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The next time I see that error, I will try those things.

I am working on an Ursviken press brake retrofit to LinuxCNC and decided to document my progress etc here, and probably ask questions along the way. If you have any hints or advice for me, feel free to say so.

This press brake came with a Compaq pc booting some form of MSDOS and a Mitsubishi FX-64M PLC. The press brake had been forgotten in a warehouse for who knows how long until the current owner ended up buying it. After installation in the shop, upon first power-up, it complained of a depleted PLC battery. Sadly, the new battery didn't recover the lost memory. After multiple unsuccessful attempts to get Ursviken to get the thing working again, they showed me this project. I said I think I can make it run on LinuxCNC.

I pulled the PC and the PLC and installed a "Fanless industrial mini-pc" with 4 ethernet ports. For i/o I am using Mesa 7i80HDT + 7i36 + 7i54 and Beckhoff ethercat EL1409 16-inputs and EL2409 16-outputs.

Original 10 axis configuration was:
Y1 and Y2 = left and right ram (top die height)
X = backgage forward/backward motion
R = backgage up/down motion
Z1 and Z2 = independent left/right motion of the two backgage fingers.
Crowning: This feature currently has a mechanical malfunction so the customer asked me if I could leave crowning as an option for later if he decides he wants it. I said yes.
VDT = variable width bottom die, appears to have been present on the machine at some point but was apparently deleted.
PSB and PSA = automatic sheet lifter with a height axis and an angular axis. My customer requested to remove that because it will be in his way more than he uses it.

Target configuration:
Y1, Y2, X, R, Z1, Z2, and optional crowning. Y2 is slave of Y1. Z1 and Z2 are independent, except they run on the same rail and must not collide.

I see this machine has tonnage control, but I do not find any electronic pressure feedback sensor on the hydraulic system. It does have two servo valves, one for each side, plus an electronic proportional valve for the entire hydraulics. The servo valves appear to pertain to motion speed for each side. I wonder if the proportional valve sets the tonnage? It might get interesting driving that proportional valve with a DC servo motor output. I plan to limit it to one polarity only and try to modulate it to about 50hz PWM. I think it might work to use a software pwmgen running at 50HZ in hal to set the hardware pwmgen to either 0% or whatever pwm % is the max mA rating of the valve coil.

X and R axis each have a Baldor 90VDC servo with tachometer feedback to the Cybelec servo amps and encoder feedback to the PC controller. The Cybelecs' drive power is set with +/-10VDC from the 7i36 card.

I will try to power the servo valves and the proportional valve using the DC servo outputs from the 7i54 card.

Z1 and Z2 axis are DC worm drive motors powered by fwd/rev contactors and basic encoder feedback to the PC.

Crowning is a common AC 3 phase induction motor on a worm gear box driving an ACME lead screw protruding from the left side of the bottom bed. It is powered by a fwd/rev contactor.

I’m heavily dyslexic, so I write it myself but let ChatGPT make it readable, even though it changes the grammar more than I’d like — it’s still better.

Regarding the question of manual tool changes, what I mean is this:

Consider that you have a toolholder with two tools in tool-changer position 1. Because you’re making a very complicated part, you need more toolholders than you have positions in the changer. In this situation, you will eventually have to exchange the holders manually.

What I want is for the machine to ask me only when my input is actually needed. I’m not too concerned about a few unnecessary moves.

What I do want to minimise is the number of times I have to intervene, and the number of points where I can mess up. That’s why I want a single point of truth for the pocket number on a ganged toolholder.

Edit:
Examples of when it should not do a manual tool change:
Changing to a different pocket that already has the correct toolholder in it.
Changing to the same toolholder but to a different tool mounted on that holder.

And if it does need me to exchange a holder, it should have already rotated the turret so the pocket to be used is positioned in front

Are you using ChatGPT, by chance?

Maybe that's just your writing style.

How does LinuxCNC know exactly when a toolchange is appropriate.

Consider this scenario:

G1 {random milling stuff}
G0 {move to some coords}
T2 G1 {auto toolchange involving pointless rapid across the whole travel, then milling with new tool}

Manual toolchange time and location makes sense.

Dear all, I am new to Linuxcnc and trying to setup a bench test before connecting motors to my machine. I got Stepperonline A6 series 400W that allow analog control. I setup velocity mode on them and I setup a mesa 7i97T to control them with analog signal and get a feedback from the servo drive. I am sure I nailed all the wiring properly, but when I setup the MesaCT 2.1.8 to generate the configuration file I have doubts on what to put into the tool when it comes to selecting the axis Scale and then the encoder scale. My A6 drive have 17bit encoders that translate into 131072 pulse/rev. But I also see in the drive parameter that it is set by default 2500 lines ( that in quadrature should be 10000pulse/rev). my max velocity in the drive is set to 3000rpm.

