[VTX1800]

Guys,
I have been away for several years.
My wife almost died from covid pneumonia over 3 years ago.
She still needs my care but she is getting stronger.
We made it to out 50th wedding anniversary this summer. Praise God.

So I am getting back to the CNC router with Dynomotion electronics.
Vectric VCarve Pro 11.5.
Vectric has some compelling videos about wrapping the rotary toolpath around the Y axis.

I have purchased a new headstock and tailstock from a mini lathe. Picture attached.
Is it possible to use the existing Y axis as the rotary 4th axis and wrap the toolpath?
I was planning to connect the stepper motor cable to the Y axis drive output.
Does this require a new program to be downloaded the the controller or does the wrapping post processor make the calculations using the existing program?
If a program has to switch and flashed every time this would be tedious between rotary and normal linear configurations.

I am willing to invest in an additional driver board for this 4th axis if it would be simpler.

I would really appreciate some guidance in accomplishing this.
I need to attend to my wife 24/7 so this activity would keep me busy at home.

The headstock has a 72 tooth large gear belt driven by a small 18 tooth gear on the stepper motor shaft.
The stepper motor steps per revolution and gear ratio parameters need to be used as well.
Are these parameters input to a rotary post processor?
If someone has already done this I would appreciate a comprehensive procedure or instructions.
I have questions regarding how the controller knows or calculates the angular steps.
Please advise.
I appreciate the effort in advance.

Best regards,
Ted Sears

[datac]

Well, I get you pointed in the right direction.

I am not familiar with Dynamotion's settings, but yes, to run a rotary axis, the axis settings for the rotary must be set to match your specific hardware. In every controller, it really comes down to indicating in the settings for the axis being used, EXACTLY how many motor steps are required to move 360 degrees, through whatever gearing you end up with. In your case, you indicated 18/72. I am assuming you have steppers, and then you also have to figure in microstepping if you are using that. With this information, your controller does all the calculating to solve the end goal.

It has been common for some to simply unplug an existing axis, then load the new parameters for that axis (rotary) and run your code. For some controllers, changing machine profiles is an easy task. Again, not sure what Dynamotion does for this. I know some controls I used over the years, this was a PITA.

IF you have a Dynamotion controller board that already has output for an additional axis (not sure if you are using 3 axis now, but two motors on one axis already using 4 drivers), then it does make the most sense to add an additional motor driver to run the stepper motor on the rotary. Drivers are cheap, and you wouldn't necessarily need a driver that matches what you already have. Wiht the additional axis set up properly in Dynamotion, it will just be ignored when running 3 axis code, OR, you could opt to pull the power from that driver when it is not being used.

I have used VCarve for wrapping many times. I actually have done the same as you, using a small lathe axis with a Stepper hung onto it. VCarve wrapping has always worked straight forward for me, then again, VCarve has just about done everything straight forward for me !

Once the axis is setup correctly in the control software, it will know exactly how far to rotate to match the operation you have planned. VCarve will allow you to indicate the diameter of the job, and create code to match the needs of that diameter. Once you get the hardware working, you can attempt a VCarve rotary operation.

Once hardware and wiring is in place, you will learn a lot just by jogging the axis. You can put a dummy piece of stock in the lathe axis, mark the top, jog it 360 degrees with the control and see how close or far off you are. On those first few attempts to cut, you can put a rubber pointer in the spindle, leave it turned off and dry run the job in the air. From there you could move to marker or pen and finally use cutting tools. No sense cutting things until you really are confident the settings are correct. If they are not reflecting the 360 degrees accurately, you will see it in the end product.

Hope that helps !

[VTX1800]

The attached image of the headstock, drive belt and gears, and tailstock.

[VTX1800]

Chris,
I have a 3 axis machine.
The X axis uses 2 motors and each is connected to a driver.
I was hoping to just unplug the Y axis from its driver and connect the new rotary stepper motor to the Y axis driver.
The post procesor I use with Vectric VCarve Pro is G-Code Arcs (inch) (*.tap).
There is a rotary wrap post processor in the available list named G-Code WrapY2A (inch) (*.tap).
If I select this post procesor where are the parameters for the stepper motor configured?
Do I have to configure a new program to flash to the controller if I am using the existing Y output?
Does the post processor make the value changes to angles and use the Y program installed?
I have not read a comprehensive description that defines this way of switching the rotary stepper motor with the regular Y axis stepper motor.
That would be the simplest way to accomplish this.
I would just connect either the existing Y axis stepper motor or the new 4th axis rotary stepper motor.
Your thoughts?
Thanks again,
Ted

[datac]

>>>> 3 axis machine..... X axis uses 2 motors and each is connected to a driver. I was hoping to just unplug the Y axis from its driver and connect the new rotary stepper motor to the Y axis driver.

