Hi.
I built an cnc machine based on OX-cnc. Mine is 1500 x 1500 mm. I have bad result and I think it is because I use cog belt.
Did you also had problem with the results since I see you changed from cog belt to Ball screw?

 

Yes, I'mean the gt3. I use one belt for each side since I use two Nema 23-motors, one on each side. I had bad result. For example, cutting 120 mm results in 120,4mm. Cutting 1000 mm, the results are 1000,4mm. My fault is 0,4mm. I thinking about changing to ball screw since I Think the gt3 belt is shagging too much when machine is cutting. What do you Think?

 

Hi Julius
I have 1605 Ball screws - I have not yet mounted to my 1500 x 1000mm OX (running 269 oz in motors on GT belt 24V drive).

what I have read suggests that somewhere around 800-1500 RPM is the upper limit for a 16mm ballscrew (to prevent whip at 1500mm length)?

1) Are you still running at 3500mm/min Max (Or did this get better after fixing issues ect)?
2) when you said 5K was your math limit - was this based on steps per second that the driver board was capable of or force required to move the gantry and cut material?

If you are running at 3500mm/min / 5mm screw pitch = 700mm/min top gantry speed. I think that this also means you are turning the screw at 700 RPM? I curious to know if max screw speed was the issue here or motor torque? I Imagine you know - belt and pully to overdrive to ballscrew could get you a higher screw RPM - as long as motor torque or screw whip was not limiting factor.

Joe - with the 1610's what speed are your achieving and what lengths and motor torque do you have? has ballscrew critical speed = screw whip been something you have experienced?

 

Interesting the link you provided tells me - At 2Amps drive current, 6 mH, 24V, 200 steps per rotation (1.8 degree motors) = 5 Rev/Sec (Max speed for circuit). If this is true then (5 Rev/Sec * 60 sec) 300 RPM at the leadscrew is the top speed for my set up with current setup parameters.

300RPM * 5mm (lead screw pitch) = is 1500mm/min at the gantry.

Good to have as a data point since anything faster requires a parameter change. It is also well lower than the critical speed for ballscrew.

 

I checked out you ballscrew suppliers ebay store, must say he has some pretty fantastic prices for ball screws and linear rails. One question for you, what softwware did you use to map the Xbox controller to keystrokes?

 

Thanks

 

I am using the TinyG board presently so 24V is my power supply upper end at the moment.

The stepper motors were part of a Kit - motor inductance was not on my watchlist at the time of purchase

It sounds like your experience is that none of these factors has yet proven to be a problem with direct drive and 1605 ballscrews (Are you using the Dewalt 611?) - that's good to hear. What spindle speed do you typically use?

Take away #2 for anyone considering - 1610 ballscrews seem the better choice (10mm pitch vs 5mm).

 

Very nice build ! Thank you for sharing...
By the way did you published the updated plates ? I would really like to make a same build.

 

hello

great work i like it

im building like this , can you help me i want to see your cad file for this machine
[email protected]

 

Hey I am curious why you say this isnt rigid enough for aluminum. I am wanting to build a CNC that can do aluminum. I was actually working on a design similar to yours, but maybe a little beefier. Could you tell me if you think it would do aluminum?

Ignore the gantries and the motor plates. I just used the openbuilds step assemblies for their actuator bundles as a mock up. I would design custom motor plates that held the motors as well as fastened the C beams to the lateral 4040's in the front and rear. I would also replace the generic gantries in the picture with an ox style gantry, similar to what you used, but with the ball screw nut mounts on the inside of the c beam.

Any input is appreciated.

 

Hi, i was building something like yours last year and bought all of my parts too.

I got busy and just continuing the build, its a 1500x1500mm using c beams and 20x60s.

I bought oversized ballscrews for it 2505 for my nema23 motors ,worried obaut whipping at that time but now before cutting out my alu plates, I've read that my nema 23 wouldnt be enough power to turn my 25mm ballscrews fast enough.

Should i get me the 1605s?

What do you guys think?

 

I actually have the ballscrew above the cbeam and using hiwin 20mm rails.

I havent ordered the 16mm screws yet ($250 for the set of 3).

I was concerned about the weight of the 25mm screws to be too heavy for the nema23 steppers and i wont get enough speed.

If i go ahead with the 25mm and comes out too heavy then ill have to remachine my mounts.

 

Here's some screenshots of my design.

See all photos here: "Prime Photos

 

I think ill just incorporate additional holes for the 1605 set.

I juat looked up the hole dimensions for 1605 and i can just add it to my plates and if 2505 doesnt work out then ill just order 1605 and swap it out.

Hopefully 2505 works though since i have it on hand already.

I cant find anyone who has implemented it yet.

 

My dillema is that I alredy have bought and have on hand the 2505 and nema 23 motors. So it looks like ill just go ahead and build it and hope it works, hopefully my motors would be able to handle the 400ipm that julius mentioned.

I wish i didnt get too excited last year and just pulled the trigger on buying these stuff before doing any research.

 

Julius,

What motors and drivers are you using for your latest machine?