Suitability of CNC 3020T for FR4 routing/de-paneling and soft plastics work?

[T1544E2048]

I'm considering buying one of those Chinese CNC 3020T (or 3040 or similar) machines, which are sold as "engraving" machines, but seem to be popular for low-cost introductory-level milling as well.  I just have a few questions for people that actually use them to make sure I'm not off my rocker in the way of expectations.  While I plan to use it for other things, the PCB app is the main reason for purchase, so that's why I'm asking here.

What I know it's not:
* I used to work at a company that had a captive tool room with Bridgeports and large CNC milling machines that were used to create and repair multi-thousand pound dies used in large molten metal diecast machines.  I didn't work in that department, but I've worked around them enough to understand that the 3020 isn't close to being on the same level as those machines.  "It is what it is" and it's not that.


What I'm NOT asking it to do:
* Create the traces on a blank PCB (home fabrication).  I know some people use it for that and it may work, but that's not my expectation or plan.


What I hope it CAN do:
* Drill and mill a series of holes and openings in your typical plastic and light aluminum project boxes and faceplates, with tolerances of +/- 005".

* Mill slots and other odd cutouts in your typical FR4 circuit boards, with tolerances down to (hopefully) 0.001".

* Take a group of large (preferably 12" x 18") finished PCB panels from a fab house, each of which has a couple dozen mixed-design odd-shaped boards, and de-panel, or assist in de-paneling those boards through either V-cuts, perf-holes, or fully-milled slots.  I know that the bed isn't 12x18 and that the panel may need to be re-positioned to get the entire area, but I'm looking for the concept to be valid.

* Create text on user interface panels using two-color stock (plastic, aluminum, etc)

* Use free or low-cost software such as DraftSight and either linuxCNC or Mach3/4 to create the CNC paths to accomplish the tasks listed above (this is one of the points I'm most fuzzy about the actual mechanics of).


Concerns that I have:
* According to a feeds and speeds table I found at http://www.precisebits.com/Reference/diamondcutfeedspeed.asp, using their diamondcut tooling to cut double-sided FR4, they recommend anywhere from 20,000 RPM to 60,000 RPM, depending on the diameter of the tool.  The 3020T only spins at 8,000 RPM.  This is my biggest worry...  Should I be concerned??  Also, the table isn't clear on whether these are recommended speeds and rates, or whether these are maximum speeds and rates...?

* There are USB and parallel port versions of the controllers for the 30x0 machines.  My understanding is that the USB versions are compatible only with the Mach3/4 software, but the parallel port versions are compatible with other software such as linuxCNC. Is that a fair statement?  Is the parallel port version the best option then, since it gives more software flexibility, even though it requires a PC with a true (non-USB) parallel port?

* Much has been said about the relatively poor quality of materials (cheap bearings, light-duty spindles, etc) used to construct these units.  Like I said above, I recognize I'm not buying a Bridgeport.  Do you think that it would be suitable for the light-duty work I've laid out above, and last maybe five years under light use?


Thanks in advance for anyone that can shed light on the questions.

[coppice]

The 3020 doesn't really spin at any speed. The spindle does that, and various spindles can be ordered with these machines. Some are fast, high power precise, and usually water cooled. Some are slower, have more play, and can run pretty hot. Its your choice.

[T1544E2048]

The 3020 doesn't really spin at any speed. The spindle does that, and various spindles can be ordered with these machines. Some are fast, high power precise, and usually water cooled. Some are slower, have more play, and can run pretty hot. Its your choice.

Well put.  I suppose what I meant to say was that, when looking at websites selling the unit, I usually see spindle speed ranges maxing out at 8,000 rpm.  If there are spindles available for the unit which do go up into the 30-50k range (and if that is really what I should be using), that would be good to know.

[mikeselectricstuff]

I have a 3040 and it works fine for milling PCB - I use standard carbide chip-breaker bits.
Haven't played around too much with feeds & speeds - As it's only used for occasional jobs I tend to just run it slowly for safety.
If using a lot you should arrange good dust extraction as fibreglass dust is abrasive and will not be good for bearings.
 

[coppice]

If using a lot you should arrange good dust extraction as fibreglass dust is abrasive and will not be good for bearings.

Its even worse for lungs.

[tsimon]

You might want to look at the Othermill - www.othermachine.co/othermill . It's made in the US and is primarily aimed at PCB design. Here is a write up I did on it:

https://medium.com/@tomsimon/lipo-charger-board-for-the-arduino-nano-39e709f459bc

Thanks,

-Tom

[edavid]

You might want to look at the Othermill - www.othermachine.co/othermill . It's made in the US and is primarily aimed at PCB design.

If he's shopping for an under $500 CNC 3020T, do you really think he's going to suddenly decide to spend $2200 on an Othermill?

[rhost]

The fastest Chinese spindles I've seen are watercooled and spin at 24k. Definitely not even close to a Jäger but they are not in that price range either. Your feed and speeds will be dependent on your end mill or drill size. I doubt it would be rigid enough for aluminum.

Sent from my SAMSUNG-SM-N900A using Tapatalk

[IconicPCB]

Jaeger is indeed the spindle to beat.

My machine ( home design ) runs 5 micron Renishaw linear scales, 100KRPM Jaeger spindle and preloaded NSK linear bearings and recirculating ball nut assemblies.