Messages

1

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 24, 2023, 14:47:30 pm »

…Something to keep in mind when doing your testing, is that the way the controllers are written they wont tell you or flag an error if you have not achieved the set feed rate,…………

In crude means the constant frequency of the motor is an indicator but in this case, I’m pretty sure I’m getting to 9000mm/min very quickly, pretty much as the acceleration setting dictates One thing I learned about videoing equipment in action, when you use a viewer with super slow-mo with fractional time display, you can very accurately clock the duration of events. In this case the longer 9” jog stroke, and compare it to the expected speed.

I also use elapsed time when I cast metal to estimate the metal velocities in the feed system. I weigh the casting afterward and from that can accurately calculate volume, and since know the cross-sectional area of the feed system all I need to do is watch the elapsed time of the pour and all that gives me a good estimate of metal velocity in the feed system.

…EDIT to add just found this for the measuring software.
https://www.youtube.com/watch?v=hnHjrz_inQU

That’s the thread I was talking about in post 47 above.

...I did start perusing some of the builds at mycncuk.com. I took in the laser leveling thread. I think I’ll just have my beams precision ground because I have access to very good source for that, but I do understand the approach with a thin walled beam, and also the grouting between concentric tubes for stiffness, dampening, and weight reduction, and the laser measurement is quite ingenious. One thing I didn’t follow, he said he would do the same on each side of the beam. I can see how he could work each side flat, but how will it insure the two sides/surfaces are parallel?...

The grinding equipment at my friend’s shop will prep the beam surfaces better than I could ever achieve. I have to choose my battles as to what I do on the cheap so I can devote my time to the rest of the build.

I’d be more interested in using a similar method to level the rail beams with other beams as I assemble and level the router bed. I’m thinking I’ll just buy a 20ft stick of the structural profile, cut them all to length, and drive them directly to my buds shop to have one side of each piece ground at the same time. Then it’s a matter of completing the machining details and assembling them accurately, which I’ll likely do with threaded fasteners to allow for positioning. Their equipment is big enough that I could give them a 4ft x 4ft weldment, but that would become impractical for me to machine, move, and construct.

As an aside, I sure hope the security cert gets sorted soon. Between the site crash and this, there's no actvity. Members can become acustom to its absence and when a site owner becomes distant and disinterested.......it can lead to the death of a forum.

Best,
Kelly

2

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 23, 2023, 20:10:57 pm »

I did some testing on my new Z.

I changed the resolution to suit the 10mm lead ball screw, and increased the max travel. I left the acceleration set at 700mm/sec2. The max rate has been set at 4570mm/min and I have been using it with these settings for the past year and a half. I arbitrarily doubled that to 9000mm/min. I put a dial on it and was jogging back and forth at those settings. It repeated without loss of steps to within .001". I applied some resistance with my hand, probably 30-40lbs, and still repeated as close as the dial could measure. The X&Y rapids at 16500mm/min. Here’s the link to a short video.

https://youtu.be/v1X02ZWP2mE

The entire Z assembly weighs 38.8lbs. The Router is 6lbs of that. The weight of all the moving parts of the Z axis including the router is 18lbs.

Not sure how it would like running at that speed continuously but I was sort of surprised how well it did given 9000mm/min on 10mm lead ball screw is 900rpm for that little stepper.

Best,
Kelly

3

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 23, 2023, 15:54:09 pm »

Steppersonline have the real deal, get ones that have all English stenciling and that the silkscreen is crisp and clear.

I had/have been surfing that site. It’s a good resource.

To some degree, and this can be mitigated by the belts construction materials, ….. I can’t express the importance of this enough as ‘look a likes’ are not ‘performance a likes’.

Was looking at the Gates Powergrip GT series. It’s a popular brand this side of the Atlantic with rounded tooth profile and high quality belts.

A hierarchical list of Skookumness……..

There’s only so much accuracy you can get out of the milling process regardless of the machine construction before you have to use grinding, polishing, lapping, edm or chemical etching.

At this point I’m thinking NEMA34 Closed Loop Steppers with 3:1 timing belt gain to 20mmx10mm lead screw on a more traditional moving gantry 3 axis design. I’ll throw some sketches out later but a pair ground 2”x 8” or 3”x 8” structural steel beams with 25mm linear rails on each, and aluminum structure for the gantry plates and moving beam. Young’s modulus being what it is, I’d certainly prefer the stiffness of steel, but at the higher linear speeds, really need the light weight of aluminum. I’ve made 2”x 8” beams that are fabricated structures with ¼” plate skins and cast honey-comb web internal structure that are assembled with fasteners and structural adhesive, then machined. They are both light and very stiff.

