[barchdesigns]

Does anyone else have the problem of your CNC becoming jerky when running a program with many small movements? I have this problem on my Fanuc 6M when drip feeding or running from memory. It happens when my tool path has many small little movements. Neither the drip feed nor the memory can run the program smoothly.

Is there an easy way to tackle this problem? I know I could go back into the CAD/CAM software and generate things differently and that will help, but what if I am stuck with the program I have, or no matter what I always have some section of code with many small movements? Are "professional" CAD/CAM packages better at generating longer line movements, therefore decreasing the size of the nc code?

I am thinking of writing a program to read through a toolpath file and "optimize it" based on certain parameters. For instance, realizing that 68 little straight line moves correlate to an arc that could be done with one arc move. Would anyone find this useful to use? Does something like this already exist?

Barch Designs
877-201-9771

[RCaffin]

That sounds like you have the machine in 'Exact Stop" mode rather than 'Constant Velocity' mode. That is exactly what happens.

Cheers
Roger

[barchdesigns]

Good idea, but G64 for Constant Velocity is currently on and modal for both Fanuc 6 machines. The problem is actually most of the time the machine crawls so slowly while the small lines are being executed, and not so much of a jerky motion. It seems to me somewhere there is a bottleneck where the required information isn't being sent/processed/received,etc fast enough for the machine to run smooth.

[RCaffin]

OK, understood. I don't have a FANUC controller, so I don't know what they do. I run Mach3 through an ESS, and we do not get that problem as the hardware can cope just fine.
It maybe a harsh view, but proprietary controllers are fast becoming dinosaurs. The signal from the tail just takes a long time to reach the head.

Cheers

[barchdesigns]

It's been a lot of discussion in the shop here whether I should replace the controls on the machine, or just keep repairing the Fanuc 6 as it ages. It sounds like you have some experience in Mach3? I have purchased a few odds and ends for retrofitting, but haven't thought about replacing the control itself yet. We put in a new Spindle Drive and Servo drives, but ultimately keep coming back to Fanuc drives to interface with the Fanuc control as documentation is limited to make other stuff work. What's it cost to change out a Fanuc control for some new control that is faster to process? My guess is $5k-$10k to do a 3 axis machines?

It's hard to justify the upgrade when the machine going slow or jerky is just an annoyance. It doesn't cut into my cost enough to make the upgrade cost effective yet. And it seems like you can buy fanuc parts everywhere for a decent price these days. Did your machine come with Mach3 or was it an upgrade you did? What kind of headaches are there, and was it worth it?

[RCaffin]

I really should let someone's marketing dept take over here!
One might ask why you can buy Fanuc parts cheaply these days - perhaps a lot of people are upgrading?

The first real Q is what sort of servo drives do you have - and even what sort of servo motors. But before answering that, let me explain how a modern CNC control works. Gone are the days of boxes full of boards stuffed with chips.

First of all, there is an underlying assumption in all the variants: control will be totally digital. This means NO analog controls at all (no selsyns etc). It usually means that the conceptual model is built around a stepper motor driven by Step pulses with a Direction signal. But that does NOT mean you have to use a stepper motor - that would not work with any reasonably powerful CNC. Instead, modern DC servo motor systems, and AC servo motor systems as well, emulate a stepper. This emulation assumes feedback from some sort of high-resolution encoder on the motor or on the driven axis. Fear not about accuracy or resolution: it is very easy to get such systems down to sub-micron resolution, and accuracy usually depends on the ball screw anyhow.

A simple home-built hobbiest-level CNC mill these days can have sub-micron resolution very easily. The rest is mechanical engineering.

We start with a PC - stock, off the shelf. The PC runs two main bits of SW: the User Interface and the Path Planner. The UI is usually very customisable by YOU. The path planner handles the high level planning of moves. Cost of PC - as you wish. Under $1k for sure these days. Ah - a catch here. We prefer Windows XP, but can work happily with Windows V7. Do NOT accept W8 or even worse W10. They are hostile to CNC concepts. And please note: the PC MUST be isolated from any network if you want it to run smoothly. I use a USB key for file transfer.

The next part is an external pulse engine. Do NOT attempt to use a PC for the low level pulse generation: PCs cannot do that adequately. (Mach3 actually can, but it relied on totally subverting the Windows XP OS.) There are several options here, built around dedicated FPGAs or similar. They can run VERY fast. The Ethernet Smooth Stepper I use costs under $300.

The link between the PC and the external engine can be USB or ethernet. (RS232C is NOT fast enough.) I strongly recommend against using a USB link: it is far too prone to noise problems. Ethernet is excellent.

Thn we have the drivers for the servo motors. I will assume you already have motors with encoders. A modern servo driver for a motor will take encoder feedback and try to match the encoder feedback pulses to the incoming Step pulses. A suitable Gecko driver will cost you $200-$300. There are a number of other brands available (well, lots). Most of these have inbuilt optical isolation at input and feedback ports: most essential.

You should isolate the pulse engine from the harsh world of Motor Power. We do this with Break Out Boards. They are probably about $100.