My confusion is now to understand what parameters to input in the mesact config. for now I just want to test a motor (x axis) without any connection. Can someone expert chime in on the value to input in Max Velocity, Max acceleration, axis Scale, and encoder scale, to make this run and proceed to next step PID calibration? 
What I need is a clear explanation on what is SCALE vs Encoder Scale input field. I seem to be confused when I read the manual of the mesact. They seem to be the same thing. I understand that the scale should be calculated based on gear ration between encoder and motor etc etc. In my case the encoder is the motor encoder and the SCALE of the axis is for now not connected to anything. The plan is later to place this motor on a 1604 leadscrew (4 mm pitch).

Thanks in advance and apologies for this novice question, but could not find anywhere a clear explanation.

electric test

I think you may be misinterpreting how the invert parameter operates,
it does not change the state of the parport.0.pin-NN-out hal pin.
(It cannot as this hal pin would be driven by a hal signal)
but rather changes the physical output polarity. You cannot
detect this change in the parport.0.pin-NN-out hal pin but only by
measuring the actual parallel port hardware output pin.

I may be misunderstanding something, but I personally would not want to think about where I need to insert an M1 to manually change a holder. I want LinuxCNC to make that decision automatically based on the tool table.

That’s not actually the case in my system.
The diameter is only used on the “tool descriptor” entries, which represent toolholders, not real tools.
These descriptor tools never get used for cutting, so they never participate in G41/G42 or wear offsets.
But yes—this could just as well use the Pocket field. I didn’t think of that originally.
I will lrady make that change in the rest off this post.

Why I believe encoding the holder layout in the tool table is better

Here is a heavily simplified tool table to show the idea:
T5 P1 X0 Z0 D0 // holder #1 in turret pocket 1
T6 P— X100.34 Z-15 D10 // spot drill
T7 P— X120.876 Z-32.657 D10 // drill
T8 P— X140.298 Z-15 D10 // drill
T9 P— X160.3 Z-15 D10 // boring bar

T10 P5 X0 Z0 D0 // holder #2 in pocket 5 (5%5 = 0 → rear post)
T11 P— X100.23 Z23.456 D0 // parting blade

The descriptor (T5, T10, T15, …) stores the physical pocket number. so they are th single sorse of trus for this.

This means LinuxCNC can always determine:
Whether a manual holder change is needed
Whether the correct holder is already in place
Where the turret needs to rotate
Which tools belong to which holder
Whether a requested child tool even exists

If we don’t have this structure, I don’t see how LinuxCNC could determine where a tool belongs.
You’d have to manually encode the correct pocket into every single tool entry.
This leads to another issue.
Problem with the pocket-in-every-tool approach

Imagine two tools in CAM that both used to be in turret position 1.
But for a different job, you need to rearrange holders.

Then you must:
Change the pocket numbers in LinuxCNC for all affected tools
Update your CAM tool library to match
Remember to do this every time you rearrange holders
Add M1 manually at the right positions
Hope nothing gets out of sync between CAM and LinuxCNC
This is exactly the kind of workflow that causes human error.


Maybe I am overcomplicating things — but in my head this system makes sense.
It gives LinuxCNC the information it needs to make reliable decisions, without forcing the user to manually sync CAM, tool table, and machine setup every time a different combination of holders is used.

I'm a bit confused, if I want to start the system with an output at 1, do I apply setp... inverter true

This should show me the output activated, but I don't see it that way; I still see it turned off. I don't know if I'm misinterpreting it or if it's not working for me, which is why I left a video showing it.

"Erratic" means "changing and unpredictable".

The behavior of your system seems to be predictable.

At startup, the system,(for example the pin 1-out) does not change when an inverter is applied.
You can watch the video I uploaded in this thread to see what happens

Hi,
thanks a lot for the suggestions.

Just to clarify: I had already tried short Dupont wires and a short IDC ribbon, but without the “every second wire = GND” scheme. The cable was about 10 cm long and SPI still failed when the hot wire or motors were active.

Now I’m going to rebuild the SPI cable exactly as you described: ribbon cable with every second conductor GND, all GND wires tied together and connected to GND on both the RPi and the SKR. I will also add a separate, thicker GND wire between the boards and keep the SPI cable as short as possible.

One question: for the ribbon cable, should I place the signals like
GND – SCK – GND – MOSI – GND – MISO – GND – CS – GND – GND,
or do you recommend a different order?

I will report back with results after I rebuild the cable.

Sold.

Coordonnées polaires:
linuxcnc.org/docs/html/gcode/overview.ht...de:polar-coordinates

For analog stuff, you could potentally use comparators to determine whether the resistance is above certain values, and then interperet their output as digital binary.