CNC Conversion of a Seig X1 Mill

[hikerbob]

I'm working on a CNC Conversion of a Seig X1 Mill (http://www.carbatec.com.au/mini-milling-machine_c2430)

I'm doing the 3 axis of the mill and will add a stepper to my rotary table as well - a 4-axis controller

Motors and driver are from ebay - (http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=180558342384&ssPageName=STRK:MEWNX:IT) and I'm using the free version of Mach3 (http://www.machsupport.com/) software and am really impressed.

The PC is an old Laptop I picked up at the tip a couple of years ago - way under spec but it does have a real parallel port (most USB to parallel won't work). Possibly longer term I'll pick up a desktop box and a 10" touchscreen monitor but so far so good.

Flexible couplings are from Jaycar (about $20 each).

I started out with a couple of MDF motor mounts for the X and Y axis, one is still on the machine. In hindsight it would have been simpler to go straight to a the metal mounts. I've tried to leave the drive shafts alone so it's taken a bit of fiddling to space to work around the thread that the handles are normally attached to.

At this stage I've stuck with the original drive threads but have started snooping at Ballscrew's and precision acme to explore options for reduced drag and potentially greater accuracy.

I've still not got the Z-axis working, it needs gear reduction and or a big counterweight.

There is lot's of material around of the web on converting the Seig machines to CNC. A range of different idea's. There are also a bunch of mod's available for the Seig machines such as longer bed's (http://littlemachineshop.com/products/product_view.php?ProductID=3860&category=-1196799916, http://www.cncfusion.com/).

I've been getting some bit's and pieces (cutters, milling chucks and arbors etc) from CTC Tools (http://www.ctctools.biz/servlet/StoreFront)

Some of the doco about the controller is confusing, the motor port settings in one document were wrong, I found the right ones in another. I'm still trying to get some comfort with the dip switch settings, two versions around but I'm less than certain that I've got them right so far. The parallel port cable supplied was not quite correct, I needed a gender changer to get it connected to the board.

Bob

[rally]

Bob,

Good luck on your conversion, looks like an interesting project.

I would suggest you look at ballscrews if you can afford it instead of standard leadscrews and maybe double check all the thrust bearings on the screws, any backlash in the mounting or the screws (or gibbs/slideways/linear bearings etc) will resut in poor finish - chatter and not so round circles !
Ballscrews have no backlash - leadscrews have plenty !

In some cases you might even lose your cutters as they bite too deep and break or just chatter themselves to death - leaving a terrible surface finish.
Small carbide endmills need to be held rigidly in order to get any useful life.
Whats the spindle rigidity in this machine like ?

Milling technique with manual mills is quite different to CNC mills due to the inherent backlash in lead screws - ie UpMilling (Conventional) Vs Downmilling (climb milling) so your milling directions will vary depending on which sort of screws you use - although a CNC with ballscrews doesnt care so much in which direction you mill.

Regarding driving the Z axis - normally CNC mills have a counterweight in Z, a much large servo drive or even a hydraulic or pneumatic counter ram to overcome the constant downward forces. So I think your thoughts will prove correct.
A heavy chain and sprocket with a counter weight and small support frame should do the trick.

Please make sure you send us through the first pictures of your 24" truss framed RC as you are making it !

Cheers

Rally

[hikerbob]

Rally thanks for the input. "you send us through the first pictures of your 24" truss framed RC as you are making it" - actually getting the fork mount for my 12" skywatcher finished will be the first astronomy project once this is all working.

This won't be a rig for heavy work but it seems to be good for small to medium aluminum and synthetic parts. It getting me started with CNC for a relatively small outlay and so far not a lot of work. The scary bit is I may get aperture fever (bigger machines) from this. The mind is already pondering CNC on the lathe :(

I've held of the ballscrews for the moment, most of what I'm doing should be reusable of I do decide to change over.

Bob

[snowyskiesau]

I have an X2 mill and a CNC conversion is in its future so I'll be watching your progress with interest.

As far as ballscrews and couplers go, give this eBay seller (http://stores.ebay.com.au/linearmotionbearings) a try. Chai has a good reputation for service. There are lots of happy customers on several other forums (details available) and I'm one of them. He will provide endmachining of ballscrews for only a few $$ extra.
I have a Gecko G540 as a controller, an ex lease computer I bought from an auction together with a copy of Mach3 and all the plugins. I got my Mach3 license from Homann Designs (http://homanndesigns.com/) and when I'm ready, I'll also get my stepper motors from Peter.
I've used CTC for tooling but get most of my stuff from CDCO (http://cdcotools.com).
Have you decided on CAD/CAM software yet? I can recommend Alibre for CAD. The basic package is available for around $100.

Good luck with the build.

[hikerbob]

Geoff thanks. I'd found some favorable comments about Chai yesterday.

Homann Designs looks like a useful resource.

I've not got to far on the cad/cam stuff yet. I need a major skill's upgrade to get to that part. Initially I think I'll use the Mach3 wizards to generate code pieces then put the bit's together as I need and look at Cad/Cam once I get the time.

