Fair enough. I can only tell you that we were testing the limits of the drive to see if it was robust enough to be put into production. We only require a lower rev of 20 but needed to run tests on an unproven component in our setting per our engineers. We were trying to reach the stall point of the motor as our approved driver would not go above 20. I did not want to run above the spec sheet. I was only stating that they can be run faster is everything is correct. I do stand corrected Ross, sorry for the misleading post.

My entire machine is running on square type rails, and they run very nicely.
But if I try to get greater speed from the motors than 600rpm, then the motors stall. I'm affraid that it might be those rather cheap chinese motors that I've got. I might save some money and get some better quality motors, perhaps even the ones from Leadshine which is pre programmed into the drives.

Hi Pete

I was referring to Kim's statement so your in the clear :)
Kim's post was just one of these "well mine's not working" statements that leaves a little too much to guesswork.

Ross

Hi Kim

Your supply voltage has an impact on this.

Ross

My setup is this.

70vdc PSU
1600oz-in motors on all axis (Longsmotor)
8x microstepping.

2010 ballscrews on x and y, 1610 ballscrew on z.

I am running same motor as before Deitech 9802 on 48 volts.
I was able to run X and Y axis to around 42m/min, but I am still using 18m/min to lower the tear and wear on pinions and rack (the rack is not perfect and I get a lot of noise on higher speeds)

Fox, mounting the spindle to the longer plate is not adequate, no manufacturer in the world does it, it was the main reason to make a new Z.
First reason is that for the same clearance you need higher gantry.
Considering that the spindle body is stiff you use its strength to stretch the Z down.
Second is that plate, spindle and bearings have smaller weight to pull up than large plate, guides and spindle.
Stiffness is the same as the bearings have constant load rating.

Here are some pictures to illustrate above statements.

MULTICAM Z AXIS
http://cnc.rs/mechmate/2011-09-27_10-29-15_163.jpg


Moving bearings VS moving rails, spindle position is a bit different as I experimented a bit but found that spindle in the middle of mount is satisfactory

http://cnc.rs/mechmate/Screenshot%20...2019.22.11.png

Also, the 90% of cutting happens while the Z i lowered all the way down.

Moving bearings has the same stiffness all the way but moving rails has lowest stiffness while lowered to do the finish cut.

I just checked the specs on the motors you are running.

I can see the phase resistance and inductance is way different than on my longsmotors.

The Deitec 9802 has a phase inductance of only 2.4mH, where mine has 22mH, and a phase resistance of only 0.65 Ohm And mine is 1.9 Ohm. I have heard before that to high a phase inductance can cause low stall speeds.

So I'm guessing that might be the trouble with my motors.

Hi Kim

Your motor wiring also impacts on keeping torque up at higher revs.
We have a habit here of wiring only one half of the coils but bipolar parallel gives the most "power" if you have 8 wires available but demands the most from your PSU. You are already high on voltage at 70V so probably little to be gained there.

I also see that you are using 1600oz-in motors.
I have been solidly whipped trying to tune large NEMA 34 size motors in the past to run at high speed. Even to the point of assuming the motor was faulty, bought another to have the weak performance of the "big" motor continue.

My only solution to stop missed steps was to use a belt reduction, this returned the power and the motor still was able to achieve the traverse speed required all be it at a higher RPM.
On my Mechmate installing a 4:1 reduction did produce a reduction in top speed over the ungeared motor so there is no free lunch.

If you are thinking about new motors probably lots of spec reading and a reread of the motors section here on the forum might be the solution.
As you are a Leadshine fan, the next level up on drivers that has the encoder feedback, the 'Easy Servo" range has the additional ability to play catch up like a servo does.

I have tested these drives and they are a very different animal even to the setup you currently have.
The heating is very low to the point of near ambient temps unless worked hard. They also manage torque differently.
In my tests a smaller 1000 oz-in motor provided far more power the larger NEMA 34 std stepper.
This is of course expensive but as I have already confessed to replacing motors randomly to fix a problem, there is nothing worse than spending more money to have the same issue remain unsolved.

