Home made Santas

It's almost Christmas, so how about some home made Santa ornaments?

Painted and finished

Cut on my CNC router of course!

Hot off the router

My missus did the design work in Photoshop and I vectorised the images in CorelDraw, before importing them into CamBam to generate the toolpaths. Finally the exported toolpaths were imported into EMC2 for cutting.

If you would like to cut your own Santas, then visit my downloads page for the DXF.

Merry Christmas!

A note on cutting MDF.

I've been cutting MDF parts here and there for years. Since I'm not doing this commercially, I haven't really considered just how nasty the dust that comes off this stuff is. It's REALLY bad for you. So I need to get some air filtration organised. Until then I'm wearing my respirator and goggles while cutting this.

Upgrading from all thread to trapezoidal ACME leadscrews

The M8 All-thread rod 'leadscrews' that I recycled from CNC #2 into CNC #3 had reached the end of their life.

All-thread has the advantage of being really cheap. I paid £1.50 for each 1000mm length and made a 'leadnut' from an M8 tapped aluminium angle bracket. However what you save in cost, you loose in backlash, efficiency and quality. Those mild steel all-thread rods flex under load like a kids toy bow.

One good way to get you up and running cheaply is to use all-thread, but relatively quickly I found that I was unhappy with the performance. They seem to have a very limited lifespan too!

Another drawback is speed. The all-thread rod I used has a lot of threads per inch. That's a lot of turning to make the axis move, so my maximum speed was a painfully slow 4mm/second.

Having said all that, they are fine for small light use tabletop hobby CNC routers. Say for etching PCBs or cutting foam and balsa. If I were to use them again, I would choose thicker rod, say M10 or M12 and limit the maximum length to 300mm.

Ok, back to the exciting stuff...

Earlier this week I decided rather than replace the all-thread with more of the same, that I would upgrade to trapezoidal ACME leadscrews. I found it quite hard to source these, but came across abssac.co.uk who sell all manner of linear goodies. I called and spoke to a very helpful guy called Phil who made me a fantastic deal on rolled stainless steel ACME leadscrew with high precision leadnuts. I placed my order at 3pm and it was delivered to my door by 10am the next day.

Close up of All thread rod.
Photo by Ervín Pospíšil, 2006.

Close-up view of a male Acme thread. 5/8-8 right-hand single-start ACME-2C (self-centering).
Photo by Yannick Trottier, 2007

New Lead Screw Stats
Thread = 5/16-8-4
Thread Diameter (inch) = 0.313 (7.95mm)
Threads per Inch = 8 (3.1mm Pitch)
Thread Starts = 4
Thread Type = stub acme
Thread Lead (inch) = 0.5000


This weekend I have disassembled #3 and fitted the ACME leadscrews and nuts to both the Z and X axis.

drool!!!

After an initial panic when the Z axis stalled regularly, I reconfigured my driver for 1/8th stepping (down from 1/4) and fiddled with the Micro Stepping settings within EMC2. Now I have a travel speed of 12mm on the X axis and 2.5mm on the Z axis without any obvious stalling. However I'm not counting this as a complete success until I can rebuilt the entire machine and perform some testing.

I'm looking forward to some testing and improved speed and quality of cut. Fingers crossed.

Update

I have replaced all the axis with ACME leadscrew and performed my first test, a 50mm circle cut with a 2mm endmill.

This picture says it all if you look closely (click image to zoom)...

All thread and ACME comparison.

There might not seem like much difference, but from an Engineering point of view these two test cuts are very different in quality. First, notice the imperfect circle with the all thread. You can see the circle 'bulge' from the bounding square where I have placed an arrow. You can't really see from the picture but all the nodes of the test pattern start and stop where they are supposed to with the ACME cut, and it returns perfectly to 0,0,0 as seen by the perfectly round dimple on the bottom left of the ACME cut. Whereas the All thread has an indistinct 'smudge'.

The All thread was cut at 240mm/minute and the ACME 3000mm/minute so that's a theoretical increase in speed of a factor of 10.

Traditional Swedish Knife Project

I always wanted a good solid knife for camping, and decided one day to make my own from a Karesuando Kniven knife blank kit.

Here is the finished result.

Casting a better CNC tool holder

The holder for the spindle on my third CNC router is a bit slap dash. I have decided to cast my own in aluminium.

First I drew the part in Autodesk 123D, generated the cutting plan in CamBam and imported that into EMC2.

Then I started cutting the part in urethane foam board.

As the part is now cut on the router I removed it from the foam, to reveal my complete part.

Next I put the part into my casting flask and packed it out with Petrobond casting sand.

Note that I'm leaving the foam part in the mould. This will be cast using the lost foam method, where the foam is vaporised by the super hot aluminium.

