This small write up is offered in the spirit of trying to inform other new users about ways to use Snapmaker. My first project was to produce laser etched wooden alphabet blocks that would suit a pre-school child. Please forgive the length of the posting. It was written to be useful.
Up until the end of March this year, I was happily working within the National Health Service in the UK. I had done so since 1976 and had trained to work in trauma and orthopaedics. I would have continued to work but as the COVID-19 crisis took hold, I was told that working would expose me to more risk than the hospital authorities would accept. I am almost 72 years of age and I had to accept my early retirement with good grace. I used some of my salary to buy a small shed and install some woodwork tools. Otherwise, I would probably have been climbing the walls with nothing to do. I also bought a Snapmaker original and this is where the current journey began.
I have owned my Snapmaker original for about three weeks and have been slowly getting to grips with it as I am new to all of the skills required. I thought that I would take on a clearly defined project just to learn what is required and to see if I could produce any work of a reasonable standard.
I decided to make alphabet blocks in wood because they often serve as a toy for pre-school children. I thought that it would be useful to detail the thought processes and the practical considerations that were necessary to start, work at the detail and complete the project. This is not intended to be a technical discussion because I have insufficient knowledge to make it such. It is aimed at relatively new people to Snapmaker and the people who inhabit the world of making via 3D Printing, laser etching and cutting and CNC carving. I hope that readers will find it an entertaining read and also useful.
The project and some of my thought processes
I thought that alphabet blocks would make a suitable beginner’s project because wood is widely available and not too expensive if any mistakes are made. It also has the considerable advantage that it is biodegradable and does not use plastics. What was less clear to me was the sort of wood which was going to be good to machine and easy to buy. In the end I settled for pine from a renewable source.
My machine tools include a bandsaw, a belt/disc sander and a drill press. In hand tools, I own a lot of measurement and marking tools, chisels, mallets, hand saws, a smoothing plane, various screwdriver blades to fit a universal handle and blade sharpening tools. I considered buying wood that was planed all round (PAR) so that the surfaces were pre-finished.
The advantage of such wood is that the sizes are very accurate but the cost increases because of the processes of storing and planing the wood before it is sold. Transport is an issue because wood is available in lots of sizes but they are generally in pieces which are too big and heavy to move with a domestic car.
Cutting and planing the wood seemed to be a good option And I chose to take that option just on that ground alone. The secondary issue is that my machine tools are really only hobby class and getting wood finished to close tolerances is not easy without commercial quality machinery.
I could not afford to buy industrial quality machines and neither did I have sufficient space to put such items. I can cut a reasonably straight line with the bandsaw but the blade inevitably leaves saw marks that would need a lot of finishing techniques to remove them. This would have an impact on the finished size of the block.
My belt/disc sander is ok for rough finishing but fine finishing to close tolerances is beyond its capabilities because of the lack of accuracy inherent in the basic quality tables and mitre fences. The decision to work with pre-finished wood at its final finished size meant I could be free to concentrate on creating the blocks without being concerned for the finishing processes.
The next series of decisions required some thought as to the size of the blocks, the number of them that would make a ‘set’ and the actual content to be written on them. I chose 40mm as the size that would fit a child’s hand easily and would not be too small to become a choking hazard. I researched various finishes of wood but finding finishes that are certified as non-toxic and child safe was a time consuming pursuit. I decided to leave the blocks in their natural wood finish.
Each block has 6 faces to etch and I decided that 20 blocks would permit as many as 120 symbols to be engraved on them. It would be a manageable set and not be too heavy for a child to carry around. At this point I decided that making a box for the blocks was an unnecessary complication so I opted to use a cotton bag that was created in the style of a rucksack. It had double drawstrings that would keep the blocks contained in one place. Natural unfinished wood and unbleached cotton fits better with today’s heightened environmental concerns and an increased emphasis on not spoiling planet Earth.
I looked at the characters and symbols that would be required and then tried to work out a sensible distribution of characters. I had a rough plan but decided to consult an authority on English letter frequencies. With 26 letters in the English alphabet I needed some help. 20 cubes would yield 30 spaces for each of four sets of five cubes.
One full alphabet would use 26 spaces and leave the 4 spare faces on the last cube to be used for vowels. I added ‘A’, ‘E’, ‘I’ & ‘O’ to set 1. Then ‘A’, ‘E’, ‘I’ & ‘U’ was added to set 2. Set 3 excluded the uncommon consonants J, Q, X, & Z. The consonants B, K, P & V were added once to set 3 and all other consonants were added twice.
Set 4 consisted of 5 blocks containing numbers 0 ~ 9 twice and arithmetic operands plus, minus, multiply and divide twice, along with 2 sets of the equals symbol. That was the method for deciding how the 120 faces would be filled and result in 20 cubes that could be used to spell a variety of words and carrying out simple arithmetic.
The CNC function of Snapmaker is limited to a size of 90mm. I presumed that the limit was to do with the practical implications of having clamps holding the workpiece and eating into the working space. Clamping individual blocks was not going to be easy and even though the laser etching benefits from a wider working area (125 x 125mm) holding a block in place needed to be considered.
I experimented with the laser etching process and holding the workpiece with masking tape. It worked to a degree but was not really a practical proposition. I needed the blocks to be placed in the same location and held in some way while they were etched by the laser beam. I decided to make a jig and used the CNC carver to cut my 40 x 40 x 10mm location jig. I had cut this jig using clamps and because I connected my computer to Snapmaker, I was able to ‘run boundary’ to ensure that the clamps would not get in the way of the endmill.
I cut my square one millimetre deep and then found that the round corner could not hold my perfect 40mm cubes. I used a chisel to cut away the excess material and then the cubes fit well. I could place different cubes in the jig and know that they would all occupy the same space under the milling bit. All six faces of each cube had to be presented to the endmill so accuracy of placement was a crucial issue to get right. In the end I made the jig 10mm deep for a more secure hold on the workpieces.
Every block was etched according to the pattern described previously, with a careful eye being kept on the proceedings throughout. I found the computer cumbersome when it was sitting on top of the Snapmaker enclosure. I chose to use the software to write the files to a USB stick and found it very convenient to use. Working from the USB stick forces you to think clearly and precisely about the task you are expecting Snapmaker to complete.
The blocks are beautifully etched and the product gives off an air of high quality. It was this exact look that I wanted to produce. I find it helps to pre-visualise what you want to produce before setting out on the task. The blocks look much like I had thought that they should look and I am happy.
I made many mistakes along the way but they were all used as experiences to enhance my meagre knowledge. Mistakes could loosely be divided into those mistakes where a lack of knowledge contributed to them and those mistakes that were caused by thoughtless actions which then required a repeat of the activity.
One mistake that I have made on several occasions is that of the workpiece speed. This has ensured that the workpiece is moved too slowly for the method used to create something. Carving a simple 40mm square by 10mm in depth has taken a whole day!
The first cut is carried out a good working speed for the material and the endmill used. The second cut is along the same path but displaced by a very small amount. I have no idea how to set that amount that the endmill traverses sideways. This would help to cut the creation time of 10 or more hours.
Cutting the first 40mm square had to be repeated. This was because the square was actually measured at 43mm. I had forgotten to take the 3mm dimension of the endmill piece into consideration. My next attempt was a success and had ended with my 40 mm square.
I had not realised that the 40mm pre-sized and finished cubes would still require some finishing. I had to very lightly run a very fine grit (800) sandpaper across all of the vertices and edges of each cube. This removed the very sharp edges and corners which would be unacceptable in a children’s toy. The touch was very light so that the cubes were not misshapen by the activity.
When using Snapmaker from a USB stick, I had assumed that when one jogs the laser module to the desired centre of the work and it states “origin saved”, that is what it means. Not the case. My newly cut jig was a little tight where some of my supplied blocks were just on the size tolerance. This sometimes led to the Y axis bed moving slightly. I had assumed that the saved origin referred to the position of the module but it does not seem to recognise where it is and the start of the saved origin is based upon the table position.
This led to some blocks being etched in the wrong position. I suspect the use of the origin should be clarified and that it should be inviolate. That is to say that when the origin has been set, the machine cannot override that position for any circumstance. I guess that will be a software adjustment.
I don’t know why but the original setting of 50% laser power seemed fine to me and then it seemed to be excessive on some blocks so that the image was darker and there was smoke staining of the wood. I cut the power back to 45% and the staining was no longer evident. Because many of the initial engravings were fine, I suspect that some process was responsible for changing the power setting and increasing it. This may be another example of setting persistence in Luban. At the very least it ought to remember the last settings used so that the operator has a known starting point.
This short review is accompanied with some explanatory images.
The image shows the template of how I selected which characters to engrave on the blocks. I divided my 20 blocks into sets of five and then I used a checklist to show me which characters had been used and which remained to be engraved.
The jig which I created to help me locate the blocks is reproduced below.
The jig was made to dimensions of 130mm square and the holes were drilled 5mm from the jig edge so that the screws would fit into the Snapmaker table corner holes. No clamps were required as the piece was carved in situ. The corners created by the round endmill bit were eased with a hand chisel so that each block could be dropped into the jig and the operator (me in this case) would know that the jig was in the correct place.
Next are some pictures of the project on the grounds that one picture is worth 1000 words…
A sack of bricks. The sack is a cotton rucksack which should assist a child with storage and carrying the bricks.
The bricks sitting on the rucksack in the sort of image that may promotes sales.
Close up shot of a pile of bricks to make them look more desirable.
Demonstrating that there are enough letters to spell words
Showing how the numbers appear in the set.