[Rob K]

I'm thinking of using a THK KR33 Linear Motion Actuator for my z-axis.

Does anyone have any thoughts or experience they can share?

Would a 10mm lead or 6mm lead be better? Will a KR33 handle a router or chinese spindle well?

Thanks

[awerby]

I'm thinking of using a THK KR33 Linear Motion Actuator for my z-axis.

Does anyone have any thoughts or experience they can share?

[But I have used similar actuators for Z axes in a couple of machines. They work fine, basically, but you'll probably need to add gas struts or a brake to keep the spindle from crashing down into the part when you turn off the power. If the structure is open and you're making dust, you might consider providing it with some bellows.]

Would a 10mm lead or 6mm lead be better? Will a KR33 handle a router or chinese spindle well?

[The 10mm lead will give you faster top speeds; the 6mm will have more mechanical advantage. The 10mm will be easier to back-drive, but this is a problem with all ball-screws, since their resistance to turning is so low. Are you using a stepper or servo motor on this?]

Thanks

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[Rob K]

Andrew,

Thanks for the feedback. I'm thinking about using steppers, but haven't finalized or purchased yet. I'm looking at a KR33 with 6mm lead, cover, and single long block. I was thinking I might want to add additional torsional support/resistance beyond the long block.

I checked out your site, and see you offer CAD/CAM software. I was leaning towards Rhino and MadCam. Would you concur, or recommend something else? I will largely be doing 2.5D and some unique parts in support of the science dept (Biology & Physics), STEM, and the GoKart club at my school.
I intend to add a 4th (rotational axis).

[A-abdel-glil]

i am actually start my Mill CNC machine of my final project... i want to ask about how to calculate holding torque for screw?
and the friction force during cutting?
also i want to ask how to calculate th stepper motor calculation of ampere, voltage, watt and torque?

and thanks

[golfietis]

I have used Kuroda linear module on my CNC. And now I can tell, that this is by far the best solution for Z axis - very small, compact and holds tremendous loadings... I used 110 mm stroke, 10 mm pitch screw.

http://cnc-lt.blogspot.com/2010/12/a...vo-z-asis.html

[awerby]

Andrew,

Thanks for the feedback. I'm thinking about using steppers, but haven't finalized or purchased yet. I'm looking at a KR33 with 6mm lead, cover, and single long block. I was thinking I might want to add additional torsional support/resistance beyond the long block.

[How would that work? These actuators are pretty solid; I doubt it would be necessary, but that depends on what you're attaching it to, I suppose. Usually, you'd be attaching the long block to your Y axis, and mounting the spindle on the back of the actuator.]

I checked out your site, and see you offer CAD/CAM software. I was leaning towards Rhino and MadCam. Would you concur, or recommend something else?

[You can't go wrong with Rhino, but I don't know much about MadCAM. You might make a general post in the CAM or Rhino forums to ask what users think of it.]

I will largely be doing 2.5D and some unique parts in support of the science dept (Biology & Physics), STEM, and the GoKart club at my school.
I intend to add a 4th (rotational axis).

[I'd suggest RhinoCAM for that; Mecsoft offers a great deal on a lab license for their Pro package if a school is purchasing it instead of an individual. It supports the 4th axis as well as offering a lot of advanced remachining functions, plus it plugs into the Rhino workspace.

Think about the 4th axis implementation before finalizing your machine design; these work better if they aren't an afterthought. For one thing, you'll double the diameter of the stock you can handle if you can position the center of the rotary axis and tailstock at the level of the table, instead of perching the whole assembly on top of the bed. Make sure the spacing on either side is sufficient for the largest piece of material you can turn (measuring diagonally between the corners of a square piece of stock)]

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[mpvmanh]

Hi Rob

I have Z axis in my shop,if you are interest in it please contact me.

Thanks
Manh
https://www.facebook.com/manhcncpart

[UA_Iron]

Those look like fairly beefy units^

The KR33 looks a little on the lighter side:
https://tech.thk.com/en/products/thk...ve.php?id=4102
But the only way to know if it will fit your application is to run some numbers and do some calculations...
The 10mm vs 6mm lead is really a question of speed vs accuracy - 6mm lead will in-affect absorb stepper motor inaccuracies better than the 10mm lead, but it will not allow you to operate as fast. Now this is assuming you have an open loop system (you will not have an external encoder from which you can do position maintenance, right?)

If you have one of these actuators on-hand you could probably easily "make" it work for your application IF it requires super high rigidity. You could mount it to a ground plate along with additional linear bearings and tie them all together with another plate.

Like I said though, it depends on your application.



I ended up designing my own Z-axis stage - it's going to take a lot of work aligning rails and the ball screw, but I think it fits my application the best.
3/4"x9"x17.323" 7050 aluminum baseplate to locate everything rather rigidly.
Misumi ground extrusions (GFSP8 - heavy duty 6061 type) for the rails to sit on - though some more post assembly grinding of the extrusion and plate may be necessary if I don't have sufficient parallelism between the two surfaces as measured with an indicator.
IKO LWLF30 rails (preloaded)
Kuroda C0 ballscrew 3mm lead
IMS/Schneider Mdrive34 stepper motor with internal encoder.