Finally, you need the SW. I use Mach3 V.062 ($200?), but there is also (free) LinuxCNC, UCCNC, and others.

Frankly, I think the cost of the hardware and SW is trivial for a commercial operation. You might have to spend more on getting someone to help you set it all up, if you have never done this yourself. But certainly the HW&SW will be under $5k.

Home hobbyists build CNC systems from scratch, and have them running. An upgrade is much simpler.

Cheers
Roger

[barchdesigns]

Interesting. I guess I am already 80% the way there ... On my Fanuc 6 machine I have DC axis drives and a large AC spindle drive. The DC drives have an encoder on the end cap, and I can get an encoder output from the spindle too. Over the last few years I have been experimenting with how to do such a changeover to a new control and I have the following boards.

PICO Universal Stepper Controller board.
Viper DC Servo drive (capable of replacing the Fanuc servo drive?)
Delta 15kW Spindle Drive

I've heard horror stories of problems programming the new control to manage tool change procedures and other machine specific programs unless you have good documentation. How bad is it to interface all the machine specific electronics like low oil sensors, etc?

[underthetire]

OK, understood. I don't have a FANUC controller, so I don't know what they do. I run Mach3 through an ESS, and we do not get that problem as the hardware can cope just fine.
It maybe a harsh view, but proprietary controllers are fast becoming dinosaurs. The signal from the tail just takes a long time to reach the head.

Cheers

This is absurd. We are talking about a 35 year old control here. None of these toys like Mach is going to keep up with a modern fanuc, or run 30 years from now.

Sent from my A3-A20FHD using Tapatalk

[RCaffin]

We are talking about a 35 year old control here.

Exactly. 35 years old. Anyone around here still running a 35 year old PC?

None of these toys like Mach is going to keep up with a modern fanuc

Chuckle. How fast a CNC goes does not depend on whether it is running Mach or a Fanuc controller. It depends on the design of the hardware and, above all else, the power of the MOTORS.
Mach3 can simultaneously drive up the 6 fully synchronised axes. An ESS can output step pulses at speeds up to 1 MHz for those 6 axes. Let's do the maths for my Mach3 machine:
Single step resolution: 0.8 microns.
Assuming 1 MHz step pulses, we have 1e6 * 0.8*e-6 = 0.8 metres/second.
I respectfully suggest that this would be fast enough.
Note two things here: Mach3/ESS would bring that 0.8 m/s to a halt at a point within 1 micron of the nominal. The second point? You would need a very large block of concrete to anchor this beast down!

or run 30 years from now.

Fair enough.
I am running Mach3 version 042.063. Prior to this we had previous versions of Mach3: the upgrade each time was FREE. Try getting a free upgrade from Fanuc. Prior to that we had Mach2, and before that Mach1. And Mach4 is coming along nicely. Adding functionality to the ESS is also just a SW upload at program start time.

This is where modern computer-controlled systems can differ so markedly from older hardware-based systems: an upgrade may require nothing more than a restart. You don't have to replace a box full of electronics. Found a bug somewhere? Next version. Need to support another g-code? Update the SW - usually for FREE. Want to add several custom M-codes? Write them, put them in the Macro directory, restart.

Why didn't Fanuc go the PC route? It just might be because 35 years ago a 'PC' was barely able to support a word processor, let along do heavy maths. (I exaggerate, but you get the idea.) Now they are locked in, and are not game to restart.

Cheers
Roger

[RCaffin]

On my Fanuc 6 machine I have DC axis drives and a large AC spindle drive. The DC drives have an encoder on the end cap, and I can get an encoder output from the spindle too.

That will work.

PICO Universal Stepper Controller board. Viper DC Servo drive (capable of replacing the Fanuc servo drive?)

I don't know either of these, but the Viper should be fine. You may get good tech support from the mfr.

Delta 15kW Spindle Drive

Mach can output a pulse-width modulated signal. Pulse width ratio => spindle speed. You would need a smal interface board: they are commercially available.

I've heard horror stories of problems programming the new control to manage tool change procedures and other machine specific programs unless you have good documentation. How bad is it to interface all the machine specific electronics like low oil sensors, etc?

GOOD questions. Yes, you need at least SOME doco! Or a detail understanding of electronics, so you can recreate the doco.

An ESS can have up to a dozen or so ouput signals and more than that number of input signals. Direct digital logic signals. Rarely does anyone use all those. But if you need a lot more slower-speed I/O, then there things like ModBus units which are essentially unlimited. Think of them as dedicated PLC units. They talk to mach3 as well.

There's a thread here somewhere about the development of an ATC for a Tormach, written by Ray. His ATC uses a dedicated processor just for the ATC. Interfacing is simple:
'Load tool 7"
"Yes sir, done that" or "There weren't no tool there ...'
The point here is that you can get 1/10 of the power of a high-end PC for $20 these days. And they are fully programmable. The older HW controllers are just obsolete.

