NEW MILL TURN ARRIVED

[BlackICE1]

If you have the money it's a no brain choice to go with the "works out of the box" machine rather than the bubble gum and bailing wire version of a cnc. If you don't have the money I'd suggest start saving to buy the Tormach rather than waste your money on something I'm sure won't work out of the box if ever. If you like the "Heathkit" version of a cnc, then by all means buy a Shopmaster product and learn how they tick while you kill off endless hours trouble shooting various problems on a machine that was supposed to work out of the box. You may get it working or it may end up a pile of parts like many of the Heathkit projects of yesterday. Many great electronics wiz kids cut their teeth on the do it yourself projects sold by Heathkit.

Funny analogy that isn't far from the truth. I'm old enough to remember Heathkit. My father built an amp and tuner kit from them, running vacuum tubes of course.

[smallblock]

I'd like to know as well, for my Mill Turn. I emailed Shopmaster and I got no reply.

I have been able to correspond with Shopmaster regarding this. My memory's vague, but I think correspondences did not work through the Shopmaster website but did through direct Email so they were good with trying to respond.
BTW, I think shimming the bottom of the three (front or back) columns for the "Y" tram adjustment is better then shimming the mill head spindle itself.

Posted by Walters 474 on another thread.

[n1tr0]

I'm not sure what the issue is between you and JT, but I have been dealing with him for over 20 years and 4 different models of his machines. He has always been prompt in answering questions and supplying any necessary parts. The Mill Turn has a cartridge design that can be removed from the machine in minutes. Frankly, I can't imagine anyone not being able to repair it by simple intuitive thinking.

If you've really been a customer for the past 20 years, I'm sure you're getting a level of service that us new guys can only dream of. Most of my emails get responded to by Catherine, not JT, and when JT does respond, he usually only addresses 1 of the many issues. I've pretty much given up on emailing at this point.

Yes, the spindle cartridge is easy to remove from the machine, it was one of the first things I had to modify so I could install my collets (one of the many oversights and mistakes made building my machine). What I don't have are any bearing replacement part numbers, torque specs, or any other details that would assist in proper maintenance or repairs. I'm sure with 20 years of experience on his machines you've probably developed a good feel for how his stuff works, for those of us starting out 'tho, it's all about the documentation.

There's something messed up when he needs to verify a customers serial number and original purchaser status before he'll share even the most basic maintenance/setup information; that level of scrutiny should be reserved for actual warranty claims.

[cbud]

I'm a machining noob that's considering the Mill Turn among other options including DIY building a PM-727m, Tormach 770, etc.

The Mill Turn seems well evolved to the 2015-2016 design. Seems intelligent. Nothing on this thread seems unresolvable with some deep confguration effort in Mach 3 or LinuxCNC.
It seems like the Z axis rapids are a stepper power issue, but that Gecko 540 is only putting out 3.5 amps per channel. So it seems that 6 or 7 amp drivers and some bigger NEMA 34 steppers would be needed along with a beefy gas strut on each side.
But those would be optional higher performance upgrades down the line if I choose.
Am I correct in assuming this is only an upgrade issue? Or is there something I am not understanding that is fundamentally structural to the Z-axis design that cannot be overcome with bigger electronics?

The Z-axis design with the 6 linear tube rails seems like a big evolution for the machine over the Patriot VFD.
Am I correct? Opinions?
It seems to be a complete upper casting redesign as the quill is completely removed.
The full bridge design seems to be as stable and stiff as rectangular column mills like a Grizzly G0704? Or am I way off base?
(I'm a machining noob remember) Please any opinions welcome. I'm looking for all kinds of rational input.

I'm expecting quite a bit of elbow grease, willpower, time and frustration to go into any machine, so I don't think I'm disillusioned with the realities of buying a low cost turnkey solution.
The value and design seem to be there.
I'm sure JT does his best. I'm willing to give him the benefit of the doubt.

I've looked for benchtop mills and lathes in my area, but they're either well worn and would require substantial refit of ball screws, mounts and electronics, or they're just gigantic full production machines.
There is a Patriot VFD 2014 lightly used option for me in my area for under $4000. It entails me getting a $200 trailer hitch for my car to transport it 90 mins away with lifting logistics involved at both ends of the transaction with no crate, but might be worth it?
I have read that JT is strict on warranty not transferring to 2nd hand owners, so I assume that I would be losing any remaining 3 year warranty as well.

