Sieg SX2.7 CNC conversion

[Edward]

Hi,


Today I fitted the Z axis ballscrew. I had to drill the top of the column, a hole of about 18mm. it wasn’t fun as my drill bits only go up to 12mm, and it takes forever to enlarge the hole with a Dremel. Then I remembered I had these cone shaped drills that drill in ever larger steps. Thereafter it was a piece of cake.


I haven’t machined the top plate yet, but by connecting the FK12 at the top plus a handy little lever I made to crank the ballscrew in both directions, I could get a rough idea of the effort needed by the motor.

Basically, to move the head down requires zero effort. In fact, if you are not careful it may start to roll down by itself. A question of adjusting the gib a little, I think, just to hold the head still.

Cranking it up requires more effort, for instance, more than moving the X or Y axes, but not drastically more. I think the 3.1 Nm motor will move it well with direct drive. We shall soon see….otherwise maybe a 4Nm motor...

In the future, I may attach a gas spring, if anything just to ease the effort on the motor and to hold the head stationary when the motors are disconnected.

I think for the moment, I may have to use the gib tightening lever when I am not using the mill, just in case the head decides to roll down and smash something pretty badly. I hope I remember to loosen the lever when in use!

Tomorrow, machining the thick plates to fit the bearings and motor, with the manual mill, painful, or as the French say...quelle horreur!

Edward

[John S]

Use a 2:1 reduction and you won't need a gas strut

[Edward]

Well, in view of your opinions, I am going to cut to the chase and go for 2:1 pulley reduction for the Z axis, as I already have 40th and 20th AT5 pulleys in my stock anyway. Just ordered the right length of belt. Also, by having belt reduction, I will be able to tighten the gib a little more, making the head firmer and at the same time avoiding the rolling down by itself. On the upwards move, the double torque gained by the reduction will help too.

I will be using the Lenze type locks for the pulleys, as I prefer them to ordinary set screws. I'll have to put the motor to one side rather than to the back of the column like John shows, only because the column cover gets in the way, and also because of the depth of my table. Eventually I will also print a neat cover to protect the belt/pulleys.

Edward

[Edward]

Just finished the Z axis as recommended, with a 2:1 reduction. It works well and not a hint of any struggle with a 3.1Nm Nema23 So I am glad I went for the pulleys.

I minimised the AT5 belt run so the motor was as close as possible to the column, to one side.

Now I am fitting a swarf guard at the front of the Y, as this particular model doesn't have any bellows there to protect the ways from dirt. So I am just fitting a U-shaped metal cover plate, 190x190mm attached to the saddle so it moves in and out with it.

I will now move to other sections of the forums to hopefully get advice or contribute. Thanks.

Edward

[Clive S]

Edward How about keeping the build log here so that all questions related to it will be in one place as that helps others doing a similar conversion?

[DamnYank]

Greetings from the far side of the pond. I encountered this thread via Google search, while looking for any kind of discussion related to the SX2.7. It seems to have not quite caught on as strongly as either the smaller mills, nor the larger X3. Thank you for posting your experiences with it here. I'll be following with interest.

What kind of modifications did you have to make to your ballscrews and/or the mill itself to get it adapted? Or, did you miraculously find some stock part that fit like a glass slipper?

Thanks again for sharing info!

[Edward]

Hi there!

Well the SX2.7 fits nicely in between the two. Far better than the SX2 in every sense, but not as good, in some respects, as the SX3. I could've easily bought the SX3, but I wanted something slightly smaller and with a better Y cross travel (180mm) The SX3 has less, at 145mm.

As far as modifications, for the Z axis, the standard ballnut will fit exactly using the original housing, so no modifications needed. For the Y axis I made my own ballnut housing, from a block of aluminium, easy to do. Otherwise all is fine.

The X axis is the one where you have to work a little. I had to mill one side of the ballnut flange, take a chunk off of about 6mm and then I had to grind the saddle at the very end to make room for part of the ballnut. I also had to grind a small groove across the saddle, not deep at all, just enough to gain clearance, as the ballscrew needs to be fitted slightly lower than the original leadscrew (because of the thickness of the ballnut). I didn't have to touch the table at all.

The rest is the usual end plates for which I used 20mm aluminium.

The only misgivings I had about it is the fact that you can't rotate the head, but as it turns out, after lots of measuring, (I did it following Hossmachine video on YouTube) it is running parallel anyway, thankfully.

It is a lovely machine, I also have the SX2, which was my first machine, in my opinion, for a CNC conversion, no comparison, I mean the SX2.7 without a doubt:)



It's not unusual to modify things a little. I did it all with a Dremel and a bit of patience, not too difficult really.

Edward