G320X Drive question

[sammy10]

I am converting a Webb knee mill that used the Milltronics controller package over to the Gecko320X servo drives and have a question.
My setup will use the following components.

Existing servo motors
72 volt 20 amp power supply
Two Gecko G320X servo drives
Two Amt-102-V encoders
C25S breakout board
Smooth Stepper controller
Mach 4 software

I didn't order anything yet.

My question is, if the geckos are disabled and I turn the hand wheels to move either the X or Y table, will the position change on the Mach4 X,Y screen or does the drives need to be enabled. I am hoping to manually turn the hand wheels and see the position change on the Mach4 screen. Would this be possible? I could use a separate 5 volt power supply to power the encoders if that would work.

Any answers would be appreciated.

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[awerby]

I don't think that will work. But once you get familiar with the MDI (Manual Data Input) function of Mach4, you won't miss the cranks. Just tell it where you want it to go and how fast, and it goes there. People always think they'll still want to crank once they've done a CNC conversion, but they get over it. If you really want the thing to act like it's being cranked, implement a MPG (Manual Pulse Generator), which is something Mach4 does support.

[joeavaerage]

Hi,

My question is, if the geckos are disabled and I turn the hand wheels to move either the X or Y table, will the position change on the Mach4 X,Y screen or does the drives need to be enabled.

No. Mach4 tells the ESS to do so many steps, and the ESS pulses the G320's so many steps and the G320's do it. If the G320 cannot do it for whatever reason is will fault out, and usually you would have that fault stop Mach. The position that
Mach displays is where Mach 'thinks it is', not where it actually is. The G320s do not report back a position, but rather if the servo is within the 'following error window' or not, ie faulty OR not faulty.

You could if you absolutely must, wire the encoders back to the ESS and Mach (in addition to the G32's), and that would mean that if you manually turned the handle the position which the machine is actually in, will....
eventually....be displayed in Mach. Note that because of the reporting communication there will be a delay of many milliseconds between what the encoder reports and when Mach displays it.

As awerby has already posted you are trying to make complicated what is very simple......use a pendant or two MPGs. Once you do so you will never use the manual wheels ever again.

Craig

[Jim Dawson]

I'm going to have to respectfully disagree with Andrew and Craig on this one. I would be lost without a CNC/manual machine in my shop. You have the best of both worlds with that Webb machine. I have one identical to it, but it's branded as an Eagle. Made by Topwell in Taiwan, and imported under a few different brand names. I'm still using the original brushed Baldor DC servos and Servo Dynamics drives, powered by a 75V power supply.

Mine started out life as a 2 axis machine with an Anilam control and is now a 4 axis machine that can be operated as a full manual, 2 axis with manual quill, 3, or 4 axis CNC, all with manual knee. Switches between modes in seconds, and I do so frequently right in the middle of a setup. For the kind of work I do, I find it very useful to be able to perform manual operations either mid job, or perform an entire job in manual mode. Just depends on what I am doing at the time.

Rather than using rotary encoders, I opted to use linear magnetic scales. They have proved to be more or less bullet proof for the last 7 years. This gives me 1 micron resolution on all axes, I have scales on both the knee and the quill. Using scales attached to the load pretty much eliminates any backlash or ball screw errors. I have about 0.004'' backlash in my Y axis which causes about a 0.001'' out of round error on a circular pocket that doesn't get compensated for. There is no substitute for a mechanically tight machine.

The heart of my system is a Galil motion controller. From what I understand, these are compatible with Mach4, I know they are compatible with Mach3. I have very little experience with the Mach products, but I know the DRO on the screen is still active in manual mode when connected to the Galil controller, at least it was in my very brief excursion into Mach3. Although, as far as I know, Mach products do not use the encoder feedback at all, a completely open loop system. Somebody correct me If I'm wrong here. The Galil controller however is closed loop, and can close the loop at the controller level even when used with Mach products.

Using a Galil controller, you can use the original analog servo drives, or step & direction with different drives if you like. Galil will handle either. In fact on my machine I use analog control on X, Y, and Z, and stepper control on the 4th axis.

You have a really nice machine there, so spending a bit of extra money to make it top of the line is worth it.

[joeavaerage]

Hi,

The heart of my system is a Galil motion controller. From what I understand, these are compatible with Mach4, I know they are compatible with Mach3.

Yes, that is correct.

Although, as far as I know, Mach products do not use the encoder feedback at all, a completely open loop system.

That is also correct. Mach CAN use encoder or linear scale feedback, but there is typically a delay of 20millisecons. This would mean that if you used the mamual handle then Mach could and would
reflect the movement but delayed by about 20ms.This would be fine for manual control but it is thouroghly inadequate for closed loop control of a servo. Of course the Gallil has no such delays and of course can
close the loop.

If OP wants to use the manual wheels,and he can, but he would require that the encoders be wired not only to the G320's but also to his breakout board. He may in fact require yet another breakout
board like a C10 ($23) in order to have enough inputs for the encoders.

A pendant allows for manual control, you twiddle the MPG or MPGs if you want two independent ones, and Mach moves the axis via the ESS/BoB/G320/servo. There is no strict need to feed the encoders back to Mach,
and to keep the cost and learning curve down for OP that is what I'd recommend. Save the headache until a little later....and you may find that you prefer a pendant over manual wheels anyway.

Craig

[sammy10]

Thanks for all the replies.
Gives me more ideas and reading to do.

I looked at different MPG's and pendents. Any comments on the best one to use?

[joeavaerage]

Hi,
for seven years I used a VistaCNC P1A pendant. It is a USB connected pendant and works well. Eventually it started to crap out...especially in warm weather??
Its been so good I should really just have bought another one but I made my own wired pendant instead. Used this MPG:

https://www.ebay.com/itm/201195367332

Made a vey simple pendant with it, the MPG, a three position toggle switch for X,Y,Z axis selection, and a spring return two position toggle switch for Incremental/Velocity jog.
Required 7 wires only. Worked out a little cheaper than a new P1A...but not a lot in it.

Either is good.

Craig