Still lots of compromises there, but I think for my needs it would be both economical yet a quantum leap improvement from my present hardware and good compromise for the range of speeds and work envelop I desire. I’d still be money in pocket after the sale of the existing machine.

Best,
Kelly

4

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 22, 2023, 15:16:42 pm »

……..That’s a nice build, don’t let it down by using those spiral wound couplings. They (wind up and unwind under load) losing accuracy………Use a bellows type if money is no object……On my milling machine I use the black style of coupling in the pic, You can get them for a reasonable price and they perform very well.

I’m with ya there. That’s just the coupling that came with the ball screw kit along with the bk/bf mounts and BS nut housing. I was able to specify the clamping diameter to fit the existing stepper but wasn’t planning on using it in the final build. I figured I’d wait until I committed to the drive motors so I could by to suit the shaft diameters. I also think those spirals couplers have considerably different (lower) load ratings in the unwinding direction too.

…Have you given any thought as to tramming the Z axis for installation and whilst in service, sometimes you may want to do this. Dave

Yes, some thought, and will be more important with the longer Z travel, but still noodling the build design. I’ve been reading a lot of build logs, YouTubing, and taking note of the features I find most interesting and promising. If I go the new build route, which is most likely, I’ll likely take a different approach to the existing gantry. I have the luxury of having an operational machine so can afford to be a bit more patient in learning and selecting my path forward.

I see on many DIY builds and some commercial offerings that timing belts are used between the steppers and ball screws to adjust speeds into the more optimal stepper range. Doesn’t this introduce error with wind up/down of the belt? Albeit small depending on the drive ration and ball screw lead.

I did start perusing some of the builds at mycncuk.com. I took in the laser leveling thread. I think I’ll just have my beams precision ground because I have access to very good source for that, but I do understand the approach with a thin walled beam, and also the grouting between concentric tubes for stiffness, dampening, and weight reduction, and the laser measurement is quite ingenious. One thing I didn’t follow, he said he would do the same on each side of the beam. I can see how he could work each side flat, but how will it insure the two sides/surfaces are parallel?

You didn’t comment on those steppers in the previous post. You had previously cautioned against knock offs. Even though all the auctions either say or suggest they are Leadshine, they are being offered in mass by all the generic importers, so??. I’m very tempted by those but also leery of documentation that is not understandable on imports. Also, haven’t yet discovered where the microstepping selection is made. Can you steer me there?

Best,
Kelly

5

CamBam help (General usage) / Re: Security Certificate has expired

« on: March 21, 2023, 16:38:22 pm »

The site is essentially unusable in its current state.  One gets a 'security challenge' after every action. LS

Yes indeed, bummer. Hopefully it gets sorted soon.

Best,
Kelly

6

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 21, 2023, 16:35:12 pm »

……..I’ve snapped some accelerator apps, with these you can take a baseline measurement and as you make adjustments see what effect they have. The idea here is to load the app and fix the phone to safe place on the Y axis post and measure the ringing, before and after you have modified the frame for example.

That’s pretty clever. I’ll look it over and see if I can add it to my testing.

……..When you have some spare time pop over to mycnuk.com and have a look at the built logs

I'll check it out.

The Z axis is done. I made the stepper mounting plates large enough to accommodate NEMA34 steppers. The CAM drawing still shows use of rack and pinion drive. I added a tail shaft support for the ball screw that tucks up inside the tunnel on the backside of the Z casting to keep it from flopping around in there. It also serves as a mechanical stop to prevent the traveling Z from being run off the rails, though I hope never to put that to the test. Fully extended it’s 37” from stepper motor to the base of the router clamp! I’ve drilled and tapped enough M5 threaded holes to last me a lifetime.

In the realm of too good to be true, these closed loop stepper packages (see attached) are all over eBay. 3 closed loop NEMA 34s and drives for that price? When I search those motor and controller part numbers I get Leadshine data sheets. Those specs indicate they still make 4NM @900rpm or about 566oz-in which is twice the torque of my existing steppers. I’m having a hard time letting go of leadscrew accuracy at my desired speeds.

As far as the rabbit hole, you’ve probably gathered I don’t shy away from fabrication and machining. I’m still pretty well connected from my professional life and have a close friend with machines in his business that could grind the mounting rail mounting surfaces on new steel beams to tolerances well beyond whats needed. I value my shop space and machine performance much more than a few hundred bucks, and I like the journey.