Ross

I think it could be friction, weight of your machine and the motors in your case Kim. I thought you could disable the stall detection somewhere in the leadshine software.

At 1600 rpm you must be loosing torque danilo ? And for a z I see not much use at those crazy speeds ?

Kim for the motors you have, right drives would be some like Leadshine ND2282 AC80-220V 0.45-8.2A where you could use very high voltage to get some RPM from those motors.

22mH is way too much of inductance and detent torque.

Fox, I said that it was tested up to 16m/min , I use 12m/min

When you get a job to cut 100s of parts of 1000 of holes to drill having a fast Z retract counts in. Same way as XY rapids. Jogging around 2x3 meters machine is no fun at 5m/min.

For a 160 eur investment in parts and some drilling this proved to be a good investment. Detailed pictures later :)

I had the phase inductanse suspected to be the trouble...

I might save up, and get my self some servo drives from DMM-tech instead when time and money is for it. :)

Danilo I do not totally agree on your assumptions. It depends on the travel you want. I want large travel, the rails stiffen the larger plate. Yes, you move more weight, in my case less relevant with the spindle being most of it. I do not see why you would need a higher gantry ? I have 650 mm reach on my z. Standard 200 mm to spoilboard. I bet mine or yours make no difference at that distance, mine might even be stiffer, as I have rect rails, plate and spindle stiffening at that point, compared to your round rail wagon, plate spindle. But its no pissing contest, your happy with yours and I am with mine.

Thanks Danilo for the specifics on the motors.

My limited understanding is to avoid high inductance motors if you want high RPM as the back EMF becomes huge with increasing RPM.
That is how your sensor less stall detection works, it detects the rise in the back EMF and trips out on a stall.

Ross

Yes, thank you for the informations. Even though I'm not running a Mechmate anymore, and haven't been for some years now, I can still get some good info on this site.

I will think about getting some better motors some time in the future, for now I'll run at slower speeds, my machine is only 1.2x1.4m cutting area, so at 6m/min it gets to the end at an ok speed for now, But I would love to get 10m/min from it, just because I could. :)

Otherwise I'll wait until I get the $2500 for a compete set from DMM-Tech or something like that. :)

Its no contest, just raw facts.

My axis has 500mm of rails and 300mm of travel.
Moving bearings works for sheet cutting machines (160-200mm Z clearance) if you want 650mm of travel for doing foam then moving rails wins as its stiffer while all the way up and same all the way down.
Removing spoilboards or lowering it for one off jobs, I don't see it justifiable to make or use. Large clearance can be good for foam only and that then asks for a dedicated machine.
In my case I had one evening of my free time to mount and tram the new Z until new job next morning.

Can you mount a 120mm long endmill 10mm ball nose and clear a 200mm material from spoilboard without removing it?

Assuming 15 or 20mm rails are to stiffen something is just not something you can hear from any machinist or engineer. I know that debate on this was on mycncuk forum and I am not willing to participate. I tend to look at the industrial machines and use solutions that they found to work in last 30 years or so. Fact is that I have not seen a sheet router with moving plate and rails of any large manufacturer.

Danilo are you going to use bellows of some type to minimize contaminate infiltration?

Well I thought about bellows, and found a shop that custom makes them. they will limit some travel but there is a plenty of it.

Bearing pillows are easy to replace or clean and cheap and only thing to replace is a bearing, I might try felt wipers first.
The ballscrew is a bit different it needs some lubrication and should definitely be protected somehow. On the other side with a good dust collection very little dust is going to get to it.

After first couple of cuts this type of Z seems more sturdy less vibration and more clearance for everyone on a budget and for the same money as old Z.

I respectfully do not agree, but I am just trying to be a devils advocate here. I am not trying to get you up the closet, as I respect your contributions, and your experience on this forum and machine. See your quote below for instance, those are opinions.. well thought out, or motivated they may be, but subjective reasoning nevertheless.

