Request for benchtop CNC mill recommendation

[4world]

You experts have probably heard this question a 100 times so if you can even point me to an existing thread, I'd thank you a million times. My last post asking this question was 9 years ago (and I didn't buy at that time). I've seen the Novakon and Syil offerings from there but that's maybe old now. Any new help would be greatly appreciated.

My conservative needs:

1. Ready to use (not a build)
2. AXIS: 3-axis
3. CNC: Full CNC (as advance control as possible, e.g., even spindle speed control via software)
4. MATERIAL: Mostly aluminum but maybe sometimes mild steel (even at slower cutting speeds)
5. SPINDLE SPEED: ~ 10,000 or so (because I need to be able to use small end mills for micromachining)
6. MOTOR HP: Around 0.5HP.
7. WORK ENVELOP: Min. approx. X=7", Y=5", Z=4"
8. MACHINING ACCURACY: 0.001" or better
9.SIZE: Around 48"W x 36"D x 72"H so it might fit in my garage with other equipment
10. OPTIONS: Later possibility of adding automatic tool changer and 4th axis
11. ADDITIONAL PREFERENCES IF POSSIBLE:

- BLDC motor

- Servo system (feedback) on XYZ motors

- Ball bearing where there's an option to keep low backlash

My background:

12. BUDGET: Initial (immediate) around $10,000 but could stretch it to $15K. With options later, could go to $20K
13. AGE: 59M
14. EDU/SKILLS: Electrical & software engineer, R&D experience in medical instruments design, with some mechanical fabrication experience (by hand, getting it done through shops, just learning Solidworks/3D modeling

15. PURPOSE OF THIS CNC MILL: Low usage prototyping work for testing new R&D ideas. At my age, it seems more economical (time and money wise) to invest in a hassle-free CNC mill (and maybe a similar lathe later if needed) where I can dump my 3D designs to automatic machines to get them fabbed rather than do a lot manually or get them repeatedly fabbed outside.

Thank you for reading .... (I'll try posting on other forums if I don't get responses here as I know your time is precious and you already answer so many questions.)


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[awerby]

You should check out the Taig mills we sell. The X and Y envelope dimensions are bigger (12" and 6") although Y is a bit smaller (4.5"). The spindle goes up to 10,000 RPM, and the overall accuracy is about what you're looking for, especially if you go for the ball screw option. It can cut aluminum and steel, and wouldn't have any trouble fitting in your space. Best of all, the price is nowhere near what you're talking about spending, even if you add the 4th axis.

[arizonavideo]

The Taig is really small.

The 440 is a good size and comes in a few different configurations. 10,000 RPM.

https://www.tormach.com/pcnc-440/

[4world]

I was almost about to buy the Tormach Premium package for 440 but then this is a damning review too convincing to be ignored:



Numerous people have similar experience as the author of the above in the comments section. It's too risky for me to ignore such a review!

[he1957]

Remember to add cost of tooling, as well as holding methods (if you don't already have what you need) because this can add up very quickly.

[4world]

Remember to add cost of tooling, as well as holding methods (if you don't already have what you need) because this can add up very quickly.

Good point! Can anyone please give me a budget I should reserve for cutting tools (not holding vise)? Say a complete set of end mills and drill bits of good quality (mostly for mild steel and aluminum)? I have never owned or used a mill before.

Thank you

[arizonavideo]

The only thing I can say is all the lower price mills that I have seen run China ball screws. If you don't check every one and the support bearing you will get loose ones.

I would guess the 440 is made all in China and they ship out some dogs.

Looking at a few blogs it looks like the 440 is running C7 grade rolled screws. For a mill that size that would be D=16mm.

I have been selling that screw and the 20mm screws for years. Literally hundreds of them. I used to re pack the single nuts for each screw. This tells you a lot about the error in the screws because of the fit. It was possible to be under .002" backlash with most of the screws like that. Many would let you get to .0015" backlash.

The thing here is how they come in in stock form. I have seen ball nuts with different size balls, flat balls, bad ramps on the returns and a few sets had ll the screws were defective. Some had over .007 lash stock.

With the double nuts its easier to hold under .001" backlash. The nuts rarely come in set up properly so that would explain the horror stories. Some are too tight, most just loose, some so loose you wounder what they were smoking.

