[joeavaerage]

Hi,
yes servos are great, so much so that I'll never buy another stepper again, no matter the price.

I use Delta servos, a Taiwanese brand made in China, but also DMM, a Canadian brand made in China, both are good quality, support, documentation and most importantly free set-up
and tuning software at fair prices. For example this is an entry level (B2 series) 400W Delta servo kit (servo, drive and cables) from my favoured supplier in China:

https://www.fasttobuy.com/220v-127nm...ol_p28069.html

At $398 they are not cheap, but good value.

There are cheaper Chinese brands, including ToAuto from this same supplier. I have no reason to doubt the quality nor the fact that they work but the support is questionable, the documentation poor
and no set up and tuning software. If this is your first foray into servos I would not make the experience any harder by buying cheap Chinese, Delta and DMM on the other hand are very worthy.
Newcomers to servos are often very taken with Clearpath servos, mainly because they are so simple to set up, and have been made that way in order to appeal to first time buyers. They are
very expensive for their power output, have very low resolution encoders and have virtually no IO compared to either Delta or DMM. They are good quality, good support etc, but too
damned expensive for what they are.

Craig

[TMToronto]

I think you have convinced me, after reading your posts and responses over time on the forum, to save up for servos on my next build. I may need to spend a little time researching the other PC based controller/software options. Were you always using Mach products (i.e., 3>4), and are there a few main reasons you prefer your Mach 4/ESS over something like Centroid's Acorn? This may be too far off topic so no need to answer if not comfortable doing so.

I believe Masso does use differential signals, although your real use case calculations certainly highlight the limitations of a lower pulse frequency.

[joeavaerage]

Hi,
yes I have used Mach for many years, firstly Mach3 and then for the last eight years Mach4.

At the time that I started there were very much fewer choices than today, and even choices like LinuxCNC have matured a lot over that time. LinuxCNC was back then,
by my estimate a lesser choice, whereas today LinuxCNC is a highly recommended control software.

Remember also that Mach3 used and popularised the parallel port which made it very cheap and accessible to many, me included.

One of the bug-bears of Mach3 is its scripting environment ( a cut down version of VB), its poor screen editing ability and atrocious MODBUS feature. When I became pissed off with those
I switched to Mach4 and have never looked back. The scripting environment (Lua in Mach4) has some challenges but is vastly more flexible and stable as is the Mach4 API, the screen editing features are light years ahead
and modules like MODBUS are a delight to use. These are all of course personal observations and no doubt others would either disclaim or outright deny them, but they are none-the-less my opinions.

Some of the 'turnkey' solutions like Centroid Acorn, Masso and Edge have all been developed over the last few years, and were not available when I was making my Mach4 choice. Even had they been
available back then I might have taken pause at the 'closed' nature of the software. You do as Masso intended or not at all, for instance whereas Mach4 is very widely flexible to accommodate a broad
range of machines and controllers. The only control solution that exceeds Mach4 in terms of flexibility is LinuxCNC but LinuxCNC requires some serious programming expertise to realise that flexibility.

In order to make full use of Mach4 you really need an external motion controller like an Ethernet SmoothStepper. There are six manufacturers of Mach4 ready motion controllers of varying features,
performance and price. The ESS suited my budget, is very well supported and cheap relative to its speed, 4MHz.

Windows based CNC software, Mach included, is a buffered motion control system as opposed to LinuxCNC which is a genuine realtime solution. A buffered solution does have some drawbacks,
but on average does very well. The absolute plethora of Windows based PC's means that you can probably find a suitable PC for free, one of the kids or grandkids cast-off school PCs for
example.

Amongst the likely favourable CNC software solutions to you are all in the range of a few hundred dollars......ie about the cost of one servo....so don't get to hung up on your choice, all of the
solutions will work. You might argue this is better than that and so on but if they are any good at all they'll all provide a solution that will happily make parts for you.

Craig

[JayneV]

I drew this simplified block diagram to help me understand which components fit where in the system for a visual representation (see attachment).

So if I understand things correctly, the motion controller software (Mach3/4, UCCNC, LinuxCNC, or other proprietary software such as Acorn or PlanetCNC) lives in the computer which processes the Gcode and sends the information to the motion controller. The motion controller takes the information from the computer and converts it into commands to drive motors, spindles or whatever and sends these commands to the BOB which basically just splits the data and sends it directly to motor drivers, VFD, coolant On/Off, etc. any signals from the machine that need to be sent back to the motion controller software such as limit switch activation, motor driver error signals etc, take the reverse path back to the computer for the software to deal with. Is this correct at an oversimplified basic level?