Ok. Yes, it is possible and common for users to use, in your case, the Y axis temporarily for the rotary axis. A lot of your small lasers do this. Just unplugging it and plugging it into your rotary does not work without making changes to the machines controller (nothing to do with VCarve... yet). Your current machine configuration as set in Dynamotions control software is a linear axis, with the specific details about that axis. One part would be to indicate which labeled axis it is (in your case Y), the number of steps to move a given distance including gearing, and finally what microstep settings are being used.

If you are not familiar with dialing in a motor in Dynamotion, you will want to learn these things first. You really need to understand the motor settings, where they are in Dynamotion and what they mean. To be clear, Dynamotion is the CNC "Controller". It sends out pulses to motor "drivers".

Basically, a 1.9 degree Stepper has 200 "steps" per full turn. Lets say.... your machine has a leadscrew that moves the machine 1/2" per full motor turn, that would be 100 "steps" to move the 1/2", IF the motor driver is set to "full step". But drivers can be set for many "step" options these days. If the driver is set for 1/4 stepping, the controller that sends out the pulses (Dynamotion in your case) needs to send 400 pulses or "step" signals to move that same 1/2". 1/8 stepping would require 800 steps... 10 stepping would require 1000 step pulses to be sent to the driver to move the same 1/2".

It's not complicated when you get it in your head. Some controllers have built in GUI's to help you figure out how many steps are required to move the distance the code is demanding, as there are various sorts of drive methods from screw to geared down screw to Toothed belt to rack and pinion. Sometimes the GUI just complicates matters. But again, you have to understand where that is adjusted, why it is adjusted and what it is adjusted to.

You mention "flashing your controller" and, yes, some controllers do not have the ability to go to a simple menu and switch to a different machine with completely different profiles. I do not know what D-Motion does, though I would hate it if you can not switch quickly.

>>>>> The post procesor.... rotary wrap post processor in the available list named G-Code WrapY2A (inch) (*.tap).
>>>>> If I select this post procesor where are the parameters for the stepper motor configured?

Stepper motor settings are not set there. Regards the post processor, I did not look, but I ASSUME the "Y2A" file name of the wrap processor automatically changes what would normally be uses... "A" to "Y", which is what you would need if you use your Y axis to do this. If the post did not do this, you would have to adjust the post to insert Y instead of A. But, I think this is what it does already because I know people do what you are asking, ......to just use your Y axis.

And you can do this. But, again, the axis named "Y" in the Dyna controller has to be changed to reflect the rotary axis and all step settings involved. And then, it has to be changed back to run the linear axis when your done. As mentioned, Some controls have a menu item where you can choose which machine configuration you want to run. You still have to configure it, then save it with a name that makes sense.

>>> Does the post processor make the value changes to angles and use the Y program installed?

As mentioned... I believe so. You can create a quick projection onto any round stock, post with that processor and open it with a text editor. If it uses "X" and "Y" axis and no "A"... your probably set.

>>>>> I have not read a comprehensive description that defines this way of switching the rotary stepper motor with the regular Y axis stepper motor.

Glad you didn't say "simple way"....... There should be..... but again, not all controllers had such an option for multiple machine configurations without futzing around. Ask another Dyna user, or read Dyna documentation until the cows come hom (I found it confusing years back).

>>>> That would be the simplest way to accomplish this.

To me, the SIMPLE way is to find out if your Dyna has the ability to send pulses to one more driver. Depends on what you have. A lot of controllers offered such as "upgrades". Could be you have the ability but it is just not used.

But, if you can find out how to switch machine profiles or machine configurations in Dynamotion, yes, your Y axis cable along with the "Y2A" post should work.

[VTX1800]

Chris,
My machine started life from the AXYZ Manufacturing Machine Company.
I drove up to Canada and toured the factory and purchased their model 4008. (size 4x8 feet)
Their software generated a binary file to their controller.
It was not G-code.
It was unreadable and unable to edit by the user.
When I learned of Dynomotion I was very impressed.
Modern electronics and true G-code toolpath text files.
I gutted the control chassis and purchased power supplies and the Dynomotion control board and driver board and IO board.
I had to configure the software driver and flash the memory in the controller.
It was so long ago I do not remember the procedure.
That was over 15 years ago.
I am certain it is possible to create a second profile for the rotary functionality.
However, I do not want to disable one profile and flash the other each time I switch modes.
I think there were eight outputs on the driver board.
I will have to research this and contact Dynomotion to verify.
Then I will ask them if I can have one profile that will accomodate both the 4 motor output for linear XYZ axis CNC and a 4th rotary axis output on a 5th port.
Worst case scenario is there are only 4 output ports available on that board and I will need a second board.
I was hoping a fellow Dynomotion user has already accomplished this application and is willing to send profile examples and hardware board recommendations.

The following URL is to a YouTube video that someone published for his addition of a 4th rotary axis.
He assigned the gantry as X and the longitudal table as Y.
Opposite of mine and not standard in my opinion.
He then used one of the two of his X axis outputs to his rotary stepper motor.
His machine is using MACH3 software and he created two machine profiles.

