[tjbaudio]

I have the Micromark version of the sx2. I plan on keeping the stock screws for X-Y CNC conversion. I do not have a lathe and I do not really want to modify the existing lead screws. When looking at it I am thinking using some T5 timing belts and machining the pulleys to replace the existing handles should be fairly easy and allow more alignment forgiveness. I was thinking 1 to 1 using the smallest size that would have enough material in the hub to machine for my needs.

For mounting I would cut some brackets out of 1/2” aluminum, use the existing bolt holes and just put in longer bolts to accommodate them.

Am I way off on this? Given the small pitch of the existing screw should I try to gear up a bit? I have 270oz Kelling motors on 36V. I have not been able to Google up any info, most searches go back to the spindle belt conversion.

The other question I have is should I add some axial bearings between the pulleys and machine? It seams I have to tighten the existing handles fairly tight to eliminate back lash on the Y axis.

I haven been using the machine stock for a year and so far the X-Y screws have been good enough for my needs. I tend to do cutouts in plastic, aluminum, and steel project boxes along with parts out of aluminum and wood. Another use is cutting openings out of 16-Gauge Steel blank plates such as Middle Atlantic Products - Custom Panel System
Thank you.

[hoss2006]

Not off at all, many people start out using the stock screws at first, downsides though are backlash and slower rapids
but that's not much of a problem on the size of an x2.
Another problem, not sure on that particular model but on regular x2's they don't have any bearings for the leadscrew on the y axis.
Will wear out quick under cnc.
fignoggle is one that use a pulley for the y axis.
Plans for the Mini-Mill and Mini-Lathe! Harbor Freight 8x12 and Sieg X2 Mini Mill, DRO, CNC Conversion Plans, Machining/Metalworking How-tos and Resources
Hoss

[tjbaudio]

Thanks Hoss, I plan on using a variation of your Z design. I have to mod it a little because my mill has the motor in the way of where you mount. I think changing out the rack and pinion for a ball screw is going to be the largest improvement I will get on this machine.

Y does not seem to have any bearings. I will have to look under it to see if there is space for a thrust bearing. I was thinking something along the lines of theses on the inside and outside: INA AXK1024 AXK1024 INA Steel Thrust Needle Bearing Cage Assembly

I will add a hardened thrust washer between the aluminum pulley and this. I assume the existing faces are hard enough? The shaft is .4” and I would let it ride on the existing hole for the belt side load. If not, I do have a rotary table as well as a boring head so I could add bearings other ways if needed.

[hoss2006]

These thrust bearings are more typical for the stock machines, similar are on the g0704,just bore a small pocket for the inner race.
Dynaroll F10-18M Thrust Bearing, Grooved, Bore Dia 10.00 mm
Hoss

[jdrew1]

I used belts on all 3 axes of my x2, for the most part it works great. My reasoning was space: I had an x2 and a mini lathe both enclosed in my hall closet, so every inch counted. The belts on x and y allowed me to hang the motors beside the table and base instead of outboard. My solution for the y axis was to open up both ends of the bore to accept thin ball bearings. With slight preload it is very smooth with no play, tons better than the original shaft running in aluminum. I would suggest using deep groove (most just call them ball bearings) bearings for the screws if using belts: I'm not sure how well most thrust bearings are designed to take radial loads, but deep groove bearings take radial and axial very well. That said, I'm still using the stock thrust bearings on my x axis and they seem fine.

My mounting plates are just as you suggest, 3/8 plate mounted over top of the original x and y bearing mounts with spacers and longer bolts. One day I'll do a build thread, but it's not done yet...only been 3 years. ;-)

Sent from my SGH-I717M using Tapatalk 2

[tjbaudio]

I finally got the time to take the Y axis end off and get some pics. It has no bearing, just a smooth shaft and a little lip at the inside end. When fully assembled the lip is flush with the face of the base. I also took some measurements. I did them twice, once in mm and once in inches. Can I assume that since it is 11.8mm I can use bearings meant for 12mm? I am also assuming the small housing/bushing I am holding in the pic will be replaced with what ever bearing system I pic.

I am still looking for a good source for those 12mm bearings.

Thank you.

[jdrew1]

I had a hard time finding a bearing with 12mm ID and small enough OD not to get in the way. What I ended up doing was ordering a pair of 10mm ID bearings from VXB Bearings on eBay and turning that step on the shaft down to 10mm. I forget the OD of the bearing, smallest I could find anyway. Maybe 18 or 19mm.

Here's a picture of what I did. The outside bearing pocket is not visible here, but I sunk the bearing in flush so I could go back to handwheels in the future if needed. The outside bore is a light press fit and the inside I left a little loose to account for misalignment.

Edit: Just reread your post: of course most people will just replace the entire block with something more suitable, I did it this way because I didn't have a proper sized piece of stock at the time. My whole build has been absolute minimum budget, using ingenuity and creative machining instead of replacement parts. Some of it looks a little ghetto, but it works great.

[tjbaudio]

Thanks for the pic jdrew1. I have a pile of scrap aluminum and no lathe so for me I think it makes sense to make the bracket. I figure it will hold the stepper any way. I measured and I think I have clearance for this one. Worst case I have to shave a mm or 2 off the center of the y slide piece. It also looks like a very good price. Maybe too good to be true?
51101 Thrust Bearing 12x26x9 Thrust Bearings With two of those I will have plenty of length on the shaft. To the point of needing spacers. That's better than not having enough room!

[tjbaudio]

Well, I just ordered a pile of bearings, pulleys, and belts. I also ordered a tap for the z axis ball screw nut as well as some 123 blocks and a dial test indicator. Looking forward to finally getting started on the next phase.

