Please elaborate. I’m new to this and am now wondering what other VFD might be available that does not cost too much. I currently have a 2.2kw PWNCNC solution.
@WaywardWoodworker reports the Huanyang VFDs don’t have this issue over RS485. They’re very popular and you can find plenty of info on them. I believe some people in the past had difficulty setting up the Huanyang Vector (GT) series, so unless that’s been resolved, you’re safer with the more common HY series. Shouldn’t be too much more than $100. You’d have to program the VFD, and it may not integrate with your PWNCNC VFD enclosure if you have one and that matters to you. It’s not overly difficult to swap out a VFD, but you’d want to do a little research if you’re not familiar with them before you buy. As @anon93936469 mentioned above, a braking resistor can be useful, and the Huanyang can be ordered with the braking resistor circuitry and a braking resistor, but you have to specify that in the original order.
I’m assuming you use the OF Buildbotics controller, not the Masso right? This only seems to be an issue with the communication when using the Buildbotics controller over RS485. If so, and you also use Vectric software, @tjp52 's modified post processor above is a great option. Doesn’t require buying any new equipment.
If you’re not using Vectric, but still have the long deceleration times, let us know your whole set-up and probably someone here can help. Lots of good minds in the forum.
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I checked the Kimber Enterprises post processing file for Autodesk Fusion360 and it already includes the same three lines:
“S100”
“G4 P5.5”
“M5”
for both tool change and end of file
Ok, nice. Are you able to check if you have the deceleration issue, or have you already done that?
True. Not best word for that. I meant it as “transfers the command to the spindle” or similar. It makes sense that the controller has the responsibility for passing on the commands in a way the VFD can understand them. So it could very well be a fault in the BB controller. However, since it doesn’t seem that anyone else with other VFDs is mentioning this, it still appears possible there is some faulty programming within the Delixi that doesn’t allow it to receive or transfer to the spindle the “decelerate to stop” command over RS485 as it should. But again, my only interest in this is curiosity. VFDs are interesting little boxes 
. I don’t have much from PWNCNC, but they’re done a great service to the hobby and semi-pro CNC community and put out quality products.
I would assume that with the close relationship between OF and PWNCNC they have done everything possible to make the integration as smooth as the respective devices allow.
That I wouldn’t know. Acorn and Masso don’t use RS485, so I’m not sure who else is using a different controller with Delixi VFDs over RS485. All this, plus if anyone else out there has the deceleration issue, would be great info to have.
I think everyone has their own needs and expectations. Many have had a good experience and produced very nice results with the Buildbotics controller as a hobby or above use that’s plug-and-play and at a very reasonable price point. But, of course, there are other and better controllers for other expectations.
I wish you well in your endeavors. Appreciate the input from your use.
Hey all,
the Modbus commands that a VFD understands are listed and explained in the VFD manual in the chapter on Modbus protocol.
The spindle deceleration is a function of the VFD, set by a parameter (braking with internal or external braking chopper with or without additional resistor, vs. leave spindle coasting) and can be influenced by the size of an additional braking resistor (the less resistance, the more watts transformed into heat thus the faster stop, at same time the more is the resistor’s size). See VFD manual for braking resistor specification. Be sure to have temperature sensor and cooling fan in your VFD control cabinet, braking resistor can get very hot.
Stop mode “STO (Safe torque off)” is always leave spindle coasting.
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All I know is that it takes a long time for the bit to stop…
Yes, it looks like so far no one has a “direct fix” for the decelerate to stop communication issue between OF Buildbotics controller and PWNCNC Delixi VFD.
So are saying you still have a very long time for spindle to stop, even after using @tjp52 's post processor work-around? It looks like with that work-around you shouldn’t be seeing much more than around 7 seconds of spin-down time.
If it’s still a problem, you’d need post for everyone a little more info, and they could probably get it worked out. At least copies of post processor and/or the last lines of gcode from a program you created. I’m not sure if any of the Delixi VFD settings come into play as well, but it’s worth understanding those related to braking. Good luck!
I have spent a considerable amount of time chasing this issue. At the top of this thread, I proposed a work around to alleviate the issue by modifying the post processor file. I’ve studied this in detail and thanks to a fellow member, Martin, who directed me to some information in the VFD manual, I’ve been able to identify the problem. Thanks, Martin for that.
The problem is not the Buildbotics controller and not the Dilixi VFD…it’s the configuration parameters for the PwnCNC tool profile.
Page 173 of the Delixi manual details the commands that the controller needs to send to the VFD to turn the spindle on, the direction of rotation and how to stop the spindle.
There are two methods to stop the spindle:
- Stop by free spin, which equates to 5
- Stop using speed reduction, which equates to 6
On the Buildbotics controller, the “stop-write” parameter contains the address and value that Buildbotics sends to the VFD to stop the spindle. It’s set to 5, and that’s where the problem is. It needs to be set to 6.
If your PWN spindle was configured by creating a “Custom ModBus VFD” all you have to do is edit the configuration and change the “stop-write” value to 6, save, then you’re good to go.
