K2 Review, KT-3925

[carlnpa]

You might try 393.70 step/mm to start.
When you get a chance would you measure the backlash in your Nook ballnut.
Your machines arrived in better condition than mine did.

[CNCadmin]

Originally Posted by tauscnc How do I make the photos thumbnailed? thanks taus

You can't yet, when linking from the photo gallery, you would have to upload them to the thread. I'm working on a fix.

[tauscnc]

Thanks Paul.

Carlnpa,

My KT-2525 had some banged up nicks, probably from FexEx but the box they sent my base was thin and not well packed. I wrote to them about that and asked that my machine be sent disassebled. I did not think UPS could handle such a large item without killing it And yes one of the boxes was bashed open but luckly it was where all of the padding was. The machine arrived very good.

I would suggest anyone getting these larger machines to get them disassembled. But there is also NO documentation with it so you have to go off the pics. It is not tough, everything fit well. CNCRobs seems to have come out ok.

I will check the backlash soon. I do notice there is more in it then the leadscrew I thought ballscrews where not spose to have much of any backlash.

I am surprised at how noisey they are also. They sound almost gritty..but I hear as long as the balls are moving and not sliding that is fine ??

Is there any grease that you use on them or do you just leave the screw dry?

thanks
taus

[tauscnc]

Are ballscrews very gritty?

I find if I turn the screw counter-clockwise it's pretty smooth. However when I change direction (clockwise) it is tough. It like they are getting stuck and I feel like I am going to break them. They loosen but get stuck again.

So far I don't see the luxary of ballscrews or are these Nook ones just cheap? They list thompson on the website but nook is what I have. The leadscrew on the Z axis is silk.

There has to be some grease they need...

UPDATE:
I called Nook and they said to use E-900 lub. The ballscrew is a standard roll screw and the info on the nut is here (SBN10325)http://nookindustries.com/ball/BallSRTInfo.cfm?id=15

taus

[ckirchen]

Tuaseef,

When I ordered my ballscrews and ballnuts from Rockford, they were extremely gritty. I dismantled the nuts and sprayed them with WD-40 over a white paper towel to see what was in there. Lot's of dirt, some grease, and even a few full chips came out.

I ordered another ballnut from Thompson a while later and it was dirty as well. Not as bad as the Rockford, but still in need of a good cleaning.

My advice: before you install a ballnut, take it apart and clean it thoroughly. They’re not hard to put back together (http://industrialhobbies.com/howto/p...ed_ballnut.htm). And, wipe down the entire length of the screw while you're at it.

Chris Kirchen

[HomeCNC]

I have used the rolled type ball screws on all my CNC equipment. About the ball screw, I have received some that looked clean on the outside and I have seen some that looked like they had some kind of flakes on the outside of the screw. Like it was burned in the heat treating process or something. I don't know enough about the process of case harding of these screws.

I took a wire brush to the screw to clean off the flakes. It is a good idea to dismantle the ball nut because it also is case hardened and could have the same flakes inside.

Also do lube the screw.

[Morgantech]

Originally Posted by tauscnc My biggest concern is making a new table for it, getting an enclosure made, mostly KEEPING this thing and the basement clean. Somehow I see chips of material ending up all over the house.

taus,
I purchased a custom built 25"x50" unit from K2CNC. Both kevin and Ron have been a great help!
I have attached a couple images that show how I put together my setup. The old steel tube drafting table works great. I used plastic laminated 3/4" aircraft ply w/T-nuts for a hold down table and my own clamps. The dust collection system, which I fabricatred, works great for cutting flat material such as crabon, ply and 1/8" alum. I use a 1 micron, 1600CFM dust collector attached to the bottom of the drafting table to keep the dust contained within the 1/4" plex cage.

Mike

[cbass]

Nice setup Mike.

I'm thinking of a similar setup using retaining walls at the edges of the cutting surface that just clear the gantry to limit swarfing on the x axis rails.