Also, it seems that some motion controllers may have a BOB combined on the same board and in the case of something like the Masso, then the computer, motion controller and BOB are all in the one device?

[TMToronto]

Thank you for sharing that Craig. It is a great review and explanation of options, and your own insights and opinions are appreciated.

[peteeng]

Hi Jayne - if your on North Island you should be soaking in a hot spa somewhere. We did 14 pools in 13 days once, I'm sure there will be one near you.... unless your in south island then hot pools are harder to find. Oh Queenstown.... yep south, you'll have to find a hotel spa then... We lived at hawea many years ago and I was a ski mechanic at wanaka, the days when you could rent for $40/week.....Peter

[joeavaerage]

Hi,
there is a place between Lake Rotoiti and Lake Rotoma. Flowing between the lakes is a modest river of icy cold beautifully clear water. Adjacent (25m) the river is a hot spring, and I mean boiling hot.
Its a common sight to see kit bags of food dangled into the hot spring whereon the food is cooked! You dare not get anywhere near the hot spring, one slip and you die a horrible death. The water that flows
from this hot spring forms a small creek, perhaps a couple of feet wide and the same deep and flows into the river. The ice cold water mixes with the hot to form a bath temperature mixture, just perfect.

The mixing occurs gradually, where the hot water encounters the cold it floats on the top. Thus when floating near there your shoulders will be unbearably hot while if you poke your bum down a little
deeper it gets frozen off by the icy water underneath. Further downstream the mixing is complete.

Its just a magic place, trees and other native vegetation all around, ducks floating in the by now warm river. Just magic!

I grew up in the North Island and there are a number of such places.

Another is Ketahi Springs, about half to two thirds of the way up Mt Tongariro. It is a several hour very steep walk to get there, about 5000 ft elevation. From the side of the
mountain is a hot spring of hot bath temperature and it forms a small stream. At that elevation in winter the place is blanketed in snow and yet you may strip off an immerse yourself in
beautifully hot water with a view extending 60 odd miles north, including Lake Taupo. Simply magic.

Craig

[JayneV]

Hi Jayne - if your on North Island you should be soaking in a hot spa somewhere. We did 14 pools in 13 days once, I'm sure there will be one near you.... unless your in south island then hot pools are harder to find. Oh Queenstown.... yep south, you'll have to find a hotel spa then... We lived at hawea many years ago and I was a ski mechanic at wanaka, the days when you could rent for $40/week.....Peter

Wow! 14 pools in 13 days is a good effort. There are some hot pools at Lake Tekapo, we were hiking there last week and walked past them but didn’t go in.

Yes, we are on the South Island. We left Queenstown yesterday and are now staying at the Hermitage at Aoraki Mount Cook. We will be here until Friday then fly back home. It was blowing a gale here last night and raining. Looks like the rain has settled in at least for the rest of today and part of tomorrow. We are going for a drive back down the valley today hoping the weather is a little better but it is still very beautiful even with the rain and limited visibility. It’s amazing how close NZ is to Australia yet the scenery is so very different. Might do some short hikes around here tomorrow whether it’s raining or not.

[JayneV]

Craig, those places sound amazing! Will definitely make a note for next time we visit. This trip was focused around the Queenstown marathon. Next trip will be all holiday. We haven’t seen much of the North Island other than a weekend in Auckland and a drive to Rotorua, so we are keen to spend more time on the North Island and the northern part of the South Island.

[joeavaerage]

Hi,

Might do some short hikes around here tomorrow whether it’s raining or not.

Watch out for the sandflies.....they have been known to carry off small children and pets! LOL

Craig

[joeavaerage]

Hi,
I love the area around Rotorua, or even better little further south around Lake Taupo and the mountains for geothermal wonders and scenery, and of course I
like Queenstown area with its majestic scenery, I find, as a Kiwi, that the traditional tourist hotspots just too damn busy and to my mind prohibitively expensive.

When I go on holiday I go to the Coast, ie the West Coast of the South Island. More scenery than you can shake a stick at, and pub around every corner and a 'hard case Coaster'
just waiting to regale you in tall tales and BS. If I had the time, and the forum allowed, I'd tell you a tale about Trev, a 70 year pot-smoking hippy that I spent the best part of a fortnight with
around Okarito. I'd only meant to stay overnight....but got captured by Trev, two young English woman.......well the story goes downhill from there!

