Chinese Dragon

Plans from MakeCNC

Episode 113 Spoilboard

Sabretooth

Some photos taken during the shoot of Episode 112

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Plans from MakeCNC

Oxygen

Had a young fella visiting with his family today.  I know it was a waste of breath, but I had to ask him “Do you like dinosaurs?”

It’s like asking a human if they need oxygen to live.

So the answer was a given.  But he wasn’t expecting what came next.  I handed him a set of about a dozen different dinosaur plans, and suggested he choose one.  After a meticulous sort and selection (he’s all of about 4!), one was chosen – a triceratops.  Has big horns for hunting I think was the rationale.

No problem, let’s go make it.  So first, camped out on the lounge floor we loaded the plans into the computer, fitted them to the board size (nesting), and set the required tabs.

Then it was off to the shed, with a small entourage in tow.  While the kids watched, I set the CNC up for the job, explaining what I was doing each step.  There was a board placed on the ground a short distance from the work area, and strict instructions that only I could step over that board.  A small step ladder placed on the other side of the board was a very convenient lookout, and it was duly manned for pretty much the entire time.

As each board was completed (this particular pattern required three 900x600x6mm MDF boards) (and yes, dust extraction and air filtration were on), the entourage were involved in popping each piece loose, then each piece was duly handed to me one at a time so I could sand off the tabs on the disk sander.

The young fella was funny.  He couldn’t get over that we were making ‘his’ dinosaur.  Nor that it was going to be ‘big’.  After all, what does ‘big’ mean to a 4 year old?  A big toy is perhaps a foot long? Maybe?  You wonder what they expect, although they are already processing the concept of limiting their expectations so as not to be disappointed.  So ‘big’ is relative, especially when compared to all the other toys that receive the same description.  He kept asking what I was doing now (or more specifically, what the CNC machine was doing now).  He was confused that even after a number of parts were cut, we were still making components for his dinosaur.  Again, you could see it was already exceeding any preconceived notions of scale.

With the pieces cut out, we traipsed back into the house, where the dinosaur was assembled.

That is when eyes got really wide.  Followed closely by a most impressive grin!

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All up, took at most an hour and a few sheets of MDF, and that was about it.  Sure beats those tiny 6″ long models made in China that keep appearing in pop-up shops in the various malls.  Nothing is better than a ‘serious’ dinosaur.  Especially one that redefines the concept of “big”.  Better than oxygen.

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Plans from MakeCNC

Episode 112 Sabretooth

Plans from MakeCNC

Episode 111 Nova Infinity Chuck and Jaw upgrade

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

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