Man, just looking at what you guys have done/are doing to setup your machines is almost dicouraging. Even after I get my machine it will probably take a good month to get everything assembled/hooked up

swarf guard
way covers
sealed machine case
spindle mounting
table surface-including hold-down system for parts-
fresh air / exhaust air
machine stand

ahhhhhh... are we there yet?


Carlo

[carlnpa]

Taus I believe gritty on the ballnut is normal. DO NOT remove the ballnut from the screw, the ball bearings will all jump out, these cannot be reassembled by us. I just installed my preload ballnut from Nook, lost about 1.25 inch carriage travel on one side but no (0.000) backlash. Nook claims up to 8/1000 backlash is normal on this screw assembly, they offer a select fit option that costs $100 to get 2 or 3/1000 backlash. I paid 169.48 for the preload ballnut. The z is silky and quiet. I agree ballscrew has been overrated, unless getting the high accuracy ballscrew assembly, might as well get quality acme. I'll take some pictures of my machine on a stand made with welded legs from McmasterCarr and with the 1/2 inch mic 6 plate on it. My machine needed that plate to stiffen the frame and reduce distortion. The 1020 1x2 inch frame is light to support the gantry load so it sags when the gantry is in the center, like 2x/1000. Still, I like the machine. cbass, you are right about the set up time.

[CNCRob]

Today I put together the work bench for my cnc. I also started the assembly of the cnc. Right now im not very impressed with the machine. All I have done is attach the gantry post to the frame. On one side, one of the four bolts is stripped I couldn't even get it to start. Also each side had a package of screws. One side had a package with 8 the same size, and the other side had a package with 3 of one size 4 of another size and 1 a totally different size altogether. None of which are the same size of the package with the other 8 in it. tauscnc was yours like this? if so how do you know where each one goes? Thats about it for this update, im hoping tomorrow will go a little better.

[tauscnc]

Hey guys,

First my ballscrew experience.

Again this is my first experience at ballscrews and as carlnpa pointed out I think they are really over rated (unless maybe you get the "$1 million" kind).

Well unfortunetly I did take it apart and tried to follow the directions on that website. To my surprise there really is not much to the ballscrew. I cleaned the inside out and got a lot of "dirt" out. I then went to put it back and the first go was ok but the balls kept falling out of the back. I then undid it again and as I put 2 balls in they got trapped and the assembly stuck O man!!! I tried everything but the balls got stuck on the ridge and there was nothing to do. I finally resorted to crank on the end and the ballnut with pliers and drove it off. In the process one of the balls let loose and pinged aross the room never to be seen again. To my surprise I did not crack the ballscrew or bend the end. The screw looked fine. I HAD TO CRANK IT OFF! Now where to get a ball? I found a ball bearing and cut it in half to find the ball is the same size (3.15mm). I used it and after about 4-5 tries I finally figured out how to assemble it back together. I was able to put in about 3 extra balls (if I recall correctly) but at the end 4 fell out and I just left it. It might be + or - 1 ball. It does run smoother but I am not sure if that is because of the vasline I used.

CONCLUSION: DO NOT TAKE THE BALL NUT OFF UNLESS YOU KNOW WHAT YOUR DOING AND HAVE HOURS TO SPEND PUTTING IT BACK TOGETHER! . I simply just applied vasline to the X axis and called it a day. I am not going to take that off.

CNCRob,

Man I am so sorry to hear about the machine and screws. First thing I would do is shoot off an email to Rob at K2 and tell him the issue.

Tell me what part and where (K2 YOU REALLY NEED TO GET A PART LIST OUT ASAP!!!!!) and I will let you know what size screw I used. Mine was fine but I was on them daily to make sure they checked because I was not going to get another "KT-2525" workmanship machine. So far, other then the ballscrews, its really nice.

I was really excited to get a machine with ballscrews but don't see the hipe yet. Again, I am sure a lot has to do with the fact that they are the lower class ones.

I will post more pics tonight.
tauseef

[tauscnc]

O yeah, on the units.

They say 2000 steps for 1 in. So wouldn't I just divide 2000/2.54" to get the steps for mm? That would come out to be 787.40157 steps?

thanks
tauseef