# Seig x2



## Blacksuit (Nov 25, 2021)

Just curious if anyone knows of another vendors besides little machine shop to purchase a air spring conversion kit for the seig x2 mini mill.

little machine shop is out of stock supposedly until January 2022. Thanks!


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## weaselfire (Dec 1, 2021)

Order now, pay with your Holiday Bonus. 

Jeff

Sent from my SM-G781U using Tapatalk


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## homebrewed (Dec 2, 2021)

You could take a DIY approach, like the mod shown here.  The downside is that the LMS kit includes a longer rack so you get a little more Z axis range.   I'm not aware of any third-party offerings for racks but that doesn't mean there isn't something out there.

Folks also have used a pulley and counterweight scheme, which has some advantages -- there is NO variation in the counterbalance force as the head goes up and down.  I really thought about this approach but, well, the LMS kit went on sale.....


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## homebrewed (Dec 3, 2021)

I wasn't correct in my previous post regarding the availability of a rack by itself.  A little more browsing through LMS' web site found two racks that might work -- P/N 1486 and 2232.  The former is pre-drilled with 4 mounting holes.  #2232 is blank.  According to the "Chris' Tips" tab, #1486 is "useful for extending the Z-axis range".  It lists for $19.95.

So if you can find an appropriate air spring elsewhere you should be able to DIY something very much like the LMS kit.  FYI, the air spring in their kit goes inside the column so it is a bit less obtrusive.  It also is more DRO-friendly, for the same reason.


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## B2 (Dec 3, 2021)

Hi Folks, 
I would like to add a pulling air spring (not a pushing style) to my bench CNC mill.  The head is too heavy and sometimes falls and I would like to provide an assisting lifting force.   I am thinking I would put a couple of pulleys at the top, a cable from the head over the top of the mill vertical and down the back to attach to an air spring.  However, I have not found a source for a long (~20") stroke pulling air spring.  Any suggestions for a source would be useful!?  I suppose I could put two in series to achieve a longer distance, but one would be a nicer design.   The head weights in at about 275-300# so perhaps two in parallel would be better balance and at around 130# each.
Thanks,
Dave L.


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## homebrewed (Dec 4, 2021)

B2 said:


> Hi Folks,
> I would like to add a pulling air spring (not a pushing style) to my bench CNC mill.  The head is too heavy and sometimes falls and I would like to provide an assisting lifting force.   I am thinking I would put a couple of pulleys at the top, a cable from the head over the top of the mill vertical and down the back to attach to an air spring.  However, I have not found a source for a long (~20") stroke pulling air spring.  Any suggestions for a source would be useful!?  I suppose I could put two in series to achieve a longer distance, but one would be a nicer design.   The head weights in at about 275-300# so perhaps two in parallel would be better balance and at around 130# each.
> Thanks,
> Dave L.


Your mill head's weight is about 10X that of a mini mill, so it's an entirely different beast.  How is the head normally supported?  Maybe there's something amiss there? Have you contacted the manufacturer regarding the problem?


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## B2 (Dec 7, 2021)

I think the weight is about right.  It is a PM940M-CNC.  The head is geared and full of oil too.   Anyway, I think I found out the problem with the Air Spring lack of sources.  It is called a "gas spring", not an "air spring".  Also when being used to pull rather than push it is called a "gas traction spring".   The head is suspended to the column via the ball nut and ball screw via a stepper motor.  The motor has sufficent torque to hold the head in position as along as the power is on.  But once the power goes off, it will fall slowly causing the stepper/screw to unwind.  Besides crashing the tool into the work/table the CNC controller looses track of position (no power) so that when restarted it thinks the z axis value is different from what it actually is.  One can tighten the gib up to prevent this falling, but then the backlash increases substantially.  


homebrewed said:


> Your mill head's weight is about 10X that of a mini mill, so it's an entirely different beast. How is the head normally supported? Maybe there's something amiss there? Have you contacted the manufacturer regarding the problem?


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## homebrewed (Dec 7, 2021)

I think the ball screw alters the mechanics so you probably don't need a gas traction spring that can exert ~300 lbs.  I'm basing my wild-ass guess on your comment about the head falling slowly (plus the substantial mechanical advantage of a screw) but I could be totally wrong!!  A temporary counterbalance scheme would help determine just what you need (and avoid buying stuff that won't work).  Overdoing it, so to speak, could be just as problematic as your current problem, right?

The range the gas spring would need also may be an issue, but I know little about gas traction springs.  If the main issue is the head dropping when the stepper is undriven, I'd be looking at some sort of power-off braking scheme, maybe a solenoid that releases the head when system power is turned back on.  Or perhaps something to add just enough rotational friction to keep the screw from turning on its own.  I wouldn't think that would increase backlash but wouldn't bet the farm on that untested idea.

It also occurs to me that someone, somewhere, has had the same problem with a PM940M-CNC and already come up with a solution.  If not, you can be famous for being the first to do it


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## silence dogood (Dec 8, 2021)

I converted a LMS 3960 minimill  from a spring system to a counterweight.  Used chains
	

		
			
		

		
	






	

		
			
		

		
	
 and sprockets.  Works very smoothly.


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## Crazy Cat (Dec 8, 2021)

I'm in the process of converting my Enco ZX-7045, which is basically the same thing as the PM 940 and the RF-45 clones. I havent done the Z collum ballscrew yet, but anticipating the same issue, I have decided to use a servo with a brake on it.  I have Allen Bradley 850 watt servos for the x and y and an old Omron RM 20 drive and a MT 750 watt motor with the standard 24 volt brake incorporated into it.

I am hoping to avoid having to do anything else,  so we will see....

I also have a converted Hi Torque from LMS, but I have never had any issue with the Z axis slipping. It is a Fusion CNC conversion, AKA Heavy Metal CNC.


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## Tim9 (Feb 20, 2022)

I rigged a fairly ugly set up to my Rung Fu RF45 clone using some angle iron attached to the mill head and regular air spring mounts to the base. I don’t have any great pictures right now. But it pretty basic.
  I apologize for the poor pics, but the air springs are the black tubes in the back. I just measured the size I needed and figured a size to lift/support 50 pounds. I figured 2 x 50 would then give me 100 pounds of lift. It definitely made a difference.


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