I have been looking at CNC routers to cut parts. It appears that the positional accuracy and repeatability of the low priced $6000-$8000 machines generally Chinese made machines have positioning accuracy of .003"-.005". It seems to me that this is not good enough for a tight fit for gluing? The machines that I have seen that have a better positioning repeatability .001" run about $16,000. Does anyone have experience with any of these machines and part cutting that they would care to share?

Thanks
Rob

CNC is never quite as accurate as say Laser, laser is exceptional in cutting accuracy and for $5000 will get a great laser, with a 1200x900 bed

What material are you wising to cut? and what are you wishing to make?

I do like the way a good CNC can finish timber and composite parts, But you will need to spend a lot to get a great CNC, The Likes of EMHW and other have machines wirth $50K+ up.

In terms of part fit, Even with laser with doing tabs you need to allow for the Kerf or laser beam thickness, Same thing with CNC so there is a bit of trial and error to get them setup right and with your parts desingn.

But my feeling is that with that level of cnc accuracy it wont be a problem, More often you will encounter material thickness variations that will cause loose or tighter fitting parts.Not so much from the accuracy of the machine.

The materials to cut would be the typical balsa, plywood lite and aircraft birch, cured composite, and maybe some aluminum and brass.

I Would look at Laser if doing mainly wood or thin composite, Like 1mm or 2mm carbon, a 100W laser will do plenty and is quiet and mess free.

Do you have a laser or CNC?

Originally Posted by RgHan

I have been looking at CNC routers to cut parts. It appears that the positional accuracy and repeatability of the low priced $6000-$8000 machines generally Chinese made machines have positioning accuracy of .003"-.005". It seems to me that this is not good enough for a tight fit for gluing? The machines that I have seen that have a better positioning repeatability .001" run about $16,000. Does anyone have experience with any of these machines and part cutting that they would care to share?

Thanks
Rob

Rob,

I guess it depends on what you plan on using it for. .1mm (.003") has proven to be more than accurate enough for my projects at home. For a business perhaps not but for home / modelling projects I've found it plenty accurate enough.

To be honest, I tend to design in about twice that much (~.25mm) as a clearance value so the parts slip together easily but still have nice fit.

I think what is more important is how the machine is designed with regard to keeping debris out of lead screws, etc as it really sucks to have a piece of debris jam up your machine in the middle of a long cutting process.

Originally Posted by RgHan

Do you have a laser or CNC?

100W Laser with a 1200x900 Bed

What brand is your laser? This is what you paid $5000 for?

Thanks

Originally Posted by RgHan

What brand is your laser? This is what you paid $5000 for?

Thanks

This Pretty close to what we have, Cant recall the actual brand.

https://www.aliexpress.com/item/1005...archweb201603_

You should be able to get one landed in the USA for about $4500-5000usd with all taxes and dutys,
Over here you looking at about $7000Aud at best for one like we have.

Best way to buy is direct from factory have it shipped to a local port and then get it collected from there.

If you are considering a chinese router...

1) Make sure it has ball screws on all axis, dual on y
2) Make sure it is using servos and NOT stepper motors or chinese drives, Demand leadshine at a minimum and perferably delta, or yaskawa or mitsubishi servos, 600 watt minimum for a 4x8
3) Demand it has hiwin linear rails no dove tails
5) ONLY GET AIRCOOLED spindle, do not get any of the watercooled garabage spindle.
6) ONLY PAY WITH CREDIT CARD from a company like alibaba, do not under any circumstance pay by check.
Realize that 95% of these machines come Jinan in China, the frames are almost identical.

This is a clients 6040 I retrofitted with one of my G540 controllers.

The accuracy achieved is always based on the calibration instrument's resolution.

G540 Accuracy Achieved On A 6040 Retrofit (.002mm)!.. (18 min 47 sec)