Thank you for sharing the info Will.

Much appreciated,
Russ

If only it were that simple. Backlash compensation motion cannot happen in zero
time, so you have to figure out what to do with the other axes while the reversing
axis is making the compensation move, and then keep the system happy while
accomplishing this non-zero time event that was not planning for by Mach4.

Even if you can pull it off, this will only work if the only thing moving the machine
is the axis motors. If cutting forces react with the machine to cause motion
across the backlash distance where the axis motor cannot control where the machine
is positioned, then nothing the software can do will fix this. Likewise any pauses
inserted by the correction attempt will allow for the cutter to remove extra
material at that position while the forces stored in the springs of the elements
of the machine that have flexed will get the chance to relax during the pause as
the cutter removes material. This can result in divots or burn marks in the workpiece.

Backlash compensation can help in some cases, but it is no replacement for a properly
designed and built machine.

Surely Backlash is not that complex:

GetNextCoordinate(Coord, dirChange);
if dirChange
then
     ApllyComp(Coord)
fi;
MakeMove(Coord);

Hi Will,

Afaik: Mach3 did its own backlash compensation (I have seen videos) because it just sent signals out through a DB-25 connector. Mo motion controllers then

Incorrect, the motion controller was the parallel port driver. That motion controller is not a separate physical device like an ESS or PMDX SmartBoB but it is none the
less a motion controller, it has code and processing power to take the trajectory planned by Mach and produce pulse streams necessary to drive the motors.

There was a time when Mach3s PP couldn't do backlash compensation. Even when external motion controllers came along not all manufacturers had support for
backlash compensation. The situation is similar today with Mach4 manufacturers adding backlash compensation 'when they get around to it' rather than as a fundamental
function. As Steve points out adding backlash compensation is by no means trivial and there will always be shortcomings with it that no software can solve. He is not
unique in saying 'fix the backlash in your machine, software can't fix your sloppiness'.

Ess looks much more affordable, However: Backlash not fully working. Only controls 4 stepper drivers and it is recommended to buy a BOB as well! So $30 on a C25 BoB. Also no mention of spindle control? Would need another Bob for spindle. Also documentation I have read is VERY unclear as to how you assign and configure the various I/O ports!

1) Backlash compensation is not working perfectly at the moment, backlash compensation will never be perfect, a beta test version is being trialled at the moment
2) The ESS can control six coordinated axes and another six out-of-band axes WITHOUT counting slave axes
3) Yes you need a BoB, you can hook direct to the ESS but if your hamfisted you'll blow the FPGA and then have to buy another ESS. DON'T DO IT!! A BoB protects your ESS
4) The ESS plugin allows you to ascribe an alias to any pin and then assign that pin by name to a Mach signal. The ESS plugin will update Machs plugin to keep them
    consistent.
5) Any output pin can be made to produce PWM. All that is required is an amplifier and filter circuit....if you make your own...one opamp, a couple of resistors and capacitors,
    OR you can buy a BoB to do it for you.

Once you start adding a couple of BoBs and  a power supply for the ESS it is the same or even more than a PMDX-424 which has its own supply and no BoB required
except for the spindle. PMDX have taken considerable effort to make their devices as easy as possible to use.

If backlash compensation is absolutely vital to you either wait a bit for the ESS or stump up the extra for a Hicon.

Craig

Hicon looks nice but it should do for the price $595 - EEK!!

While it is not very prominent on their site they offer the Hiconn in a hobby version for ~$450 IIRC.

Hi,
just had a look at the Vital Systems site and found:

Note: We now offer 7541 version only. 7544 version is now obselete bacause of lack of demand

So the slightly cheaper version is no longer available.

Craig

So the slightly cheaper version is no longer available.

Because it was still to expensive for most hobbyists.

If you want a really good breakout board for the ESS, that includes VFD control, look at the MB2 from CNC Room.

Thanks Ger, never saw them before.
Actually, the ESS/MB2 combo looks like a pretty good deal. Shipping from Thailand doesn't look so bad either.
I like that type of terminal, if they are of good quality.

Hi,
just had a look at the Vital Systems site and found:

Quote

Note: We now offer 7541 version only. 7544 version is now obselete bacause of lack of demand

So the slightly cheaper version is no longer available.

Craig

Hi Craig,
Can you send me the link to that. I just went to http://www.vitalsystem.com/portal/store.php and added one to my shopping cart for $435.00 so as far as I can see they have not been dropped but it could be I am doing something wrong.

Mike

Hi,
I found the quote on the MONTENC Lite page. I see the price for the cheaper device is still there at $495 but just above the price list was the note
about the availability of it.

http://www.vitalsystem.com/portal/motion/motenc/motenc_lite.php

Craig

Thanks Ger, never saw them before.
Actually, the ESS/MB2 combo looks like a pretty good deal. Shipping from Thailand doesn't look so bad either.
I like that type of terminal, if they are of good quality.

CNC Room breakout boards are very high quality. I was using an MB2 with my UC300ETH, until they made a dedicated board for the UC300ETH, the UB1.