Nomad 883 (v1) - Progress so far

CNC Machines Nomad
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Ok
So couldn’t wait to get the thing when i got it , it just sat there nagging at me. ( too many things to do)
for about a week or 2 intstalled the software and proceded to make the first cut. all i tried was “engraving” with the ballnose a few letters should have been pretty strait forward. looks like my MC settings where off a bit : no spindle spin it crashed in the wood part ( peice i had laying around) so cracked up my friend google and whent and look for some gcode practice ( raw Gcode )

so 2nd test was going square ( moving all axis ) and starting motor and then ending the program.
that all whent swell but did not have time to play with the beast for a while where april and a few days ago hooked the thing up to the PC again whent into windows and proceded to launch a Gcode i was working on for the 3rd try . the code consisted of just miling slots for a fan in the PC . (will try to attach images later. ) wasn’t that strait forward . had a few things wrong the endmill was crashing in the table and stoping the spindle. i had a Z-0.25 at the beggining ( the part was only 0.0600 thick ) fixed that all went swell till windows hibernated ( grrr. ) did not have time to retry till the next day. turned that off and did a 3nd try ( finishing the necessary slots for the fan) and all went good . so 3rd time was the charm literally.

so just got some more matts to play with ( still haven’t used the stuff in the kit tough) still wondering what to do next.

btw speed 10k rpm , F4 and about 0.0050 per pass did not have any problem with the aluminium. (probably could go much ticker on the passes)

i would recommend ordering the vise ( that i do not have) would make fixturing much easy. Also getting a/some 1/4 end mill as well as a collet for it .

1 Like
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Thanks for sharing your “bring up” experience!

It sounds like you’re on your way.

i would recommend ordering the vise ( that i do not have) would make fixturing much easy.

Do consider the C3D sea-of-holes bed, some step blocks and clamps as well.

mark

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Don’t do aluminum with 1/4 end mill. Nomad does not have enough power to take any benefit from this size.
Mark has a nice post in the forum about Aluminum end mill choices. He has excellent results with 1-flute mills.

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Don’t do aluminum with 1/4 end mill.

DEFINITELY NOT! Not enough torque.

Mark has a nice post in the forum about Aluminum end mill choices.

I just did some updates to the posting to fill in about variable helix and some detailed information about metal machining.

mark

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well thats odd why would it not have torque with a bigger endmill wouln’t this allow for slower RPM and thus more torque ( sorry im noob when it comes to machining . from the book he gave me i should not even be able to mill properly at 10k rpm with 1/8 as the actual RPM should be around 12.8k (from the small calc i did from the formulas in the book) i still did it . i think that torque isn’t the only thing at play here . figuring that more circular movement of the endmill would give more leeway not less. anyway i will probably do some more calculations anyway .

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well thats odd why would it not have torque with a bigger endmill wouln’t this allow for slower RPM and thus more torque ( sorry im noob when it comes to machining. from the book he gave me i should not even be able to mill properly at 10k rpm with 1/8 as the actual RPM should be around 12.8k (from the small calc i did from the formulas in the book) i still did it . i think that torque isn’t the only thing at play here . figuring that more circular movement of the endmill would give more leeway not less. anyway i will probably do some more calculations anyway.

The Nomad is incapable of RPMs higher than 10K. Anything that says otherwise is incorrect. I have that officially from Jorge.

I can’t tell what formulas you’re referring to. My best guess is the standard milling formulas which relate how to mill optimally for a give material and end mill. Guess what? The part of the physics text that derives those formulas starts with “assuming infinite torque…” (Massless elephants on frictionless roller skates).

Those calculations tell you the optimal feeds and speeds, assuming infinite torque, based on the end mill geometry and the chip load as posted by the end mill vendor for the stock (material). They don’t tell you that you cannot go slower or what the impact is. Nor do they tell you how to get the best result when one cannot meet the optimal conditions.

Let me try to explain this simply. I’m hope you can see why torque is the major factor.

The end mill is rotating, and has little moment of inertia. It is entirely up to the spindle to keep the end mill rotating against the frictional forces of cutting. More flutes, more friction, more required torque to keep the end mill spinning at the requested RPM.

A 0.25" end mill is going to have a larger chip per tooth than an 0.125" end mill. More bite, more friction, and more torque is necessary to turn the end mill into the stock… sufficient force must be applied to do the cutting (and continue to do so).

The formulas work well largely because mills often have significant torque (they are designed that way) - close enough infinite (at least for the practical cases). With a small mill like the Nomad, the spindle has very limited torque and so have limitations on what it can do.

Real machining physics requires dealing with frictional forces and how the end mill deflects when moving through the stock. With limited spindle power/torque there are situations where an end mill cannot be rotated at the requested RPM - and kept at that RPM - the spindle will stall.

Most end mills are design for a maximum cut depth of 1/2 D (diameter). They aren’t designed to cut deeper than that. Yes, there are some that can go D and yes there are cases where a 1/2 D end mill can be used deeper is soft materials. Regardless, the point is there is a limit to how much flute can be exposed to the stock - by design.

Nothing says one cannot go less than that maximum depth. This reduces the friction and the necessary torque. But that solution may not, in effect, be faster than other solutions. Wider and shallower may turn out to be slower - overall - than narrower and deeper.

Is there a feeds and speed solution for a 0.25" end mill milling Al alloy on the Nomad? Perhaps. If there is it is likely to be slower than the 0.125" or not much faster.

mark

P.S.

If you search the forums, you’ll see that those that tried to use the 0.25" collet and an end mill to mill hardwoods (much easier to machine than Al alloy) were unable to do so easily - the spindle stalled.

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I’ve computed some speeds and feeds on Aluminum, and to show you what Mark said about is correct. This is from my end mill library:

0_25_inch_cut.png1365×162 18.5 KB

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thanks for the explanation. i see what you where talking about now . anyway got both 1/4 and 1/8 anyways ( 1/4 probably be used on another future project … il stick to 1/8 then .
am i correct in assuming that the spindle has about 50W of torque ?

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That’s it - ~0.07 HP.

mark

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@gscotti That looks like a google or excel sheet. Do you mind sharing? Looks awfully handy!

Also, thought I’d add this as relevant to the discussion: