Compare Z axis for new machine

I have been looking around at different z axis and would like to get some input on the differences, capabilites of the selected options. I am open to other suggestion. My goal is to cut aluminum, and I am hoping to be able to cut 2mm per pass. At the moment I am doing about 12 inch/min and would also like to speed that up as well. My goal is the have a nice stiff machine that will be up to that job. I figured I would start with the z axis and work my way backward to find the machine I want.

THK Actuator KR33B Ground ballscrew LM Guide PITCH10MM STROKE240MM NSK CNC Route | eBay

6" Z Axis Linear Motion Table for CNC Router with Ballscrew | eBay

Ballscrew Z Axis | CNCRouterParts

So between the three that I have found.

The first one is a THK and I hear a lot of good things about how good they are. Any thoughts?

The second one looks bigger and I was wondering if this would make things stiffer for the material that I am wanting to cut

The third is the same but 2 - 3x more $$$. Is there a difference that I am not seeing that makes this one so much more. Will it be stiffer, and more suited to the task?

I look farward to any comments or suggestion.

Thanks

I've been real happy with a Parker-Daedal 404 series actuator for my small DIY router. Here's a link for a 404 actuator on ebay: Parker Daedal 404XR 150 mm Stage | eBay

Here's a link for my small router: http://www.cnczone.com/forums/diy-cn...ml#post1050994

To answer your specific questions though, The THK actuator looks a little small to me. The 6" Z axis linear motion table uses unsupported rods and even though it has a short travel, unsupported rods can flex more than you might want. I've been personally drooling over the CNCRouterParts Ballscrew Z axis for some time and may incorporate that into an old ShopBot PRT router that I hope to refurbish soon.

I wouldn't go near that first one, the ballscrew is 10 mm per rev, not to be confused with a 10 tpi screw, I.E. turns per inch. So it's 2.54 TPI, thats a fast lead. It is also very narrow, too narrow in my opinion. the horizontal load on the z bearings would not produce good results for your application Id think. It's designed for a high speed light weight application.

I think the second unit would be fine for wood but those unsupported rails wouldn't be my pick for aluminium.

Have a look at this one

Z Axis Module for Professional CNC Router 21cm Approx 8 4" Travel DIY | eBay

So I agree with the first one looks narrow and I didn't notice the pitch of the screw. I will also agree that the second one may not be up to the job for the aluminum. So I am now looking for something between the other one from cncrouterparts and the two suggested.

I like the look of the one suggested by DonFrambach

Parker Daedal 404XR 150 mm Stage | eBay

Why are you wanting to get the cncrouterparts one if you have this one already. I understand that it would be for a different machine but the one you suggested is a lot cheaper. Would you concider it an upgrade? If so should I just go with the cncrouterparts one.

Thanks for the link from RonaldoNZ,

Z Axis Module for Professional CNC Router 21cm Approx 8 4" Travel DIY | eBay

it looks very nice and strong. It may be a little more then I was looking at spending. Shipping was over $300. Athough i'm not opposed to spending the money if something like that would be the best value to the task that I want to do. The mount on it is for the nema 34 motor as I have the nema 23 motors. So if I went with that I would have to upgrade the motor as well. Is there another suggestion that could keep the motors that I have, and a little better on the price.

So I think I am getting closer to finding something that would work but not there yet. I am now between the cncrouterparts and the Parker Daedal options(Links below)

Ballscrew Z Axis | CNCRouterParts
Parker Daedal 404XR 150 mm Stage | eBay

Any other suggestions or input?

Thanks

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I wouldn't go near that first one, the ballscrew is 10 mm per rev, not to be confused with a 10 tpi screw, I.E. turns per inch. So it's 2.54 TPI, thats a fast lead.

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Imo, that's an ideal lead for a router Z axis.

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Originally Posted by cncmadness

Why are you wanting to get the cncrouterparts one if you have this one already. I understand that it would be for a different machine but the one you suggested is a lot cheaper. Would you concider it an upgrade? If so should I just go with the cncrouterparts one.

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The Parker Daedal is great for my small router. It looks to me like the CNCRouterParts Z axis is more robust and better suited for a larger machine like my old ShopBot.

Don

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Originally Posted by ger21

Imo, that's an ideal lead for a router Z axis.

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Interesting, is that what you are running on your machine?
Id have thought that lead would ..lead (cough) to a lot of backdriving of the motor and would require some counterweight setup, I'm making various assumptions about the scale of machine the op is planning however. But I can see the advantage of the speed given a drive system strong enough to pull it.

On another note, you run a machine with rails mounted on the z carriage yes? Could you point me to a picture of your setup if so? I'm very interested in having a look at how you have spaced the distances of your collet end, z rail ends, spindle mount and gantry bottom.

I designed my current machine 10 years ago, when just about all homebuilt machines were very slow performing. This used 1/2-10 acme, which is just way too slow.

My new machine is slowly taking shape, and will be using 1/2-8 4 start acme. THis is the same lead as 1/2-10 5 start, which many have used successfully on their Z axis over the last 5 years or so.

Yes, you definitely need more power than a lower lead screw would. But you should design your machine for specific goals, and supply adequate power to meet those goals. If you don't want to buy a bigger motor, than yes, you'll be stuck using a lower lead screw and subsequent slower speeds. You do also have to worry about the spindle falling when power is off. This can be handled in several ways. Spindle break, springs, pneumatic cylinders,...


On both my machine the rails are mounted to the Y carriage, with the bearings moving with the spindle. The new machine has two spindles operating independently. Here's my build thread, but note that the Z axis is different near the end than it is at the start, as I changed spindles. The first post has a link to a long design thread that I worked on for a few years before I started building. http://www.cnczone.com/forums/cnc-wo.../138890-z.html

Because of the two spindles, my goal was to make the two Z axis as compact as possible, to get the largest usable work area and smallest footprint, and still have it be accessible by both spindles.