Have a look:

YouTube video:
Adding a Rotary 4th Axis
https://www.youtube.com/watch?v=RcoK24qO1zA

I will contact Dynomotion Monday if necessary.
I am still hoping for examples and recommendations from another Dynomotion user.

I will let you know.
Please stay in touch
Thanks,
Ted

[VTX1800]

Chris,
OK. I just opened up the control cabinet and checked the output board.
There are only four outputs and I am using all of them.
So, either pull the Y axis cable off and plug in the rotary stepper motor and create another profile.
Or, purchase another output board and create a new profile with all 5 outputs.
Next, to check prices.
Cheers,
Ted

[datac]

>>> There are only four outputs and I am using all of them.

Interesting. They must have started with a 4 axis capable control card ?... All they have on their web site now are 8 and 16 axis, which has a caveat I suppose in that some of these control boards were designed to use an "axis" for a wing of I/O. In other words, you could have an 8 axis card, but can only run 4 axis because the other four "axis" have been switched to function as Inputs and outputs. Not sure. Just saying it is possible.

Such a complicated world just to run a simple machine, Eh ?

I looked at their configuration data in the manual. Really ? OMG. All that calculation garbage that 99% of machine users could care less about just complicates things. I really did not see any clear direction on just how to SAVE one machine profile when in a certain configuration and SAVE another in a different configuration. To continue reading that user manual... well, in the words of Larry the Cable Guy..... "I'd rather put my wiener in a meat grinder" !

As complicated as the whole KFlop setup is, you would think this is possible. But like I said, not all CNC controls let you save a profile and reload at will. Some only let you change the parameters for the one machine in use.

So, if you call them, be sure to ask that ! If you can load a profile modified for the rotary, your all set to use your Y cable..... well, once you set the rotary settings into the control.

[VTX1800]

Chris,
This is a heavy maching (1500 pounds ).
The spindle motor is a variable frequence 5.5 HP unit which has its own controller.
Rack and pinion drives for X and Y and a screw drive for Z.
The massive gantry has a stepper motor and transmission at both ends for X axis motion.
Another stepper motor in the head for Y motion.
And the fourth motor to drive the Z axis though another set of gears.
One gantry end has a stepper motor rotating in one direction and the other end a stepper motor rotating in the opposite direction.
All 4 stepper motors are each 5 amps.
I attached a picture of the current machine.
The new addition of the rotary 4th axis is in the friont corner.
Next week I hope to get in touch with Dynomotion, and purchase the KSTEP board.
Then the task of assemly and the software configuration.
Cheers,
Ted

[reg.miller]

The attached image of the headstock, drive belt and gears, and tailstock.

Hi VTX, I'm glad to hear your wife is recovering. It sounds like what you both went through was terrible. I hope she continues to make it back to full health.

You photo of the A axis is interesting. I'm trying to add a rotary drive to my homespun CNC and was debating using a toothed belt vs worm drive, metal gears or v-belt.

I have a old US made hobby lathe with a smallish chuck and tail-stock I was considering as a starting point. It's old enough to be well made and still in pretty good condition. It is fitted with v-belt pulleys but I could add toothed pulley wheel.

It's interesting to see your proprietory AXYZ rotary axis used toothed belt, that at least means it's a suitable option.


I see a lot chinese indexed chucks advertised but they seem to set a position and then require mechanical locking/clamping, so that tells me off the bat they are not strong and have a lot of play in the drive mechanism.


I'm cutting metal so I need quite a solid drive with very little rotary backlash to resist fairly high cutting forces. Can you provide any feedback on how solid that mechanical solution is?

Thanks.

[VTX1800]

Hi VTX, I'm glad to hear your wife is recovering. It sounds like what you both went through was terrible. I hope she continues to make it back to full health.

You photo of the A axis is interesting. I'm trying to add a rotary drive to my homespun CNC and was debating using a toothed belt vs worm drive, metal gears or v-belt.

I have a old US made hobby lathe with a smallish chuck and tail-stock I was considering as a starting point. It's old enough to be well made and still in pretty good condition. It is fitted with v-belt pulleys but I could add toothed pulley wheel.

It's interesting to see your proprietory AXYZ rotary axis used toothed belt, that at least means it's a suitable option.


I see a lot chinese indexed chucks advertised but they seem to set a position and then require mechanical locking/clamping, so that tells me off the bat they are not strong and have a lot of play in the drive mechanism.


I'm cutting metal so I need quite a solid drive with very little rotary backlash to resist fairly high cutting forces. Can you provide any feedback on how solid that mechanical solution is?

Thanks.

reg.miller,
No absolute measurement of backlash. The toothed belt drive appears to be solid.
Can you experiment with an inexpensive stepper motor and toothed belt with a gear reduction?
I had to disconnect the Y axis stepper drive output and save a rotary configuration for that output.
Clamped the spindle motor on the gantry to a fixed position in line with the rotary axis.
This allows the X axis motion to stay in the centerline position.
Regards,
Ted