Now that we have the new spindle on our mill, and the linear rail+ballscrew conversion for the Z-axis have been working for a while, it's time to upgrade the X and Y axes.
Jari has made some good progress on the table/X-axis. The IKO 15 mm linear rails are mounted, we've machined and attached the bearing holders for the ballscrew, made a motor mount for the servo, and also worked on the steel saddle plates. The new talbe is much bigger than the old one, and will allow about 500mm of X-axis movement. That's going to be enough to machine fin and bulb moulds for an IOM in one go - something that we can't do right now.
Here's a close-up of the motor mount, all parts machined from aluminium using our own mill. There's room for a coupler between the 12mm motor shaft and the 8mm ballscrew end. The motors we are using are 1.6 Nm continuous torque DC brush motors from Camtronics. Keeping to the KISS principle, we are hoping the motors are strong enough to work in direct-drive (no belt reduction or gears).
This photo shows the ballscrew (16mm diameter, 2.5mm pitch, from metallstore.de), the ball-nut, and the X-saddle plate with some steel bars under it to make room for the ballnut. Next up is a similar assembly for the Y-axis. That's going to be a bit more complicated since the parts will eventually have to be mounted on the very mill we are making them with! Hopefully not too many iterations of disassembly/assembly will be required...
Jari has also made a new tool-holder:
Jari has been busy planning and building a new spindle for our CNC mill. The project is now about half-way so I thought I'd take a few pictures and write some text.
So far we've been using the stock spindle on the Opti BF20 which has a Morse Taper #2. The original motor burned out at some point so we had to replace it. But as our machine has run for probably hundreds of hours already the bearings are showing some serious wear. We measured a runout of more than 0.05 mm...
On the left the new spindle, Morse Taper #3, from littlemachineshop, a bargain at $34.95 !. It's sold as a lathe spindle, but we thought we'd get the longest spindle they have to place the bearings as far apart as possible for rigidity.
This is part of a larger upgrade plan for the mill which will include replacing the dovetail ways of the stock mill with linear bearings, replacing the standard acme screws with ballscews, and upgrading the control electronics to use AC servos.
The linear bearings are 15mm wide and manufactured by IKO. We got the ballscews from metallstore (I think they are made by HiWin), and the Sanyo AC servos are from last years surpluscenter sellout of Sanyo AC servos. Three 400 W servos will direct-drive the ballscrews (I hope the torque will be more than enough, otherwise we will have to resort to gearing as is often done with servos). A 1 kW servo will be used as the spindle motor. I'm hoping that using a servo as the spindle motor will allow rigid-tapping eventually. Finding affordable servodrives for the AC motors (sinusoidal 3-phase commutation based on hall sensors and/or 2000 ppr encoder) is not easy, so I've actually had a go at building my own drive (also check out Tero Kontkanens effort).
Everything will be controlled by EMC, with a Mesa Electronics M5I20 PCI-card for I/O.
Some pictures of the spindle assembly and toolholders below...
Continue reading A new spindle for our Opti CNC mill
Back in October-November Surpluscenter was 'giving away' brand new servos at 40usd/servo when the cost for new ones can be 1000+usd/servo ! So we just had to get these for our next cnc upgrade. Here are some 400 W Sanyo Denki P5 100VAC brushless servos. The bigger servo, third from the right is a 1 kW model. The catch is that these servos need an advanced servo amplifier/drive to operate. There are several amateur/open-source efforts which aim to produce such a drive cheaply or DIY:
To finance theÂ amplifier development/purchase and the rest of the upgrade, I am selling three of the 400W servos.
Below some IKO LWL 15 rails which will also be used:
Spent today milling a new motor mount for the ABB motor we are planning on putting on the Opti.
Here's the raw material, a 120x20 mm aluminium bar. The 6-flute 6 mm endmill we used is visible in the left upper corner.
Continue reading Motor mount for new Opti motor