Sieg SX2 Plus build

[russell]

My new mill arrived last week. TNT did a good job of getting it from Leicester to Montpellier (South of France) in 40 hours but it then took them 6 days to get it the last hundred miles. However, it arrived in good condition.

Mill as received. I then stripped it down, washed everything in paraffin, and checked everything. The base was pretty good really but I blued up the surface plate and scraped it in:

The Y slide fitted pretty well despite the visually rough machined surface so I just smoothed it off a little with a diamond lap leaving just enough texture (I hope) to hold some oil.
The only fault I've found so far is the gib strips:

The photo shows a close up of one end of the X strip. The dimples are only partly formed and are such that any movement will give a wedging action and stiffen things up. I will deepen the dimples and put points on the adjusting screws (as recommended by Arc Euro) and see how they go. If they are still unsatisfactory I will then fit a dowel to prevent side to side movement.

The base is the same as the X1 rather than the X2 type. There is very little room to fit ball screws so I will make adjustable delrin nuts to fit the existing leadscrews - must try to find an M12 x 2 ACME tap.

I'm wondering what the best option is for the Z axis. There seem to be three options:
1. Lead screw at the side as with the CNC Fusion kit. Don't really like having the leadscrew so exposed.
2. Lead screw above the machine as in the Hoss conversion. However there is very little space between the motor and the column.
3. Lead screw behind column. This seems to be the neatest solution but I'm a little concerned that it may encourage the head to tend to tip and give jerky motion.
Any views on the best solution please.

All for now.

Russell.

[rnr107]

I'm wondering what the best option is for the Z axis. There seem to be three options:
1. Lead screw at the side as with the CNC Fusion kit. Don't really like having the leadscrew so exposed.
2. Lead screw above the machine as in the Hoss conversion. However there is very little space between the motor and the column.
3. Lead screw behind column. This seems to be the neatest solution but I'm a little concerned that it may encourage the head to tend to tip and give jerky motion.
Any views on the best solution please.

Russell.

Hi Russell,
There is one more option you haven't listed which is better:
Remove the rack (cremaillere in french) and place the lead-screw in the slot between the head and the column. ;)

Laurent

[russell]

Thanks for the suggestion Laurent, however the slot between the head and the column is just under 12 mm and even if the recess on the head is enlarged there isn't enough room for the leadscrew and nut. I'm leaning towards a modification of option 2 with the leadscrew (ballscrew) fixed to the top of the head between the motor and column and a rotating ballnut mounted high up so that it clears the motor in the up position of the head.

Russell.

[rnr107]

It should works, just not as elegant as that:
http://www.thompsonmachine.net/mm2kit.htm

;)

[russell]

Thanks for that link. I hadn't seen it. However that conversion is for an X2 mill. The SX2 Plus is somewhat different and has less room behind the motor.

Russell.

[craigrobbo]

Good job, i wanna watch this as i wanted to convert mine.

[russell]

O.K. It's two weeks since I started this so it is time for an update.

I've finished scraping in the X and Y slides and improving the gib strips. Both slides work nice and smoothly now without side to side movement.

I've fitted thrust bearings to the leadscrew supports and modified the ends of the leadscrews as shown:



As the leadscrew has an undercut next to the start of the thread I machined the tread away for 1 mm so that there is a good location for the thrust bearing. The thread on the end of the leadscrew was cut off and the remaining end reduced to 1/4 in to suit the flexible couplers. The end of the 8 mm part was threaded 5/16 x 32 for a nut to adjust the preload on the bearings. I'll fit a grub screw to lock the adjustment. Just waiting for an ACME tap to be delivered so I can make the acetal anti-backlash nuts. I had to reduce the width of the bosses on the mounts to 26 mm to get everything to fit.

I've also been drawing up a Z-axis arrangement and find that I can just fit the ballscrew behind the motor if I make a cut out in the plastic motor mount.

Russell.

[rnr107]

Nice machining....! How did you do that? Have you got an other mill? Lathe?

I've also been drawing up a Z-axis arrangement and find that I can just fit the ballscrew behind the motor if I make a cut out in the plastic motor mount.

Good! I knew it must be possible some how. This should looks good!

RNR

[russell]

Nice machining....! How did you do that? Have you got an other mill? Lathe?

That was done on a sixty year old Atlas lathe with a homemade collet adaptor to ensure concentricity.

Good! I knew it must be possible some how. This should looks good!

I've just had another idea for mounting the Z ballscrew. Thread the end of the ballscrew M10 and drill and tap the top of the head casting to take it with a grub screw at the rear to lock it in place. It should all fit without any other mods. The ballnut has to be fixed above the motor in it's highest position so the assembly will be quite tall.

Russell.

RNR[/QUOTE]

[russell]

Three weeks since my last update. I don't know where the time goes (well, yes I do - gardening, making new wheels for sliding patio doors, other projects).

Still, the M12 x 2 trapezoidal tap arrived from China last week so I was able to make a couple of anti-backlash acetal nuts for the leadscrews based loosely on the Brian Pitts design:

Y leadscrew anti backlash nut.

X leadscrew nut.
and finally (for now):

Base assembly (almost) complete. Just have to fit some mounting brackets for the home/limit switches.

I can now adjust it to give me 0.5 thou backlash on the Y axis without it getting unduly stiff. However, the X axis gets stiff when the backlash is reduced below 2 thou so I have some investigation to do there.

Now to start on the Z axis. I've done some layout drawings and find it is just possible to get a 16 mm ballscrew to fit behind the motor on top of the head so that's the way I'll go. The ballnut has to be mounted rather high up though.

So - back to the workshop.

Russell.