End mill selection

1

Howdy. First time poster here.

I’m new to CNC in general, so, while trying to not get into overly extraneous detail, here’s what I’m wunnerin’…

I’m using an X-carve to cut Magnum Magnetics magnetic sheeting. If you’re unfamiliar with the stuff, it’s flexible PVC sheeting impregnated with ferrous metal particulates; typically used for vehicle signage. For obvious reasons, cutting shapes from it by hand is out of the question, and the stuff’s metal content ruins razor blades pretty quickly - requiring constant blade swaps when using a drag knife - no good. The drag knife also creates “furrowed” edges as the blade plows through the material… again, no good… especially around tight curves.

While certainly not the first to give it a go, I’ve devised a method using what I call “channel boards” with the X-carve to mill shapes from the sheeting. Results thus far have been very pleasing… nice, clean, burrless edges and no raised furrows as with a drag knife. I imagine most of you can already envision what I’m doing, so there’s no need for a lot of explanation and it isn’t really pertinent to my question anyway. However, if more details are desired, no problem… 'jis lemme know. (The mill plunges through the sheeting and rides between the walls of a pre-routed channel… yada, yada, yada)

I first used an end mill that Inventables sells - Solid Carbide 2 Flute Straight End Mill (.125") - Here’s a link…

… also purchased some .0945" Kyocera 3-flute straight mills via Ebay. They might make slightly cleaner cuts, but wear faster. Once worn, neither do such a great job. I’m cutting only .030" of sheet-thickness and the Z can be adjusted so that a “fresh” section of the end mill is cutting, thus getting more use from it. (Incidentally, I’m thinking on how to make the Z “oscillate” between a min and max height while riding through the channels, thus using all of the mill’s cutting length throughout a job).

The above being said…

My original thought - the whole reason for getting the machine - was that an end mill intended for metals should be able to chew through a mile of the magnetic sheeting before dulling… but have since come to realize, that while the assumption likely is true, said end mills might not produce the desired cutting results when applied to plastics. Thus far, I’ve experimented only with the straight-flute plastic/wood cutters mentioned above and a few down-cut spiral 2-fluters (straight flutes win, hands down).

The stuff is plastic, but I reckon the metal content makes it a bit abrasive or sumpthun… thus, as with razor blades, the hastened wear on the end mills.

Sooo…

I’m looking for an end mill that does at least as good a job as those thus tested, but that last longer. I’m willing to pay for premium if need be, just don’t want to waste what little money I have left.

Will something intended to mill metals work on plastics in the first place? Is a “coated” end mill what I’m after?

Any recommendations?

Regards,
Kevin

2

Hi Kevin,
I’ve tried similar with my Roland sp300 realizing that’s not the way to go. Are you cutting with the X-Carve or scoring? Scoring always seems to work better for me.

3

Hi, Chris…

The edges aren’t as clean; Scoring doesn’t quite “cut it” for me.

My critics are correct, I suppose… I’m too nit-picky.

LOL!

Anyhoo…

Thanks for the speedy reply.

Actually, I’m rather impressed with milling mag-sheet. Granted, it isn’t ideal in so far as I’ll need dedicated channel boards for each design (though one board can hold multiple patterns top and bottom). Dust collection takes care of the mess, mostly. Fun fact… NEVER use an air hose on milled mag-sheet, lest a billion or so tiny magnets go everywhere. It has its downsides, but…

A bit more detail…

A piece of the sheeting, mag-side-up, is adhered to the channel board (MDF works) before the channels are milled. The workpiece sticks to it, mag-side-down… everything’s stuck securely in place, kinda like vinyl film on backing paper. The channels are a cut wider than the end mill used for cutting the workpiece, so there’s no further contact with the channel walls, and the end mill’s bottom is kept above the channel floor. The end mill touches nothing but the workpiece being cut. After the job completes, G30 moves the spindle clear and the waste area is “weeded” away, along with a good deal of chips that dust collection couldn’t get to (in the channel under the workpiece). A quick vacuum gets the rest of the mess up as the cut-to-shape magnets are lifted from the channel board. Load up a new workpiece and run the job again, but ya gotta keep an eye on cut quality as the end mill starts dulling after two or three runs (change it or reposition Z). Repeatability isn’t an issue as bump stops are used to consistently position/reposition the channel boards. I’m not cutting one-off shapes, but instead runs of 10, 20, whatever I can fit in a 24" x 29" workspace (24" wide mag-sheet and 30" wide vinyl rolls).

I feel like I also received a bonus; the ability to do something that I doubted would be possible, not with all the disparate equipment and the extended tool chain involved. The X-Carve is accurate enough, so that with proper registration and a measure of care, I can lay vinyl film prior to milling.

Yeah…

It’s contour cutting… and wonderfully… across almost the whole deck (only using 24" of X; 29" of Y).

With a fresh straight-fluted mill (or fresh .030" section thereof), the cuts are pristine… and I’m not saying the mills mentioned wear so quickly as to make the whole concept untenable or anything, quite the contrary… but, as they say, there’s always room for improvement.

Thus, my previous inquiry about end mill selection. I’m now a little invested in the whole enterprise and it works too well to not investigate potential improvements. I’m making money as it is, but can’t afford spending it on more expensive end mills unless doing so is justified.

Regards,
Kevin