My Dominator 3x4 is almost through the second section in the manual. Since I’m putting the CNC on a cabinet of my own, I’ve discovered a couple things and AI has given me one idea. In addition to using a torsion box beneath my machine, I opted for the “Rigidity Upgrade” (three 40x80 extrusions beneath the main grid).
To avoid vibration resonating through my table I bought hard rubber sheets. I want a surface that’s consistent, dampens vibration, but has minimal compression. The hardness I chose is “Durometer 70A”. My second reason for the sheets is that the rear X-plates are 1 mm too tall, and I don’t want them to be a bearing surface for the whole machine. McMaster-Carr sells it in 4" x 36" strips (1/16" thick) with a paper-backed adhesive on one side. For a 4’ wide machine I cut four to 80 mm wide lengths. I started with two lengths under one end of the front and rear Rigidity extrusions and put 18" under each end of the middle extrusion. (Same length rests beneath each end of the middle one). 80 mm-wide, 460 mm-long pieces of the last strip completed the coverage under the 1st and 3rd extrusions. The narrow strips left over cover the remainder of the center extrusion. The McMaster-Carr part is #5652N133.
To secure the CNC to the table, I ordered “gussets” from the company from which Daniel gets the extrusions. They’re called “8020” and they sell components online. They sell 40 mm x 40 mm triangular pieces that secure (horizontally) to the extrusions. Then I had to come up with my own way to secure to the table (vertically). For a solid wood table, a lag screw will suffice. More about the torsion box in a moment.
I ordered nine (9) gussets, planning for three to bolt down each of the Rigidity Upgrade (RU) extrusions. If you’re not using the RU, the 40 mm gussets still work, but they do offer them at 80 mm. Gussets are part #40-4332, and their fasteners are #75-3422.
But 8020 hasn’t amazed me with their service. First, they shipped the wrong X-extrusions, so assembly waited for them to coordinate with Daniel. Then, when they shipped the gusset/fastener package, they included the right packing slip but didn’t include the gussets! Their customer service took three calls to reach the right person. To add insult to injury, it turns out McMaster-Carr sells the same components as 8020, and at 60% of the 8020 price. Gussets are #5537T937.
About bolting to a torsion box: The skins on mine are MDF, which can’t be trusted to hold a threaded fastener, and I can’t slip a nut under the top skin. I can add bolts beneath the bottom skin, but the air cavity doesn’t provide strength against compression of a through-bolt. I bought a length of aluminum tubing and cut pieces just a bit shorter than my torsion box depth. With an inner diameter 0.344", an M8 bolt slips in easily. A 28 mm fender washer and nut under the table completes the connection. Again, McMaster-Carr:
Aluminum rod (36") #89965K357
M8 bolt (part number depends on the length you choose)
M8 nut #91290A471
Washer, 28 mm #98363A113