[jdrew1]

It's always nice to have a pile of new shiny parts to play with. :-) Good luck with the build.

Drew

Sent from my SGH-I717M using Tapatalk 2

[tjbaudio]

It's always nice to have a pile of new shiny parts to play with. :-) Good luck with the build.

Drew

Sent from my SGH-I717M using Tapatalk 2

Stay tuned for pics in a few weeks!

[tjbaudio]

Well, after practicing with my new dial test indicator for a few hours, I started boring out the pulleys to match my lead screws. I got pretty good at finding center and getting the boring head to produce the hole I needed. So I clamp down the fist pulley and go to town. Drill 1/4” hole out to 3/8 and it looked pretty good. Bore out to .4” Hole does not look right. Put it on the shaft and its off center! Looking closer, some where between the drilling and boring steps some thing moved. I decided to just stop for the night. Next day I get back at it and I can't find anything lose. All I can figure is I bumped some thing when I swapped in the boring head.

Any way, I started over and produced 2 good pulleys and then went back and trued up the bore in the pulley I hosed. It is concentric now but it's just under 7/16” I will see if the local hardware store stock of bushings can be made to fit my 1/4” stepper shafts or I will order a new pulley and put this one in the parts bin.

Note self, order extra of anything I am going to cut. Second note to self, shipping from econobelt.com sucks.

[tjbaudio]

Wow, I can't believe it has been this long. This has been one hell of a year for me and my family. We ended up moving cross country. I finally have some sort of work space setup again and will be getting back to work on my little project.

[Fastest1]

Good to hear. I just came across this thread. Work piece holding gets us all at times. Dont let anyone fool you into believing they get it right the first time, every time. Only after lots of experience.

[CNCfun&games]

Words of wisdom from Fastest1

“Work piece holding gets us all at times”

and particularly under CNC control.

I believe you are wise in retaining the Hand wheels on Both your
X & Y axis. You will like the increased capability of Both Manual & CNC operation.
Spend a couple of bucks and buy a hand wheel with a fold up handle for the Y axis.
You will be glad you did.

W. Smith Mission Viejo, CA

[tjbaudio]

I have the x axis mount almost done. Still needs a couple of holes drilled and taped for a shield.
I did this with just an idea in my head how I wanted it. No prints, just measure and make a part.

After the main plate had the mount and shaft hole cut in I set it up to measure for the next step.
Attachment 214922

Then I machined two blocks and did some more test fitting. I had not trimmed the bottom yet. I did not know exactly how long they needed to be and wanted them as long as possible. You can see where I marked a cut off point for the main plate so it can clear the mounting bolts. Once completed I will also remove the x axis lock and replace with another adjustment screw.
Attachment 214924Attachment 214926

My vice is a real POS. It always rides up when tight. I ended up adding a 123 block with a clamp to hold it down. For this cut I also needed to hold down the part so I added a clamp off the 123 block. For the wide plates I just held them down in the vice directly.
Attachment 214928

At the end of the night I had the final assembly. I had to cut out a clearance area so I could put the belt on after the pulley was in place. I have to adjust the slot on the left for just a little better fit. Oh yeah, and a mess to clean up.
Attachment 214930Attachment 214932Attachment 214934

Some tools that have been helping are better clamps and I just got some Dykem. I do have a question on that, as I was marking out cuts it worked very well to use the sharp point of the calipers to scratch the Dykem? The calipers are much harder than the aluminum and Dykem. I also have a nice carbide scribe for other marking needs.

When this part is done I will have a computer controlled power feed. I don't have a hand crank to put on the X drive yet. However the shaft is available if I need one. Also since I did not modify the original machine it only takes a couple min to swap the motor for the original crank. Next step will be the Y axis.

[tjbaudio]

CNCfun, I really like that Y layout. Yours is much more simple than what I had in mind. I may have to change my design now.

[tjbaudio]

Success! I have it assembled and working with LinuxCNC. Speed is nice for a small machine. Max speed of .5in/s and an acceleration of 1 in/s^2 runs stable. Backlash with stock screw and nut is .006”

I will post a pic or 2 in my next post.

[tjbaudio]

Here are some pictures and some video of a test.
Attachment 215058Attachment 215060Attachment 215062

I also ordered a longer timing belt so I can change the Y axis to the design CNCfun has.

[tjbaudio]

I finally finished the bracket for the Y axis. It was really nice having the X on a motor. I could setup my cuts and then use the stepper as a power feed. I set options for increments of up to 1”. Doing the pocket for the stepper was easy that way. I could do 1/16” deep cuts at 20ipm, 3/8” 4 flute endmill@ 2500rpm. The bearings fit nice. My only concern is I used a PVC fitting to make a ring to keep gak out of the outer bearing. I hope it can stand up to the oil. I used grease on the bearings for lubrication.

My problems started in testing. The Y axis likes to skip steps or stall with very little force. I can stop the table with my hand even at low speed. X axis can do rapids at 40ipm. The Y axis has problems at 10 ipm. I tried swapping X and Y drives and swapped in another motor of the same model. The Y axis has some friction when turning by hand but not much. Also I can turn the handle even if the motor is on and trying to hold. It's not that hard to break the holding torque.

Perhaps I messed up in my motor selection? I have:

20 tpi stock lead screws.

Keling KL- 4030 set for 1/4 stepping, 3A (max) on 36V

Keling KL23H276-30-8B http://www.kelinginc.net/KL23H276-30-8B.pdf
Wired parallel bipolar.

I picked the motors based on low inductance. They are 4.2A motors but I figured they would run strong enough and nice and cool at 3A I guess I was wrong.

According to my Fluke all the coils measure within spec and are hooked up.

Any other ideas?