watching a “Laser Origami” video on YouTube:
What I’m doing is completely different, but the seed of an idea of making a jig was planted. I made an MDF jig to hold a blank in place and cut two butterflies. Each is a mirror image of the other. The jig has feet which fit snugly into the holes in the laser cutter’s bed. I marked one corner of the blank. So long as I don’t move the X or Y axis until the job is complete, I can replace the butterflies accurately.
I put the butterflies back into the blank and hold them in place with masking tape. Then I defocus the laser by 4mm and engrave butterflies’ markings. Then swap the butterflies over and engrave again.
Cutting and engraving relies on the RD Works laser software taking the position of all the items in a job into account, even those that aren’t output. I created the two DXF files from one Corel Draw image — one with the blank’s outline and the butterfly outline, the other with the blank’s outline and the butterfly details.
I’m in the process of making a larger jewellery box in 6mm poplar ply. I chose poplar over birch for several reasons: 6mm birch ply is difficult to get, it is expensive and it’s at the limit of what my laser cutter can comfortably handle. The drawback of poplar is that the grain is barely visible and not nearly as beautiful as birch.
I think staining one wood to look like another wood is naff and I won’t do it. Staining wood a colour is ok for me and I’ve been experimenting with Chestnut Rainbow Colours. Chestnut’s web site looks like it fell out of a rent in the space time continuum from 1990 and I’ve never seen black in a rainbow. But the black stain, when heavily diluted, brings out poplar’s grain and looks great.
I diluted the stain 1 part stain to 12 parts Osmo Polyx oil and applied a very thin coat with a cloth. A second coat (drying a I type this) completes the finish.