Messages

1281

General Mach Discussion / Re: Denford Triac still waiting (patiently) to run

« on: January 05, 2021, 07:50:34 PM »

Hi,
OK, the G340's are Step/Dir drivers and are capable of up to 250kHz pulse input.

Depending on the resolution of the encoder you may well require Step pulses of 100kHz.

What are the specs of the encoders? How are the servos coupled to the leadscrews? These two will determine the resolution, which
will in turn determine the max signalling rate.

Machs parallel port is still popular because its free, the downside is that it runs ONLY on 32bit Windows 7 and earlier PCs,
and they are a vanishing breed. Second drawback is that its default pulse speed is only 25kHz which in all probability
will not be adequate for driving your servos.

I would recommend an external motion controller like an Ethernet SmoothStepper (4Mhz) or a UC300 (400kHz)  or a 57CNC (125kHz).
All of these devices have Mach4 plugins and unless you are invested in Mach3 for some reason then I would recommend  Mach4. All development
on Mach3 ceased six years ago and not withstanding that it still works and has a loyal fanbase it is obsolete.

Note that the UC300 and Ethernet SmoothStepper require a breakout board, and the 57CNC benefits from one. Depending on the level of
sophistication you can pay as little a $20 for a single port equivalent BoB up to $200 for a fully developed three port equivalent BoB.

Craig

1282

General Mach Discussion / Re: Z Axis Drift With Servos...I Don't Understand It

« on: January 05, 2021, 07:24:40 PM »

Hi,
the Active high/ Active low switch if applied to the Dir signal will change servo direction, but you don't need to do that. You can leave the Dir signal alone.

All you have to do is change the Step signal, if I recall correctly Delta call that 'Pulse'.

Are you using single ended (open collector) or differential?
If single ended, how are your signal inputs wired, ie do they require current source or sink?

The fault I'm imagining really only happens with single ended signaling. I'll try and explain what I think may be happening. Lets say BoB has a pull-up resitor fitted.
Thus when a move completes and the Step signal is idle it will go high. Lets imagine also that the servo drive accepts a pulse on a negative transition. When a pulse
stream of 200 pulse comes along there are 201 negative transitions but only 200 positive transitions, and thats why you get drifting.
If your BoB had a pull-down resistor instead the there would be 200 negative transitions and 200 positive transitions. An oscilloscope would be the best way to
diagnose that.

I am in the middle of a new build and am at the moment wiring the B2 series Delta servos. With the resolution I want, 5000 pluse/rev, I require
signal speeds of 417kHz and so perforce am using differential signalling, and I have made my own line drivers for it.

I had experimented with single ended signalling but the drive started playing up beyond 225kHz. Given that the spec for  max single ended signalling is 200kHz,
I can't complain, but I wanted a bit more, ergo differential signalling.

Craig

1283

General Mach Discussion / Re: Z Axis Drift With Servos...I Don't Understand It

« on: January 05, 2021, 03:11:07 PM »

Hi,
Im wondering if the signalling to the servo drives is 100%

What model servos and what model drives? Are you using differential signalling or single ended?

One suspicion I have is that if for instance you signal the Z servo to go upwards by 200 steps, it goes up 200 steps, but when you
signal it to go down it will go down 199 steps. Over a period of time that will result in the Z axis being higher than it should and furthermore will
grow as time passes.

This fault can occur with stepper or servos if the signalling is not quite right, commonly the drive is expecting active low step signalling when
your BoB is using active high. It means that one step is missed at each Z axis direction change.

Craig

1284

General Mach Discussion / Re: Denford Triac still waiting (patiently) to run

« on: January 05, 2021, 03:00:29 PM »

Hi,
to determine what hardware is most appropriate we need to know what the hardware has to do.

In particular you say that you have Gecko drives for the servos. What model and what specs?
That will determine what signals the drives require which in turn determines the best mix of hardware to use.

Craig

1285

Mach4 General Discussion / Re: Fusion 360 and issues with Mach 4 G-Code

« on: January 03, 2021, 09:54:12 PM »

Hi,
are you going to use index homing?

I never bothered and with good quality roller plunger snap action microswitches I can get 0.02mm repeatability from session to
session without index homing, and 0.02mm is close enough for me.

If you don't want index homing, just don't enable it. If you do then you'll have to assign pins, input assignments....all the usual stuff for
inputs but for three new index inputs.

Craig

1286

Mach4 General Discussion / Re: Fusion 360 and issues with Mach 4 G-Code

« on: January 03, 2021, 09:09:15 PM »

Hi,
homing is a shared activity.