Best,
Kelly

7

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 18, 2023, 17:11:47 pm »

........Some (many) regulators 'relieve' excess pressure.  If it's a good one, it'll keep the pressure constant within a couple of PSI regardless of whether it's being extended or compressed.  In this particular case, a very small regulator seems to be more 'sensitive' than a big one would be.

Another solution to help mitigate that issue would be to use a cylinder much longer than the required stroke.  I didn't find that to be necessary. Lloyd

Since I'm already at 12" a much longer cylinder wouldn't be very practical, but simply running a small line to a remote rervoir that was large compared to the swept volume of the cylinder would make any pressure change quite small and make it zero air consumption. Since I only need to counterbalance maybe 20lb, that could easily be done with a 3/4" bore x 12" stroke cylinder. (double acting would make it package better). That would be inexpensive to the tune of like $30-$40. I'll keep that one in my back pocket if needed. Thanks for the suggestion.

Best,
Kelly

8

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 18, 2023, 12:56:49 pm »

…….So, if it's too heavy, counterbalance it with a small air cylinder + regulator that has a stroke just longer than the Z travel.  Our older (of 2) ShopSabre routers has a heavy spindle, and uses a 1" cylinder to balance it, so the stepper is only working against inertia and cutting forces, not weight.

Just thinking about this Lloyd, how are you maintaining the cylinder pressure/counterbalance force throughout the stroke? -In my case 12” of stroke. I can certainly see how the regulator does so initially and as the cylinder volume expands, but what eliminates the charge from being compressed and pressure/force increasing on the return stroke?

.......Kelly, Before you pull the trigger, there are some things to know about the motion control options open to you.............

Not going to buy anything just yet. There are a mind-numbing number of options as far as motors and drives and I've been reading up and learning (a lot). The R&P drive does keep economical steppers in the sweet spot of their performance, so I understand why the manufacturer took the approach they did for the niche their product offering serves.

I have an extra stepper from the 4th axis. It’s the same as the other three. I’m going to finish up the Z with that stepepr and experiment with speed and acceleration settings to see how fast I can actuate it without lost steps, maybe in both horizontal and vertical positions so I can see if my inertial calcs are correct. From my reading, manufacturers recommend keeping the inertial load <10x the rotor inertia, and <4x for high speed/performance systems.

I have a suspicion that the X-Axis could become the limiting factor on speed. So, to test that premise, I think I’ll just replace the router in my machine as it presently sits with a mass that brings it to approximately the same entire mass as my new Z assembly and do the same test with speed and accelerations settings and see what performance can be achieved with the existing hardware.
Might be good enough. We shall see.

I still need to raise the gantry and my may go ahead and take your advice on measuring beam deflection, but I can tell you with relative certainty, the two biggest culprits in the (poor) rigidity and deflection of my present machine are the four corner posts (which are terrible), and the track wheels. I can literally feel the posts deflect (a lot) in the Y direction under inertially induced loading as the machine runs so I’m sure they also deflect under load and were major contributors to the waviness you saw when I machined the decorative ribs in polycarbonate air cleaner lid. Those flimsy strap type posts are also mounted to a 16 gauge steel skirt on the plasma table which also deflects.

I’ll make a tubular steel subframe weldment and stout corner posts to remedy this and am already committed to replacing the wheels with linear rail.

Best,
Kelly

9

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 17, 2023, 16:17:30 pm »

…..It’s not a 38mm lead acme screw, it’s T8 2\4\8 mm pitch or a 3\8 12 something like that. I had a look in the packing list but the pitch is not mentioned. Probably 2 mm.

Wow, I’ve been mistaken about this all along and somehow had it incorrectly measured to be much higher lead. 1 revolution indeed produces 8mm of Z motion or lead. This is actually good news because it’s very near the lead of the 5mm or 10mm ball screws I have. The bad news is the new Z axis is quite a bit heavier but its probably no worse off than the X-Axis as far as required stepper torque.

15 revs a second is 900 rpm I doubt that you’ll have much torque at all.

