Sieg X2 milling machine CNC conversion

[ROCKet STAR]

I don't think that the forum has a milling machine thread yet, so seeing as I've just bought one with the intention of converting it to CNC, I thought I would start one.

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I have needed a milling machine for some time, as the tiny milling attachment that I have for my Taig lathe, just does not have the working envelope for some of the things that I need to mill. Hare and Forbes recently had a sale, so I took the opportunity to purchase a Sieg X2 mill. I have also been planning on building a CNC router, so I figured that converting this mill to CNC would be good practice for that.

Searching the net, it seems that the X2 is a popular machine for CNC conversion, so there is plently of info to turn to for guidance.

So far I have purchased two 270oz/in NEMA23 steppers for the X and Y axis, as from what I have read, they are more than sufficient for driving those two axis when ballscrews are used.

http://www.ebay.com.au/itm/NEMA23-270-o ... 43ab219331

For the Z axis, I have purchased a 425oz/in NEMA23 stepper:

http://www.ebay.com.au/itm/321013523721 ... 1497.l2649

The reason for the larger motor on the Z axis, is that it requires more torque than the X and Y axis, to lift the heavy spindle.

For the drivers I have purchased three of these:

http://www.act-motor.com/productinfo/de ... 77_87.html


More to come...

[PJR]

[ROCKet STAR]

[rocket_troy]

Should be an interesting thread and good luck with the build Chris. I will say, that you'll probably regret not up-scaling to say the X3 but I'll be interested to hear how it goes. I have a Super X3 that was already converted to CNC and I've regretted not going for the X4 although if you're not milling Stainless or harder these mills will do wonders.

Cheers,

TP

[ROCKet STAR]

I had considered the X3, but the X2 seemed adequate for what I want to do with it... That said, I guess that the desire to go one step further comes with realising your current capabilities. I'll see how I go with the X2, it should certainly solve all my immediate problems.

There are a couple of other things I plan on doing to it other than the CNC conversion. Firstly I plan to swap out the Jacob's chuck for a collet chuck. I'm not keen on the idea of putting expensive end mills in a Jacob's chuck. Secondly, I have seen that there is a belt drive conversion kit available for the X2. I'll do that mod purely because the standard geared drive is quite noisy.

[OverTheTop]

I have some steppers that I have yet to find a mill (or other project) big enough to take. They are on an 11cm x 11cm frame (Coke can for scale):

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Yes, you read correctly. 65V 5.3A windings 3/4" keyed shaft

[rocket_troy]

Yup, I have a Nema 42 and a Nema 34 sitting here that I might use to power a small lathe spindle. The 42 has a 19mm shaft, but my favourite is the 34 - when connected to say a 240V driver like say a 2MA2278 I can rev it up to the point where it literally sounds like a dentist drill There's something amazingly kewl about hearing a large motor rev that high:)

TP

[ROCKet STAR]

Those are some serious steppers OTT!

My next consideration is ball screws...

Most of the X2 conversions that I have read about have used ball screw kits such as the ones sold here: http://cncfusion.com/minimill1.html

The kits look good, and would probably be a quick and easy solution, but I think they are probably a little pricy for what they are. I reckon I should be able to achieve the same thing for about half the price if I shop around and DIY it.

I found a supplier based in Melbourne who sells ball screws on ebay, and they look ideal for what I want. I purchased the following ball screws from them...

For the X axis:

http://www.ebay.com.au/itm/290680791701 ... 1497.l2649

For the Y axis:

http://www.ebay.com.au/itm/300675527621 ... 1497.l2649

and for the Z axis:

http://www.ebay.com.au/itm/290680793551 ... 1497.l2649

I also purchased some couplers for connecting the ball screws to the stepper shafts.

http://www.ebay.com.au/itm/170903221636 ... 1497.l2649

I will still need to source suitable bearings, and make/buy mounts for the steppers and screws.

[ROCKet STAR]

Bits and pieces are starting to turn up for this, so I should soon be in a position to start actually doing something with this...

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X and Y axis stepper motors. Still waiting on Z axis stepper.

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Three stepper drivers.

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Parallel port breakout board (interface between the PC and the stepper drivers).


My latest consideration has been bearings for the ball screws...

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The ball screws I have ordered come with the ends pre-machined as depicted in the illustration above. As such I require bearings to fit a 12mm shaft. Given that leadscrews in applications such as this are subjected to both radial and axial loading, a bearing is required that can manage both. A bit of reading later I determined that most people use double row angular contact bearings. The common bearing of choice in this application is a shielded 5201.