<End of Part 1>

My First CNC Router Project

My first CNC Router was built from timber and 12mm birch ply with M8 threaded rod, and drawer runners as the linear bearings. It wasn't very accurate and was somewhat feeble. However it did make a good laser cutter, with the addition of a 400mW laser diode. It had a cutting area of 300mm x 300mm.

Sadly I don't have any pictures but I do have these grainy webcam videos...

My Second CNC Router Project

I'm writing this article retrospectively, really as a what not to do more than anything else.

Unfortunately at the time of writing this I have not found any photos of the completed beast but below you can see an early photo of the build process with the X and Y axis part completed.

Looking back it was flawed from the outset because of the size and choice of materials.

In my humble opinion, MDF is not suitable for CNC Routers over about 500mm in size. This beast had a footprint of 800mm x 600mm. I used 18mm MDF that was doubled to 32mm in critical areas, yet it absorbed humidity and sagged under it's own weight.

Just found this rare photo of #2 in it's complete state

In addition to the MDF issues, I used M8 threaded rod and M8 bolts for the leadscrew and ballnut. At the length required to drive the long axis, the threaded rod, flexed and wailed like a scalded cat under load.

Finally, a movable gantry is way more difficult to make rigid for those of us who are financially challenged, than a fixed gantry design as illustrated on my third CNC router. I recycled number two into a table top for my third CNC project.

Having said all that, it was a capable tool right up until the moisture absorption and sagging, rendered it inaccurate and full of backlash. Above you can see a large spruce box that I carved with the beast.

12 x 8 Workshop Project

You can imagine with all my bodging that I needed somewhere to make a mess without putting others in danger. So I build this 12 x 8 workshop to my own design as a house for my growing crap collection.

Here is a build photo from a third of the way through that shows the construction.

I decided upon 12 x8 feet simply because its a multiple of a standard 8 x 4 (full) sheet of plywood. The floor and roof are 12mm WBP ply. All framing is 2 x 4 inch spruce. The cladding is 12mm weatherboard cladding. Going with thinner weatherboard cladding may have led to warping and splitting

I've created a great little space to work in and I'm really happy when I'm tinkering in here.

My Third CNC Router Project

At the weekend I 'finished' my Third CNC Router. Simply, its a robotic cutter, that cuts a shape in sheet material such as plywood, and that shape is something I have designed on my computer. A kind of wood printer.

This is the first mill that I have built that is anything close to satisfactory. My first ever was built of timber and was too small. too slow, badly built and inaccurate. My second CNC router was built of MDF, and was four times larger than the first. However it was still slow and unfortunately MDF absorbs moisture and loses its stability and accuracy. Number three has been built with chunky aluminium channel (C-section) to my own design from lessons I learned with the previous two and is super robust.

So far, so good.

It has a respectable cutting area of 500mm x 400 mm.

Close up of the home made linear bearing system and M8 threaded rod leadscrew.

Julius Ceasar's face cut in urethane foam.

Here is a video of number three in action. Here I am resurfacing a sacrificial cutting bet top, so that the material to be cut is perfectly in alignment with the Z axis. 19mm straight cut router cutting birch ply. 1mm pass at full speed (240mm/minute).

Tiny Teardrop Camping Trailer Project

One day, as you do, I was searching the interwebz for boat building plans and I came across the perfectly formed delight that is the Teardrop Camping Trailer.

A commercially built example

image copyright Cozy Cruiser Mfg Inc.

The Teardrop was first invented by 'bodgers' in the Great Depression to allow the masses to have access to cheaper vacations. They originated in workshops and barns across North America to the bodgers own designs and and also by following rough plans from magazines such as Popular Mechanics.

I just loved the idea and had to build one. You can read my build thread over on the excellent Teardrops & Tiny Travel Trailers Forum of which I am a member. In the meantime, here is the end result of my efforts...

Here are some more photos, including some of the build process.

Definitely NOT a Completer Finisher

As part of my Degree, I had the pleasure of having a 'Team Roles Inventory' conducted upon my person. It was invented by somebody who goes by the jazzy name of Dr Meredith Belbin (see photo).

(looks like a nice old geezer)

copyright, Belbin.com

The reason I mention it now is that the Completer Finishers amongst you will notice that I tend to leave rough edges. I like to think that's because I am a Plant and I am unencumbered with all that finishing nonsense.

"Plants are called wake creative, unorthodox and a generator of ideas. If an innovative solution to a problem is needed, a Plant is a good person to ask. A good Plant will be bright and free-thinking. Plants can tend to ignore incidentals and refrain from getting bogged down in detail. The Plant bears a strong resemblance to the popular caricature of the absent-minded professor/inventor, and often has a hard time communicating ideas to others. Multiple Plants in a team can lead to misunderstandings, as many ideas are generated without sufficient discernment or the impetus to follow the ideas through to action."

So, no comments about high speed rotating blades held on with duct tape please!