Bob

[Bassnut]

A very interesting project, been a while since I looked at this stuff. The links are interesting too. I cant believe the price of the stepper/controller kit, I guess that would be much cheaper than servos. It doesnt look like your useing encoders of any sort, even for readout only, (not that you need them), is that right?.

[snowyskiesau]

If you're using steppers, then no encoders are required as is the case with servos.
You'd need a much bigger mill to justify servos

Some of the cheap controllers as sold on eBay have a bad reputation for reliability and are prone to lose the magic smoke with little provocation. It's not that much more expensive to go with a better controller such as those from Xylotex (http://www.xylotex.com/) or Gecko (http://www.geckodrive.com/).
Gecko drives are practically unkillable and therefore a good choice for hobbyist.

Stepper motors from China are incredibly cheap but freight is a killer. Homan Design (http://homanndesigns.com/)and Ausxmods (http://www.ausxmods.com.au/) are 2 local suppliers of all things CNC. A good US source is Keling (http://www.kelinginc.net/index.html)

[hikerbob]

I've now got the Z axis under CNC control. I'ts a rough up with some timing pulleys I had on hand but I have a bigger ratio set on order. The Z axis motor is running at full power to drive the axis which heats it up more than I'm happy with. Hopefully with a bigger ratio I can back the power setting on the controller down. X and Y run quite cool and with the feed rates I've been using I have not had any sign of missed steps.

I used the mill with CNC control of the X and Y axis to make the mounting bracket for the Z axis motor (very satisfying). I just had to manually drive the Z axis at the right times. The fit of the nema 23 stepper to the bracket was perfect.

I'll rebuild the X and Y mounts in the near future using the mill to make the components.

I ran the roadrunner gcode sample which comes with Mach3 last thing tonight and did 2 cuts with the tracking looking very good.

Fred no encoders at this stage. I'm treating this as a learning exercise and am trying to keep the costs down as far as practical. I think I've now spent around the $400 on the conversion which has given me a CNC controlled mill for about $1k. I will probably get the full version of Mach3, so far I'm really impressed.

I picked up a couple of limit switches today which I've not fitted yet (they will go on the rebuilt X and Y bearing brackets) and have an emergency stop button almost ready to go but need to get it hooked up.

Bob

[gary]

Hi Bob,

Welcome to the world of CNC.



If you have not done so already, for the home positions, recommend you use
optical switches rather than mechanical switches as they can provide for
improved repeatability for referencing. Some flags for the sensors can
be milled on the machine from sheet metal or plastic.

With Mach3, you can define soft limits, so you may decide to forgo limit
switches at the other end of travel. However, in the scenario where the REF
ALL HOME step has not been performed in Mach3, the soft limits may not
be valid and you might decide to add limit switches, either optical or mechanical,
at the other end of each axis, to prevent a crash into the mechanical stop.

As has been noted, the ball screws and ball nuts are seriously worth considering if
budget permits. Their mechanical efficiency is such that they provide a fraction
of the frictional losses compared to the existing screws and though their
backlash is not zero, it certainly can be orders of magnitude less than what
it would be with your current screws. Double ball nuts are another step up again
from single ball nuts, but you probably don't require the levels of precision that
double ball nuts can provide.

A license for the NFS Wizards, which are the "Mach3 Addons for Mill", is
recommended.

[hikerbob]

Gary thanks. I've got a vague inkling that those who know the topic better than me see a lot of value in ballscrews :) That may be something for next year, I'm wanting to get a set of servo's for the mount I'm working on sometime while the aussie $ is still good.

I've not fitted the limit switches yet and had not thought about optical but that does make sense. I'm using the soft limit's but want the physical limit switches for a backup to soft limit's

Today's project was a drain tray and backboard. Still a bit to go with it (eg a drain) but the main structure is in place with some ugly welds in the corners. It's done in 1.6mm aluminum tread plate with some big chunks welded in to bolt the mill down to. I'll put some rails underneath as well. The electronics will go in behind the backing board. No photo's yet sorry.

I had a play with some cad stuff today, I have a copy of DraftSight and I downloaded a converter to output g-code. I've still got to play with that some more to work out how to create the right properties on a drawing to make the difference between a thin line and a hole or pocket.

Bob

[snowyskiesau]

Bob,

FWIW, I've priced ballscrews for my X2 mill at $175 that's delivered and with ends machined to suit (I supply the drawing of what I require).
These are for RM1605 ballscrews (16mm diameter) but with your mill, I think RM1204 would be enough and cheaper still.
You can get BF/BK ballscrew supports from the same source or you can make your own bearing housings - there are lots of plans to choose from.

If I wasn't in the process of moving and putting all my tools into storage, I'd be dong the ballscrew/CNC conversion right now. :)

[hikerbob]

Geoff $169 USD for two RM1204 and nut's. Add in an RM1605 for the z Axis and some shipping and I'm up to almost $300US. I'll hold off for the moment and see how it goes for the work I'm doing.

Bob