With the Mill Turn upgrades in castings, linear slides, DRO, cabinet, and oiler, and the Father's day shipping included, I think a 2016 Mill Turn may be a decent option?
For you guys like @smallblock, that own current and older units, are the 2015-16 design improvements in the linear slides valuable for the Z-axis stability enough of an improvement over the Patriot VFD to be worth the extra $2500 to $2700 for a current unit?
The sales descriptions on the website make it seem like a total game changer. Is this hype or is having the whole casting slide up and down on dual ball screws a substantially better design for rigidity and clearance?

My main research concern is the height, clearance over table, and travel of the Z-axis. Do you guys find that the 10.5 inches of travel is enough for your projects?
I'm looking at doing hobby stuff. Making scooter and small vehicle parts, maybe a clock project.
I would love it to last me 6+ years as I learned and tooled up. (I already know SolidWorks and SolidCAM fairly well and have a workable Mach 3 post processor, but am looking at Fusion 360 now)
I would like to use TTS style holders (maybe knockoffs if cheaper) and those add 2 inches to tool height. Will combining a low profile 4 inch vise and a 3 inch end mill be out of the question?
Or do you Mill Turn owners not really have this problem because you can use the Lathe spindle or turn the vise sideways for taller projects? So is this just an issue of setup convenience (which is less of an issue for a hobbyist)?
I do recognize that the Z-height has not really been increased over the years in evolution. Is it a valid assumption that the Mill Turn takes into account 80% of all customer work envelopes and the 14 inch travel is not an issue, even with TTS style tool holders?
What are your experiences?

The other research issue is table size seems narrow at 19 inches, compared to a dedicated mill of 26 x 9. I recognize that the table hasn't grown much in decades, so I am assuming that 19 inches is not a stability or work holding issue given the relatively narrow ways on the X-axis?
What are your opinions on this?

Question:
There seems to be Two Z axis ball screws on the shopmasterusa How it's Made page. Are both of these screws driven by separate steppers? Or are they driven off a common pulley and shared stepper?
If so, is the 2nd Z-axis stepper on the A channel driver?

[smallblock]

As far as choosing a machine goes, you need to make that decision based on your budget and needs. the working envelope is pretty much the same as most mills in this size. The Mill turn uses the Gecko 540 drives which are a great package because they are simple and reliable. I think the system Shopmaster uses was developed by Camtronics and they buy them from them. The older machines used a 7 amp system with 4 gecko 203 drivers, but there was a lot of wiring to do. I think you can still order that system from Camtronics. The overall machine is a big improvement over the earlier ones even though the z rapids are slow. About 20 IPM was the most I could get, and to be safe I dropped it down to 12. However, later I did change the motor drive pulley to a 24 tooth, changing the overall ratio to 3-1 and increased the speeds to over 20 IPM. The top pulleys are driven by a single stepper and a large 3/4" belt. Your question about the A axis got me thinking though- since the A is unused, a person could slave that to the Z and then put 2 motors face to face or in tandem driving the Z pulley, effectively doubling the power. That would allow you to change the ratio to 2-1 or maybe even 1-1 and get much faster rapids.

[cbud]

I'm about to join you Mill Turn owners next week.

What exact vise and size did you guys get for your Mill Turn?
I'm thinking that 4 inch is not enough jaw opening and thinking about this 5 inch:
5" x 4.92" Lock Down Precision Milling Machine Vise - Vise - Toolholding & Workholding - Products

Wanted some input on vise sizing because I'm guessing it's not your typical table X travel clearances due to the lathe chuck and tail stock.

[n1tr0]

You can fit a 6" cnc vise, but it wiil limit your travel. I usually leave the 6" tucked away and do most of my work with a 4". The Shars is a decent starting point.
Regarding the previous talk about the z-axis speed, changing the gear ratio and a bigger motor is likely the best bet. All your typical bipolar steppers are going to lose most of their torque by the time they hit 400rpm, so changing the gearing is pretty crucial. I've built a number of machines that use individual motors on the z-axis screws, but I run them on independent controllers with a homing procedure to get the axis level. The trouble with independent motors is that when you power the machine off, the z-axis ball-screws usually want to backdrive at different rates ending up with a skewed head or bed.
When I get around to building a new controller and doing some upgrades, I might go with a 5-phase stepper with a brake, like this unit from Oriental Motor. The 5-phase steppers tend to have a torque curve that spans a huge rpm range and having the brake keeps everything in place with the stepper disabled ...

