General Centroid processing speed & accuracy question

[Simon]

Hey all,

so I am not an expert, at all. But I would really appreciate the opinion from someone who knows a lot about the Centroid control systems and other systems like Beckkhoff, Heidenhain, Fanuc, Mitsubishi, Siemens.. industrial CNC controls in general.

I only know words like xxx blocks look-ahead, kHz/MHz step frequency (always confused already there, is that usually per axis or in total? Would make a lot of a different number if that number is total on a 5 axis simultaneous operation I reckon..), xxx milliseconds/nanoseconds refresh rate and so on. Don't really know where the bottleneck usually sits with that though. I pretty often maxed out previous controls causing them to jitter and not get behind the G-code input, already with smoothing filter turned up etc. - not knowing what's the fault - control, motors/drives, code or something in between.

Now, when I talked years ago with someone from a machine tool builder in Germany, he told me pretty much all these entry systems (like EDING CNC in Europe) are not fast enough, there was one entry system (Beamicon Triple Beast) which had a 2MHz max step frequency it could handle (per axis/in total?). He told me if I want to do high speed work there is no way around something like a Beckhoff control, where the industrial PC alone would be 1400€ before tax, with servos and servo drive prices similar to Yaskawa 7 series.

When I look at the brochure of the Delta A3 servos they are talking about 4Mpps (mega points per second) maximum input step frequency at pulse + direction. Now when my control is talking kHz, and my feed is somewhere at 15m/min, the bottleneck would be obviously the control if I'm not mistaken? And when adding a linear encoder on all axis additionally, things get only worse for the control in terms of handling surfacing and such?

Would highly appreciate some input there from someone. Also, which control and what type of servos and drives would be most beneficial for high speed high feed surface machining? Would the Centroid Oak control make any difference compared to the Acorn?

And what's exactly the difference in all that between a Centroid, for example, Hickory and a Fanuc control with High speed machining option? Fanuc explains it as "High speed machining options provide look ahead, enhanced acc/dec control, and automatic feedrate control to increase both speed and accuracy". Would the same kind of performance be feasible with an Acorn control?

Asking because I would love to use Acorn. I like the community behind it, I like the pricing, I like all the how-to's and resources, I like that they are not some Chinese Fanuc rip-off from Aliexpress and not some "Request for quote" and "get in touch with our technician" type of company.

- Simon

[suntravel]

If you want linear encoders on all axes, you have to use at least Acorn 6.

max. pulse output 1250 kHz
max. pulse input 6000 kHz

Uwe

[spikee]

I'n my humble opinion, for such high demands, ethercat is probably better

[Simon]

If you want linear encoders on all axes, you have to use at least Acorn 6.

max. pulse output 1250 kHz
max. pulse input 6000 kHz

Uwe

Thank you Uwe! Have you implemented linear encoders with a Centroid control before?

I'n my humble opinion, for such high demands, ethercat is probably better

So there would be only the Centroid Hickory with the EtherCAT bus system, correct?
Well, Chinese harmonic drives get cheaper by the day, 5 axis CAM gets more and more accessible and parts get more and more complex. 5 axis is going to be the future nonetheless, we could work on a Deckel FP1 like 70 years ago but choose to build our own mills/routers and get it done with CNC

- Simon

[suntravel]

Hi Simon,

my lathe is with Acorn 6, 4 axes and linear scales for closed loop.

Uwe

[floridamachineshop]

If you want linear encoders on all axes, you have to use at least Acorn 6.

max. pulse output 1250 kHz
max. pulse input 6000 kHz

Uwe

I saw these figures in the Acorn 6 installation manual, but I wasn't 100% clear if it was for each individual axis, so all 6 axes can send/receive at that maximum rate simultaneously, or if that spec represented the controller's total capacity to handle pulses and that specification had to be shared across all the axes in motion at any one time.

[cnckeith]

each axis can run at the max rate stated in the documentation.
all at the same time.

[Simon]

each axis can run at the max rate stated in the documentation.
all at the same time.

That is awesome.
To explain myself a bit: I do wooden form work, which led to me milling it out of aluminium and sometimes steels as well, as we were making smaller and smaller parts with higher accuracy needs. There are, unfortunately, tighter corners as well, so I often have to finish the surface with a 1/8" or smaller ball end mill. High quality tooling with shrunk fit tool holders, no backlash (pre-tensioned) ballscrews, negligible runout, rigid workpiece fixture.
We always run into the same problem: Feeds/speeds/stepover/roughing toolpaths and Fusion specs like smoothing and so on are right on, machine is geometrically pretty darn good, but in the end I always get some type of "pitting" on the surface. That results in some painful manual finishing work to be done and accuracy suffers from that as well.

When we looked at a new machine they offer software options for exactly this phenomenon. They include a picture of a surface like mine, and another one pretty much perfect picture of a surface with the option turned on. I mean with standard smoothing, cutting down the code, your accuracy will obviously suffer but they advertise as if with such control software options that is negligable as it appears to work different. There is also not a lot of info how it actually works - just faster processing speeds, refresh rate, some advanced maths behind it, servo tuning, some whatever, I don't know.

I don't know anything behind the mathematical or electronical challenges behind a CNC control, but would love to know whether or not this could be a feature with Centroid controls in the future. I would definitely pay for it as an upgrade if it is not ridiculously expensive.

[cnckeith]

each axis can run at the max rate stated in the documentation.
all at the same time.

