Sieg SX2.7 CNC conversion

**Edward** · 03-01-2017

Hi guys, my first post after following this forum for months. I hope you've all recovered from the festivities:)

I am converting a Sieg SX2.7. So far I have converted the X and Y axes with bog standard chinese ballscrews, and Nema23 2.2Nm direct drive (i.e. no pulleys) , driven by Leadshine EM806, 68V psu.etc. So far so good.

For the controller I am using Kflop with KMotionCNC. I've tried a couple of the little cheapo chinese stand-alone boxes that were discussed in another thread. Although they moved the machine OK, the movement (particularly around arcs) just sounded a bit clunky compared to the silky smoothness of the KMotion. For many other reasons (particularly stability) I settled for KMotion, also tried the KFlop with the Mach3 plug in, which worked just as good, but to be honest, I kind of prefer the simplicity of the KMotionCNC.

Anyway, now I am at the stage of doing the Z axis. I've taken the old leadscrew out, luckily the existing ballnut support can be reused, no need to machine a new one as the standard ballnut with the six bolts fits perfectly in the hole (though only using 4 of the bolts).

BTW, the X axis was more difficult to fit, as typically there is very little room under the table for the ballnut, a little grinding of the saddle was necessary, which I did partly with a manual mill and then the Dremel to get a nice final finish, so it wasn't too dramatic. The un-ground rough part of the saddle casting wasn't level, so some material had to be removed for the length of the ballscrew to have clearance.

I am thinking of using a slightly more powerful motor for the Z, Nema23 3.1Nm. and my question is....do you think I can get away with coupling it direct (I use Oldham couplers) , with no pulley 2:1 reduction? My initial thoughts are to try it direct to start with, and if I notice that the motor struggles or looses steps when cutting, then it doesn't take too much effort to machine a new plate to house the pulley reduction and put the motor to one side. Direct coupling looks a bit more elegant and it's easier to fit, but it's no good if it doesn't work.

Since what I think I've learned from this forum is not to use motors bigger than necessary, I wonder if, from your experience, you think that direct coupling for the Z will work in this case.

The only other observation is that I have both the EM806 and the AM882 drives and with identical settings, the EM806 whistles a little on standstill whereas the AM882 is completely silent. Both are very quiet and very good when moving, with a very subdued mellow Symphony that is delightful to the ear:)

Edward

**Clive S** · 03-01-2017

Edward Welcome to the forum its always nice to hear that some do actually read and do their research as it seems you have

You have stated ( with no pulley 2:1 reduction) is this not a contradiction? I personally prefer using belts with a reduction as it is better for resonance and you get twice the torque.

You have done well in your choices of drives they are both very good and the correct Voltage PSU

**Edward** · 04-01-2017

Hi Clive, thank you for your welcome.

Let me rephrase this. I meant without using pulley reduction, i.e. no pulleys, just direct drive.

I have no problems with using pulleys either, I use them a lot for my motion control projects. And for the Z, being more distant from the swarf, it makes even more sense, plus the extra torque from the reduction, etc. Still, since I am cutting the fixing plate tomorrow, I am in two minds...

Edward

**m_c** · 04-01-2017

Nice to see another KFlop user on here!

I'd personally go for a belt reduction, but if trying direct mount is relatively easy, it's worth trying. Whether it will work, will most likely depend on what you try doing with it.
The worst thing I would expect to highlight any lack of torque, would be during drilling, especially when you try retracting the drill, when you're fighting against the weight of the head and the drill still trying to dig in.

Regarding the EM drive being noisy, have you ran the autotune function?

**Edward** · 04-01-2017

Hi m_c, the Kflop is great isn't it:)
I may ask you about limit switches with the Kflop, as no doubt you have done it. I would like to use IO0 to IO4 on the JP7 connector, but I've never done this. I will reserve the question for later on, one thing at a time:)

Regarding the EM drive, it's not particularly noisy, just the usual little buzz that some drives emit on standstill, which can get annoying over time. Yes, I tried the dip switch4 down and up. I did the same with the AM882 which I have on the other axis, identical setting and motor, but this one doesn't make any noise. I seem to remember I have the little yellow selector wheel with the arrow on 4 which selects a particular Leadshine motor and applies relevant parameters. I may try and set the wheel to something else and see what happens.

Edward

**Edward** · 04-01-2017

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** · 05-01-2017

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

**Edward** · 05-01-2017

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** · 10-01-2017

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