[ilovestuffforre]

Alright, I'd like to start off thanking everyone that has put up information about their Sx3 or X3. You all know who you are. I've been through ALL of the Sx3 build threads, websites, YouTube videos, all of them. Multiple times. You've all been an enormous source of confidence, information and inspiration.

But I'd like to add in my Sx3 CNC conversion experience now.

First off, I wanted to do this entire CNC project as cheaply as possible at first, then upgrade later. So for now, no ball screws, home or limit switches, spindle control, Z axis counterweight, no bells or whistles.

Secondly, large inspiration to begin the CNC conversion was from the capability to add a 3d printer to the mill, so the 3d printing setup planning was wrapped into the CNC conversion planning.

So firstly the total cost was about 600 USD flat. I'm pretty happy with that.

310 for G540+power supply
200 for 4 stepper motors
30 for 3d printer extruder parts
20 for pulleys and belt
20 for cables and parallel port PCI card

I'm using the G540 with 381oz steppers for the X and Y connected directly, and the new 465 oz 3.5 amp nema 34 connected to the Z with a 1.33 ratio set of Chinese XL style pulleys. I made all the motor mounts from scraps, and I completed the X and Y axis first, so I could CNC the Z bracket instead of manually milling it. I built a 3d printer direct drive extruder and hot end from scraps around a nema23 and bolted it to the side of the head.

Now I know I seen a lot of talk about using ball screws, but I wanted to see for myself how well Mach3's backlash compensation works. I have about .0105 backlash on the X, .0095 on the Y and .0035 on the Z. She seemed to cut pretty good for awhile. Actually shocked me how well everything worked, engraving all sorts of fancy stuff.

But after a few days now, I've noticed some problems.

1. The Y axis backlash amount seems to change .003-.004 randomly every few hours, and even worse, the backlash is different depending on which direction the axis was moving. Is this worth trying to fix? Or should I just go ball screws? (eBay models for 30 bucks with ballnuts?!?!?)

2. The Z worked well at first, max speed of about 30 IPM going up. But it is now giving me trouble if I leave the worn down, most used range of the column, which has limited me to 9 IPM going up. This is due to a lack of a counter weight system or gas spring setup. I do need something badly. But what sort of Z rapids are you all seeing?

3. Did some 3d printing tonight for the first time, and my homemade hot end jams up a lot, needs some work. But I managed to print two layers of an object. I'm using one of the eBay 14 dollar PID temperature controllers to control temperature of the extruder. That's really the only electrical add on for the 3d printing side of things.
Not to mention I did some serious stalling while zig zaging around at 80 IPM. Is 20 inch/sec(?) too much acceleration? Around 60 IPM zig zagging I no longer stall. I can do 100 IPM straight rapids on the X and Y though.

4. And somewhat most annoying, if my speed comes down to 2 IPM or less, the steppers for X and Y will basically stop and go into stand by? Even if I'm running 8 IPM, sometimes a curve calls for a very slightly movement of one axis, and at that point the axis stops? I've setup my minimum speed in MasterCAM to be 3 IPM, but this hasn't solved the problem. Mach3 will still drive the motor below the MasterCAM recommendation. Mach3 doesn't seem to have a minimum speed setting, but is there anything I can do outside of gearing the steppers to solve this?

I'll get some pictures up soon, and again I'd like to thank the entire Sx3 community for all of your contributions. There's wonderful stuff happening on the internet!

[bhurts]

1. What are you oiling your ways and screws with.
2. Have you disconnected your motors and run through the travels manuely.
3. What is the rating of the power supply your using for your motors.

Ben

[ilovestuffforre]

1. Way oil and a brush.
2. You saying to jog the mill by hand and see how she feels? Great idea.
3. It is a little weak at 7.3 amp, 48volt.

[ilovestuffforre]

Alright here's some pics..

^ X axis stepper mounting and homemade Delrin coupler.

^ Y axis stepper mounting.

^ Crummy shot of the Z axis belt drive.

^ 3d printer extruder/nozzle add on.

^ 3d print extruder assembly, direct drive nema 23.

^ The Gecko G540 + power supply in a Tupperware.

^ The eBay PID temp controller plus the solid state relay. Used to control temp of the 3d printer nozzle.

^ 3d printer extruder with filament going in.

^ First two layers of a 3d printed cat. My Z height was too high first layer.

^ An engraved and contoured Totoro keychain.

^ Set of 3 keychains. About 3 scrapped as well, was the first thing 3 axis machined.

^ Trying to show the contour finish.

^ An engraving that took 2 or 3 hours due to the amount of zig zagging. It came from a picture which left all the chain lines tiny zig zags lol.
It was also hundreds of Z lifts, and the Y axis did float around towards the end of the engraving.

[ilovestuffforre]

Any word on how to alleviate the problem of the steppers being pushed too slow? I lose a lot of steps every time I go below 1 or 2 IPM.

[ilovestuffforre]

Alright, got my new J head extruder from eBay and ran my cat print again. It looks like crap lol... I lost steps a good number of times throughout the print.


So my question is, does a stepper have to stall in order to miss steps? Or can they miss steps silently?

This is at around 25 IPM, (600 mm/min) I don't understand why I'm losing so many steps?

[LeeWay]

I would start with some of the calibration cubes. You can tell more about what is actually happening that way.
Have you calibrated the axes yet? Checked the gibs, couplers etc? You have to do some troubleshooting before you pin it on the steppers, especially if you didn't hear it.

[ilovestuffforre]

Ya that is a good idea on the cubes, maybe too easy though. I have calibrated the axes, and checked my gibs, I did tighten them up a hair the day before the print, but as suggested above, I did turn the steppers off and rotate the couplers/screws smoothly by hand. And good point on the couplers, I will have to mark my couplers to make sure they're not slipping.

