I finished installing my Vexta PK266-02A steppers from MJPA. After tuning the VRef up to 3.5V (it could go as high as 2 X 2A = 4.0V) and adjusting the PFD at 1.0 on Y and Z (the 2 axes I changed steppers on), Z is now running at 65 and Y is running at a solid 300. When the bushings get worn in a little, I should easily get a consistent and reliable 400 on Y.
Oh, I ran a #7 drill through the holes on the Y stepper before I tapped them to 1/4-20 - no problems whatsoever.

 

Dorsal, thanks for posting your results! If I remember, you have ACME rod on your Y axis, or have you installed the new belt mod? Good to hear the tapping of the holes to 1/4-20 works once drilled with a #7 drill, this will make it much easier to install the steppers.

 

meistertek, I'm still running the 3/8-12 Single-Start ACME rod on Z. I think the Z-axis speed is unimportant enough to my machine's operation that changing it to a belt-drive would not be an efficient use of resources. :ugeek:

 

Installed my two new Vexta PK266-02A steppers on both my Z and Y axis. Here are the before and after results:

Old velocities and drive setups:
Y: Stock Stepper, ACME 3/8-12 carbon steel drive nut, 28 ipm
Z: Stock Stepper, Stock 1/4-20 All Thread and t-nut, 12 ipm

New results with the two new steppers:
Y: Vexta PK266-02A Stepper, ACME 3/8-12 carbon steel drive nut, 45 ipm
Z: Vexta PK266-02A Stepper, 1/4-20 All Thread and t-nut , 30 ipm

This mod was a great way to really improve cutting speeds for a very low cost. I may still convert my Z axis to ACME 3/8-12 to see if I can get even more speed.

 

Here are the details of how I added the new steppers, my gantry is not removable so I used a trick to help install the screws for the Z axis stepper. I drilled and tapped the existing holes for new 1/4-20 screws after Dorsal mentioned that it worked great for him. The 1/4-20 screws I used are the same length as the smaller screws that came with the stock kit.
Attached files

 

Wow, nice post meistertek! Great idea for slotting the screws!

 

Thanks guys! Tapping the stepper holes and slotting the tips of the screws made this mod so much quicker to do. The performance increase with the two new steppers is pretty good for the $26 and few shipping $.

 

You can find it here, Mark. http://www.interinar.com/public_docs/PK266-02A.pdf

 

I just took a photo of the instruction sheet that came with the Vexta Steppers shipped to me. However the link TigerPilot posted is an even better sheet than the one that shipped with the steppers.

 

Guys, I was wondering if it would be possible to increase the speed of an MKI with ACME drives to over 100ipm if the drive ratio was say 3:1 between these Vexta steppers and the ACME rod. One way to do this would be to add a belt drive between the ACME rod and the Stepper shaft, I might try this out next week. Or maybe I should just break down and get the belt drive kit

Anyway, does anyone know where I can get the same belt that is used on the X axis in the stock kit, as well as the pulley that goes on the stock stepper? I suspect that they are available from McMaster Carr, I'll do some searching there.

 

Meistertek, I assume you mean the X axis. The parts list is at the phlatboyz.com website, in the members section. If you can't find it, I have it somewhere. I actually picked up an extra belt from McMaster Carr when I bought my bushings. It was cheaper there, but I remember they only had the expensive aluminum pulleys. The orginal parts are from "Stock Drive Products".

-Kwok

 

Thanks Kwok and Mark, I have a little designing to do to see how this is all going to work, but right now I imagine the same small pulley as is on the Y axis on the ACME rod for the X axis and possibly Z and a larger pulley connected to the stepper. I am thinking this would allow a speed increase as it seems the steppers have plenty of turning torque at mid RPMs but always freak out and skip at high RPMs. It would be cool if the larger pulley would end up being the same size as the one on the stock Y drum, I always like keeping the number of different parts down to a minimum if possible.

Maybe this will be the start of a pulley driven ACME rod kit, if anyone would be interested in such a weird mod!

 

Thank you very much for the heads-up on these motors gang! I am very happy now that I've swapped out the easycnc Minebea motor on my Mk1. I was getting a max of ~14ipm before stalling, now its doing 40ipm. Haven't even changed the vref yet. Could push it but I'm satisfied for the moment (budgetting for new paraglider wing, then maybe the MkII).

Next is the Z axis. It does tend to wander about. Back to the Mods section...

 

Ahhhh! I have noticed this phenonoma but did not know why.

I used to notice that the steppers would be hot after I came in for supper and returned back to the workshop an hour later.

I started making it a habit to turn everything off as soon as I finished using it.

But now I understand.... Cheap controller! Just like everything else from EasyCNC!

I have been over to Johns and seen his shop. He has a variety of controllers and steppers from many sources. The man is a walking talking electronics whiz! He has obviously become addicted to CNC machining and does a lot of research.

He was the source of inspiration for the MPJA steppers. A great asset to the forum... Thanks for all you contribute John.

 

I just read on the CNCZone ,in the thread about the Toshiba 3.5A driver, that you can set the idle current, or reduced current, in Mach3. I don't know how, but I'll have to find out.