Hi folks, i mainly work with brass/alu on my shapeoko pro. However I’m doing the exact same piece but in copper, The tools and cutting paths are exact the same, and all works well, including deep narrow boring paths, except when i come to do the deep logo engrave. The copper just looks like it’s melting. I use a vaccum for chip removal on brass and alu and have no issue, so i am thinking something different is needed with copper for this engrave. My typical Feed per Tooth is always 0.025mm. I have tried three tools, an expensive Datron, a cheap Spetool 4 flute, and a very cheap 2 flute 1/8", all at 90deg. They all work fine on brass/alu but all have same issues on copper. I wonder whether I need lubrication. Note: this is a deep engrave not an etch. The bottom of the engrave is 2mm from the top surface.
The copper bar i am using is C110, I don’t have temper details.
If you work with this metal a lot and have successfully deep engraved it then I’d appreciate any tips.
oooh that is some pure copper, a lot of folks say it isn’t that bad if you know how to work with it…but I’ve never seen anyone actually show their results
I’ve done a little bit of copper work with various unknown copper alloys, the thing I’ve found universally true is that colder is better. A bit of mql iso in a fogubuster made a material difference in my experience.
I’d be interested in seeing photos of your current copper results though, might help more experienced folks give you some more specific advice.
So the brass is a normal engrave pass. Excellent finish. The copper is (middle row) exact same pass. Top row with a machine oil flood. With Q U at normal fpt, and the CK at 0.05mm fpt.
Bottom row is slightly better at 0.5x cutting speed and oil flood.
I always assume slower cutting speed is worse as chip is thinner, so more self-adhering, but the last pass is slightly better.
Pure copper is soft, whereas tellurium copper delivers a hard alternative with high tensile strength. As discussed, the tellurium content within C145 copper causes clean, short chips. This enables manufacturers to cut the material five times as fast as cutting pure copper. In addition to improving machinability and speed, this also reduces tool wear so tooling will last longer.
No need for coolant, air blast or vacuum unless you’re going very deep into a pocket.
I was doing super low DOC and around 65 IPM. I don’t have the file anymore but probably around 0.005" DOC on a 1/8" end mill maybe even less. I cut for like 7-9 hours straight on the same end mill. Here’s what the chips look like.
Thanks for the advice. I think my error here was not thinking about a machinable copper. I seem to have a solution for the logo, which is totally counter intuitive to me but if it works it works - very very small feed per tooth. Putting the piece under the microscope I noticed a lot of what looked like bad finish (in the engrave) was actually chips that have slightly re-adhered and can be brushed out. I also notice that the stock itself is quite hot to touch, much more so than brass or alu. This is probably why my typical adhesive based stock holding techniques are also somewhat failing.
I’ll take another crack at it today. Once I have some speed & feeds I’ll post up for folks future reference.
my guess is that your tiny feed approach will work for a one off or so but it’s probably a very early death for your tooling and as you said, adhesive work holding is likely to fail.
If it’s just for aesthetic purposes, another copper alloy might be just the ticket. Or you can just cut it in brass and copper plate, it’s easier than most people think and opens up some fun possibilities