During the print I heard a lot of stalls, but it did seem to lose a group of steps silently as well. The second half of the print is a bit better after reducing the speed to about 20 IPM, but the errors then were silent. I will do some investigating thank you.

[LeeWay]

Yeah, its kinda hard to determine what is happening without using some geometric shapes.
I had a Mendel Prusa and I gotta tell you that calibration took a long time and many many prints to get close to correct. Once there, then it was to see how accurate I could get it. I got it fairly close to perfect before I was satisfied with it. It used a J-head hot end as well.

[ilovestuffforre]

What sort of print speeds did you use on the Prusa?
Everyone seems to just love that j head. (Not Bridgeport lol)

[LeeWay]

I don't recall the feed rates, but it was faster than 25 IPM I think.
Here is a link to my thread.
http://www.cnczone.com/forums/genera...del-build.html

[ilovestuffforre]

Any idea on how to fix the the steppers coming to a stop at the lower speeds? It's really a big pain, seems to spring up on every new job.
I thought about gearing the steppers as the final solution, but I don't think that's correct as it would only reduce my lowest speed possible, not eliminate the dead zone.
The problem occurs basically below .8 inch per minute. Shows up real bad on very slight angles, due to the slower axis having to slow way down to match the faster axis. I had to increase my rapid speed to alleviate the issue.
Would be real sweet if Mach3 had a minimum speed setting. But does anyone have any other ideas for the mean time?

[ilovestuffforre]

Yes! The guys over at mach support pointed me to the solution immediately, it was the step pulse duration. Changed it from 2 to 3 uS and the slow speed problem is completely gone.

[ilovestuffforre]

Attachment 258594Attachment 258596Attachment 258598Attachment 258600Attachment 258602Attachment 258604Attachment 258606Attachment 258608

Some updates, counterweight system is on couple flywheels and two alternators haha.

The 3d printing is working a whole lot better since I increased the step pulse from 2 to 3.

I made a mount for my dremel / die grinder, to hold it in the spindle. It is a cable driven grinder, and the cable is fed through the draw bar hole. Im really happy about the design, this allows me to keep the same zero while switching from r8 tools to the grinder. I did this for engraving, but I'm still breaking a small sliver off of the engraving bits tiny point. They work ok after breaking, but not as small of an engrave line.

[ilovestuffforre]

Ok, bit the bullet, ordered ball screws. It was $150 USD shipped in 4 days from china, for a 620mm X, and a 300mm Y, plus two bk and bf blocks, end machining, and three helical couplers.
My oem leadscrew system were failing, I tightened the Y axis too much and the stock bearings were being destroyed, backlash went from .009 to .03. The X axis wasn't doing too hot either.
Ball screws arrived, I had a buddy mill all the sx3 oem screw plates and brass nuts to accept the BK blocks and ball nuts respectively. Huge improvement, mill can run 3d prints at least three times faster now around 85 ipm, (yet to max it) rapids of 120 ipm are a breeze, machine runs quieter, the motors and screws are slowed nearly half speed. From 20000 steps per to 10160 (rounded guess.) I haven't done any real work with it yet.

[ilovestuffforre]

Alright, got some pics of the ballscrew fitment, and the latest 3d print.
Attachment 261366Attachment 261368Attachment 261370Attachment 261372Attachment 261374

The thing prints beautifully at way higher speeds than before. The Y axis does have .008 backlash, which needs some attending to. The X axis Im happy with at .002. But overall a huge improvement.

[damianpoirier]

Nice job! Thanks for your run down of problems and solutions. I've planned on doing this to my CNC (which is about 98% ready to go),

[ilovestuffforre]

Nearly one year later now and she still runs beautifully. Has completed large 14 hour 3d prints, and has made enough metal chips to bury itself at least 20 times.

The rapids came down from 120 IPM to 85 IPM recently due to lost steps on rapids randomly.

Accuracy is pretty good, within 10 thou on say a circle without adjusting the stock to leave. The tram on the head forward and backward is out pretty bad and needs shims under the column.

Backlash is still about .002 on the X and .008 on the Y.

All 3 gibs are pretty out of whack, it's a challenge to get them tightened correctly.

The Z axis gib keeps bending near the adjustment screw on top just from movement of the head. This causes the head to be very loose.

The spindle is also quite loose with at least 3 thou of slop in it, with both locks engaged. And if I pull on the table, I can get 10 thou with just arm strength with a DTI in the spindle.

Heavy hogging in aluminum with .5 inch EM or lighter hogging in steel can be very violent with pulsing jerks of the table. Similar to what I've heard about climb milling with heavy backlash. It has alot to do with a larger depth of cut, and even at .2 inches a minute it cuts OK for a second then jerks a rattles bad for a quarter second, back and forth. No issue if under say .25 depth of cut or very lite peel milling. Or really the issue vanishes with tools under .375 diameter.

My feeds and speeds are .25 3 flute endmill making a .25 slot at 13 IPM at .200 depth of cut, down to 1.375 inch deep. Very tricky to keep enough coolant on the cut to prevent chip welding and chip removal gets tricky too. If I don't constantly spray with water coolant, the 3 flute fills it's flutes in about 45 seconds of cutting at this rate.
And .01 material left, finish surface machining with a .5 inch ball I run at about 70 IPM. Or .5 inch ball roughing at 8 IPM .125 DOC. This is all at a maxed out RPM of 3700 RPMs. Just got comfortable drilling at 10 inches a minute plunge as well, at about 2k RPMs for most drills under .5.

Final thoughts is I wish I would have gotten a larger older knee mill. Mainly for the gibs and strength. Although this Sx3 has treated me quite well. Will post pics of parts made soon.