Episode 115 Here be Dragons CNC

Multiple Materials

I’ve been trying out some different materials on the CNC, using some of the other router bits in the Toolstoday.com Master Collection.

Using the 51411 “Spiral ‘O’ Flute” upcutting plastic cutting solid carbide bit, I tried a bit of polycarbonate.  This is 3mm thick, which ideally suits the plans I currently have.  I started with some clear, to try it out as much as anything.  I slowed the feed rate down (given I am currently restricted to 12000RPM), then slowed it down further.  I found it ran pretty smoothly at 10mm/sec.  I plunged at the same speed, but for future reference, ramping the bit down should be a better approach.  With a 1.5mm depth of cut, things worked pretty well.

dragon-1My next endeavour will be to approach the same model again, but choose different materials for the different components.  So far I have about 4 different polycarbonate colours (one being fluoro), some aluminium and brass in the design.  Hopefully it will all work together and not look too mismatched.

Clear red poly for the flames, aluminium for the nostril smoke, and for the centreline of the body (up to and including the tail), brass for the small plates on the underbelly (like Smaug and his gold-encrusted hide), and a combination of solid green poly and fluoro green poly (for the scales, and head).

Work in Progress

While I wanted to wait until the project was complete before showing it, I have just finished a mammoth step, so decided to share the progress.

Starting with a slab of American Walnut

DSC05827It has been resawn into two pieces, and joined together to create a slab of the required width

Then, after 24 hours of solid routing on the Torque CNC

DSC05838And a quick initial application of Danish Oil (as much to find where I need to do additional sanding), the result is starting to show some promise. (The gauges are only to test fit, they will not join the project until it is pretty much complete).  The top station (the celtic design within a circle) is not just decoration, it will also be a clock.  The gauges are all high quality German-made ones I bought from Carbatec.

DSC05849Exhausted getting this far, and I still have to have it finished by Sunday!!  And tomorrow is a day away from the shed :(

Big push at the end coming – how unusual………

A logical conclusion

Using the same steps discussed in the last entry, I have taken a vector drawing of a Celtic Cross (created by “CarveOne” on the Vectric Forum), and produced a 3d rendering of the design.

This is the first time I have really tried using multiple paths on the same object.

The first pass was a roughing pass – used to remove as much of the unwanted timber as possible with a strong router bit, and higher feed rates to perform the task quickly.

DSC05816For this I used the 46294 3D carving bit from Toolstoday.com  It has a Zirconium Nitride (ZrN) ceramic coating, so this bit is also appropriate for routing in aluminium, brass, copper, cast iron and titanium alloy.  It makes very short work of the camphor laurel!

DSC05818There wasn’t a lot of material that needed to be removed, but it is still a worthwhile step to minimise any unnecessary load on the finishing step (and router bit).

DSC05820The final design was then carved using the 46282 3D carving bit.  This has a 1/16″ diameter tip, so can really get into the details.  Even so, there is a bit that is even finer, if even more detail is required (with a 1/32″ round nose tip).

I was using these at around 80mm/sec.

Once the design was cut, I swapped over to a solid carbide 1/8″ upcut bit to first cut around where the gaps were meant to be inside the design, and then to cut around the outside, down to about 12mm deep.

DSC05822For a sense of scale, the cross is about 300mm high, and 200mm wide.  Straight off the router bits, there is no need for sanding where the carving bits have been.  There is a bit of feathering on the outside of the cut out, but that is both a function of the timber, and insufficient router bit speed.

I deliberately didn’t cut all the way through the timber, so there was no need for tabs to hold the cut pieces in place.

To release the cross from the surrounding material, I turned the whole thing over, then ran a basic flattening profile on the back, taking off 2mm at a time with a surfacing cutter – using the RC2248 replaceable tip cutter.

DSC05825

Once this cut down to the required depth, the cross was released.

Each project presents different challenges, so I get to know more and more about how to use the CNC router effectively, and how to incorporate it as another workshop tool.

I had a look back at some tests I did on the CNC Shark using 3D carving bits – the finish I am achieving here is chalk and cheese compared to my early experiments.  I don’t know if I can attribute it all to the platform, but having such a solid, heavy duty CNC router certainly is not harming the finish that I can now produce!

 

Celtic Knot

I’ve been working on becoming more familiar with Vectric Aspire, which is used to both create objects (including three dimensional ones), and turn existing designs into the code required for the CNC machine.

In this case, I wanted to work out how to make a celtic knot design.

3To start, I have defined a sheet of material 600x900x16mm.

Next, under “Gadgets” there is an option for a “Celtic Weave Creator”

4This creates a vector that can then be used to generate the 3D pattern.