[cbud]

... However, later I did change the motor drive pulley to a 24 tooth, changing the overall ratio to 3-1 and increased the speeds to over 20 IPM. The top pulleys are driven by a single stepper and a large 3/4" belt...

I measure the Z axis motor shaft as an imperial 1/2 inch and the belt at 3/4 inch. McMaster has an L series aluminum for an astronomical price, but where did you find a reasonable 24 tooth pulley to fit that ID and belt width? Or did you turn and cut it yourself?

[cbud]

You can fit a 6" cnc vise, but it wiil limit your travel. I usually leave the 6" tucked away and do most of my work with a 4". The Shars is a decent starting point.
Regarding the previous talk about the z-axis speed, changing the gear ratio and a bigger motor is likely the best bet. All your typical bipolar steppers are going to lose most of their torque by the time they hit 400rpm, so changing the gearing is pretty crucial. I've built a number of machines that use individual motors on the z-axis screws, but I run them on independent controllers with a homing procedure to get the axis level. The trouble with independent motors is that when you power the machine off, the z-axis ball-screws usually want to backdrive at different rates ending up with a skewed head or bed.
When I get around to building a new controller and doing some upgrades, I might go with a 5-phase stepper with a brake, like this unit from Oriental Motor. The 5-phase steppers tend to have a torque curve that spans a huge rpm range and having the brake keeps everything in place with the stepper disabled ...

Thanks, I'm leaning toward the Shars 5 inch, but need to doublecheck measurements for lathe chuck and tailstock clearance against the vise mounting holes and table slots.

I hear ya about the 2 motor Z axis setup with leveling and backdriving challenges. Thanks for the heads up. The Z speed is slow, but I'm just starting to cut air. I'll look into an ethernet stepper, 7 amp driver and a 960oz - 1200oz stepper from ebay in the future. I've got some homework to figure out an optimum pulley ratio against RPM and torque.
For me that 5 phase stepper is crazy overkill. In spec and price !!! Looks like it's made to run hard core in a 24/7 production factory and has its own special 5 phase inverter.

What did all of you guys do about limit switches? Do you run without them?
I was planning on doing an in series wiring of 6 micro switches to the last 2 open inputs on the G540.

My first change is to add an EMI filter to the VFD line side because I get quite a bit audible buzzing noise from the steppers that cannot be adjusted away with the G540 gain. Most on the Y axis.
I don't know where the feedback comes from, but I notice there's no filter on the VFD so it's a place to start.

[n1tr0]

I don't think there's much need for limit switches, you've got the e-stop if your program starts heading for one extreme or another. I would like to add a hard stop to protect the wiring of the y-axis from getting pinched. If you were thinking of using limit switches for finding your home/zero, you've got the VFD. I recommend picking up a USB pendant for moving the machine around. The controls are flaky enough already, don't get one of the wireless pendants, I've heard nothing but horror stories. VistaCNC has some nice pendants, but the cheap ones will also get the job done.

[n1tr0]

I've got some hardware issues and bugs I'd like to sort out.
On the hardware side I've noticed the belt driving the z-axis is wearing unevenly and one of the toothed idlers has a loose retaining nut and no way to hold it to tighten it up (I'm assuming all the upper sheet metal needs to be removed?). Does anyone have specifics on the belt (length, tooth style, etc?) and any experience on tightening things up or adjusting the pulleys to fix the wear?
While dealing with the belts, I'm wondering if anyone has instructions for 'tramming' the head/beam. Based on my fly-cutter, it seems to have a slight tilt.

The other hardware issue I have is with the bearings in the spindle. I followed JT's instructions for tightening/preloading the bearings, but they still get crazy hot after running for a bit. I've been milling aluminum with some very small bits, so the F&S calculators usually have me running pretty high rpm's. I'd like to upgrade the bearings or replace the spindle all together. It definitely shouldn't be getting as hot as it is and the truth is that I'd like to re-gear the spindle so I can run even higher speeds eventually as well as installing a power drawbar (that sheet metal is always in the way of tightening/loosening the drawbar or I have to wait forever for it to climb high enough to clear from the top).

