Belt drive spindle.

ethan-downey

Ethan Downey
Im having trouble setting the correct RPM for my spindle. Just wondering if there is a setting for the Masso to enter a belt reduction for the spindle?

My motor has a max RPM of 5000 and a 2.5 reduction to give a spindle speed of 2000 RPM, however this is not correct when i enter 5000 RPM into the spindle RPM setup, as it gives me a slower spindle RPM. When i enter 2000 (5000/2.5=2000RPM) into the spindle RPM than my spindle spins faster. To get the spindle to spin at 2000 RPM, i have had to fudge the speed setting in Masso and than any RPM before 2000 is wrong.

Hope this makes sense. Im sure im doing something wrong somewhere.
 

testyourdesign

testyourdesign
Need to know the way you have Masso Spindle Settings Setup. Can you post a screenshot of your spindle settings?

Most of us try to increase RPM speed so that we can increase the feed rate with the same chip load on the tool. Why are you slowing the RPM down?

Cheers, Stephen Brown
 

masso-support

MASSO Support
Staff member
the way spindle RPM is calibrated is by knowing the ratio and entering the maximum RPM value.
  1. Let's say you know that your motor maximum RPM at full speed signal of 10v is 1000 RPM.
  2. An have a 5 ratio pulley setup that increases the RPM 5 times.
  3. So the value that you will need to enter in MASSO setting is 5000 RPM.
 

ethan-downey

Ethan Downey
Thanks for your help @testyourdesign and @masso-support.

@masso-support, thats how i thought it should be but it wasnt working out that way.


I did 2 test runs and measured the voltage. The results showed the 0-10V from masso is right but the driver that was sent to me was 0-5v. This driver is advertised as having both 0-5 and 0-10v, but tonight i found out that it is shipped out from the factory as only having 0.5v. They never advertised it as that so i got caught out. It needed to be requested before shipment.

The driver also has PWM but it only 1-3 kHz. This is below the Masso 4 - 65 kHz thats listed here. https://www.masso.com.au/masso-documentation/?section=spindle-connector

Is my only option to accept there offer to get a new 0-10v one shipped out?
Is it possible to convert 0-10 V to 0 - 5 v?
Or use the PWM?
 

masso-support

MASSO Support
Staff member
Hi Ethan

You should be able to convert the 0-10V output to a 0-5 volt output using a simple resistive voltage divider.

2 resistors in series both the same resistance. Apply the 0-10V across both and the center position will be half. I have attached a diagram.

The one thing I cannot tell you is the value resistance you should use for the resistors. I would try 4.7K each and see if that worked. If the value is too low it will load the output of the Masso dropping the voltage and if it is too high the VFD will load the circuit giving the wrong speed. The 2 resistors need to be the same value to get 50/50 split as the output voltage is the ratio of the 2 resistors.

It may be possible to replace the divider circuit with a 10K Variable resistor as you can see in the Variable voltage divider circuit. Note that you must not wire it backwards or you will put a short circuit across the Masso output and damage it at one end of the pots travel. If you wire it the right way around then the resistance across the Masso output will remain constant no mater what value you set the POT at. This circuit has the advantage that you can measure the voltage going in and adjust the output to half or to the required speed which ever works best for you.

Please note that this is untested and I am guessing at resistance values, as the required value will depend on the input loading applied by your VFD and what current the Masso can provide but the voltage divider circuit is an easy method of dropping a voltage.

Cheers

Peter
 

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masso-support

MASSO Support
Staff member
Hi Ethan

Just had a thought that is even easier and requires no circuit.

Just lie to Masso and tell it the maximum speed is twice what you want. If you want 5 volts at 5000 RPM then tell Masso that the spindle runs at 10000 RPM full speed under spindle settings. The VFD doesn't care and I won't tell it if you don't.

That way the output voltage will be half. eg at 2500rpm the output voltage will be 2.5 volts which is what you want.

Reading above your spindle output at the shaft is 2000rpm when the motor is 5000 so i would enter 4000 into masso and i think that will bring everything right. Work on your tool speed not the motors speed unless you are changing pulleys. The VFD will take care of the motor. So if you set the spindle maximum speed under spindle settings on the F1 screen to 4000 then ask it to run at 2000 it will output 5 volts and ask it to run 1000rpm it will output 2.5 volts which should what you want without any wiring changes needed.

Let us know how it goes.

Cheers

Peter

EDIT: Just a note that this method will send up to 10 volts to your VFD if you set your speed in CAM to more than the desired 2000RPM. If your VFD is not able to handle more than 5V then the the Voltage divider may be the better option however I understand that you have already been sending 10V to your VFD with no ill effects in which case this will work fine for you.
 

masso-support

MASSO Support
Staff member
Thanks Patrick,

I only just looked at it now and see that they didn't mention or link to making the actual Hobby Horse build video I made. It was meant to be a 2 video project. I'll get over it.

Cheers

Peter
 

ethan-downey

Ethan Downey
Hi Everyone.

Sorry for the late response and thank you all for your input and help.

(@masso-support) Peter, Thanks for both your suggestions. I tried the easier option yesterday of tricking Masso with setting it at 4000 RPM but it didnt fully work. The RPM varied a lot throughout the RPM range and struggled to run at low RPM's.

So today i made the voltage divider as you specified. IT WORKED A TREAT! I can not thank you enough!! I used the 4.7K Resistors. The RPM is out just a little so im going to redo it on Friday using the 10k Variable resistor so i can fine tune it.

P.S Nice horse!
 

masso-support

MASSO Support
Staff member
Thanks for the update Ethan. I'm glad to know it worked for you and the Variable resistor should sort out the rest for you.

Better than having to buy a new VFD thats for sure.

I was really pleased with how the horse came out.

Cheers

Peter
 
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