I'm just getting into CNC and though I'd start build building my own. I've built a few 3d printers, so have some idea about the electronics and motion control, but obviously there are important mechanical differences. Could you let me know what you think about the design I have come up with? I'm intending to use it for some aluminium parts as well as wood, plastic and carbon fiber. It will probably only for a few hours each week with the occasional longer job. I'm not in any rush. It's in a room in the house so I'm trying to make sure it's as quiet as possible to minimise complaints.
The bed is 480mm by 850mm, cutting area is 400mm by 620mm. I'm aiming for 100mm of Z travel so I can cut stock up to about 40m in height. The sides are 100mm by 50mm by 6mm mild steel angle section. The bottom bars are 20mm by 20mm by 3mm mild steel box section, bolted to the angle section. The gantry is 120mm by 60mm by 6mm box section mild steel. The rest of the metal work is basicly 6mm aluminium plate. The ball screws are 1210, they stick out the end of the pillow blocks because I ordered before designing, I will cut them short. The linear rails are HGH15. All cheap Aliexpress. The steppers are NEMA23, 4Nm. The spindle is 800W, water cooled, ER11. I'm using the BlackBox controlled by OpenBuilds, I realise that it's 24v supply limits the stepper speed but I've accepted that for its simplicity. The bed will be 15180 aluminium extrusion with MDF on top. The distance between the outside faces of the cars are Y:224mm, X: 115, z:150MM
I'm hoping (maybe naively) that I can initially print the aluminium parts in ABS, and make it usable enough to cut the aluminium replacments.
Please be brutal but constructive In particular, does anyone know how flat and perpendicular the outside faces of angle section are likley to be?
Hi,
rigidity is key....it will determine the usefulness or otherwise of the machine.
Where a CNC machine like this differs from a 3D printer is that this machine MUST contain the cutting forces WITHOUT DEFLECTION.
Physics tells us that there must be some deflection for some applied force....so the design is to minimise the deflection to less that your desired accuracy/resolution
of the machine.
If you require rigidity R to machine plastics and wood, then you'll need at least 5R to do aluminum and 25R or better to do steel.
The only obvious fault with what you have drawn is the vertical uprights holding your gantry aloft, they will deflect side to side at the slightest
provocation. They need to be either way WAY thicker, like 30mm steel or something, or have a cross section like a rectangular tube.
Thanks for the help Craig, I guess its back to the drawing board but then that's half the interest. I'll look at mounting the gantry directly onto the sides instead.
Feedback on Tabletop CNC design
In particular, does anyone know how flat and perpendicular the outside faces of angle section are likley to be?
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