Cheers
Roger

[dertsap]

simplest solution is to buy a cam software that will put out arc moves rather than short line segments . Gutting out a fanuc control to add an inferior product like mach would be foolish in my opinion .
Most modern controls will have have a hard time with short line segments . High speed machining options can run these types of programs smoother and much better , but even then they may not necessarily run these programs at top feed rate if the feed rates are quite high , and this I've seen many times .
The problem isn't the machine , it's the code

[RCaffin]

Gutting out a fanuc control to add an inferior product like mach would be foolish in my opinion .

Funny - my Mach3 system runs arcs very fast. And very accurately too. It is quite easy to hold diameters to under 10 microns. (Below that I have to calibrate for TIR on the spindle.)

But I agree about antique SW CD systems which cannot handle arcs properly. They are obsolete.

Cheers
Roger

[dertsap]

I own numerous production machines that run mach , and Ive run most fanuc controls as well as most other professional controls in the market . Mach is inferior !
I fail to see the point in turning a perfectly good machine into an abortion when there's a more appropriate and simple solution .

[RCaffin]

Ah well, to each his own.
But I wonder - what version of Mach were you running? Granted, some of the older versions had some limitations.

Cheers
Roger

[dertsap]

I'm running an older version , I've had issues the latest mach versions . Mach 3 itself is no longer in development and mach 4 is going nowhere . Add a few more new versions of windows and mach will be dead in the water or leaving people to search out dumpster computers to run it
That fanuc control may be old but I've worked on 30 yr old mori's that I'd put up against a new haas any day . Just because it's old it doesn't necessarily mean that it's worthless .

[RCaffin]

Ah, OK.
If you ever want to try it again, get Mach3.042.062 and install it. Preferably under XP Pro. That combo is generally considered the best there is.
You can use later versions of Windows - W7 is OK, but it is advisable to use an Ethernet Smooth Stepper with BreakOutBoards in most cases. That combo is rather good. I am production machining to 0.01 mm with it.
Later versions ... who wants any later versions anyhow?

Mach4 ... well, it's coming ... still. Much hoorah, but it's not ready yet. Dunno what the devs are doing wrong.

Cheers
Roger

[barchdesigns]

Ahh the ever problem with PC's lasting more than a few years..... I used to drip feed on some old Fanuc's where we had to buy a $100 computer just to have it sit next to the machine and drip feed it. The problem over time was always the computer having an issue after a few years, and never the fanuc controller. I agree the Fanuc control is SOLID and works year after year. Replacing parts on the Fanuc now are cheaper than ever and easy to work on and repair these old analog boards. Changing to a computer based system has always been a hesitation which is why I was testing the waters with retrofitting instead of gutting it head on.

If Mach still has issues with small straight line moves at high feed rates then there is no point to go the route of changing the Fanuc to a PC based control (btw I had a Hurco machine a while back that was PC based and had a LOT of problems with the PC control side staying up and running)

Seems like still the BEST thing to do is fix the G code to make arcs instead of "small straight line moves that resemble an arc" to make your G code size much smaller and have fewer lines of code. However if some of the code is unchangeable (either by limited CAM software, or just plain stuck with the code I have) then where does that leave this topic? Back to writing a script/program to adjust the small straight lines into arcs before sending it to the machine?

Are there any other options out there? Any other ideas?

Barch Designs
877-201-9771

[dertsap]

If your needing to drip feed your code, then is it easy to assume that your surfacing . What cam software are you using .

[dertsap]

Ah, OK.
If you ever want to try it again, get Mach3.042.062 and install it. Preferably under XP Pro. That combo is generally considered the best there is.
You can use later versions of Windows - W7 is OK, but it is advisable to use an Ethernet Smooth Stepper with BreakOutBoards in most cases. That combo is rather good. I am production machining to 0.01 mm with it.
Later versions ... who wants any later versions anyhow?

Mach4 ... well, it's coming ... still. Much hoorah, but it's not ready yet. Dunno what the devs are doing wrong.

Cheers
Roger

I see no reason to fix whats not broken

[barchdesigns]

Actually it's not much surfacing at all. Here is a real world example of my shop's parts that has a toolpath with many small straight line moves. I'm not sure if links to products are allowed on this forum, so if you just use your favorite search engine to look up "Wicked Aluminum" you will find the Raspberry pi cases that I make on the machine. Most of the excess code is from arcs around the part that was generated in code to be 20 little line moves instead of a single arc, but all in just the XY plane. There is no time when I use any XYZ arcs or moves at all.

I use BobCAD/CAM. I've had their software for over 10 years and it's always done what I need it to do. The last few years however I have transitioned into managing my shop and letting others do the CAM programming, while at the same time upgrading the software to the newest version. While it's worked out, we don't always get nice clean toolpath output code using arcs. Sometimes we can go back in and change things for the better, but wouldn't it be nice if it just worked!? Maybe it comes back down to lack of training with the software, but the big picture overall problem is still just classified for me as "An Annoyance" and it doesn't cut into much production time, other than the machines would complete each toolpath a bit faster overall. But it wouldn't make me any more money.