That is awesome.
To explain myself a bit: I do wooden form work, which led to me milling it out of aluminium and sometimes steels as well, as we were making smaller and smaller parts with higher accuracy needs. There are, unfortunately, tighter corners as well, so I often have to finish the surface with a 1/8" or smaller ball end mill. High quality tooling with shrunk fit tool holders, no backlash (pre-tensioned) ballscrews, negligible runout, rigid workpiece fixture.
We always run into the same problem: Feeds/speeds/stepover/roughing toolpaths and Fusion specs like smoothing and so on are right on, machine is geometrically pretty darn good, but in the end I always get some type of "pitting" on the surface. That results in some painful manual finishing work to be done and accuracy suffers from that as well.

When we looked at a new machine they offer software options for exactly this phenomenon. They include a picture of a surface like mine, and another one pretty much perfect picture of a surface with the option turned on. I mean with standard smoothing, cutting down the code, your accuracy will obviously suffer but they advertise as if with such control software options that is negligable as it appears to work different. There is also not a lot of info how it actually works - just faster processing speeds, refresh rate, some advanced maths behind it, servo tuning, some whatever, I don't know.

I don't know anything behind the mathematical or electronical challenges behind a CNC control, but would love to know whether or not this could be a feature with Centroid controls in the future. I would definitely pay for it as an upgrade if it is not ridiculously expensive.

if you want to run fast and as smooth as possible, use the Centroid Hickory CNC controller.
more info here. https://shopcentroidcnc.com/hickory-cnc-controller/

While Acorn and AcornSix perform better than their competitors, there is only so much you can do with the step and direction axis motor drive interface.

Our g code smoothing technology enhances a well designed and configured machine tool even further and works with any of our CNC control platforms. more info here. https://www.centroidcnc.com/centroid_di ... manual.pdf

machine design can not be overlooked, a great cnc control will not perform well on a bad machine design. rigidity, axis motor gearing as well as axis motor sizing (torque/rpm etc) are very important.

[Simon]

each axis can run at the max rate stated in the documentation.
all at the same time.

That is awesome.
To explain myself a bit: I do wooden form work, which led to me milling it out of aluminium and sometimes steels as well, as we were making smaller and smaller parts with higher accuracy needs. There are, unfortunately, tighter corners as well, so I often have to finish the surface with a 1/8" or smaller ball end mill. High quality tooling with shrunk fit tool holders, no backlash (pre-tensioned) ballscrews, negligible runout, rigid workpiece fixture.
We always run into the same problem: Feeds/speeds/stepover/roughing toolpaths and Fusion specs like smoothing and so on are right on, machine is geometrically pretty darn good, but in the end I always get some type of "pitting" on the surface. That results in some painful manual finishing work to be done and accuracy suffers from that as well.

When we looked at a new machine they offer software options for exactly this phenomenon. They include a picture of a surface like mine, and another one pretty much perfect picture of a surface with the option turned on. I mean with standard smoothing, cutting down the code, your accuracy will obviously suffer but they advertise as if with such control software options that is negligable as it appears to work different. There is also not a lot of info how it actually works - just faster processing speeds, refresh rate, some advanced maths behind it, servo tuning, some whatever, I don't know.

I don't know anything behind the mathematical or electronical challenges behind a CNC control, but would love to know whether or not this could be a feature with Centroid controls in the future. I would definitely pay for it as an upgrade if it is not ridiculously expensive.

if you want to run fast and as smooth as possible, use the Centroid Hickory CNC controller.
more info here. https://shopcentroidcnc.com/hickory-cnc-controller/

While Acorn and AcornSix perform better than their competitors, there is only so much you can do with the step and direction axis motor drive interface.

Our g code smoothing technology enhances a well designed and configured machine tool even further and works with any of our CNC control platforms. more info here. https://www.centroidcnc.com/centroid_di ... manual.pdf

machine design can not be overlooked, a great cnc control will not perform well on a bad machine design. rigidity, axis motor gearing as well as axis motor sizing (torque/rpm etc) are very important.

Thank you for your answer.
We will definitely try out the Hickory control. First of all, this community is just great, your support is great. The products seem to be well made with lots of thought behind it, in the USA, and still affordable.
If we were to buy a new machine with a Fanuc control, it throws us in a sterile environment, with sales persons which are still very knowledgable, but hesitant to give out details (rightfully so, it's probably a very competitive market) and there is no real community behind it like it is with Centroid; we have to take them at their word. They are though, with all respect, still on a different level - but that comes with different cost as well. I am eager to see how the Hickory will perform. We would probably use Yaskawa servos with Bus connections. The machine is very rigid, Japanese made cast iron with oversized linear guides and ballscrews. For finishing ops there is no to us measurable deflection. Ballbar tests are (according to a befriended service guy) great. We've even sent out shrink fit tool holders to be balanced and measured out for run-out. Shop is not in a highly fluctuating temperature climate. No floor vibrations accumulated from other machines sitting aside of it.

We looked at Brother Speedios which seem to be amazing. Completely different mechanics/general machine layout though. But it would be perfect for surfacing as well. They showed us mold parts, and they looked absolutely flawless - with a cycle time I couldn't really believe. From what I've been told by others they are basically a Linux CNC control, with lots of Brother's engineering on top of it. Even though they are drill/tap machines, everyone I've asked about them is absolutely loving them, doesn't matter if they are machining castings, doing smaller mold work, higher accuracy work, large quantity work. Is centroid not also Linux based?