Another machine rigid tapping (stepper machine)

[samco]

Pjm on irc has been keeping us up to date with his machine progress.
At the moment he is using 3 printer ports

He is using a 360ppr spindle encoder on the spindle.

There is a lot of info and more pictures on the emc wiki.
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Pjm

YouTube - rigid tapping with EMC 2.3 beta

YouTube - rigid tapping with EMC 2.3 beta

[elmerfud]

I like this build, how much Z travel have you got?
What brand of compound table is that?
The AC motor conversion must be quiet and punchy.
3 parallel ports must involve some know how.

[cyclestart]

elmerfud
This isn't samco's machine and Pjm isn't a member here, or at least not under that name.
The emc wiki page (linked) makes some mention of the mechanical parts, but is not very specific. The z travel looks absolutely huge.
Very nice looking unit,

[pjm]

Hi,

I didn't think I had a log in to the site, but after some digging through 2008 emails, I found it!

Anyway, to answer some of the Q's on the machine, the Z travel is about 600 MM and X, 300mm, Y 240mm. The bulk of the machine was recycled from an old multi-cam engraving machine that I recovered from a skip, in the pictures the Z column was in fact the old horizontal support column from the multicam. Behind the Z column is the lead screw with 2 bearings on it, and another support column made of a 1" ground bar, with recirculating bearings, this was done because I had the parts, but also for slop prevention. The actual XY table was recovered from the local scrap yard, it was extremely rusty and was locked solid, it probably took a few weekends of work to clean it up and free up the slideways, which thankfully were covered in thick hardened grease. Once cleaned up I fitted a pair of leadscrews / ball nut assemblies that were recovered from a lazer glass etching unit which was scrapped. The X axis has about 0.003" slop and Y about 0.002" slop - I intend fixing this as soon as the machine has earned enough money for new preloaded bearings.

The motor was originally the chinese one that came with the littlemachineshop mini mill head, but it was replaced with a 3phase unit and VFD found at a car-boot-sale for £5 - a bargain. I did have one mishap during the build where a wire from the braking resistor came off and went through the grill of the VFD causing a 'bang' which resulted in me needing a new driver module which cost be about £50 ;-(. Anyway it is now operational and is driven from EMC2 via a pulse train at the desired RPM, so 6K rpm = 6KHz out of the parport.

The base of the CNC is a piece of 100mm square box section that I chopped up to make the two equal parts, these then have 6 X 10mm reamed holes in the back end which mate with 6 reamed holes in the Z column which is also 100mm square box section. The entire machine sits on a stand made from 50mm steel box, and welded together.

The actual PC that runs the CNC has 5 parports, of which 3 are being used. The remainder will be used for a X/Y rapid traverse joystick, and perhaps some additional switching for light/coolant/aux stuff etc. I have a webcam to mount on the Z axis too so I can check the operational status of the machine whilst I'm surfing the net during a cut etc. I've uploaded a quick video of some rigid tapping of aluminum at http://www.youtube.com/user/uhfdashsatcomdotcom - it is just a quick test of 5 X M3 tapped holes, done at 750rpm. I've made a lot of stuff on the machine, milled out some pcb's etc, and so far it seems pretty capable.

The Gcode is mainly done either by hand for simple stuff, or using the cambam demo with the EMC2 post processor.

Anyway if you have questions, please ask, and also I can provide foto's of parts of the machine if you want to look at it etc. Actually, there are a few of the build photos online at http://pjm.dyndns.org/cam/cnc_built_...umb/index.html - not particularly up to date but it should give you an idea of the build process etc.

cheers,

Paul. (pjm in #emc IRC channel)

[elmerfud]

Oh, I misread the the author not being the builder. DUH

PJM, I love that machine!
Clearly you are a tradesperson (I was too).
I plan on a build like this in the foggy future too.

[cyclestart]

Originally Posted by elmerfud Oh, I misread the the author not being the builder.

And I wasn't aware the builder was monitoring this thread

but it was replaced with a 3phase unit and VFD found at a car-boot-sale for £5

The whole build shows that type of resourceful thinking. The VFD allows running that motor on household current ? ( I'm electron challenged )

edit/ Ignore the question, Google is my friend. Nice find !!

[pjm]

>PJM, I love that machine!
>Clearly you are a tradesperson (I was too).

Hi,

Thanks for the comments, I'm pleased so far with the machine certainly - for me the mechanics were the easier bit, the real magic is done by the EMC2 guys! I'm still upgrading the machine, basically to exercise my brain!

I'm not in the engineering trade, I do computer security stuff for a job, but I have engineering in my genes as my father is a CNC programmer currently working on Haas / Heidenhain machine centres etc, and his father was an engineer also, I'm getting my son who is 6 interested in engineering too, he's currently assisting me with tidying up the wiring on my CNC as I'm moving the controller into a metal box to try and eliminate some of the noise from the VFD which is introduced onto some of the signal wiring etc.

regards,

Paul.

[Andre' B]

That video is either of a left handed tap or I have some aliasing going on with the frame rate.

[pjm]

Hi all, just a short message to point you at http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Pjm - the machine has been updated, and now has all the electronics suitably mounted in a sturdy metal box, plus it now sports a nice hammerite green colour!

I'm currently playing with closed loop spindle speed control, where by it takes the spindle velocity out of the encoder, and compares it with the commanded speed, and adjusts accordingly. If anyone has done this, I'd be very pleased to hear from you, as PID loops are completely new to me, so I'd like to get a clue about them.

I'm also considering improving the IO with a mesa 5i20 or 7i43 card, I cant decide which one to go for yet!

http://pjm.dyndns.org/cam/32ghz_feedpjm/feed.jpg shows a picture of an item recently milled, it is a 32GHz scalar feed horn to be used with a dish, for the hopeful reception of some deep-space probes! No rigid tapping needed on this part though ;-(

thats all for now,

regards,

Paul.

[samco]

YouTube - Rigid Tapping M3X 5 750rpm

YouTube - Rigid Tapping M3X 5 750rpm

[vlmarshall]

Excellent!