Craig

[JayneV]

Hi,
I love the area around Rotorua, or even better little further south around Lake Taupo and the mountains for geothermal wonders and scenery, and of course I
like Queenstown area with its majestic scenery, I find, as a Kiwi, that the traditional tourist hotspots just too damn busy and to my mind prohibitively expensive.

When I go on holiday I go to the Coast, ie the West Coast of the South Island. More scenery than you can shake a stick at, and pub around every corner and a 'hard case Coaster'
just waiting to regale you in tall tales and BS. If I had the time, and the forum allowed, I'd tell you a tale about Trev, a 70 year pot-smoking hippy that I spent the best part of a fortnight with
around Okarito. I'd only meant to stay overnight....but got captured by Trev, two young English woman.......well the story goes downhill from there!

Craig

Craig, we too prefer to holiday in the less touristy type places, although as a tourist there are always some must see attractions. We really enjoy day hikes and it doesn’t take long to find trails all to yourself. Luckily Kiwiland is only a short flight from Sydney so now that borders are open again we can hopefully make many more trips to explore this beautiful place. Anyway, I’m sure we could go on and on and on about travel that could fill an entire thread. Might get back to reading about CNC motion controllers while enjoying the wet view from our room balcony…….wet, but still very beautiful.

[joeavaerage]

Hi,
yes you are right of course, miles off topic.

Your diagram of the basic arrangement is spot on. I have modified it a little to show some extra functionality.

In particular I have shown a Motion Buffer in the diagram. The PC plans a trajectory and posts a numeric stream corresponding to the controlled point in each axis in time slices, commonly 1 ms slices.
The motion buffer is a part of the controller, and may vary in length. For instance my ESS has a default motion buffer length of 180ms. Lets say the PC (Mach/UCCNC etc) produces an
instruction to move 0.002mm in a 1ms time frame, it could take as long as 180ms for that instruction to be honoured by the motion controller/BoB/Machine.

This is a common, even required feature of Windows based CNC software. The reason being that Windows is multi-tasking and cannot supply the motion controller with continuous live data, but
what it can do is calculate a bunch of trajectory and stuff it in the motion buffer. Thereafter Windows can go away and do other tasks, hopefully getting back to fill up the buffer again before it runs out.
If the buffer runs out the machine stalls, and usually does not restart, so running out of data is a failure.

I have also shown a separate path for data returning from the controller to the PC. The data returning to the PC will be the machine position as calculated by the controller, the state of all the switches etc.
My ESS reports to the PC 40 times a second. Lets say a switch operates on the machine and the PC is waiting for it. It could take up to 25ms for the switch even to be reported to the PC. If now the PC
wants to make some motion in response to the switch even it will do so but delayed by the length (variable) of the motion buffer. The combined delay could be over 200ms, which is way WAY too slow in many cases.

For an event like a limit switch the delay would be too long. The motion controller must handle the limit event autonomously in order to do it in a timely manner.

It is these delays that make Windows CNC solutions 'Buffered' and not 'Realtime'

LinuxCNC runs on a specialised distro of Linux that IS realtime, that is to say it does not require a motion buffer, or more precisely it does but of a few microseconds only. This means that LinuxCNC can be
a closed loop feedback controller. For this reason LinuxCNC is highly favoured for CNC use, but you have to be OK with Linux.

Craig

[Dongguan]

https://fuyouda.en.made-in-china.com...g-Service.html
CNC Stainless Steel Milling Machining Brass Metal Parts 3D Printer Parts Red Copper Throat Pipe CNC Machining Service

[Titaniumboy]

Maybe the diagram could also show that Mach 3 (and maybe Linuxcnc?) can go directly from the computer to the bob without needing a separate motion controller?

[JayneV]

Craig, thanks for the excellent explanation. It is all becoming much clearer how the control system works. Yeah, my diagram was very over simplified to get the basic idea of where the parts fit in the system.

@Titaniumboy I presume you are referring to connecting the bob directly to the computer parallel port? I’m not really interested in taking that route for a couple of reasons. Firstly, I need to find/buy a computer with a parallel port which means a fairly old machine. As I only have Mac computers at home (not counting a couple ancient windows laptops which I can’t get too start up, I’m pretty sure they have hardware faults of some sort), I would prefer to buy a reasonably recent refurbished pc which likely won’t have a parallel port. Secondly, and more importantly, from everything I’m learning, an external motion controller board would create a smoother more reliable setup.