5I have also placed a border around the outside.

Next, under the Modeling tag (the 3D section), click on the extrusion tool.

7By using the existing selection, and a small curve vector (not shown), the 3D object is created.

8It shows starting points, paths and how the paths are dealt with when they overlap.

10By first choosing the 3D Roughing Toolpath and a larger bit to waste away as much material as possible,

11 then the 3D Finishing Toolpath with a ZrN tapered ball carving bit for a final pass.

FWIW, I am slowly entering the CNC router bits I have into the Tool Database.  No point having tools in there that I don’t have.  I’ve been including the router bit number (all being Amana Tool CNC router bits) so I can reference back to the Toolstoday.com website to confirm spindle and feed rates, especially for different materials.

13Finally, with the path calculated, the simulator is run to see what the program predicts the outcome will be.

14Looks pretty good!  I wasn’t going for anything particularly artistic, or complicated here – just learning the basics. All very interesting stuff.

Swiss Cheese

Slowly perfecting my processes, in this case for what is called a profile cut, where the object’s outer border is defined and the CNC router cuts the shape out.

I’ve been using a 1/8″ upcut solid carbide router bit – the 46100 from Toolstoday.com for the job so far, but knowing that it is not the correct router bit for the job.  What I should be using is something like the 46184 1/8″ solid carbide compression bit, or the 46180. (46237 and 46227 are also interesting bits, being 1/16″ diameter, which would be needed if doing nested work in 3mm MDF.)

Few reasons.

1. An upcut bit produces a lot of tearout in MDF.  While I can easily fix this with a quick sand of the top surface before removing the sheet, it would be preferable to avoid that step.

2. The upcut bit, especially at speed and with a large depth of cut, tries to lift the material being cut.  MDF is not a stiff structure, especially in a nesting situation which really turns the board to Swiss cheese.  It becomes almost impossible to stop the board being lifted, so I had to increase the number of passes from 2 to 5, and even then had a few lifting problems.

Not a fault of the router bit, I’m just using it as I don’t have another one of that diameter (or smaller) to work with 6mm thick boards in a nested layout, especially where I need grooves cut in the workpiece that are 5.9mm wide so they can slot together.

I’m cutting at 80mm/sec, and with about a 2mm depth of cut (DOC).  I know the CNC machine and the router bit can easily handle a lot more DOC, but my holddowns cannot keep up.  If I had a vacuum table, or even used a fair amount of double sided tape, that would be much less of an issue.

To stop the individual pieces being cut loose and walking into the cutter, wrecking them, I added tabs to each piece generally 2-3 per piece, 4mm wide and 1mm deep.  These are easily cut and sanded away at the end of the job.

It is important to ensure the cut goes all the way through in that final pass.  I have been using 0.5mm, but am thinking 1mm would work better.  Certainly, that means the router bit is cutting all the way through and partially out the other side, but that is why the tabletop has a sacrificial layer added.

What I made this time is the tropical fish (Angel Fish)……..

CNC-1 CNC-2 CNC-3and a stegosaurus!

CNC-4 CNC-5

It is very addictive!

And just for a sense of scale, here are both projects photographed alongside a bottle of wine (not so easy to see sorry!)

CNC-6

Now I just have 148 designs to go!

Plans from MakeCNC

Tambour Sun Lounge

Managed to finish off the Tambour Sun Lounge this evening – went together surprisingly quickly in the end.

It is made up of 137 individual, interlocked tambour slats, produced using the Lonnie Bird Tambour Router Bit Set from Toolstoday.com.  I made quite a few more than I needed, as I wasn’t sure how many I’d break testing the load limits, or, when I started the project, just how long a tambour I’d end up requiring.  The slats I have left over can be turned into a small drinks table, and/or a lumbar support.

I’ve now made over 300 tambour slats with this set, and it is still going strong.  This project uses approx 90 meters of slats, so if you work that out – 2 passes with one of the router bits, and one with the other, that is 270m of routing, and about the same distance again on the tablesaw, not to mention multiple passes on the jointer and thicknesser.  All in one day – over a km of timber passed through one machine or another.  I slept well that night!

I made the slats about as thick as I could manage, and still be able to slot them together.  Granted, it would be possible to go even thicker if you were prepared to make the slot on the bottom of the slat wider.  However, I tested this tambour by standing on it, on one foot.  That it survived that torture test (just) demonstrates just how strong they are (and the timber obviously).

So that’s it – job done.  The full step by step writeup will be in the next edition of “The Shed” magazine.  If you haven’t seen it yet (available in Australia and NZ, and I imagine digitally elsewhere), it is worth checking out.

 

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