Heavily CNC converted Opti BF 20 Vario

[JMI80]

Hi,

My first post. I'm a CNC machinist from Finland. At work I use VMC and as an hobby I have converted Opti BF 20 Vario to CNC with my friend Andy55.

Andy55 has built our Geckodrive stepper electronics and take' s care of the
computer things also. We use EMC2 control. I take care of the mechanics.
Few pics of the current state of the project below. There's actually only
column and base left from the original machine anymore...

You can watch a short video of the machine on action from here:

http://www.anderswallin.net/2007/07/...f20-in-action/

Put enough volume, sounds are good!!!
I will post more videos later. Rapids are painfully slow, put with small steppers
it's better to have low acceleration/ top speed and have good reliability.
I have stalled steppers too many times with higher rapids.
DC servo's are coming...

[JMI80]

Little bit of history about this project:

This project started about five years ago and was simple low cost CNC project
at the beginning. Only handwheel' s were replaced with stepper motors at the
beginning and I made wooden bench for the machine. We were looking for a
machine with 500 mm X- travel, but Opti BF20L, Grizzly G0519 or similar low cost machines were not available then and we could not afford Wabeco F1210 E.

When you learn more about CNC machining and want to drive faster and faster, you have to start tuning your machine! First part to replace was standard 600W DC spindle motor since I run out of spindle power all the time. I burned couple control board fuses and finally when the spindle speed control board itself burned instead of fuses, change had to be done. Standard spindle motor was replaced with 0,75 kW three-phase induction motor and variable-frequency drive (VFD).

[Brunow]

Whow! Hobby use?

Nice!

[andy55]

JMI will post more pictures later, but there are some pics and text about our efforts on my blog:

the stock DC motor on the mill gave up quite early, so we replaced it with a standard AC motor:
http://www.anderswallin.net/2005/11/...duction-motor/
http://www.anderswallin.net/2005/11/...ew-opti-motor/

Then we thought the stock spindle and spindle bearings weren't that great either. So we got an MK3 spindle from littlemachineshop and built some bearing holders and a spindle box around that:
http://www.anderswallin.net/2006/10/...opti-cnc-mill/
http://www.anderswallin.net/2006/12/...dle-installed/
It's belt driven with 1:1 ratio. Much quieter than the stock spindle.

Finally, the X-axis travel was a bit short, so we made a new table, and while at it replaced the dovetail ways with linear ways and the trapezoidal leadscrews with ballscrews:
http://www.anderswallin.net/2007/02/x-axis-progress/
http://www.anderswallin.net/2007/04/opti-bf20-on-rails/


hopefully we can show some videos with the DC servos soon. Maximum rapids should be much better than with the current steppers.

[JMI80]

Originally Posted by Brunow Whow! Hobby use? Nice!

Yes, for hobby use. This mill has been used a lot to make plugs, moulds and rig parts for IOM RC yachts.

I'm also interested to see how good performance it is possible to get out of small mill like this with "little tuning".

[svenakela]

Dudes, perkele!!!
That's a freakin good looking machine. Oh lucky I am, having a VFD waiting to be mounted.

[JMI80]

Here's few pictures about column and base machining.

I had a chance to use VMC and machine the new T- slot table, drill and tap IKO rails M3 and ballscrews bearing housings M8 attachment threads to column and base at school where I did my CNC machinist vocational examination.

When we disassembled column from base, there came a big surprise: at factory they had "trimmed" column attachment
place with angle grinder! I machined that straight at school.

Column and base were first attached dovetail ways downwards against parallels, and attachment surfaces for
drilling and tapping operation were facemilled.

I could use the VMC only four days for this project, so it was not possible to do all parts needed to get the new table and IKO rails in use. After I had drilled and tapped the column and base, I took them back to my workshop and assembled Opti to original configuration. Then I machined ballscrews bearing housings, XY axis saddle plates etc. during weekends.

[JMI80]

Next tuning part for the mill was new spindle:

MT3 spindle itself is from littlemachineshop:
http://www.littlemachineshop.com/pro...2027&category=

25 mm aluminium plates holding the bearings are machined with opti. I would have wanted to make those from steel as well as ballscrews bearing housings, but that was just too tough steel milling project for Opti at original configuration. It would have been possible with small cutters like 6 mm end mill, but it would have take so long time that I decided to use aluminium and bigger cutters.

There is 1:1 AT5 Belt drive. Bearings are FAG standard accuracy
angular contact bearings. Spindle radial runout is around 0.015 mm.

Yesterday 0.75 kW spindle motor was replaced with 1,5 kW motor.
It's the biggest motor that will fit in this spindle housing. Omron Varispeed V7 Vector VFD was also purchased about a week ago. With VFD we have used RPM' s up to 5000. Three-phase induction motor torgue start's to drop pretty
much after 3000 rpm/ 50 Hz, but at 5000 rpm there's still enough torgue to do light finish milling or drilling with small drills.

First tests showed that there's pretty much increase in torque and power with 1,5 kW motor:

I can now take 1,5 mm deep cut in aluminium with 40 mm face mill (40 mm wide cut) and it goes very well with 1200 mm/ min feed. RPM was 3000. That cut take's about 55% spindle power. 2 mm deep cut goes somehow with 900 mm/ min feed, but it doesn' t sound good anymore and machine doesn' t like it.

I would be interested to know how big cuts and what kind of feedrates it is possible to use in aluminium with with bigger mills like Grizzly G0519,
OPTI F 45 or Enco SQ COL MILL/DRILL???

[svenakela]

JMI80, are you A. Wallin at the EMC mailing list?
Hmm... I just checked your website, yes you are Mr. Wallin.

[andy55]

Originally Posted by svenakela JMI80, are you A. Wallin at the EMC mailing list? Hmm... I just checked your website, yes you are Mr. Wallin.

that would be me...

so now the question is who are you really? 'Lernaean Hydra", "anonimasu", "jymm" ?

[digits]

Wow - that is a great 'conversion', or should I say rebuild!

I am realy envyous of your enclosure though - it's lovely

Is that cutting video with your 0.75kw or 1.5kw motor - you can really hear it bogging down as the cut begins, but it sounds completely chatter free to me

[svenakela]

Originally Posted by andy55 that would be me... so now the question is who are you really? 'Lernaean Hydra", "anonimasu", "jymm" ?

Nope, just Sven. But it was a looong time since I posted. I'm mostly reading.