One of the things scaring me away from windows based software is windows itself. I know there are many, many people running their CNC machines with windows based software so I probably shouldn’t worry. When I ditched windows for Mac nearly 15 years ago it was because I was fed up with the computer always wanting to perform updates or mysteriously losing a driver for the printer when I wanted to quickly print something or crashing for no apparent reason. It drove me up the wall so I bit the bullet and paid the money for a mac and never looked back. I still have the Mac desktop purchased in 2009 and it works flawlessly, it’s just getting a little slow, but it hasn’t crashed once in all those years. Sorry, went off on a windows rant for a minute. LinuxCNC sounds like a good option. Is it possible to boot into Linux residing on an external drive on a Mac without touching with the internal macOS hard drive to have a play with LinuxCNC to see if I like it?

Regarding the buffering required if using windows, does that cause any issues when operating the CNC? For example, if you need to hit the emergency stop for some reason, is that handled by the motion controller stopping the machine instantly or does the E-Stop signal need to go to the software to process and act on the signal, with the associated buffering delay? Or if you just need to pause the machine for some reason and then unpause it again later, does the buffering cause issues like maybe losing its place in the program cycle? Is there any real benefit having a real time system like LinuxCNC over a buffered system like windows, or does it not make much difference?

[mactec54]

Craig, thanks for the excellent explanation. It is all becoming much clearer how the control system works. Yeah, my diagram was very over simplified to get the basic idea of where the parts fit in the system.

@Titaniumboy I presume you are referring to connecting the bob directly to the computer parallel port? I’m not really interested in taking that route for a couple of reasons. Firstly, I need to find/buy a computer with a parallel port which means a fairly old machine. As I only have Mac computers at home (not counting a couple ancient windows laptops which I can’t get too start up, I’m pretty sure they have hardware faults of some sort), I would prefer to buy a reasonably recent refurbished pc which likely won’t have a parallel port. Secondly, and more importantly, from everything I’m learning, an external motion controller board would create a smoother more reliable setup.

One of the things scaring me away from windows based software is windows itself. I know there are many, many people running their CNC machines with windows based software so I probably shouldn’t worry. When I ditched windows for Mac nearly 15 years ago it was because I was fed up with the computer always wanting to perform updates or mysteriously losing a driver for the printer when I wanted to quickly print something or crashing for no apparent reason. It drove me up the wall so I bit the bullet and paid the money for a mac and never looked back. I still have the Mac desktop purchased in 2009 and it works flawlessly, it’s just getting a little slow, but it hasn’t crashed once in all those years. Sorry, went off on a windows rant for a minute. LinuxCNC sounds like a good option. Is it possible to boot into Linux residing on an external drive on a Mac without touching with the internal macOS hard drive to have a play with LinuxCNC to see if I like it?

Regarding the buffering required if using windows, does that cause any issues when operating the CNC? For example, if you need to hit the emergency stop for some reason, is that handled by the motion controller stopping the machine instantly or does the E-Stop signal need to go to the software to process and act on the signal, with the associated buffering delay? Or if you just need to pause the machine for some reason and then unpause it again later, does the buffering cause issues like maybe losing its place in the program cycle? Is there any real benefit having a real time system like LinuxCNC over a buffered system like windows, or does it not make much difference?

Windows when running a CNC Control is operating in real time so it is not as Craig has been posting, LinuxCNC will not run on your Mac Platform you need a PC just for that to be installed, and not all PCs are suitable for a Linux install, LinuxCNC control by itself is not very good, it needs a motion controller also to be of any good, when you use an external motion controller, they all use a buffered system, Mesa makes the best boards for LinuxCNC control, here is a link for you to find out about LinuxCNC and a Good video on LinuxCNC

Getting LinuxCNC

https://mesaus.com/

https://www.youtube.com/watch?v=1dy8Dgzcgq4

[joeavaerage]

Hi,

Windows when running a CNC Control is operating in real time so it is not as Craig has been posting

BS Matec, all Windows based CNC control systems are buffered. The motion controller is realtime, but the PC suppling the trajectory data is not.
See "Professionals Guide to Windows 7 Embedded Standard 2nd Ed.' by Sean Liming. Chapter 8 particularly.

Regarding the buffering required if using windows, does that cause any issues when operating the CNC?

