Thoughts on this?

(Terry Morris Carlsbad, CA) #1

So I cut this out tonight, thickest wood I’ve done so far (only done 1/4" or thinner until this 1" piece) but on the final cutout the machine shut off and disconnected (literally at 99.8%) but it was easy enough to finish it with my Dremel and some sanding. I think the 1/4" bit was rubbing the walls inside the outside cutout. So, the question is, what is the proper fix so this does not happen in the future?

My thoughts are either a bit with longer flues (mine was only 3/4" while the cut depth was just a hair over 1") or somehow make it cut wider (pocket) so there it does not get pinched between the 2 walls??

In other words I believe it over powered the spindle motor due to friction though it did not sound bad or anything and did not burn the wood. And I was keeping it vacuumed out well so the fact I ran out of flute is my (NOOB) best guess. Oh, and the settings were all the default for the bit that CC decided to use.

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(Terry Morris Carlsbad, CA) #2

Well, it did it again on cutting out the lid (only .75" thick) so I think my flute length theory is dead.

I am letting CC make the settings but maybe I need to change them?

DPP 0.009
Stepover 0.113
Feedrate 75.000
Plungerate 12.500
RPM 8333.000

I still don’t know how to calculate best settings so maybe someone can give me a clue (or just tell me what to change to what).

These were both hardwoods and the dark one is walnut but I don’t actually know the other one but it’s a quite a bit softer than the walnut.

Only other mistake I made was the gap between the lid inside lip. Gave a little to much so the lid wiggles. I want to make and sell these so I need to get educated on proper cutting for this stuff (the lid I can figure out) but the settings for cutting I need help with.

BTW I found a DIY food safe oil/beeswax recipe I really love for food contact wood. If anybody wants it let me know.

Oh, and yes I know the grain in the lid is going the wrong way but I used a scrap I had and it was just slightly larger than the lid so I had no choice.

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(William Adams) #3

Lovely boxes! (I’ve been working on an automated generator fo such boxes: Fitted box design generator underway and posted one to cutrocket recently: https://cutrocket.com/p/5c9fb998c0b69/ and having the rounded bottom is a feature I’ve just added)

Please see:

There’s an interactive version at:

https://public.tableau.com/profile/willadams#!/vizhome/Carbide3DCNCFeedsandSpeeds/Sheet1?publish=yes

See https://www.youtube.com/watch?v=S9bceJxpqG0 for concepts on this and see the series #MaterialMonday: #MaterialMonday on YouTube for specifics.

You should test feeds and speeds in a piece of scrap using the technique at: https://precisebits.com/tutorials/calibrating_feeds_n_speeds.htm

Another consideration is Climb vs. Conventional Milling and tooling engagement — where possible avoid slotting and add geometry and cut as a pocket (Adding geometry to cut as a pocket with a finishing pass ).

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(Byrne Pedit) #4

Hey! My first impression was “he’s running the grain the wrong way”. Then I thought about it. If structural integrity was an issue, indeed you should run the grain long-ways. But the thickenss and size of your piece suggests this is not so. So run it however you want.

When we had wood floors installed a couple years ago, the decision was whether to run N-S or E-W. I thought of making a joke about running at 45°. Before I could crack it, the installer suggested the very same plan. We did it and are thrilled.

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(Phil Gorsuch) #5

Looks great! I think you already answered your question - the Nomad spindle motor does not have a pile of power and spinning the (relatively large) 0.250 end mill puts it even further into the red. If you have a long deep slot, particularly towards the bottom when the walls start to deform in ever so slightly you will be using a lot of power just to overcome the friction/cutting area and probably your piece slowly pushed it over the edge into shutdown. The answer is indeed to make that slot a bit wider with some stepover such that the friction/cutting area is reduced at any one point in time. Havent used CC for quite a while but suspect pocket is indeed the way to deal with it.

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(Phil Gorsuch) #6

And whilst I think about it cutting past the flutes tends to block the chips from exiting the flutes (particulalry in slotting) so if you are thinking about doing a large number of these an end mill with longer flutes is probably a good idea from a cut quality/tool lifetime point of view.

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(Terry Morris Carlsbad, CA) #7

I think I will switch back to an 1/8" endmill (just for the outside cut) and make a pocket cut for this but I still need an 1/8" endmill with 1" flutes I guess. Any recommendations?

BTW the whole reason I got the 1/4 endmills was to use a ball endmill on the inside edge to have a radius bottom around the edge and it did work perfectly for that. And the rest of the inside was a 1/4 flat to pocket out the rest and that also went without any issues.

Or, is it OK to use the 1/4" endmill (.75" flute) if I do a pocket on the outside edge? Or will it still rub abd cause too much friction?

I still have lots to learn and am greatful for this forum and it’s members for helping me.

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(Phil Gorsuch) #8

1/4” end mill should be fine if the outside pocket is wider than 1/4”!

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(Terry Morris Carlsbad, CA) #9

Thought I would post an update for anybody interested.

I thought I had the issue licked as I mad the outside cut a pocket and on the first one it finished without any issues. But the next 3 tries it failed again and again, I tried slower feeds and such to no avail and I was watching it closely one of the times when it stopped and it was moving in a straight line and just bit into the wood and stopped dead, it really didn’t seem like it was struggling, no slow downs on 90% and not even touching the walls when it happened. I could easily move the spindle motor with 1 finger where it stopped.

I came to the conclusion that the 1/4" bit was just too much for the machine period.

The only reason I used the 1/4" bits was to get a 1/4" radius at the bottom inside edge (which it did beautifully) and I just figured why not use a 1/4 flat end mill for the rest at the same time. Turns out that was a mistake.

So, for now I am switching back to my trusty 1/8" and I will do without the fancy inside radius. BTW I cut 2 with the 1/8" last night and both worked flawlessly.

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(William Adams) #10

The 1/4" endmills are supposed to only be used in softer materials such as Renshape.

You could use a 1/8" endmill and leave a set of steps on the inside, then make a finishing pass w/ a 1/4", or just model the whole shape and use a ball-nosed 1/8"

There are a couple of endmill sizes in-between 1/8" and 1/4" — 3/16" obviously, but also 4, 5, and 6mm — perhaps one of them would make a suitable compromise?

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(Vince) #11

How many flutes are your cutters? Switching to single flutes will minimize load per revolution while still keeping chipload up.

For a 10,000 rpm machine I would think its better to have the higher sfm a 1/4 will be running. Datron makes some really nice single flute ball mills that work beautifully.

In my experience with a similar wattage spindle is that large endmills are very possible to use if load is adjusted accordingly. Adaptive load cam really helps with this. I was able to run a 6mm in aluminum so don’t give up!

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(system) closed #12

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