Mini Mill X/Y Tram and Gas Springs

[jtrout13]

Hi all, this is my take on adding a column brace and X/Y tram adjustment into the mini mill, as well as converting it to gas springs for head support.

Here you can see the back of the mill with the standard recipe column brace and Y tram, except I used oval point set screws for the adjusters with locknuts on each.

Here you can see the X tram adjustment brackets I made similar to those of another user, still using locknuts and oval point set screws.

I also converted to a head support with 2x 15lb force gas springs with 7" of travel, which I got from McMaster-Carr. Swivel rod ends and mounting balls round out the package, and I used pre-formed brackets on the head itself, as shown in the next few pictures.

 

[velocette]

Hi
Congratulations this is a great (Modification - Addition) to an X2 Mill.

Excellent pictures you now have a mill that will run sweet and true.

This is right on top with the very best of X 2 Mods.

Thanks Eric

 

[gmac]

What specification are the gas struts that you used? I'd like to mod my mill in this way.

Cheers Garry

 

[jtrout13]

What specification are the gas struts that you used? I'd like to mod my mill in this way.

Cheers Garry

Garry, I see you're located in Canada (go Leafs!) I used 2x McMaster-Carr #9416K371 struts which have extended length of 18.62", stroke of 8.27", and a force rating of 15lb. If you want more info, PM me and I can give you a materials list with part numbers. You can compare the parts from McMaster and find similar ones from MSC Canada or whatnot, because McMaster does not ship outside the US.

 

[gmac]

"Go Leafs" my God man I'm a Habs fan !!!!! Thanks for the info, I'll work from that and if I get jammed I'll PM you for the details. Your mill is almost the same color as mine - I painted over the awful BusyBee green and yellow!

Cheers and thanks again.
Garry

 

[B-RAD]

I need to get the gas strut on my SX2 build yet, thanks for reminding me!

 

[jtrout13]

I need to get the gas strut on my SX2 build yet, thanks for reminding me!

I forgot what user it was, but it was you. I used your dimensions for the column brace, you saved me a lot of measurement time. Thanks!

 

[B-RAD]

No problem, I'm very happy with the brace, I hope you are!

 

[peter cook]

Nice work.

 

[dennisa49]

Hello, as Peter said, nice work.
I am curious about the cylinder attachment points and the plates that are used as mounts. Could you tell me how they are fixed to the milling head please?
I have always felt that the single cylinder would be an asymmetric force. Your mod with two cylinders over comes this.
There are no off the shelf kits available in Australia, maybe the Canadian supplier may ship to us.
Many thanks, Dennis

 

[AndrewMcW]

Hey Dennis - You should be able to get some suitable gas struts in Australia from eBay, or StrutsAustralia.com.au or GasStrutAustralia.com.au
I bought a pair recently from eBay (seller: "aussie_living") for my Sieg SX2P.
The McMaster-Carr strut model mentioned above provides 15lbf each, 30lbf total. I tried to measure the "weight" of the head (on a bathroom scale) and got about 12kg, so you need ~120N total. The struts I bought were 150N, but hopefully ok...

Good luck!
Cheers - Andrew (in Sydney)

 

[dennisa49]

Thanks Andrew, I am ok with the struts. The brackets that support the head interested me. I had in mind to bolt the bracket to the left side of the head, looking at the machine. The idea of a cylinder on both sides is great, no unequal load.
I reckon the load is about 20 kilos, travel of 250mm. Did you use a cylinder on both sides? Often overthinking on my part perhaps.
Thanks kindly for the help
Regards, Dennis

 

[AndrewMcW]

Hi Dennis,
I haven't actually fitted mine yet. The design I'm going to use is based on this:

http://www.rysium.com/projects/189-mini-mill-modifications

This design also uses 30lbf struts.

How did you arrive at the 20kg?

 

[dennisa49]

Good day Andrew, it looks like a very elegant solution.
The weight of an SX2P is around 72kgs.
I believe the head to be about 25 - 30% of the total.

The well known hardware chain sells gas cylinder operated struts. They have a couple that fit the bill nicely.

I will proceed with care I reckon, easy to implement, getting the best result
may be the trick.
Good luck with your mod.
Kind regards,
Dennis

 

[moditwell]

Hello to jtrout 13. I see a very nice mod using gas strut. I was concerned about the support point on the upper bracket of the gas strut. Let's assume that the CG of the head is some where near to the symmetry line of the motor then your design would have a turning moment about the CG.When the head moves up it would rotate clockwise and rotate the other way moving downwards. The effect is not apparent due to the dovetail and gibs in place. I just weigh the head and it's 12kg, the motor is 2kg. The small control box and R8 spindle weigh 1kg. So anyone doing this mod should get a 150N gas strut. There's no perfect position to mount the gas strut if you need a perfectly upward force against gravity.The nearest one can get is using the existing M10 original SIEG screw hole but then the gas strut cannot be mounted straight up.

 

[peter2uat]

I can report that a one-sided gas strut with 150N -15kg(30lbs) and a stroke of 205mm(8") is enough AND allows to mount a DRO on the right side which is more important than the small tilting force - which by the way is eliminated as soon as you clamp the head for milling...
This gas strut is a replacement item for a BMW 3 E30 Cabriolet 09/87-02/93, but similar ones with 18mm diameter and LOA 495mm are available.

 

[John Antliff]

I've recently started (as a response to our Level 4 lock down in March) a project to "CNC" my Warco mill and the question of counterbalancing the knee/table to reduce the load required on the Z axis screw was considered. I decided to fit 2 gas struts from Ali-express 500N each with a stroke of 190 mm which just about covers the useable extents of the Z axis. I calculated that the load (with my large dividing head) was around 130kg so I went for about a minimum 30kg positive downward bias. The following results were obtained when I measured the pull required on the Z handle at 3 different heights. At the highest position it required 9 foot lbs to raise the table and 4 foot lbs to lower it. At the mid position 7 foot lbs to raise and 5 foot lbs to lower. At the lowest position 6 foot lbs for both directions. I'm assuming that these gas struts will leak over time and thus their assistance will diminish. I could not ascertain, prior to purchasing them, at what position the rated assistance would ocurr so I assumed that it would ocurr at maximum compression. As you can see the brackets required are taylor made. On the right hand side it got very cluttered and difficult to install such that it missed both the Y axis DRO scale and the power control box and my home made self-act assembly. My conversion was designed such that the manual use was unaffected as I considered that most of my work will not be via CNC - time will tell! I have decided to use a stand alone frequency generator to drive, whichever axis, I wish via the appropriate stepper motor thus avoiding having to load up Mach3 every time I want to do a simple job. I had considered using cables and pulleys instead of gas struts but that would have been close to impossible and very cumbersome. My friend has used this idea on his bench mill for counter balancing the moving head as his mill is not a knee type and as long as he has some positive force downwards it performs pretty well.

Hope this helps.