I bit of searching on the net turned up lots of 5201 bearings, however for the vast majority of them I couldn't find any information relating to tolerances, and given that one of the things that can introduce backlash into the system is bearings, I wanted to be sure that the bearings I purchased weren't going to be too sloppy.

If anybody on here has ever had more than a passing interest in skateboarding (as I once did) they will probably be familiar with the ABEC rating system for rating bearing tolerances. I decided to use this distant memory as a basis for selecting bearings. Basically the ABEC system is a scale of odd numbers, 1 through to 9, that gauges the tolerance to which a bearing is constructed. 1 is the bottom of the scale with the loosest tolerances, and 9 is the top of the scale with the tightest tolerances (and prices to reflect that ).

I bit more reading and I turned up this page http://www.cnccookbook.com/CCBacklash1.htm that suggests that ABEC3 rated bearings should work "well enough", so that is what I decided to look for.

I couldn't find an ABEC rating for most of the Chinese bearings I found on ebay, and the few that I could were mostly rated ABEC1. I did however find a supplier in the US that was selling ABEC3 rated 5201 bearings for a good price, so I decided to go with them.

http://bestbearingbargains.com/5201-12m ... aring.html

[Space Mark]

I use FF/FK and BF/BK bearing blocks which are designed for this style of ballscrew on my CNC mill. They came with some nice japanese bearings in them, however one is wearing out already (makes a clunking noise). The support blocks are really nice because they are big chunks of steel designed specifically to hold these ballscrews.

You can get "panel mount" and "flat mount" style ones. If you have 16 or 20mm ballscrews I probably have some flat mount ones you can have leftover from upgrades. I'd have to look at what I have around, as some were damaged when removing them (after several hours of frustrated drilling through them to get them free lol.)

http://stores.ebay.com.au/MISS-MY-CNC/B ... 34.c0.m322

When you get to making your CNC router, get some decent stepper drivers, like what Gecko make. Those chinese ones don't have a very good reputation but have a very good price point.
http://www.soigeneris.com/stepper_drives-list.aspx

[ROCKet STAR]

Hi Mark,

I had a look at the OTS bearing blocks, and they look good. I think they will probably be the way I go when I build a CNC router. As for the mill however, I don't think they would really be suitable, due to the space constraints in the existing castings. My plan is to make some stepper/bearing mounts specifically for the purpose. I do currently have a manual milling machine that would be suited to the job of making them!

As for the stepper drivers, indeed I have heard that the Chinese stepper drivers can certainly a bit hit or miss... My understanding of it is that while they all look very similar, they all seem to be variations on the same design, with some being better than others.
It was a toss up between Chinese drives and the Gecko drives, but given that I am currently spending more money than I would like on renovating my house, I thought I would try and save a few bucks and chance the cheaper option. I was careful to select one that I had read of someone else having some good sucess with, so we'll see how they work out. If they turn out to be crap, I'll take it as a lesson learned.

[rocket_troy]

[ROCKet STAR]

[ROCKet STAR]

A little more to report...

chuck.jpg (91.98 KiB) Viewed 14734 times

I swapped the Jacob's chuck that came with the mill for a collet chuck. I went with an ER16 chuck as I already had a full set of ER16 collets. Most people seem to go with a larger ER32 collet chuck with the X2, but I'll see how I go. I can always buy an ER32 at a later date if the ER16 proves too small.

ballscrews.jpg (88.48 KiB) Viewed 14734 times

The ball screws arrived! They seem pretty good. The ball nuts move smoothly along the screw and they seem to be a good close fit with no noticable backlash or unwanted movement. Hopefuly that should equate to very little backlash on the mill once they are installed.

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I recieved the connectors I will be using for the interface between the ends of the stepper motor cables and the control box. They are just four pin XLR audio cables, which can be picked up on ebay for a couple of dollars each. I bought way more than I will need. Should have enough for my router too.

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Limit switches.

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The Z axis stepper also arrived, however on unpacking it, I found there to be a problem...
One of the wires is completely severed, close to the point where it enters the motor, and two of the others are partially damaged. I have no doubt that I could repair it easily, but It's still a bit of a PITA, so I have emailed the seller in China to see whether they will replace it.

[rocket_troy]

Oh, I can sooooooo relate [sigh]. I purchased one of those $300 4th axis (advertised for engraving apparently) thingies under the completely naive impression it could be useful for small soft milling jobs. It also arrived with wires cut (no biggie), but worse, major dings in the frame and main belt sprocket. As it turned out, the belt was way way way too loose for anything more mechanically challenging than laser etching[grimace]! Yup, stuff from China can be hit & miss, but stay well clear of these things [period]

TP