On the software side of things I have a few big problems, two of which might be related. I'm hoping someone with a decent running machine can post their machine settings and maybe their XML profiles. The computer that came with my machine was missing a lot of the files (shortcuts to nowhere on the desktop) and has had a lot of odd behaviors.
My most immediate problem is with the canned G73/G83 peck drilling cycles. They should rapid down to the start of the peck height, peck at the specified feed-rate, then retract at rapid speed & repeat. Mine is travelling down to the peck height at the feed-rate, doing a more-rapid peck, then retracting at the rapid rate (most of the time). If I'm doing multiple holes the machines does a diagonal move from the bottom of the finished hole start of the next hole failing to retract first snapping the drill bits and ruining my parts. I can work around the tool-snapping by hand-coding each hole separately rather than using my post-processor, but nothing I do seems to fix the downward feed rates and friends machines running Mach3 and the same g-code don't have any of these issues. EG.

G83 X5 Y5 Z-10 R2 Q0.5 F100
X10 Y10
G80

The second software bug concerns the Config/Safe_Z Setup. Most of my work is in metric while the machine's core config is all in inches. If I specify a safe-z-height in the config the number changes every time I switch units in my gcode using the M20/M21. A half-inch becomes 12.7, then I load up another program or restart mach3 and the value has jumped to 127, pretty soon it's escalated to 10" or 254 which I'm assuming is the z-max defined elsewhere.

The last software issue seems to be tied to the CV settings. I noticed Mach3 was rounding some tool paths that appeared straight with right angled turns . In the motion mode section of the general config the machine was set to exact stop instead of CV, but I had to disable CV for angles >80 degrees in the CV control to fix the odd rounded corners, but now other tool paths have gotten really jerky (lots of very brief stop and go). I had another issue a while back where having the backlash compensation turned on in mach3 would cause the machine to make a banging noise at the steppers when they were changing directions and they'd miss a bunch of steps.

Thanks.

[instructor37]

I can't help you with the hardware questions because we have the older style machines, but I would suggest you first save your XML file settings and then delete Mach 3 from your computer and re-install the latest version from the Mach 3 website. The early versions did have some bugs. On the Jerky motions, this may be caused by running in CV mode. I would switch to Exact Stop and then adjust your backlash max% down to about 50. In CV mode the axis will travel to its stop point at the same velocity and then stop suddenly, this can cause a loud clunk sound as the motor is trying to stop the carriage instantly. Especially noticeable if you are running high rapids or stopping a lot of weight. In Exact Stop mode, the axis begins to decelerate before reaching the stop point making the motion much smoother. CAUTION- when threading you need to use CV mode, because Exact Stop will change the feed rate as it decelerates and wipe out your threads unless you have a large relief before the stop point.

[n1tr0]

The reinstallation is probably a good start. It did come with the latest version of mach3, but I have had weird errors like when it refuses to turn on the spindle because the spindle script is missing. Rebooting usually resolves these little glitches, but it could be a corrupt install. I really wish there had been some QC checking over my machine before it shipped.

[instructor37]

The reinstallation is probably a good start. It did come with the latest version of mach3, but I have had weird errors like when it refuses to turn on the spindle because the spindle script is missing. Rebooting usually resolves these little glitches, but it could be a corrupt install..

Also, make a copy of your XML files after you have done all the setup - steps per inch, backlash compensation etc. Then save those XML files on a thumb drive. Go into Mach 3 directory and find XML Backups and delete them all- you probably have a lot of them, as Mach3 creates a backup file every time you make any change. Mach3 has a tendency to pull up a backup file sometimes after a re-boot or an e-stop shutdown, rather than the XML you want to use. We have a number of XML files we use for various operations, each with its own particular settings like Mach Turn Threading, Mach Mill Tapping etc.

[cbud]

Regarding the belt:

My Z axis stepper mount was way off square and caused a flopping of the belt as it changed directions. That might be causing your uneven belt wear. The angle iron used in the top frame is not square at all.

I first marked off the tooth spacing timing marks on both large ball screw wheels with a Sharpie to align with the belt so I didn't throw the bridge out of tram - if it ever was in tram from the factory. I stacked spacer washers in the top holes of the mount in trial/error until I got the Z axis stepper pulley to have even tension on the top and bottom of the belt. I made a small wooden V-block to bear against the tensioner pulley wheel and used a woodworking bar clamp to squeeze the adjuster pulley toward the rear angle iron to set the tension while I tightened the bolt on the tensioner puller.

