Best components?

[rodw]

Having read this thread and noting your background. I would suggest you look at LinuxCNC becasue its got a full range of industrial quality interfaces from Pico systems and Mesa.

Depending on the PC you are going to use, a Mesa 5i25 or 6i25 (PCI/ PCIe) interface and a 7i76 daughter card would cover your needs. I use a Mesa 7i76e card which is essentially the same thing that is connected by an ethernet connection. The thing that stands out with the 7i76e is that it has 32 inputs, 16 outputs, 5 stepgens, spindle control, spindle encoder input, 2 MPG inputs, and 3 analog inputs before you need to add some daughter cards that provide almost unlimited expandability. Mesa also has a range of hardware to drive servos, encoders and resolvers of all descriptions. In my view, a 4x4 table requires a lot more inputs than whats available on a standard parallel port BOB.

The advantage LinuxCNC has over Windows is that it is installed on a Real Time Operating system that guarantees precise timing so things are guaranteed to happen at 1000 times per second while the Mesa hardware stepgens can operate at up to 10 MHz.

[Outlawtaz]

Having read this thread and noting your background. I would suggest you look at LinuxCNC becasue its got a full range of industrial quality interfaces from Pico systems and Mesa.

Depending on the PC you are going to use, a Mesa 5i25 or 6i25 (PCI/ PCIe) interface and a 7i76 daughter card would cover your needs. I use a Mesa 7i76e card which is essentially the same thing that is connected by an ethernet connection. The thing that stands out with the 7i76e is that it has 32 inputs, 16 outputs, 5 stepgens, spindle control, spindle encoder input, 2 MPG inputs, and 3 analog inputs before you need to add some daughter cards that provide almost unlimited expandability. Mesa also has a range of hardware to drive servos, encoders and resolvers of all descriptions. In my view, a 4x4 table requires a lot more inputs than whats available on a standard parallel port BOB.

The advantage LinuxCNC has over Windows is that it is installed on a Real Time Operating system that guarantees precise timing so things are guaranteed to happen at 1000 times per second while the Mesa hardware stepgens can operate at up to 10 MHz.

Interesting thoughts on the Linux. Definitely gives me some more to think about. I used to do some computer work so I have a pile of HP desktops with Xeon quad processors. If Xeon do computing for most servers, I think they will do just fine for a CNC control

[rodw]

Grab the LinuxCNC installation ISO and see how you go
Getting LinuxCNC
There are a number of simulations you can play with without any hardware installed.

[wizard]

Interesting thoughts on the Linux. Definitely gives me some more to think about. I used to do some computer work so I have a pile of HP desktops with Xeon quad processors. If Xeon do computing for most servers, I think they will do just fine for a CNC control

I suggest you read the LinuxCNC web site because there are issues with many motherboards. You can't assume that Intel hardware will work with a realtime kernel. There are numerous threads that dive into a specific boards usability.

Don't let these concerns stop you from testing the hardware you have. The motherboards may be perfectly usable.

[ger21]

Also it still appears that trying to communicate to pulse generators over USB is unreliable under Windows,

That's really not true. Some of the better options available have been using USB for many years.
Having said that, USB is more susceptible to noise, so with all else being equal, an ethernet connection is usually a better choice, due to better noise immunity.

I just need to learn the CNC interface and motors and possibly update my VFD knowledge.

There's not much to it.
You have your control software, which will talk to a pulse generator/ motion controller.

The motion controller sends step/direction signals to the stepper drives. In some cases, the drives are wired directly to the controller. In other cases, a breakout board is used to provide the terminals to connect motors and other devices. Breakout boards can also provide additional functionality, like analog 0-10V speed control for your VFD, which is typically converted from a PWM signal, or step/direction signals.

Your stepper drives also require a DC power supply, usually between 48V-72V.