In general no. When you Estop the contents of the motion buffer are aborted so the Estop happen immediately. If you FeedHold however the contents of the motion buffer are executed before the machine stops.
In the case of my installation that means 180ms worth of movement AFTER I hit FeedHold

In the early days of Mach3 when everyone used a parallel port it was not uncommon for the motion buffer to be 1/2 a second or longer. Under those circumstances the motion buffer delay was
noticeable and sometimes even objectionable. These days with nearly everyone using an external motion controller and more powerful PCs its possible to reduce the motion buffer down to well under
100ms. Smurph runs his Mach4 installation with a motion buffer of only 30ms. The PC running my machine (dual core Atom, no graphics card) is so low powered I use the ESS default of 180ms.
Its near enough to instantaneous to be good enough for me.

The reason I pointed out the motion buffer delay was to show why Mach cannot be closed loop controller, or more precisely use the PC to close the loop. The motion controller
in JayneV's diagram is realtime however, and not therefore subject to the crippling delays and so can close the loop. Controllers like Galil and Dynamotion come to mind.
With all modern AC servos now closing the loop at the drive, the need for the PC and/or the motion controller having the smarts to close the loop, the need for smart controllers like
Galil is diminishing.

Craig

[mactec54]

Hi,



BS Matec, all Windows based CNC control systems are buffered. The motion controller is realtime, but the PC suppling the trajectory data is not.
See "Professionals Guide to Windows 7 Embedded Standard 2nd Ed.' by Sean Liming. Chapter 8 particularly.



In general no. When you Estop the contents of the motion buffer are aborted so the Estop happen immediately. If you FeedHold however the contents of the motion buffer are executed before the machine stops.
In the case of my installation that means 180ms worth of movement AFTER I hit FeedHold

In the early days of Mach3 when everyone used a parallel port it was not uncommon for the motion buffer to be 1/2 a second or longer. Under those circumstances the motion buffer delay was
noticeable and sometimes even objectionable. These days with nearly everyone using an external motion controller and more powerful PCs its possible to reduce the motion buffer down to well under
100ms. Smurph runs his Mach4 installation with a motion buffer of only 30ms. The PC running my machine (dual core Atom, no graphics card) is so low powered I use the ESS default of 180ms.
Its near enough to instantaneous to be good enough for me.

The reason I pointed out the motion buffer delay was to show why Mach cannot be closed loop controller, or more precisely use the PC to close the loop. The motion controller
in JayneV's diagram is realtime however, and not therefore subject to the crippling delays and so can close the loop. Controllers like Galil and Dynamotion come to mind.
With all modern AC servos now closing the loop at the drive, the need for the PC and/or the motion controller having the smarts to close the loop, the need for smart controllers like
Galil is diminishing.

Craig

For the last 35 + years Ac servo drives have been able to close the loop in the drive, so not much has changed it does not have to be a modern drive

There are no crippling delays as you say, if a system is designed / setup correctly.

Why do you post about things you know nothing about Galil / Dynamotion, there is always a place for these controls, there will always be a need for them, your vision as to what they are used for is very narrow, I went through the Galil training as an installer, and there are more used in the industry for other applications than CNC which has very small usage for CNC machines

Again, A Window's PC can work in real time, for a CNC Control and most do when used for CNC machines, SoftServo was the first true PC Windows based control in the world, and it runs in Realtime from a PC Windows operating system

Saying that a Windows based PC can't do Realtime is just crazy and a lack of Knowlege on your part,

How is it done, the CNC software when developed correctly locks one of the CPU Cores (which = 2 Threads) this is dedicated to run your application in Realtime, the only reason to have an external FPGA (Motion Controller) is computers in general don't run fast enough, for some applications

http://softservo.com/data_sheets/Ser...l_Brochure.pdf

[joeavaerage]

Hi,

Again, A Window's PC can work in real time, for a CNC Control and most do when used for CNC machines, SoftServo was the first true PC Windows based control in the world, and it runs in Realtime from a PC Windows operating system

Native or retail Windows cannot do realtime, but there are ways around that, like dedicating one core as realtime scheduler, for instance Interval Zero sells such a solution.....but its far away from a hobby solution. The license cost of
the realtime core costs more than Windows does.

All Windows PC based CNC solutions that do not use the a realtime core HAVE to be buffered.

SoftServo uses such a realtime core and therefore achieves genuine realtime performance....but at eyewatering cost.

Galil DMC-40x3, the current model three axis controller is $2200USD (from Galil website) is not a hobby solution.

Craig