Desktop cnc mill options?
Hi pmdude: I’ve run both bitty little homebrew machines and “real” machines, and I have to agree with ckeith1’s comment that if you’re expecting comparable performance from a stepper machine as you’ll get from a servo driven machine, you’re in for a rude disappointment.
I currently run both a Defiance VTX-1 machine and a Haas minimill (both servo).
My buddy just came back from a shop in Montreal that ran a Tormach (stepper).
When I quizzed him about the Tormach on the phone, he always told me what a great machine it was.
Well he ran the Haas last week and promptly said: “I take back everything I said about the Tormach being an industrial quality machine. It’s slower than molasses on a cold day”
Since then he’s run the Defiance too (it’s about the same size as a Light Machines Benchman) and he made the same remarks again.
This despite the fact that the Defiance is nowhere near the machine that the Haas is, and the Haas itself, is a low end machine compared to an Okuma or a Mori.
So, if your need is to make reasonably accurate parts reasonably quickly, you’ll be disappointed with anything less than a proper VMC, but you’ll have to drop twenty to forty grand into the pot to get something worthwhile in that class…unless you’re willing to take a chance on an older machine and face a possible retrofit.
If you can live with the limitations of a slow machine; my buddy still has very good things to say about the Tormach. (but he’ll never confuse it with a real machine again)
It is, however, less than the cost of a toolchanger on a real mill, and that’s important too!!!
Service has been reported to be very good so far, and the Tormach has been reliable apart from one minor glitch early on that was resolved cheerfully and promptly by Tormach.
Oh yeah: the differences between toy mills and real mills:
1) speeds, both milling and rapids.
I regularly run my Haas flat out with feedrates over 100 IPM and 6000RPM on steel parts and I’m not really competitive at those rates compared to machines with better spindle speeds, better mechanical features and better controls. Rapids are in the 700IPM range…way too slow to compete on any sort of volume production jobs.
The Tormach features a whopping 60 IPM rapids so far as I remember.
I wouldn’t own a production machine without it, neither would I give up a full enclosure and coolant.
3) Cutter life:
Bigger heavier smoother machines do FAR better in this regard…my buddy reports going through several endmills to run a job that I can do on my Haas without noticeable damage to a single cutter.
That’s the benefit you reap from a spindle whose bearings alone cost one third of the Tormach’s entire price.
4) Depth of cut:
Better heavier more accurate construction, bigger ballscrews, more powerful motors all contribute to the superiority of the industrial machines.
Bigger thermal mass, better damping, hunky ground ballscrews and linear ways, better controls for lookahead and acceleration ramping etc etc etc are the factors that contribute most here, and the cumulative differences are very noticeable.
A hobby class stepper driven machine will churn out an approximation of a part that is unlikely to be good enough to function as a part of a precision assembly like a mold.
I can bore four leader pin bores and four guide bushing bores in a mold base (without match boring them) on my “real CNC” and be able to just put the mold together without farting about. (the pins and bushings have less than 0.001″ clearance)
I can mill a core to tenths with cutter comp, and when I tell it to take another tenth, it will do so reliably.
That’s about all I can think of offhand.