Started making my flat clamp jig for cube carving

I was using the laser to etch 40mm cubes with the letters of the alphabet and everything was fine. I bulk ordered some cubes and was surprised to find that the laser worked well but could not make any impression on the wood where the hard annular ring wood was. The mock-up image shows an example of the end grain that was causing the laser not to burn the wood. The darker wood is the hard compressed ring of the tree. This was disappointing because I did not want to have edge burn or smoke staining by holding the laser beam longer over the tougher wood. Besides which; it was a natural part of the grain and with every block being taken from a different part of the tree, or even a different tree, it would be a very difficult task to plan a laser etched letter or number for the six sides of each block.

Enter the CNC carver. I have some doubts about finding the best carving combination between workspeed, endmill and a softwood like spruce. I still may end up just painting them as coloured bricks and leave the carving or etching to a much more even surface of wood. I like maple but that is a bit expensive for kids toys. Anyway, the next issue was that I used a jig to hold my blocks for etching. You can see them elsewhere on this forum.

A similar jig for CNC carving would not be useful because it could not hold the block very steady when it was being carved. I see that my blocks have a tolerance from a nominal 40mm of ± 2 or 3 tenths of a millimetre. Clamping a block for carving while allowing access to the endmill and ensuring that the bit does not crash into the clamps appeared to be an insoluble issue. I discovered some flat cam clamps and these will do the job if I can extend the jig beyond the 130mm square table of SM1and that will provide room for the clamps. The pattern that I hope to build is illustrated by the following mocked up image.

The flat clamps exert a cam mediated compression effect when tightened and as long as I fit a pair of cam clamps, and the cube sits in a cube holding depression, I should be able to hold the cube workpiece still enough for CNC carving. The first problem to solve is that the steel pins which the clamps revolve about have to permit the clamps to revolve freely so that the workpiece can be clamped and unclamped at will. The clamps occupy a lot of space and if this wood block were to be held to the table by cap headed set screws, they would obstruct the movement of the clamps.
I am going to hold the wood to the table using countersunk hex set screws. This will allow the clamps to pass over the screw fixing without obstructing the clamps.

The steel pins shown also need a lot of room to be embedded into the wood correctly (20mm depth) so that the clamp does not sit proud of the wooden jig. My piece of wood is American walnut and its dimensions are L200 x W150 x D40mm. This is a fair bit larger than the 130mm square bed that was supplied as standard with SM1. It will not matter as to engrave the cubes, the bed movement will be limited to 40mm on the ‘Y’ axis rail and the ‘X’ axis movement will be the CNC head moving, not the workpiece.

The next image shows the underside of the wooden jig affixed to the SM1 table. With the table screwed to the ‘Y’ axis rail, the wooden block sits next to the ‘Z’ axis rail. There is about 1mm of clearance space between the two so when the table moves along the ‘Y’ axis, it will not crash into the ‘Z’ axis rail. The excess of wood extending beyond the SM1 table (at the bottom of the image) will face towards the door of the enclosure. Because of the excessive length of this wooden jig, the door will have to remain open during block carving so that the jig does not crash into a closed door.

The last picture to show you is the top face of the jig. It is a beautiful piece of American Walnut wood made from glued blocks of wood 40mm in depth. You may be able to identify the centre mark which will be the set origin point of the CNC end mill. Soon, I will start to carve a 40mm square with easing points at the corners so that oversized tight blocks will not bind or be difficult to remove. The set screws are 45mm in length and are made from A2 stainless steel with an M4 hex fitting. The countersinking was completed and the heads of the sets screws are fixed to the corners of the SM1 table. The holes were moved inwards a little to prevent the wood from splitting when it was drilled and countersunk. The excess of wood beyond the SM1 table boundary is the piece that will face towards the open enclosure door.

The arrangement of the clamps (shown in the mock-up illustration at the start of this post) will require me to drill two 20mm holes that extend to a depth of 20mm. I have to wait until the 15mm deep cube holding square has been CNC carved and then I will know where to place my cam clamp holding pins.

That’s all for now. I hope to have a bit more to show after the weekend. All comments are welcome.

Would it not be easier to 3d print some screw clamps with screw holes in them that align with the holes in the stock wasteboard? your design is far more beautiful and I can’t wait to see it finished!

Possibly. I have no idea how to print 3D since I have not had my SM1 machine very long and I have not yet come to understand the 3D printing process. I have used the laser and the CNC aspect of the machine. The failure in the block etching was not understanding why the wood created an issue for me.