Mach provides the basic data, for instance the homing direction each axis is to take, the homing order, the offset (if any), the homing speed
and softlimits.

The homing procedure itself is a realtime procedure and must perforce be done by the controller.The homing axis is set in motion and is meant to stop
when the switch activates. The ESS can do this immediately whereas if it reported back to Mach it would take tens of milliseconds, way too slow, the machine
will have crashed into the stop before then.

In the ESS plugin:
PinsConfig: is where you assign a pin to each of your home switches
InputSignals: is where you map each pin to its logical event, Motor0Home for example, and enable it
Homing: any pins and/or events you have enabled in the InputSignals tab will be replicated in this tab and you can attach more data, like
approach speed, backoff speed and whether you are going to use index homing.

So there are four pages that you need attend to set up homing, the Homing/Limits tab in the Mach Control plugin
and the three (PinsConfig, InputSignals,Homing) tabs in the ESS plugin.

Craig

1287

Mach4 General Discussion / Re: Fusion 360 and issues with Mach 4 G-Code

« on: January 03, 2021, 08:13:19 PM »

Hi,
so what data are you populating the SoftLimits page with?.

If you are using X- and Y- as home switches then at least one, say SoftXMin=0 or SoftXMax=0 must be true for each axis

For instance my existing mini-mill has 180mm x 180mm x180mm of travels. The X home and Y home switches occur with
the tool at x=0, y=0, and the Z axis home switch is at the top of travel, Z top=0. My SoftLimits are:

X    min=0 max=180
Y    min=0 max=180
Z    min=-180 max=0

Craig

1288

Mach4 General Discussion / Re: Fusion 360 and issues with Mach 4 G-Code

« on: January 03, 2021, 04:34:15 PM »

Hi,
I don't like the Fusion generated G28 either, I use the drop down menu box in Fusions Post page to not use G28 but to go
to the prevailing work zero, ie the origin of your workpiece.

As for problem 1.........How are you homing your machine? Soft Limits are declared in machine coordinates and only make sense
if the machine coordinate zero is at some defined and repeatable location.

Try this analogy.

Imagine the XY extents of your machine to be a rectangular paddock. When you turn your machine on all that Mach knows is that you're somewhere
in that paddock. Lets say however there is one tree in this paddock, it does not really matter where it is, but obviously it does not shift.
So you drive Mach to the trees position and declare that position as 'Home'. Now you can declare that the Northern boundary fence is 52 yards
North of Home, the Eastern boundary fence is 74 yards to the East of Home....etc. These declarations of distances to the boundary are the
equivalent of Machs Soft Limits. You could now set an automatic lawn mower to mow the paddock and it would know how to avoid banging into the
fence by using the knowledge of the boundary distances.....but only if it knows where 'Home' is.

Homing your machine to a define and repeatable location is essential to use Soft Limits.

Craig

1289

General Mach Discussion / Re: Adavanced CNC programmer but new to Mac3 ---Questions

« on: January 03, 2021, 03:54:53 PM »

Hi,

PS i have Programmed almost every Fanuc and Siemen controls on Mills and Lathes but never worked with Mac3

Should add, that you have extensive CNC programming experience will help immensely. Mach4 is designed to be as close
to identical to Fanuc 21 as possible. Mach4Hobby does not have parametric programming whereas Mach4Industrial does.

Craig

1290

General Mach Discussion / Re: Adavanced CNC programmer but new to Mac3 ---Questions

« on: January 03, 2021, 03:48:46 PM »

Hi,

Axis --How to set actual home position-When you move the axis to home switch positions how do you reset or declare that as zero position on the axis motor ?

With Mach3, and likewise Mach4, when the home switch activates, the axis backs up the switch de-activates the machine coordinate for
that axis is reset to zero, or alternately, to an offset that you program. If you do not have a home switch assigned to that axis, or you can program
it if you wish, to 'Home in Place'. Under that circumstance the moment the axis is homed it immediately sets the machine coordinate to zero.

I have been using Mach4 for six years....so my memory of Mach3 is now pretty patchy. In Mach3 you write macros in Visual Basic, or in fact a variant
of it called Cypress Enable. I personally never liked VB and so I elected to change to Mach4 which uses Lua as a scripting language. While Lua
and the modular architecture take some learning it is very much more powerful and flexible than VB/Mach3.

If you are new to Mach then I would have to recommend Mach4, all development on Mach3 ceased six years ago and not withstanding that it still works
and has a loyal fan-base it is  becoming obsolete.

Craig