CNC pre-buying questions

Mostly Printed CNC - MPCNC Advice
21

Very subjective question. I rarely use more than 5" in either direction, 3/4" Z. I used 13" one time to cut the LR parts.

22

Thanks, Ryan.

I felt there was no right answer and have several different thoughts on it.
One is you canā€™t have too much capacity and the other is that I wonā€™t get that space back once I fill it.

23

Build it as small as possible, going bigger is simple, learning on a large machine is difficult. I have that on the specs and size pages.

24

Thanks for the advice, Ryan.

How about 24X24?

25

You can do a lot of wood work with a machine that size. Donā€™t overdo it on the Z though. It would be hard to cut metals with a machine that size, but certainly flat work will be ok.

26

Thanks, Jeffeb3.
I donā€™t have any thoughts of metal at this point.
What would you suggest the Z axis be?

27

Total size? or Part size?

Mine has a 24"x24" cut size, so the machine is a bit larger than that. Iā€™ve only had one situation where I wished it was larger, but I worked around that.

I agree that your z-height needs to be as little as you can get away with. Mine is larger than it needs to be, so Iā€™ve grown accustomed to using stacked 3/4" MDF to raise the spoil board up to the router to reduce how far down the Z has to reach.

28

Thank you, David.

I was meaning work area.
As far as z-height, I put 4" in the calculator even though it defaulted 3"

I assume that is above the table and not the work piece and needs enough room for the bit and bit change as well as the work piece.

29

There is not a number, above which will be bad and below will be good. But a Z that is twice as long is 4x less rigid. So 3" is 75% more rigid than 4".

Edit: But, at some point it is rigid enough, so donā€™t pull your hair out trying to optimize it.

2 Likes
30

Thank you.
Is that 3" (for example) from the table top to the bottom of the collett or what is being measured?

31

I think it is from the bottom of the legs to the bottom of the gantry. You should mount the router so the collet is at or a little below the bottom of the gantry.

@vicious1, can you confirm?

1 Like
32

correct

33

Iā€™ll start with 3" since that is what the default is.

Default knows a lot more than me.

Thank you

2 Likes
34

Ok. Now Iā€™m curious.

Hereā€™s my current heightā€¦ are you saying Iā€™m too tall? Iā€™m currently using 1.5" of MDF to raise my spoilboard up to the router, but will having the legs themselves this long cause issues still? It might explain why I always feel like my machine isnā€™t as rigid as some other pieces. I only made it this big because sometimes I pull the extra MDF off when routing the top of tall pieces.

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35

Just observing this: your foot looks custom. It is screwed down and rigid?

36

Thatā€™s the old foot.

1 Like
37

Itā€™s not necessarily the legs that is the problem, itā€™s the z length hanging down. The legs give you a little flop, but the z tubes will flop more. Raising your cutting surface up closer helps with that.

1 Like
38

Ok. I always thought I was good there. Something was just worded recently that made me think otherwise.

The foot is the original one. It is screwed down.

39

Conduit sizes have me confused now.
Went to 2 places and measured 12" and 3/4" EMT conduit.
The measurements were way off spec.
For example, the 1" measured from 29.6-31.3 mm and the 3/4" was 22.33-24.65.

How much tolerance do the printed parts have?

40

Hi Larry,

I was able to get 1" stainless drops at my local Alro outlet store for around 2.75/pd. Check Ebay, shipping may drive the cost up however.

B