My solution was not to waste the 1200 blocks of spruce but to find another way to process them. My flat clamp jig is that method. It can do with a few tweaks but it is now complete and working.

I will include a few images to demonstrate. The first image shows the holes for the stainless steel dogs that the clamps are fixed to and these have been cut in the jig top. They were 20mm holes that were 20mm in depth and they were cut with a specially designed forstner bit. The additional space at the corners of the block holding square were to ease blocks that may have been oversized.

The next task was to add the clamps and try out the jig. You can see the block in the jig and the very snug fit it makes once the clamps are closed.

Once the jig has been attached to SM1, I use a centering block so that the end-mill bit starts at the centre of the block.

Carving a block was possible without the block being pulled out of the jig by the machine.

A carved block… very roughly carved but I was experimenting with a cutter and workspeed. All things being equal I would have expected the cutter to rip the block out of the jig if the cam clamps were not holding it.

More anon…

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ahh, i did not realize you were using the SM1. 3d printing is easy, make any 3d model that is smaller then your work space, then slice it, and print it. obviously there is a little more to it, but for the most part it is that easy. and your jig looks great! I hope some day i get good enough at tooling to build something that nice. i look forward to seeing your future projects.

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Thank you for the kind comment Adam. I guess the jigs that I have produced are the result of trying to find easy ways to reproduce worthwhile results. I will not give up on laser etching but will have to find a better material to use for the workpiece. I have just sourced some really nice paint for kids toys. It would be awful to make something nice and then have to paint it with something toxic. I may be able to laser etch again, if the paint is very opaque and covers in one coat. The carving really needs good material too. That American walnut looks fine but when machined, it tends to break into tiny piece rather than carve. I much preferred the maple I used for previous jig so I may redo this one.

I have some simple cars and trucks to make next, so very little Snapmaker work but my ears could do with a rest and my neighbours will thank me because my workshop is a shed in the garden. There is a lot of noise when carving and I think it is partly from the motor and possibly even more noise is coming from milling bits that are variable in quality.

Here, one can buy milling bits by the dozen for maybe £12. I have some suppliers listed who charge double that sort of money for a single end mill bit. I may try one just to see whether that will make a significant different to my machine carving. I am hoping to improve on my use of Luban too, which is frustrating piece of software which throws up variables and inconsistencies at just the wrong time. I have an issue reported in the Luban thread at this time.

There appears to be no runout from the chuck spinning but the bits every one of the supplied milling bits exhibit a degree of runout to some extent. This means that the side to side movement creates a form of machine induced chatter which creates noise and a rough edge to the machining.

i seen the rough chunking that you are describing in the picture. I will admit your talking tooling that is over my head. but is it possible the side to side motion you are describing (i take from the context this wobble is called runout?) is a result of moving the tool head too fast? it just seems like each chunk is out of the softer wood and the harder grain is left, similar to the issue you were having with the laser. i’m sure you have thought of that as you know far more about this then i do. mill bits here are varied so it would not surprise me if its a the result of sub-quality components.
also i must express concern about laser engraving over paint on objects intended for children, the high heat from the laser could cause toxic chemicals to form even from safe substances (the same way a vape pen turns vegetable glycerin into toxic carcinogens by exposing it to extreme heat), i would think it safe for kids that don’t put toys in their mouths, but it looks like the toys your making are for young children without such discretion.

i’d love to learn more as i may run into this issue sometime in the near future, so please let us know what you find out.

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Good points Adam; The feed speed is very slow to obtain the best finish. There are various formulae which tell you what the ideal feed speed should be and I am nowhere near overwhelming the endmill bit with too fast a feed rate. There are many calculation parameters for feed speed, material and bit type. If you ever want to make the calculations you can use this free application I have linked, which is web based, or you can download the application onto your Android or iOS device.

I think my fundamental mistake here was in not understanding the properties of the material when it was being worked. This is probably because my original laser work was more than acceptable and I was sidetracked by being very lucky and getting excellent results with very little input from me. A materials scientist would have seen these pitfalls long before I had considered them. I will try a different material and better quality cutting tools. It is a little frustrating but that is the nature of things and the process by which we all pay our dues and gain experience.

I had not considered the point about heating materials that are safe. I have every extensive data sheets on the chalk-based paints I have bought. I will write to the company and ask about its performance in a fire. I suspect that the legislation is so tight before products are awarded non-toxic status that they have considered the issues. In any event that will be my starting point. Thanks for the thought.