However, if you’ve selected “PwnCNC VFD” from the tool menu, that is pre-configured and the parameters that make up that profile are not accessible to view or change as far as I can determine, but you can create a “Custom ModBus VFD” with the necessary parameters, which is what I did to test this out. I’ve attached the configuration that I’m using.
BEFORE any changes are made to your configuration, it would be advisable to go to the ADMIN section of your Buildbotics and create a backup of your current configuration. I’ve been in the computer industry long enough to know that things don’t always go as expected, no matter how sure you may think you are, so always have a plan ‘B’.
It’s easy to test the change to see if it’s working as expected. Just select the MDI tab and enter ‘M3 S10000’ and press ►. This will accelerate the spindle to 10,000rpm. Check your VFD and your buildbotics displays to verify the speeds are the same. Press ■ and the spindle should decelerate to a complete stop within about 6 seconds or less. Test various speeds just to confirm everythings ok. The spindle may not always display the exact speed you’ve entered but it should be within a very few rpm of the value entered on the MDI tab.
With this fix in place, the “work around” that was proposed at the top of this thread is not needed.
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Great post Tom - this kind of conversation is what the forum is all about. Thanks for your time in problem solving and posting the fix. 
Did you contact onefinity to update their " pwncnc" configuration settings in their next update to correct this?
Hey Tom @tjp52,
That refers to a normal stop command. But does this also apply when you assign an input to the function 8 Free Stop or 43 Emergency Stop, as discussed here with Daniel @PwnCNC?
According to IEC 60204-1, to meet the requirement for an emergency stop, which is finally reaching Safe Torque Off (STO) which is the case for Stop categories 0 and 1, requires that the spindle is electrically cut from power in the VFD, so it is usually left coasting in the final stage of emergency stop. Braking would mean that it is not cut from the VFD as the spindle (which acts as an induction generator then) would need to deliver its deceleration current to the internal brake chopper. This would only meet the Stop category 1 if it is ensured that the spindle is reaching the Safe Torque Off (STO) requirement at the end of the emergency stop procedure.
No, I didn’t contact one-finity…only reason is that the spindle is supplied by PwnCNC and my thinking was that they should connect with onefinity. I did convey the information to PwnCNC but my gut tells me they’re not too interested. The other thing is, I really am not sure who’s responsible for the controller software…is it Buildbotics (the manufacturer of the controller) or is it Onefinity (who I’m led to believe has customized the controller software).
Hey Tom @tjp52,
The Onefinity CNC Controller is a software and hardware fork of the Buildbotics.com CNC Controller and is not produced by Buildbotics, but entirely by Onefinity. If you write for support to buildbotics, they will tell you that they are not responsible but only Onefinity is. Buildbotics is free and open software and also free and open hardware.
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Ok. Thanks for the clarification. I’ll pass the info along to onefinity and see what they do with it.
Edit: added 1.4.0 Alpha 3 (Macros update)
Noted, We’ll see if we can get it in the next firmware release.
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Not a puzzle at all.
The buildbotics controller is a “translator” and “traffic cop” that reads the G-Code program then translates what it reads into commands that tell the VFD what to do with the spindle and to tell the stepper motors (X,Y & Z) how many steps to move and in which direction. The manual for the Delixi VFD, on page 173, defines what commands it responds to and the ModBus configuration on the Buildbotics has provisions for entering this information. So an “M5” is translated to a “stop” which is configured in the tool profile. In simple terms, that’s basically all that it does.
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Hey all,
the Modbus data structure and a complete list of Modbus functions that a VFD supports should be listed in the Modbus/RS-485 serial communication chapter in its VFD manual.
Usually a VFD supports much more functions than an average CNC Controller will in fact use (remember that a VFD works very well on a Masso G3 which does not support Modbus at all and only provides control of FWD/REV RUN, and SPEED (frequency).
The Buildbotics Controller (that supports Modbus over RS-485 serial communication) honours the VFD functions listed here, which by the way allow you to create a custom Modbus VFD entry for a VFD that is not listed on the ‘tool-type’ pull-down list on the TOOL page. You look up the values in the Modbus chapter of the VFD manual and you make sure that if they are given in hexadecimal you convert them to decimal first, and enter them into the Custom VFD table on the Buildbotics Controller TOOL page.
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This thread is way to long and i didn’t bother readying more than the first couple posts. The VFD controls the acceleration and deceleration of the spindle not the controller. I have had a bunch of 2.2kw spindles over the years and none of them take 45 seconds spin up or down. I set all my VFDs to 6 seconds spin up and down and there is no issues and no braking resistors. Read the vfd manual, even cheap import vfd have no problem with 6 seconds spin down if the PWNCNC one cant i would be surprised. just keep setting it lower and lower until it errors out then move it up a second or so. if the controller is limiting the starts/stop speed of the spindle try to increase motor acceleration in the controllers software. an M5 command should stop the spindle at 6 seconds also.
You sir are my hero of the day. this works perfectly.
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