I do for one do not think I need to built a dedicated foam cutter for my business, but I do like that I can do it with my machine when the needs comes around so often. My extended Z was not intended for milling steel at 600 mm, but wood, plastic and foam, all at relative speeds. I have all sort of weird jobs coming along, for which the extended Z gives me options, instead of restrictions.

I think I have, but I have not researched that properly I admit, fact is that none of the big manufacturers use round linears, use rack an pinion, use v-guide rails, use mdf spoilboards, use round tubular frames etc. MM has. are you using rectangular linear guides on this new machine on all your axis ? and helical rack and pinion or ballscrews ? Probably not. That's the point I was trying to make originally when things are posed as facts, it's makes everybody with an MM a bit silly.

Cause you say you live by the book of the big manufacturers : why do you not use an air drill and mount it with an offset, no need for toolchange and equal pricing and fast ?

http://i.ebayimg.com/00/s/NTc2WDEwMj...T~0X5/$_20.JPG

Your spindle ( I imagine chinese) is not intended for drilling hundred thousands of holes (speeds, torque, bearings). Or are you actually adding this Z as your second Z and sacrifice the drill spindle ( they do not cost the world)?

In fact I can, gantry height foremost determines clearance in my book/situ, not your Z. although you can move your cutter higher up then me I will agree. I can even mill 45 degrees or 90 degrees with my Z ( not with the same clearance though :) ) also somthing I will not do daily, but does come handy at weird jobs. I do not have an MM- Z by the way.

It depends on how you look at things, fact: they do stiffen things, especially with bolt holes every 50 mm... compared to a plain sheet without. But they do not offer as much as my 15 mm thick alu sides I have forming an U of my Z. I have also left room/option for putting on a front slab as well, but I think it's more then stiff enough right now.

this sentence should be with OR. My mistake.

cut 100s of parts OR 1000 of holes to drill. Someone who drills 1000 of holes everyday for sure needs an air drill or some dedicated drill.

And I would like to see a solution to fit the dust collector hose, spindle and an air drill in the mechmate car.

For a same gantry height or mount position of Z axis I can't see how it would clear the same height with position of lower bearings being the limiting factor. Do a comparison drawing like I did with spindle in up and down position and post it here I would like to see your solution.

What I say is always based not on theoretical assumptions but drawn from my personal experience on working with the machine. Maybe I just like to leave large foam work to someone with a machine more capable of doing it and earn more while cutting sheets (this is subjective). This same applies to the thread about metal routing.

I still just admire you guys that make use this for a living. It is a real expensive hobby for me. But I like to make things. I like to improve things. I think I see what both of you are saying. I will say there is never a perfect design but one that is most feasible for the individual application. Sometimes if we get out of our own way of thinking we can learn more.

As far as the adding a drill, I have looked at making a lower speed 80mm spindle for drilling and milling that could be easily swapped out when the high speed spindle is not feasible. Have not got much beyond the thinking stage but with the constraints of the Y car, this looked more appealing.

I missed this one. 5 years ago when I started to think of building a MechMate I had zero cnc real life experience. Mechmate for me was a big piece of iron, biggest machine I have ever seen and not SILLY at all.
From that time I saw and learned a lot. A MechMate is a very good startup machine for someone meaning business or a hobbyist. There are couple of proofs on forum that guys advanced to some heavier machines.

About big manufacturers... I said use "solutions", the design decisions. Not use same components, if we all had that kind of money we would not be on this forum. Every machine is a next step up in quality and value, Mechmate design for me takes the perfect all around good machine for the money. And a great experience as you will hopefully find out.

MechMate did came from improving the previous design I think... Shopbot. These days some components are more available and cheaper so we can use them to improve or build new machines for us. Not that everyone has to.


