[Mavigogun]

I aim to carve some large blocks of HDPE plastic, and am looking for tooling that can reach 7" or more. Are such tools available with a 1/2" shank? The intended AVID CNC employs a 4HP spindle that MIGHT accommodate an ER32 collet receiving 3/4" shank tools.

[Ashley-techprolaser]

First,it is difficult to find 7" tool; secondly, if you need to engrave a depth of 7 inches, you do not necessarily need a very long tool (unless you need to drill), because the cnc router engrave it layer by layer.But if the hole you carve is too narrow for the spindle to go deep, it will be difficult.

[routalot]

I fear that finding tooling may not be your biggest problem.My experience with a few types of plastic suggests that the internal stresses within the slab can lead to rather a lot of distortion when the item is taken from the machine.Anything much larger than a cigarette carton will definitely not be flat on the bottom face when machined to a high proportion of it's depth.Try a sample before going too far down the path.

[Mavigogun]

I appreciate the threat of distortion. The HDPE billets themselves, at about 75lbs, will be annealed, spending almost 2 full days in oven between melt, soak, and cooling. The stock will be actively cooled, as necessary, if heating becomes an issue. The end product will resemble a brick with relief carved into one face- that is, there will always be a large amount of mass backing the carved face, and high aspect ratios will be avoided.

[joeavaerage]

Hi,
HDPE is about the worst machining plastic there is. It forms strings rather than chips, a PITA. I use flood cooling with ALL plastics, and HDPE especially,
its less about cooling but trying to flush away the chips. If you fail to do so the chips get recut and weld themselves into a lump or stick to the tool.

Craig