My place...

'Type in your company slogan here'

2013-12-26 17:02









Link / News Box


Your Link

Your Link

Your Link

Your Link

Your Link


Text Box

Use this box to type any specials, new updates or even gallery pics here.


CNC - 2.2kW Chinese spindle upgrade.

When the BT30 spindle project kind of failed I kept using the ER16 collet spindle for a while but in November 2013 I decided to upgrade the machine to one of the popular Chinese 2.2kW 24krpm water cooled spindles. I found one on EBAY which had a fairly short nose on it which I liked so I picked that one up for $300 including shipping.

I had some aluminium plates intended for mounting the BT30 spindle to the machine which I decided to use for this spindle instead. In order to do that I needed a way to mount the spindle like I intended to mount the BT30 spindle, ie via a flange. So I built a sleeve/flange/clamp type of adapter:


The internal bore is a nice tight fit to the 80mm outer diameter of the spindle and tightening the clamp screw seams to lock it place firmly, seams to do the job.



You can see the dicky connector hanging out at the back. Although the quality was a bit better than I thought it would be this was one thing I decided I had to change before even powering the thing up. There's not even a proper earth connection in that thing but more on that later on.


The spindle with its flange adapter is then mounted to the bottom plate of the new Z-axis assembly:


And then the bottom plate is mounted to the back plate:



Instead of having to run water lines back and forth with the risk of them wearing out and eventually rupture and leaking I decided to at least try fitting the cooling system to the Z-axis assembly. To be honest, I didn't do much research into how much cooling these things really need so I may end up redoing the whole lot but anyway, here's what I came up with:


This is a PC watercooling reservoir/pump, model XSPC 750 v4 to be precise and a small radiator, model MagiCool Mini II with 2 40mm fans mounted to it. The pump is specified to 12.5 litres per minute which feels like more than enough (provided it can push it thru the channels of spindle that is). The issue I'll most likely have, if any, is that the radiotor/fan assembly is too small and won't be able to dissipate the heat. There's room for one more radiator/fan assembly of the same size so if it turns out to alomst work I might fit that. Otherwise I'll have to revert to something bigger and have the system off the Z-axis assembly.

Anyway, the cooling system sub assembly sits right behind the spindle motor, like this:


Right, back to the connector.

This is a motor designed to run at 220V 3-phase. However, I'd like to run it using the inverter I already have and that's designed to be powered from 400V 3-phase which means that the DC-link in the inverter is aroung 560V and this is the voltage that the wiring and connectors needs to be able to handle, with margin to spare. There's no markings what so ever on the connector on the spindle and I didn't feel comfortable using it - especially so when there's not even a proper earth connection included.


So I decided to use a 4-way HARTING connector specified for the job. In order to fit that I had to fabricate a little adapter. (This aproach by the way was inspired by another CNC machine builder so I can't take all the credit):




Now, that's more like it if you ask me.


Then it was time remove the old Z-axis assembly from the machine and mount the new one. Not much to say about it really but here are a couple of photos:




My intention was to use the same inverter I had been using for the ER16 spindle. This was a 3kW inverter and this new spindle is a 2.2kW motor BUT the inverter was rated for 3kW at 400V output while the new spindle is 2.2kW at 220V so the actual output current of the 3kW inverter wasn't quite up to the task. Never the less I thought it could work since I most likely won't run at full power for very long periods and it did work - initially.

As I was setting up the inverter I played around with the setting for the switching frequency (or carrier frequency as it's sometimes called) and all of a sudden the inverter tripped with an over current fault. After some tests it turned out that it kept tripping as soon as the output was turned on, no matter if there was anything connected to it or not.

Looking at the manual for the inverter I noticed a little tiny note right next to the setting for the inverter frequency saying that one should contact the factory for derating figures when raising the swithcing frequency - oops. I suspect me increasing the switching frequency might be what killed the inverter, I don't know. Anyway, it was 1992 vintage and underpowered to begin with so it had to replaced with something.


I ended up getting a used 4kW Danfoss VLT MicroDrive for a good price. It's specified to 9A continous output and the motor at 8.something so it should be a good match. I've done the initial setup of it and it seams to work just fine. Here's photo of the new, almost finished, setup:



As of this writing I haven't yet connected the inverter to contol box so that it can be controlled from Mach3. This inverter has a MODBUS interface so I'm thinking of going that route instead of discrete signals. Doing it over MODBUS allows some cool feedback from the inverter to be displayed in Mach3, like motor current, motor power, any warnings and so on. I'll play with that next.






Copyright 2013 Henrik Olsson. All Rights Reserved.
Template downloaded from:
FrontPage Templates