Amazingly enough I didn't need a pin spanner wrench even though those pulleys have pin holes. I was able to just create enough friction force using a standard box wrench with a twisting / shearing motion on the bolt head to stop the pulley from spinning while I tightened / torqued the bolt. The open ended fork end or crescent wrench might not work in doing this. I think I needed the box end of a box wrench.

I'll eventually need to make another Z axis stepper mount with an angle adjustment wedge and screw if I upgrade the BoB, Z driver, and Z stepper size - but that's way down the line.

[smallblock]

Regarding the belt:

I made a small wooden V-block to bear against the tensioner pulley wheel and used a woodworking bar clamp to squeeze the adjuster pulley toward the rear angle iron to set the tension while I tightened the bolt on the tensioner puller.

Here's a simple mod I made on my machine to make the Z axis belt tensioning a lot easier.

[n1tr0]

Just noticed another possible mistake in the machine config. The X,Y,&Z axis appear to be using 5mm lead ball-screws. I'm not sure why the machine config was done in inches, but my machine came setup with 20312 steps/in in the x-axis, 10157 in the y-axis, and 40656 in the z-axis. The Gecko G540 uses 2000steps/rev, this means if you're leaving it in inches it should be 20320 for x, 10160 for y, and assuming a 4:1 ratio on the z-axis 40640.

I also found that the y-axis shaft coupler was relatively loose and the primary source of that axis' backlash. It looks like all the backlash in my x-axis is coming from either the ball-screw mounts or slop in the nut. I haven't found an easy way to test/tighten those parts, but it's not a loose pulley or belt.

[smallblock]

The ball screws are metric- very close to 5 TPI, but not exactly.

[smallblock]

On my machine, I found the Y coupler got loose after a while, so I swapped out the factory set screws with some top quality dog point units that were about 5mm longer and put a jam nut on each one- since then they have not loosened up. On the X, if the belts and pulleys are tight, the next common source of lash is the thrust bearing on the tailstock end. Pull off the rubber dust cover and stand at the end of the machine, grab the cross slide table with a hand on each end and push and pull toward and away from you. Watch the thrust bearing for any back and forth motion- if you have any, then tension the nut. Those Chinese ball screws are usually good for about 0.001-0.002" lash, but with backlash compensation, you can get it right on- here is a video showing the machine travelling 10" and then coming back 10" to zero.

[n1tr0]

The ball screws are metric- very close to 5 TPI, but not exactly.

Being metric, you can use the screw's lead and steps/rev to get some exact values; an inch has been exactly 25.4mm since 1959.
It's easier to have metric hardware setup in Mach3 with metric as the default units, then steps/mm become super simple, (y)400, (x)800, and (z)1600 for the 3 axis and setting the native resolution for each axis in the cam software get's really easy as well; 0.0025, 0.00125, and 0.000625mm. With backlash compensation I was able to get mine to travel out and back to the original location just fine, but when machining with backlash compensation enabled the machine makes some horrible clunking noises. It could be that bearing end-support you mentioned, so I'll give that a shot next.
- updated - tightened end-supports, both x & y were loose, tightened finger tight, x ~+20 degrees, y ~+40 degrees.


I'd definitely like to give the lift-struts & z-pulley upgrade a shot while I'm getting things squared up. If anyone has the actual belt info (pitch and length) or a part# for a pulley they've used, can you please post it? Pictures of how you've got your struts mounted would also be handy.

If anyone has already upgraded their x-axis pulley to go 1:1, some part#'s or details would be handy. It'd be nice to order up the parts without stopping to pull it apart & count the teeth. It looks to be using a standard 3/8" wide 190 tooth XL belt. The stepper shaft is the standard 1/2", but I can't quite get my calipers in there to verify the shaft size on the screw side of things. I might just replace both pulleys and the belt at once using a lower-backlash solution like the GT or Powergrip belt profiles.
- update - When tightening x-axis support bearing I was able to get a good hold on the screw and work the stepper back & forth. It looks like a great deal of the backlash is due to the belt backlash (6 full steps = 9 degrees = 0.0625mm or 0.00246") so I'll definitely be switching belt & pulleys. It looks like the shaft for the screw side pulley is between 9/16" & 15mm? If anyone has theirs apart and can confirm the exact size I'd appreciate it.

The last big outstanding hardware concern is the spindle. If anyone has some details on the bearings and the rebuild operation, I'd like to start researching a fix or upgrade for the bearings (or whole spindle assembly) before they cook themselves. Thanks.