Milling Aluminum Z-axis plunges down


I have tried milling 1/4" aluminum plate using the dxf’s for the front and back plates of the MP3DP. When milling the first hole, the z-axis plunges down. I tried three different speeds when going in the z direction and got the same result. Attached is the tool info I used when creating the gcode. I set the depth of cut to be 7 mm and the z was to only remove one mm per pass.

I tried a similar setting but on oak plywood. The parts came out very well and a tight tolerance when compared to the model.

I am using a DW660 with a 1/8" Double flute carbide endmill I bought off the V1 Website. I know I need to use a single flute for best case but I read on the aluminum thread that a double flute should still be ok.

My z does tend to move downwards with the 660 on as well. Before starting the gcode I get the bit to be above the material and then click print. Doing this I add an extra pass to make sure the part is milled all the way through.

Any ideas about why this is happening?

Not sure what the issue is here. You can drill a hole, or helix, try the helix if you are having issues.

Don’t forget to add your finishing pass as well.

This is a good thing (means you have a smooth axis! You can use the LCD to position you Z axis and add g92 Z0 in your starting Gcode. That will hold it in place and set Z=0.

I may not have explained the plunging down well enough there. It starts out with the first two or three passes with the hole and it seems fine. But then it plunges straight down and even goes past the full depth of the material. The whole gantry/table shakes so I immediately shut the spindle off and stop the print. The hole is made but it is not circle at all.

On the plywood it was fine and had no issues, but with this aluminum it just shot straight down and shook the whole table.

You could also try stepping down less than 1 MM at a time in the drill holes maybe even go to .2 mm go extreme for a test.

Otherwise I would say get a single flute bit. Because it is obviously catching to hard on the two flutes and getting pulled down instead of pealing the chips up and out.

I am not a pro but that’s what I would try.

I tried the drilling helical and the holes work fine now. I changed my z to go down at 0.5 mm/s. Then I also changed the x and y movement to 3 mm/s. So with these changes the holes cut fine. But I am experiencing jostling at random times. It seems like the bit is moving that little bit off from the path and catches on material outside the path. This then causes it to move around and mess up the tool path completely.

I square up my machine before I make a cut. Making sure the stepppers are the same distance away on each side. I then use a speed square to check the x and y on the gantry. It’s square from what I can tell.

Would a trochoidal tool path at like 1-3 mm depth of cut be recommended here? Or can I do more than that since there is so much less friction on the bit?

What size is your machine, most importantly the dimension from the bottom of the gantry to the table and your material?

You might want to try some plastic first as the settings for it are between wood and aluminum.

The dual flute is harder to get right in aluminum. You have to take a big enough cut to get the heat out. Twice as easy with a single flute to get right.

It’s 30”x30” area. My gantry is 4.25” above my spoil board. I secure the aluminum with kreg jig screws bc of there shoulders.

i have a single flute 1/8” carbide windmill coming soon. But I guess I’m just anxious. Plus it does help with the learning the machine.

Move the metal all the way up as absolutely high as possible. Put some wood or something under it, that will make things much easier. That is a really tall machine. Rough explanation for each doubling of Z length you more than half the rigidity. The legs factor in as well that is why I say rough.

I am not sure if you can see it in my newer videos but I put it all the way up.

Now that I have done a few things on I am not sure why I had it in my head to give it that high of a z. I will shorten my legs to have a 2-2.5 inches or less on the z.

I will raise the metal until then. Thanks for the advice.

On a side note, is 3/4 ply plenty of strength for the MP3DP?

I know the feeling I’m in the same boat, each rebuilt gets shorter. I had made one tall enough to print the largest piece…I never use it, and it is covered in dust. It should be getting rebuilt very shortly. I am actually printing the parts right now.