INTRO
High-density polyethylene (HDPE) is a thermoplastic polymer produced from the monomer ethylene. With a high strength-to-density ratio and a high-impact resistance and melting point, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber.
HDPE is commonly recycled, and has the number "2" as its resin identification code.
MILLING ON EVO
HDPE can be milled on EVO with some precautions on cutting parameters.
As for all types of plastics, the main challenge is chip evacuation (to avoid melting plastic and clogging the tool), so feeding relatively quickly with a quite low spindle speed is a solution, but beware of the rigidity limits of the machine . Also a low amount of flutes on your tool will help to achieve a good chip evacuation.
We recommend that you test your parameters before launching your program, to find the right feed/speed for your combination of tool/material. Start with safe parameters and low depth of cut, and increase progressively to find the sweet spot for your setup.
Parameters used in the video :
Machine : Mekanika EVO S / High-Z / AMB 1050W
End mill : Ø 6mm / 2 Flutes Carbide / Upcut spiral
Feed rate : 3 000 mm/min
Spindle speed : 13 000 rpm
Depth of cut : 3 mm
MILLING ON PRO & FAB
HDPE can be milled on PRO/FAB with some precautions on cutting parameters.
As for all types of plastics, the main challenge is chip evacuation (to avoid melting plastic and clogging the tool), so feeding relatively quickly with a quite low spindle speed is a solution (and you can run a lot faster compared to EVO as rigidity is not a problem for PRO/FAB). Also a low amount of flutes on your tool will help to achieve a good chip evacuation and keep the feed rate acceptable.
We recommend that you test your parameters before launching your program, to find the right feed/speed for your combination of tool/material. Start with safe parameters and low depth of cut, and increase progressively to find the sweet spot for your setup.
Parameters used in the video :
Machine : Mekanika PRO S / Standard-Z / VFD 2200W
End mill : Ø 6mm / 2 Flutes Carbide / Upcut spiral
Feed rate : 4 000 mm/min
Spindle speed : 15 000 rpm
Depth of cut : 5 mm
MATERIAL TIPS
- Avoid tools with more than 2 flutes for better chip evacuation.
- Prefer upcut bits with a wide angle spiral (or bits specific for plastics).
- Use ramps or helix instead of plunge to increase your tool's lifetime and avoid melting plastic.
- Chips produced should be quite thick, and not present melting/burning marks.
- The tool must never have material stuck in it, but even with good parameters, plastics tends to stick to the tool. Using air to blow it off the tool is a good way to avoid this.
- If the surface finish is not good, it can be related to various things:
- check that your stock is fixed strong enough and not vibrating
- check your tool's edges to see if it is damaged
- use the shortest tool possible for the job
- Test different feed/speed (most likely: reduce feedrate or increase spindle speed, within the machine's capabilities).
- Different HDPE grades and formulations may behave differently. Find the specific characteristics of the one you are working with & test your parameters.