Hello Guest it is March 28, 2024, 01:43:02 PM

Author Topic: What controls the main spindle drive  (Read 1462 times)

0 Members and 1 Guest are viewing this topic.

What controls the main spindle drive
« on: February 19, 2022, 06:39:19 AM »
I'm going to replace my spindle drive board on my Denford CNC but need to know what signals are given out by Mach to control the spindle speed. Everyone who knows me I'm useless at electronics so any advice is appreciated, the only thig I'm sure of its not gas regulation 3  :) :) :)
Re: What controls the main spindle drive
« Reply #1 on: February 19, 2022, 05:25:17 PM »
The main thing Mach3 can do is output a pulse train with a variable mark/space ratio at a selectable frequency, typically 25hz.  This can be smoothed with a simple RC circuit to produce an analogue voltage to control the speed.  An important question is what drive board you are going to use?  Are you currently controlling the speed of the Denford from Mach3?  The reason for asking is that at least some Denford machines had a speed controller that was not isolated from the mains so some form of isolator is needed to keep mains voltages away from the CNC controller itself. 

For more details on this see here...
http://www.mycncuk.com/threads/7992-Denford-Novamill-Mach3-conversion/page2?highlight=Denford+Novamill+Mach3+Conversion
Re: What controls the main spindle drive
« Reply #2 on: February 20, 2022, 02:15:31 AM »
Hi John thanks for your quick reply, my Denford Triac is a 1988 machine with the spindle driven by a LYNX board, I've been told the Parker 508 inverter is a suitable match. The spindle stopped giving the selected speed then started hunting and finally stopped. I looked at the old LYNX board and found the inputs and outputs for driving the spindle and controlling the speed seem a straight replacement. But being an mechanical engineer if it don't move I don't understand it, electronics are a mystery to me.
Any advice would be appreciated.
Re: What controls the main spindle drive
« Reply #3 on: February 20, 2022, 05:32:15 AM »
Hello Jim, well first a few questions.  From your description of the problem it seems you must be using Mach 3 to control your machine so I guess it has been converted from the original Denford controller but kept the spindle drive - is this correct?  And you can currently control the speed from Mach 3?

Assuming that the answer to these is yes, then probably there is a PWM to DC voltage converter in the breakout board between your computer and the stepper and spindle drives.  Could you check that there is a wired connection to pin 3 of the Lynx card? 

The Triac seems to use the Lynx 08 drive from the Denfordata forum.  I have found the manual for this online and will attach a copy.  It confirms that the drive DOES have an isolated input, which is fortunate.  The Parker 508 DOES NOT have isolated control inputs and is NOT suitable.

You can buy a refurbished Lynx-SM-08 drive from these people:

https://nicontrols.com/uk/lynxsm08-control-techniques.html

The SM bit just means that it uses "surface mounted" components on its PCB, yours (being made in 1988) would have used "leaded" components.  This looks like it should be a direct replacement for your board.

I think people have also used Sprint drives, for example the 400i, which also has isolated inputs.  However that can only supply 4A, but there are other Sprint products with greater capability.  (I believe that the Novamill (which I have) originally used a Sprint drive.)

https://www.transdrive.co.uk/shop/products/dc-drives/sprint-electric/analogue/2-quadrant/sprint-electric-400i-0-55kw-4a-240-110vac-2q-isolated

So you should be able to buy a replacement Lynx drive - if not then there is probably a suitable Sprint one but the wiring will need changing round a bit.
Re: What controls the main spindle drive
« Reply #4 on: February 20, 2022, 06:08:00 AM »
Hi John, A bit about me before I start, I'm 76 a Brummie mechanical engineer who loves CNC but don't understand it.
I lecturer for 20 year in mechanical engineer and when I retired took the chance to buy a Denford Triac from the college.
I converted it with the aid of a mate to Mach 3 and have been using it for 12 years and apart from a failed contactor and several old computers that failed. its been faultless. Been making model steam train parts with it to stop me going senile
The machine is a Mach 3 conversion and I control the speed from the Mach 3 software.
Pin 3 comes out and goes into a spindle drive card on the main terminal board to the axis motors, stops, limit switches and emergency stop button. I noticed lately the spindle could be stopped by a cut that used to be no problem and the spindle speed does not maintain a constant speed through the day.
I purchase a Parker 508 off Ebay some 5 years ago but it looks like it will be going back on ebay.
I have noticed the first resistors on the Lynx board has burnt out but this was like it when I purchase the machine so ignored it.
Can I show my Ignorance as far as electronics goes, is the Sprint 400 board big enough as its rated at 4A.
John your a gent and appreciate all you have told me, its been invaluable.
« Last Edit: February 20, 2022, 06:24:59 AM by jimthefish »
Re: What controls the main spindle drive
« Reply #5 on: February 20, 2022, 06:51:49 AM »
Jim, happy to help.  It is just possible that the fault is the motor brushes, so worth checking those before you spend money on the drive.  Given the age of the machine it would be worth replacing them anyway.  Mind you if the Triac is made like my Novamill actually getting at the motor is a nightmare!
Re: What controls the main spindle drive
« Reply #6 on: February 21, 2022, 06:29:24 AM »
Hi John just checked the brushes they are fine, the motor driving the spindle is a Lenze 0.75hp is the Sprint Electric 400i 0.55kW 4A is it man enough?
Re: What controls the main spindle drive
« Reply #7 on: February 21, 2022, 08:44:35 AM »
.75hp is 560 watts, just a bit marginal I'd say.  Would probably work most of the time but controller might trip out when pushing the cut.  I think there's a slightly larger sprint that will supply 6.8 amps?
Re: What controls the main spindle drive
« Reply #8 on: February 21, 2022, 09:01:02 AM »
John your a star, been talking to transdrive, they said the same. There website has all the pictures and definitions of what's isolated and what's not wrong. He recommended the 680i which is isolated but the web page says its not. They are going to rectify the description and pictures. To add to my confusion the Denford manual says its a 500w motor and the label on the motor says 750w, so best to go big just in case
Re: What controls the main spindle drive
« Reply #9 on: February 22, 2022, 05:55:48 AM »
Hi John I always try to finally respond to those who help on the Mach forum. Decided to take out the LYNX board and have a look in clear light before committing myself to buying a new unit, well under the magnifier notice a broken wire on it. Soldered it back together and it all works. They quoted me £250 to refurbish it, not bad for soldering a loose wire, Thanks for your help, I've learnt a lot about spindle drives thanks to your input. Cheers mate.