x1 Head Counterweight

[socalcnc]

Counterweight or Air Spring. Whats the best way to help on the z axis on the x1 micro mill. I have it all cncd now and oviously need something to help the z axis due to weight of the head. Parts list or pictures would be a great help to a CNC newbie. Thanks
Ray
Lakewood, CA

[philbur]

What size stepper motor are you using. Have you reworked the way/gib. Have you considered a bigger stepper. It should not be necessary to use either a counterweight or air spring if you don't want to. They always seem like a bit of a work around to me, rather than fixing the root cause.

regards
Phil

Originally Posted by socalcnc Counterweight or Air Spring. Whats the best way to help on the z axis on the x1 micro mill. I have it all cncd now and oviously need something to help the z axis due to weight of the head. Parts list or pictures would be a great help to a CNC newbie. Thanks Ray Lakewood, CA

[socalcnc]

I have the 269 oz stepper motors from Xylotex. Yes I have it adjusted the best it can be. Works ok down low but motor starts chuggin when raising. Dont mind using an air spring or counterweight to take the tension off the head if I need to, just dont know how people have done it or what parts I need. Like I said im knew to this.

[digits]

Originally Posted by socalcnc I have the 269 oz stepper motors from Xylotex. Yes I have it adjusted the best it can be. Works ok down low but motor starts chuggin when raising. Dont mind using an air spring or counterweight to take the tension off the head if I need to, just dont know how people have done it or what parts I need. Like I said im knew to this.

I didn't find any need to counter balance mine, but it does run slower than the X & Y - 600mm/min rapids vs 1100 for X&Y.

Have a look at http://www.embeddedtronics.com/micromill.html for a counter balance.

I would be interested to see what you do implement - I'm considering a spindle motor upgrade, and am half tempted to fit a gas-spring when I do.

Cheers.

[MIKE JEFFERS]

i fitted a counter weight to my x1 because it was quick and dirty with the
intention of fitting a bigger motor or such later on but it works fine so i just
left it
a bit of steel bar 100mmdiax 150mm long drill&tap m6 hole in one end
2 bits of ali bar bolted together in a L shape bolted to top of coloum (z-axis)
rh side.
with the bottom of the L pointing to the back
2 rollers/skate wheels or similar can be modded to suit
length of bike brake cable
attach one end to the middle front screw of the gearbox/motor control cover
with a small bracket,attach other end to weight (again with some form of bracket run cable over pullies and thats it
hope this helps
mike

[SPEEDRE]

Speed re here. This is an issue I've grappled with also. Building the brackets is no problem but how much weight to use is. Is it just trial and error or is there a common weight in lbs? I'm no mathwizz so just suggest a weight in lbs. Any ides as to it's shape?

[biomed_eng]

Go for the spring. I always prefer the solutions with less components or moving parts.

[MIKE JEFFERS]

the spring is more involved you have to get the right length/force then you may restrict the travel at extremes
a counter weight is less fuss (and costs less or nowt)
as for weight it should be the same weight as the head 22lb if i remember
correctly, but as you are just trying to help things along less will do
think my weight is about 10lb and its just a cylinder 4"dia x 6" approx

[biomed_eng]

How about these constant force springs? like these:

https://sdp-si.com/eStore/Direct.asp?GroupID=65

They are compact and are about half the height compared with an air spring of the same stroke.

There are minimal if no calculations necessary with this type of spring since you just buy the spring that has the desired load (weight) rating. They have a variety of load ratings from .23 pounds to 41 pounds. You can add springs together if you want a higher load rating.

[pastera]

The constant force springs would be great except the limited lifetime and cost. You need to get a high fatigue life spring for it to last and they are ~$20 with a max tension of 11lbs. You would need at least two springs, a shaft and bearings to make it work.

I was looking at using an air spring rated at twice the load with pulleys to increase the stroke. T

Aaron

[MIKE JEFFERS]

seems a bit more complex than some wire and a weight (imho)
mike

[biomed_eng]

Good point, I didn't think about the need for bearings. Constant force spring would be good for where there is limited vertical space. As the space required is about the same as the stroke.

A gas spring is great for simplicity however the vertical space required is greater that 2 x the stroke. Force is not constant over the stroke length. If space doesn't matter, the air spring is a great way to go.

A weight counterbalance is great too, since in this application, the head only moves vertically, thus the additional mass doesn't negatively affect performance as when added to a gantry mounted head.