Beds and clamps (CNC) 😜

I am not sure if this is the best place for this post but if the moderators need to move it, you have my permission to do so. :laughing:

I started using my CNC module today just to get a feel for its accuracy and ease of use. I wanted to engrave 2mm plywood coasters that were 100mm square. I tried all manner of clamping the pieces and could not make the clamps work effectively for two layers of wood (4mm). I was using the second layer as a spoil board in case the milling piece broke through the workpiece.

I have noted how the clamps are used in many demonstration video presentations but found the clamping action somewhat uncertain unless there was far more of the clamp placed onto the wooden workpiece. I get the rationale behind the 90mm square limit and I thought that it could be resolved by having a few more tapped holes in the bed. This would permit a variable method of workpiece clamping that could allow more metal to hold the workpiece while keeping it outside of the work area.

The clamping method used is quite time consuming to get set up and to arrive at a satisfactory solution that holds the workpiece firmly enough… so that it does not move under the influence of the speedily revolving milling bit. I would like to see a development that permitted a holdfast type of clamp. I use them all the time for my woodwork workbench and they are super fast in use and very secure, especially for odd shaped workpieces.

So what I was hoping to promote was the idea that the CNC plate should have a few rows of holes in it. If they were as now and threaded, it would allow for some asymetric clamping options that would help with irregular workpiece shapes. If the holes were not threaded as now but able to take a clamp similar to the holdfast clamp illustrated below, the holdfast clamps can clamp a workpiece outside of the area of interest upon which one wants to work.

Your thoughts would be very welcome. :thinking:








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When I see thath right, are youre clamps wrong mounted on the first picture.

I’ve drill also new holes in the plate, to mount different parts or screw it from underneath.

Hi Benjamin; I deliberately mounted the clamps wrongly (as shown) in an effort to get the smallest area of clamp (that was compatible with effectiveness) to hold the workpiece. Mounting the square workpiece so that the edges were parallel to the base-plate would have required the clamps to be fitted diagonally from the corners of the workpiece, pointing inwards towards its centre. I would then have had much less room to machine the workpiece.

More holes drilled into the base-plate is one partial solution which I have considered and may yet undertake. (possibly Snapmaker staff would consider making an accessory base-plate that has been drilled and tapped with several well placed rows of holes; similar to the image of my workbench) I suspect that the base-plate could usefully have been enlarged so that even if the machining area had remained similar to the currently available dimensions, the base-plate would have created more options for clamping the work. It would have required a somewhat larger footprint for the machine so that the β€˜Y’ rail could have moved further to the right to accommodate a base-plate with enlarged dimensions.

I have a wish to laser etch some 40mm cubes on every face. To resolve the clamping issue I had decided to cut a jig which consists of a 40mm square machined into to it to a depth of say… 15mm, possibly more if that depth does not prove to be stable. The cubes I have were cut to reasonable tolerances for wood so they will all fit into the jig which I will use to find the centre of the base-plate and the cube. The idea is to etch the letters of the alphabet onto each of the faces of the cube. I wanted to be lazy and have a basic pattern where I could just change the text in Luban and then know that each cube would sit in the correct place for laser etching.

This has promoted an experiment where I cut a piece of wood to 130mm square and drilled a 4mm hole at a point which was 5mm equidistant from both the edges and the apex of the piece of wood. This means that I have enlarged the area that can be carved to around 120mm and the cutting bit will miss the heads of the screws. A refinement may be to counterbore the holes so that the heads could sit below the surface of the wood block. This particular option is only because I want to make a jig for a specific purpose. It could be a technique which is adapted to other workpieces providing the operator does not mind the finishing required after machining to remove or plug the holes made in the material for the screws. The attached image should be instructive.

Kind regards,
Jeff

Hi Benjamin. Further to my clamping issues; I purchased some assorted cap head screws that had a 3mm socket rather than the 2.5mm socket screws that were supplied with Snapmaker. The first image shows an assorted selection of 725 M4 screw, nut and washer pieces in A2 Stainless steel and the cost was minimal. Β£17.28 (20.42 CHF).

Potentially, I had wanted to use the low profile head variety of cap head but could not find any stock which was readily available. The alternative was to use the button head screws but I believe that the cap head offers a bit more security to the allen key, being deeper in the socket profile.

With my new assortment of screws I will substitute all of the supplied ones so that my 3mm screwdriver will fit the sockets very securely. I found that there is some play with the 2.5mm socket and they feel like they may become out of shape to me. The screwdriver blade sometimes gets stuck (possibly because it is permitted to revolve further than the flats in the socket) and this change should be beneficial.

The other image shows the clamps applied as required and they were very solid because they are now flat on the surface of the workpiece.

Kind regards,
Jeff

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