|Viv Watts||17/01/2015 20:47:43|
7 forum posts
Thought this may be of interest to other members who might have a Myford VMB milling machine and how I converted it to CNC.
The machine has developed over time. Here is its current state of play...
The Blue bits are mostly the added items
It has digital readouts for X Y and Z1 and Z2. This was the original task. They are all of the chinese scale variety. The X, Z1 and Z2 being commercial designed for the job scales. The Y axis was a modified LIDL scale which works fine.
The next task was to monitor spindle speed. The Myford variable speed control was fine but looking up the conversion chart was tedious. A chinese digital frequency readout (£8) was purchased and with little modification could display RPM. A segemented disc on the top main drive pulley provided the pulses.
The next task was to power the Z axis as the gear ratio o nthe hand whell was very high. I actually used a motor for a bread maker which worked fine but was later replace by a stepper drive for CNC (see later).
You can see above modifications to the hand wheel (Red) and a counter balance ball (when it spins fast it will shake without it). Nexit is a home made Z axis jog/drive control knob (black on blue box). Make to look like normal machine tool knob. It seem natuaral to reach up to drive the z axis.
Of interest may be the red aluminium ring around the drive spindle to aid gripping to tighten chucks etc. Just behind the z axis hand wheel is a blue cover for the Z axis micro switches which use the z axis DRO to hold slidable limits for up and down but rearly used.
Above is the Z axis drive mechanism. A pulley is fitted directly on the hand wheel shaft. The motor is mounted at the rear.
Above is Z drive belt cover fitted (made out of MDF).
And a rear view of the z axis motor cover with drive cable.
Above is X axis drive assembly. The original bearing casting is replace with an aluminium plate. A oilite bearing is added. Picture shows stepper and to the rear the X and Y jog joystick. Drive to the hand wheel is through the two screews which engage into a drive pulley. The hand wheel knob is removed for safety.
The Y axis drive is achieved with a stepper mounted under the bed (just enough clearance with the raising feet. Again a cover to keep the muck out which was CNC'ed on the machine itself.
X axis limit switches, X axis scale signals, Y axis limit switch cable routing.
The above shows the original myford VFD motor drive (center right black box) cabinet.
The CNC controller board from planet CNC top left. Three stepper motor driver units top right. Bottom is stepper power supply with temperature sensing board added to control fan in supply an two mounted on cabinet door.
|Michael Gilligan||17/01/2015 20:56:00|
15427 forum posts
Very tidy job, Viv
|John Stevenson||17/01/2015 21:21:13|
5068 forum posts
So the Z axis is still uses the worm drive and original acme screw ?
Are X and Y on ball screws ?
Edited to read semi-English.
Edited By John Stevenson on 17/01/2015 21:22:01
2904 forum posts
Nice job Viv. Is it cutting metal now?
|Viv Watts||18/01/2015 11:58:53|
7 forum posts
Still has original screws in all axis. Considering how to add anti-backlash nuts.
No its not Mach 3. I use a self contained CNC controller and connect via USB.
Yes it has been cutting metal. After parts for itself then first project was a probe.
|John Haine||18/01/2015 16:15:11|
|2998 forum posts|
Nice! Thanks for posting.
|John Stevenson||19/01/2015 16:07:44|
5068 forum posts
I am part way thru one but with a difference.
I bought a VMB from the Myford sale or rather some bits for a VMB as it had been heavily robbed.
That's all i got but it is all new. Decided first off what with what was lacking to convert immediately to ballscrews as there is no way you can get the Z axis to behave after running through a 90 degree direction change with a couple of ex-winch gears.
Not even an enveloping work wheel.
I don't have a current photo of where it is at, at the moment and away from home for a week or so but this is the latest shot I have.
The ball screw showing is actually the Y axis screw just poked into position as it's short. The stepper has been fitted and sits inside the column with a 2:1 toothed belt drive reduction to go to the top of the screw. The top bearing for this is part of the stepper plate.
Don't know if that would fit on a standard VMB because of hight but as I was missing the spindle, quill and all the motor attachments I'm now using a very special motor as the spindle. This has an ER32 collet system built in and can run from 1000 to 7,200 rpm which because it has been built for a special job that will require it to not use cutters larger than 6mm will be ideal.
In retrospect i could have dropped to an ER20 or 25 but I have standardised on ER32's
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