In 6/2003, I purchased an early prototype of a desktop K2 CNC machine. I used it a little early on for making a few very simple parts that I suppose I could have made other ways. I was initially surprised that the machine had a tendency to stall (at as little as 30 to 36-IPM), so I haven't used it since.
I FIRST WANT TO SAY THAT THIS IS NO INDICTMENT OF K2CNC. I AM A NEWBIE and for all intents and purposes, I think people should assume that I don't know what the heck I'm doing. FURTHER, this machine was a prototype, and I only paid $700 for it (no controller, but did include steppers).
So I've been reading and decided to drag it out again and investigate ways to fix/improve it.
It initially shipped with white plastic nuts on what I guess are Acme screws. The seller also included brass nuts separately.
In the last couple of days, I've replaced the X and Y-axis nuts with the brass ones. I found that I can now drive faster (no stalling at 36-IPM, can often get away with 48-IPM, and can even go for a little while at 72-IPM before stalling).
The Y-axis had quite a bit of grease on the screw and in the nut. It was kinda hard to turn on the screw. The X-axis had very little grease or lubricant, and the nut was easier to spin but noticeably kinda chattery (if that is a word). I guess both plastic nuts caused some chatter or vibration that the brass ones don't seem to exhibit.
I've learned that geometry is critical. After replacing the Y-axis nut I noticed that it stalled at very low speeds (10-IPM). I loosened up all the machine screws that I had to remove, jogged it around a little, then tightened them up. A HUGE improvement. I think I still have some work to do in that regard.
Perhaps shimming nut "brackets" would be helpful. Anyone ever have to shim?
The nuts don't seem to have any backlash feature to them, and I'm not sure that I'd be able to add anything like that as there isn't much clearance.
The machine uses 1/2-10 screws/nuts. The nuts have a .70 outer diameter, a .98" flange diameter, and are .74" long.
I've included two movies of the unit under power. You can hear that it does make some resonating noises under "normal" operation. You can also hear it stall in the second video.
I've also included a couple of pictures of the nuts/screws.
I'm using a 3-axis Xylotex controller with PACSCI 116oz/in steppers. The unit originally came with steppers that were larger, but I got new steppers w/ the Xylotec unit and I'm afraid one of the things I've done it put smaller steppers on where I need larger ones. Like an idiot, I sold the old steppers on the bay a long time ago. If this is a case where the larger steps would make all my problems go away, I sure am going to feel like an idiot (again).
My reason for posting this is that I'm hoping some experienced users can provide some pointers on things I can do to improve the unit. Any helpful advice would be appreciated.
I'd like to get the speed up to whatever a 10-TPI screw machine should run at with steppers. If possible, I'd like to minimize backlash (although I haven't used the machine enough for backlash to be a problem, I'm trying to foresee the future). Any and all tips/pointers for these or other matters would be helpful.
I plan to use the machine to cut small plastic and wood parts, and perhaps aluminum some day, too.
Many thanks for any and all help.