I’ve been surfing around on a few linear motion manufacturer's sites that seem to have decent tech info available online for their products just to get a sense of the art of the possible.

https://www.anaheimautomation.com/marketing/stepper/high-torque.php

The products and info at this site seem to be representative. A plain Jane NEMA 23 is $69 but as you have mentioned, drops from 270oz-in full torque to 25oz-in at 15 revs/sec. In the attachment below I pasted the curve for the best higher torque NEM23 they offer in this regard. It drops to ~80oz-in @ 15revs/sec and costs $179. By comparison, their plain Jane NEMA 34 is still making 380 oz-in @15revs/sec and costs about the same. There is a lot of info left out about the driver and nature of the corresponding drive scheme, but if I’m going to build a new controller, this is why I was thinking I should quit noodling it, just buy 34s, and enjoy very high torque in the more usual speed regimes.

….You have been using the millright settings with is good for the unmodified machine, I did the calcs for X and Y (couldn't find the Z axis pitch) and at the quoted speeds the motors are running around 270 rpm at 300 rpm is full torque and it drops fairly fast after that.

…..The Accel and decel are governed by the jerk control setting, this should be ok though.

OK, jerk control. That’s yet another new one for me. Where is that at? or is it a non-grbl feature?

Just as fyi attached pdf are my present machine settings and what is reported in the console dialogue when I connect to the controller. I don’t understand the settings versus what I have measured for the R & P drive and Z acme screw.

Somewhere I got this information:

MegaV Stepper Motor Specs:
NEMA 23 frame stepper motor
Total Motor Torque: 270 ounce/inch
Digital Stepper Driver Max Amperage: 4 Amps/phase @ 48Vdc
Default settings for Mega V:
$100=57.288 X steps/mm   3200 steps/rev
$101=57.288 Y steps/mm   3200 steps/rev
$102=200.000 Z steps/mm  1600 steps/rev

Comparing what I have measured for XY&Z displacement per revolution, and looking at the GRBL GUI, I confirmed the stepper drivers must indeed be set at 16 microsteps on X&Y, and the Z driver at 8.

It also means the X&Y Steppers are running at approximately 90rpm for 5000mm.min target speed, and the Z would need to turn 625 rpm for same speed so required Z speed is evidently much less.

Where is the stepper driver microstepping setting and how is it changed? Is it software or DIP switch settings on the driver hardware?
So I connected to my controller just to see if I could alter the Z axis resolution. I typed $102=100 and tried to jog it .5”, expecting it to travel .25” and it did. So if I make the appropriate adjustment to $132 Zmax travel, it appears I should be able to accommodate my new Z axis with the existing machine. Same goes for installing ball screws on X&Y if the steppers can handle it. Light bulb is may be turning on.

Best,
Kelly

10

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 17, 2023, 01:07:30 am »

…..I’m thinking that the Z axis is heavier than the old assembly, and if I recall correctly

It is heavier. So is the router. I’ll weigh it, but seems to me like the torque required to develop the same axial force on a 5mm ball screw, must be much less than the 38mm lead acme screw that is presently in the machine……..Like in the range of 38/5 = 7.6x less right? So even if the Z/router is twice as heavy, that leaves quite a bit of margin for reduction in stepper torque at higher speed, would it not?

……..your motors were 370-400 oz/in,

They list them as 270oz/in.

you can get Nema23 4 amp (560 oz/in) motors that would bolt on I have one on my lathe X axis and a Nema 24 4 amp on the Z, they are just longer.

I’ve been assessing torque at 15rev/sec, but the only time I’d ever be at that speed is cutting foam and as you have noted, this may be more easily handled with acceleration setting which as you’ll see immediately below, may be target rich territory.

If you use the original motors then you may have to back off the GRBL Acceleration values. You can change these values by using one of the many Gcode senders, if your not familiar with the process (there are plenty of examples on youtube) then GRBLaser has a very easy to use GUI to do this as well.

I have a confession. I’ve been using GRBL Machine for over a year now. All of the dialogue boxes have been expanded and I forgot the settings/parameters were even down there (see atatched). Apparently the settings have been the condition for the last year+. What would be a reasonable acceleration setting and does it control spool up & down? Meaning will it control both the rate it decelerates and the rate it accelerates in a 180 degree return direction?

With the extra height and added weight  there will be a greater turning moment on the Y axis assembly (and the beams)

I would only be cutting foam with large Z extension so not much of a challenge there. I’d raise the bed or install a platform for hard materials so the extension would be minimal. I think it will be quite stiff in the first few inches of travel, at least compared to my present machine. The centerline distance from the router collet to the X-axis bearings is only ½” greater than my present machine. Considering the new router motor is .78” bigger in diameter and the ball screw ~.25” bigger, I thought I was doing pretty well with that.