For your use it looks like you might wand better screws if you run vary small cutters and do mostly 3D work.

Really it would not be all that hard to go to a ground screw or see if they can install ground screws, they use them in other mills.

I could re do the screws fairly fast and get you under .001". I also do a bellvill preload system that ill stay tight forever.

[4world]

The only thing I can say is all the lower price mills that I have seen run China ball screws. If you don't check every one and the support bearing you will get loose ones.

I would guess the 440 is made all in China and they ship out some dogs.

Looking at a few blogs it looks like the 440 is running C7 grade rolled screws. For a mill that size that would be D=16mm.

I have been selling that screw and the 20mm screws for years. Literally hundreds of them. I used to re pack the single nuts for each screw. This tells you a lot about the error in the screws because of the fit. It was possible to be under .002" backlash with most of the screws like that. Many would let you get to .0015" backlash.

The thing here is how they come in in stock form. I have seen ball nuts with different size balls, flat balls, bad ramps on the returns and a few sets had ll the screws were defective. Some had over .007 lash stock.

With the double nuts its easier to hold under .001" backlash. The nuts rarely come in set up properly so that would explain the horror stories. Some are too tight, most just loose, some so loose you wounder what they were smoking.

For your use it looks like you might wand better screws if you run vary small cutters and do mostly 3D work.

Really it would not be all that hard to go to a ground screw or see if they can install ground screws, they use them in other mills.

I could re do the screws fairly fast and get you under .001". I also do a bellvill preload system that ill stay tight forever.

This is very sensible advice. Thank you arizonavideo.

Tormach should do more QC and use ground screws or the other system you if they are selling such expensive mills (at least give customers the option to pay more and get machines that use higher quality material).

Now I am seriously looking at the Microproto (MicroMill DSLS 3000). I'll see if they can install better ball screws for some extra charge. Do you have any recommendation on which ball screws or the belleville preload system you mention?

Thanks

[dazp1976]

This is very sensible advice. Thank you arizonavideo.

Tormach should do more QC and use ground screws or the other system you if they are selling such expensive mills (at least give customers the option to pay more and get machines that use higher quality material).

Now I am seriously looking at the Microproto (MicroMill DSLS 3000). I'll see if they can install better ball screws for some extra charge. Do you have any recommendation on which ball screws or the belleville preload system you mention?

Thanks

Agreed. Good advice.
I've just been looking at my double nut C7's I got for my PM25 clone.
Needed an extra spacing of 0.08mm on 1 and 0.05mm on the other to get them to a tight-ish point.
Tin foil/cooking foil whatever you want to call it seems good enough to me for thin shimming
Just need to try them out (eventually when it's all built). They're at a point where they only spun about 1 rotation when flicked by hand so see how it goes.

I've abandoned trying thrust bearings on these stock Chinese C7's now too. They just don't sit correctly on them.
Going to give 7201-2rs AC bearings a whirl, fit much better on the shaft end.

[arizonavideo]

On the micro mill.

They list the lead screws as.

1/2 inch 20 pitch Cr-Mo leadscrews with adjustable split bronze nuts on all axes.

This is not even a ball screw but a Acme screw with bronze nut. Not really a good system.

You don't need a large mill but i can say anything about the mills smaller then the PM-25 because I have not used them.

Perhaps others have a better idea for a small mill.

[awerby]

There's now an option for ball screws on the Taig mills; the model equipped with them is the 5019 ER. The ball screws are 5 pitch, so rapids can be much faster than with the standard 20-pitch screws, and soft materials can be cut faster.

[109jb]

MACHINING ACCURACY: 0.001" or better

IMO, if you really require 0.001" or better accuracy then you are in profile linear rail and ground ballscrew territory.

[shaggyd]

I have an Intelitek Expertmill with tool changer and tooling for sale on ebay. It will fit most of your needs. The only thing it's missing is 10K spindle. It has a 5K spindle which you can override with a POT. It's my understanding the bearings are only rated to 7,500 RPM. Asking $2,900. It cuts aluminum nicely for a benchtop. I would go with something bigger (more rigid) for cutting steel.

https://www.ebay.com/itm/VIDEO-Intel...eEiJ:rk:1:pf:0