The advantage LinuxCNC has over Windows is that it is installed on a Real Time Operating system that guarantees precise timing so things are guaranteed to happen at 1000 times per second

There really is no advantage here, as all of your timing in Windows controls is handled by the motion controller, not the software. People today are running machines from $250 Windows tablets with no problems.

[rodw]

I suggest you read the LinuxCNC web site because there are issues with many motherboards. You can't assume that Intel hardware will work with a realtime kernel. There are numerous threads that dive into a specific boards usability.

Don't let these concerns stop you from testing the hardware you have. The motherboards may be perfectly usable.

I don't think motherboard issues are much of a concern anymore. I use a USFF PC running a J1900 Celeron CPU and a touch screen per the image. I am Running Linux Mint with the PREMPT_RT real time kernel and compiled LinuxCNC from source to get driver suipport for the modern hardware I use. The good news is there is now a test distribution ISO that is based on Debian stretch that means you can build an equivalent system to mine from the one ISO with no stuffing round.

Linuxcnc is much less fussy about parallel ports than Mach3. Laptops are not a good candidate for Linuxcnc as they have too many power conservation features that affect latency that cannot be disabled. Faster CPU does not mean its low latency.

In short, its not so much an issue about motherboard compatibility, but its about having a machine with low latency and thats a function of the motherboard and possibly the Linux kernel used, not LinuxCNC.

When you move to using the Mesa ethernet hardware with external hardware stepgens, latency becomes much less important than if you are using a parallel port. This is because the parallel port requires an additional base thread that runs much faster than the 1000 Hz servo thread to generate the step and direction pulses within the software. The mesa hardware on the other hand is told to generate a step pulse at a given frequency until Linuxcnc tells it to change the speed. (Which it can do 1000 times per second).

There are tools supplied with LInuxCNC to measure latency and its well described in the documentation.

[rodw]

There really is no advantage here, as all of your timing in Windows controls is handled by the motion controller, not the software. People today are running machines from $250 Windows tablets with no problems.

Thats the fundamental difference between LinuxCNC and the Windows solutions. LinuxCNC is_the_Motion_Controller. For that reason, LinuxCNC will NEVER support USB hardware because the USB BUS has high latency.

Another feature is the HAL Component architecture which allows the integrator with specific requirements to write a HAL component that once installed, becomes an extension of the core system as its is attached to the Servo thread and serviced 1000 times per second. This allows a very robust and modular design paradigm.

Having full access to the LinuxCNC motion controller is a significant advantage for applications such as Plasma torch height control (my interest) or even a reciprocating cutting action for milling machines designed for stone.

[ger21]

and possibly update my VFD knowledge.

Most of us are using cheap Chinese spindles from Ebay, and the Chinese Huanyang VFD's that come with them. These VFD's are cheap, and usually work well for the price (~$140). There's always a risk when buying cheap chinese stuff from EBay, but these are pretty reliable these days. Most people that have issues are due to using incorrect settings, or having no clue what they are doing.

In the US, most people that decided to get a higher quality VFD go with the Hitachi WJ200.

[Outlawtaz]

Most of us are using cheap Chinese spindles from Ebay, and the Chinese Huanyang VFD's that come with them. These VFD's are cheap, and usually work well for the price (~$140). There's always a risk when buying cheap chinese stuff from EBay, but these are pretty reliable these days. Most people that have issues are due to using incorrect settings, or having no clue what they are doing.

In the US, most people that decided to get a higher quality VFD go with the Hitachi WJ200.

What about Yaskawas? I have a fair bit of experience with them. It was a VFD that Haas used on some of their first machines before they finally made their own. They also used Magneteks but I hate those. I know that the Yaskawa F7 has been made forever and is used in millions of applications.

[ger21]

The big industrial routers I use at work use Yaskawa VFD's. Never had a problem with them.

But for hobby use, I believe they are much more expensive, and not as readily available.

You really can't go wrong with any of the big manufacturers, and there are quite a few of them.

[Outlawtaz]

Been a busy week but I thought I would ask another question... Has anyone bought stuff from Alibaba/Aliexpress?

