We're finally out of the office and into the workshop. First thing to do is cut your 12mm mdf blank rectangles to make your blanks from. I'm only going to make one half of "Cubism Gal" or "Cubby" to her friends. I'll need 12 - 280 x 250 x 12mm rectangles. They get cutout on the table saw.
As I'm writing an Instructable with a CNC theme, I need to address one small problem? There's hundreds of CNC machines and similarly post process software, to write the machine language CAM. I have an Axiom AR4 Pro and it uses UCCNC control software. They're a great combination IMHO. I purchased mine in Australia from BG Precision. You may have something different, but you're going to have to tell Fusion which post processor you're using? In my case UCCNC does not appear in Fusion's list of available post processors! Here's a youtube by Autodesk's Lars Christensen that'll show you how to install a post processor:
Like a lot of things computer based...it can get difficult to sort out and you may have to seek out support from machine or software suppliers to get you going? I'm going to assume that you have all that worked out? Given what I know about CNC, I would highly recommend you use a local business with backup resources to purchase your machine and software from. I'd hate to have been lured by a cheap price and imported a machine, as when I got started in this game I definitely needed help from my local supplier to push through the first few weeks.
8mm dia hardwood dowel
Good quality cross-linked wood glue
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Step 1: Final Check
With the first rectangle of mdf in hand place it on your CNC table atop a piece of 3mm scrap.Setup your rectangle parallel to the work surface by using a square. Our XYZ origin is dead centre, so draw intersecting diagonals to find the centre point.
Fire up your computer and software. Home All to erase any previous memories. Now toggle the XYZ arrows and move a pointer installed in the collet to get right over the top of that center point. Once there, zero your X and Y position. Lift the Z axis up and change the pointer for your first tool. In my case a 3.15mm dia flat end mill. Tighten in the collet and set up your Z axis touch pad. Lower the tool to touch on it.
A note on tightening and loosening collets. You need two spanners, one to hold the spindle, the other to turn the collet. For tightening use left hand to turn collet pulling towards you. For loosening swap spanners and use your right hand pulling towards you. Loosening by pushing away from yourself will see you skin your knuckles!
Your machine control screen should show X = 0, Y = 0 & Z = 35mm* (may vary dependent on machine?). Load a file and you should see a representation of the toolpaths in Plan view?
Almost ready to start the machine, but first a final check:
1/ Toolpath image matches what you had in mind?
2/ Toolpaths aren't going to clash with your clamps?
3/ Clamps tightened?
4/ Spindle speed set for your tool?
5/ Dust boot on and extraction running?
6/ Eye and ear protection on? If your dust extractor is the bag type, I'd wear a respirator as well! If you can smell sawdust, it means you're breathing it!
7/ Standing by your emergency stop button?
Step 2: Rear Blank
Hit Cycle Start and watch the action! Once the Contour cut is finished change tools to an 8mm dia drill. Re calibrate Z axis with a touch pad, every tool change and adjust spindle speed to suit. As each 12mm piece is completed replace with new mdf rectangle and repeat until all completed.
Now release your part from the surrounding mdf by using a jigsaw to cut tabs. Cut four 8mm dia dowels 62mm long. File a flat on each one to allow air to escape when hammering them in. Stack your 12mm layers, glueing the faces each time. Glue up the dowels and hammer into the holes. Now clamp the lot and allow to dry.
Step 3: Front Blank
Repeat previous step for Front blank. Stack them all up (6) and start glueing. We won't hammer the dowels in this time as it can be a bit stressful for the mdf. I use two 8mm dia steel rounds that won't absorb the glue. Hit them in opposite each other to align the layers. Now clamp. When you've got 3 clamps in place, pull the steel rods out using vice grips. Clean up as much squeezed out glue as possible with paper towel and continue with more clamps.
Once glue has cured drill out the 8mm holes again to remove set glue. Cut dowels half the required length (50mm), glue them up and hammer them in from each side.
You should now have Front and Rear blanks with dowels intact.
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