The linear rails will add some stiffness when bolted to the aluminum extrusions, I don’t know if this would be enough though.

This may become a non-issue if I sell the old machine and replace the beams.

long unsupported sections of ballscrew tend to whip about at high rpm. To some degree this can be mitigated by using a rotating ballnut and putting the ballscrew under tension you need a heavier built frame to do this though.

The unsupported section can never be greater than 30”. I could be wrong but sure seems like a 20mm ball screw should be pretty stout and stable below <1000rpm.?

ps. I just use the windows built in app snipping tool to take shots of parts of the screen.

Thanks Dave. I thought there was way to capture the entire console dialogue. Really appreciate your input.

Best,
Kelly

11

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 15, 2023, 14:43:16 pm »

I bought an ER16 collet adapter and a cheap set of collets. Not ideal as far as runnout I'm sure but I only did so to accomodate the use of drill bits. I suppose in a pinch it could be used for a 3/8" shank cutter. The two main reasons I wanted 1/2" shank is of course sturdier bits but I also have a large collection of contour cutters, such as vee, coves, round overs, etc, which can be useful in my lost foam pattern cutting in fast 2.5D as opposed to having to cut them in a slower 3D routine with smaller ball nose bits.

My Z-axis new hardware is pretty close to done and I'm very happy with it. I'm a bit stuck on the overall project right now trying to decide if just sell my present machine and replace it with my own build. It appears I'll need to replace the controller to accomodate the the new Z ball screw since I dont have access to the OE controller settings. If I could convince myself, that I could get the desired X&Y speed with 5mm ball screws and Nema 23 steppers on X & Y, I'd do so. At that point there's not much left of the old machine and I may as well just replace the beams, build a new controller, sell my old machine and be way better off in both economics and machine quality.

I went back and re-read Dave Benson's earlier posts in this thread regarding the risk of overcapitalizing such a hobby machine, drivers, and steppers. The rub is, if stepper torque really starts to suffer above 300rpm, I'm 2x-3x short of myXY speed goal. However, 5mm BS should require 10x less torque, for a given inertial mass and cutting load. So seems like itshould work with good drivers.

I also noted Dragonfly's earlier post that he has used 5mm lead BSs with Nema 23s without issue albiet somewhat under my speed goals.

I'm just a bit out of my element on the subject machine controller and drive electronics, but am tryng not to let not knowing what I'm doing get in the way of making progress

Best,
Kelly

12

CamBam help (General usage) / Copy/Print Console Dialogue GRBL Machine

« on: March 14, 2023, 22:21:32 pm »

I knew how at one point because I have pdf copies of my own console dialogue, but I'll be darned if I can remember how to copy or print the console dialogue from GRBL Machine Plug In. I searched (and searched) and found where I asked the question on teh second to last post at the GRBL Machine plug in thread.............. but I cannot find the answer. Having a brain cramp!

Best,
Kelly

13

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 14, 2023, 01:09:10 am »

PC690?  I did a lot of work with those before switching finally to the 3 phase liquid cooled spindles.  I burned up more than a couple of those PC690s running in aluminum.

Yes indeed. I have a few of 690s too. I also have quite a few of it's big brother. I doubt my 690s will see too difficult of duty with me. My big envelop needs are foam cutting and that's like running unloaded. After being stuck at 1/4", I do look forward to the 1/2" collet and the additonal power cant hurt. I did buy a Super PiD for speed control and CAM interface and my occassional harder materials......but I'm never more than a new router mount casting away from a spindle.

Best,
Kelly

14

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 13, 2023, 22:08:31 pm »

More Pictures

Best,
K

15

Members Machines / Re: Contemplating some upgrades to my CNC Router

« on: March 13, 2023, 22:04:59 pm »

I've started on my Machine upgrades. Increasing the Z-Axis travel from 4" to 12". Of course, I had to incorporate some lost foam castings....because that's what I do  . 20mm Linear Rails, 16mm Ball Screw. From the attached pictures, all three axis will be converted to 20mm linear rail. If you look back through the thread, it's quite an improvement to my existing machine hardware.

In the pictures I show retaining the rack and pinion drive on X & Y but for +$150 I can convert the X & Y axis to 20mm ball screws. If so, at this point, the only thing left from the original machine will be the steppers, controller and extruded aluminum beams. I'm having evil thoughts of just selling my machine and upgrading those too. I'd have a a much better more rigid machine and probably money in my pocket from the sale of old machine.

Glad the site is back in good health.

Best,
Kelly