Curious about having to pay import duties, taxes, etc. I've been reading alot about the Leadshines and they look like they may be the way to go...

[ger21]

Look up BST Automation on AliExpress. They are supposedly excellent to deal with, and a have been used by many members.

Afaik, there are no taxes or duties.

[CaistorAl]

I bought a few things from Aliexpress.

Had no problems.

One purchase I cancelled the order a day later because I found a cheaper price elsewhere on Ali, and they processed a refund in a few days time.

So far it's been pretty good. And they are good about answering emails, question, from sellers, etc at least so far in my limited experience.

Just watch the shipping details. And choose which country it's going to ship from too.

As for duties/ taxes...well the only sure way to get around those is the day you go to your grave LOL.

[Outlawtaz]

As for duties/ taxes...well the only sure way to get around those is the day you go to your grave LOL.

Well, thats always true. LOL I was just curious if you got charged those... Like did the shipment get held up? Or did you pay up front? Ive never used it before so was wondering how it worked or if it was even a thing

[ger21]

Tax/Duty can vary greatly from country to country.
In the US, there shouldn't be any, afaik.

Unless you are buying a machine, and need a broker to bring it in, which can cost a lot.

Most of these sellers just ship DHL, and I've not had any issues with the smaller things I've bought (gearboxes, spindles, breakout boards).

[Outlawtaz]

Tax/Duty can vary greatly from country to country.
In the US, there shouldn't be any, afaik.

Unless you are buying a machine, and need a broker to bring it in, which can cost a lot.

Most of these sellers just ship DHL, and I've not had any issues with the smaller things I've bought (gearboxes, spindles, breakout boards).

Thanks!!! Well, I got bold and bought a bare kit today. Its not anywhere near what I want to build but now I have a test bed to play with things and see what I want to do.

Speaking of that, anyone any experience with the closed loop Leadshine steppers? I was looking at those and they arent too much more expensive than the open loop. Also, the closed loop would greatly increase my ability to meet the tolerances and repeatability I want...

[ger21]

Closed loop steppers won't be any more accurate than open loop steppers.

[Outlawtaz]

Closed loop steppers won't be any more accurate than open loop steppers.

Using closed loop would be the closest thing to a commercial setup using actual servos. With the encoders, any missed steps would be compensated for. Additionally, having an encoder allows the control to see any uncommanded input and is able to move the motor back to the held position.

So I guess I need clarification to why you think it wouldnt be more accurate. Or am I missing something?

[ger21]

Additionally, having an encoder allows the control to see any uncommanded input and is able to move the motor back to the held position.

LinuxCNC and Dynomotions KMotionCNC are the only hobby controls that can do closed loop operation.

But even then, closed loop steppers close the loop at the drive, not the control.

With the encoders, any missed steps would be compensated for.

Not necessarily.
Steppers miss steps because they don't have enough power to move to the commanded position.

If an open loop stepper stalls, then an identically sized closed loop stepper will also stall, usually causing the drive to fault. There's no extra power to move it back to the correct position like a servo has.
Now, if you are just talking about a few missed steps here and there, then yes, the closed loop steppers will be able to make those up.
But a properly sized open loop stepper system should never lose steps in the first place. Imo, any machine that loses steps at any time is basically worthless.

So, yes, it's potentially more accurate, but a properly designed open loop system should not be any less accurate. If that makes sense.

It's really not that much more money to go with much more powerful AC servos vs closed loop steppers.

[Outlawtaz]

LinuxCNC and Dynomotions KMotionCNC are the only hobby controls that can do closed loop operation.

But even then, closed loop steppers close the loop at the drive, not the control.

Makes sense. So there is no feedback loop to the control from the drive then?

It's really not that much more money to go with much more powerful AC servos vs closed loop steppers.

While I agree, I think true servo drives on a smallish type router would quickly move into the overkill range. Thats why I was exploring closed loop steppers.