My first project and LOTS to learn

Special Interest Groups CNC Milling
#1

I’ve been learning Fusion 360 and designed a plaque which I then exported to STL and scaled it smaller for a first shot. I’t now 6"x4.5"( design is 20" long ) and figure I’ll use a piece of scrap pine in hopes of saving myself from broken end mills learning the speeds/feeds etc.

I received a 20 piece 1/8" kit of end mills with the CNC which look alot like some of my Demel bits. Half have ~10 flutes and the other have similar flute count but with some cuts in the opposite direction. I have no idea if these will work well or not.

I also got 5 other end mills which I think are called knife end mills and have various V shaped profiles.

The spindle is a 400W aircooled model and spec’ed to do 500-8000 RPM.

My rough cut tool I was going to try is a 10 flute, 15mm long, 2.9mm OD end mill.

I’ve setup the slicer( Kiri:Moto ) with these settings for the Rough cut:
Step over: .5
Step down: 2
Feed rate: 1000
Plunge rate: 250
Leave Stock: 0

Any insights about this plan, setup, end mills, etc would be much appreciated.

#2

one mill end snapped. Slowing down the feed rate, reducing the step down and slowing plunge rate.

Step over: .5
Step down: 1
Feed rate: 700
Plunge rate: 150
Leave Stock: 0

#3

Doug,

I am a beginner myself. However, the flat end mills I was introduced to at the shop are all spiral downcut, and have 2 flutes; nothing like what you’re describing.

-e

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#4

Thanks and there’s probably a reason for that. I’ll see if I can find out more on this and place an order for some end mills.

#5

The grub screw holding the Z axis Acme threaded rod had some loose. I don’t know if that is what caused the end mill to plunge deep into the wood and break or if it was a symptom. I noticed this when I resliced, loaded the GCode and ran the Z probe script. There was a stall on the movement going up and then another stall going down

Will google on that to see if it’s a common issue and if there’s more than tightening it as the ultimate remedy. I did find out there are 2 grub screws for the Acme rod and 2 grub screws for the stepper motor. Both gub screws on the Acme rod were loose.

#6

While searching for info on the grub screw issue I found a thread on mods a guy did to his 3040 and it looks like the first thing to get is a 1.25 HP Makita router to mount on this baby. With the Makita he said:
“aluminum @ DOC of 1-1.5mm @ 380mm/min for rough cuts and a finish pass of 0.5mm DOC @ 280mm/min. I use a 3 flute 1/4in high helix end mill from Suncoast tools for aluminum, it makes a quick job of clearing chips and leaves a surprisingly nice finish.”

https://www.homedepot.com/p/Makita-6-5-Amp-1-1-4-HP-Corded-Fixed-Base-Variable-Speed-Compact-Router-with-Quick-Release-RT0701C/204247210

#7

Thanks to @Rex asking about another piece of software(MeshCAM) I watched the intro video for it and learned about defining the “stock” in the CAM/slicer software and by doing this you can set where the project gets cut. ie does it get cut into the top of a chunk of wood or does it get cut through the material down to the spoil board so the tabs show and the part becomes separate from the stock.

I had thought I’d asked about end mills back when I got this 3040T CNC almost a year ago but couldn’t find it. Turns out it was asked in the Google groups forum and I’d forgot to search there. This spells it out and from that it looks like my 10 flute bits are really finishing bits and not really roughing bits. So I will have to tone down my cutting until I get some 2 flute roughing bits. Cheap ones at first so I’m not breaking $50 bits as I learn this.
https://www.mscdirect.com/basicsof/end-mills