Please report back after couple of years using a MechMate and inform us if you have accomplished the "Good quality edges" on acrylic that you asked about. Thanks :)

Ok, now that all that is out of the way. Is the 1610 ballscrew preloaded?

Its standard order rolled ballscrew 50$ delivered from Aliexpress. I think it has around 0.05mm (0.002 inch) of backlash or bit more just like the other ballscrews I ordered from china. For a router perfectly acceptable.

On a mill I have two ballnuts working together to lower the backlash, loaded with a strong spring. Putting oversized balls is a simpler solution but for sure increases wear.

Good memory. Will do. My machine is supposed to make first cuts this week somewhere, reason I was looking on the forum for some answers on issues. When everything is running I will update my thread with pics (made a lot during the process-but skipped the thread updating in favor of building lately).
As I wrote I already have modified the Z as it seemed a weaker point to me, and I use a beefed up frame. But if cut quality/speed is not what I hope, I will upgrade after a year or so an make the gantry to a single beam 200 mm steel beam and use linear guides ( already have 2x3meter THK for my Y ) then it will look a lot like those major manufacturers ;) but then my frame becomes the weakspot...so yes you are never really done....soo... first things first.... :-)


I have a question for you: Is it normal that steppers make a irregular hissing sound when they are idle ( machine stands still - no movement ? ) It dissapears when moving jogging all sound fine then. I have it on all axis. Deitech 9801 motors leadshine AM882 drives. Auto tuned drives by flipping the miniswitch.

Get yourself some low inductance 600oz motors, and you should double or triple your speeds.
I've seen someone switch from 1600oz motors to 400oz motors (Nema34), and get a 5x increase in speed.

Those 1600oz motors inductance is way too high. They are far bigger motors than anyone needs on a router, and really a poor choice for a router. But since they're cheap and easily found on Ebay, I've seen many people buy them thinking bigger is better, and then find out they don't work well at all.

Is the teaser installed yet?

Installed and working, no vibrations at all on the cutter (sounds different, tone is deeper)
I also upped the feedrates a fair bit around 30% , with same motors and AM882 I managed up to 2000 RPM on the 10mm pithc ballscrew so around 20m/min rapid feedrate.

Maybe my case is not that comparable to others using BWC or similar V wheels as mine were made out two deep grove bearings, but these cheap linear bearings made a whole lot of difference for me. As four cost around 28$ thats cheaper than wheels, my gauge plate was around 40$ and the 1m of rail already mounted to aluminium carrier was around 50$.

Dust is no problem the wipers do the job I just did not oil the rails. if it wears in couple of years for 68$ I'll replace them :)

Got the vertical Z lined up in seconds.

How did you set the adjustment to tram the spindle?

Replaced the MM with this :)

http://www.cnc.rs/mechmate/Leadwell%20MCV.jpg

Preparing couple of parts for new machines.

Oh no did you sell the MM? :)

Unfortunately had no space for it any more.

But I am building a smaller one :)

looks like you don't use plywood anymore :-)

plywoon no more, but wood - under the machine. :)

Can't live without some piece of wood being the part of the machine :)

for my next transition .... from Mach3 to Linuxcnc.... Blame is on "digger' as he supplied me with one excellent piece of hardware .... Mesa 7i76E

Oh you'll like Linuxcnc, give PathPilot a go while you're at it. Nice simple interface that looks Mach3-ish

These two builds of mine might be interesting to some so here they are

2070 x 3000mm 3kw spindle
http://cnc.rs/mechmate/3kw_2070x3000.jpg


1500 x 3200mm 5.5kw spindle
http://cnc.rs/mechmate/5.5kw_1500x3200.jpg


belt drive
http://cnc.rs/mechmate/belt_drive2.jpg

Forgot one, this spindle is the real deal it just barely fit inside the Y-car

http://cnc.rs/mechmate/5.5kw_spindle_cnc_router.jpg

Nice, are you building MM's now for a living or are you seriously expanding the hobbyshed ?