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Author Topic: N00b - DRO innacurate / calibration  (Read 861 times)

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N00b - DRO innacurate / calibration
« on: April 05, 2020, 06:18:43 PM »
Hey, I'm new to CNC and the forum. I have a 2030/3040 CNC router hooked up to an old pc tower with windows XP. My business partner purchased this little setup in a job lot on eBay and there is a bunch of extra boards and stepper motors in a box, I have no idea what any of it is so I will probably be asking questions about all of that at a later stage. The lot has been sat in the workshop for years, we never touched it and said partner left the business last year. What with the current lockdown situation I figured it would be great fun to get this little machine up and running  :o
The learning curve has been steep! I have never had anything to with CNC until last week, I am a TIG welder. Never heard of Mach3 and I've got a basic level of CAD experience. So, I have managed to get up to speed with CAM in Fusion, created g-code, run it through Mach and I now have an engraving of my logo in a piece of ply. I was pretty chuffed with myself to be fair. But it hasn't been without trouble, I've pulled what little hair still grows on my head more than once over.

Right now my problem is with the axis' being inaccurate. Just to re-iterate, the CNC is the bog-standard cheapo thing off eBay, the controller is a "T-D 3 axis controller" with the JP-328C board, Windows XP.
So I have gone through the calibration and got my steps per kinda sorted etc. The numbers there are:
G's - 0.00509. Pulse. 5 Dir - 1
x- Steps - 398.5. Vel - 1000. Acc - 50.
y- 540 - 1000 - 50
z- cannot get it anywhere near

Basically it won't stay accurate. I run my programme and at the end when it goes back to zero it's in a completely different place and most of the time it hits the stop and the motor freaks out. If I lay a ruler on the x-axis and run up and down the bed, each time it loses or gains a few mm. Same on the Y and the Z is just all over the place.
I have no idea what it could be and I can't seem to return any results on my searches... Please help.
Re: N00b - DRO innacurate / calibration
« Reply #1 on: April 05, 2020, 10:57:38 PM »
Hi,
your steppers are 'losing steps'. That means that at the speed they are being asked to run the torque
of the steppers is so low that ocassionally it misses a step or two.

It may be that you are demanding that the steppers try to go too fast, all steppers lose torque as speed increases,
consequently losing steps is less of a problem at low speeds than high.

It may also be that you have a low voltage (24V) for the stepper drivers and/or stepper drivers that can only handle
low voltages which make the 'losing steps' problem worse.

What drivers do you have?
What voltage power supply to the drivers?
What are the specs of the steppers, the inductance particularly?

Craig
My wife left with my best friend...
     and I miss him!
Re: N00b - DRO innacurate / calibration
« Reply #2 on: April 06, 2020, 06:41:11 AM »
Hey Craig.
Thanks so much for your reply. Reducing the velocity has helped the x-axis, it runs pretty accurately now. I can't get my head around the y-axis, though. I set it to run 200mm in the axis calibration widget, it runs 208mm, make the advised adjustment. set it to run -200mm and it runs 190 ish. Just end up going round in circles.

I don't know the answer to any of your three questions... I didn't get any paperwork in the sale.
Drivers? The standard driver in Mach3...
Voltage to drivers, do I need to get my voltmeter out?
Stepper specs? This is the number on it 57HD-15S
Re: N00b - DRO innacurate / calibration
« Reply #3 on: April 06, 2020, 06:56:16 AM »
Hi,
without information about your machine and/or the components that make it up I can't tell whether
its plain faulty or just trying to operate beyond its limits.

All I can tell you from 57HD-15S is that its a NEMA 23 sized motor, what I really want to know is its inductance. Inductance
is a good figure of merit that will give you an indication how it will perform at speed.

The Chinese (and others) are famous for producing high torque stepper motors but with really high inductance so they
crap out at speed. They make and sell them because they are cheap and most first time buyers don't know any better.

If I had to guess I would say you have med-high inductance steppers (6-12mH) and 24V drivers, they will work OK
but very slowly only.

If you want to make your machine work properly get low inductance motors and high voltage drivers.
In 23 size look for 1-2mH, 1mH preferred and reject anything over 2mH. You want 80V drivers and an 80V, prefereably
transformer/rectifier type 80V DC supply.

Craig

My wife left with my best friend...
     and I miss him!
Re: N00b - DRO innacurate / calibration
« Reply #4 on: April 06, 2020, 11:39:10 AM »
OK, understood. Thanks again!
I mentioned in my first post that I have a box full of stuff and I don't really know what most of it is. If you think I would be better off asking these questions on a non-Mach forum, please point me to your recommendation.

There are the stepper motors on the left, 60BYGH301B 31,Nm. A bunch of limit switches and a Mach3 manual control box
The boards, three of the same: Mach3 interface board BL-Mach-v1.1 D302. The one in packaging: DDMMV2.1
The two aluminium boxes. Neither of them has any kind of identification on them as to what they are. They do have information about the inputs and outputs.
The boxes with the vents. One with the lead coming out of it: Sunpower SP-240-24. The other one: AC->DC S-120-24

I can look the majority of it up, but its just those two aluminium boxes with no ID I really need help with.

Would you suggest I have a go at swapping out these motors?
Re: N00b - DRO innacurate / calibration
« Reply #5 on: April 06, 2020, 12:41:13 PM »
One thing I  have noticed when moving the table around is that you can hear the motor bug out occasionally. I was wondering if the pulsing from the computer could have anything to do with the axis' going out of calibration?
Re: N00b - DRO innacurate / calibration
« Reply #6 on: April 06, 2020, 04:23:45 PM »
Hi,

Quote
One thing I  have noticed when moving the table around is that you can hear the motor bug out occasionally. I was wondering if the pulsing from the computer could have anything to do with the axis' going out of calibration?

Very highly likely.

Craig
My wife left with my best friend...
     and I miss him!
Re: N00b - DRO innacurate / calibration
« Reply #7 on: April 08, 2020, 04:53:37 AM »
So I just wanted to get this machine up and running for a bit of fun, but it is rapidly turning into this huge thing and I'm not sure I should be jumping into this project, apart from the fact I just spent $170 on Mach3...

Please remember once again that I have no clue what I'm doing.
Can that T-D 3 Axis controller be replaced by the DDMMV2.1 and Mach3 Interface Boards? Or will I need some stepper drives on top?
I figured those two board would let me use a laptop with XP on it, but when I run the driver test the graph is just all black, and nothing happens with the 'special driver'. I saw in a different thread something about a smooth stepper board?

kinda regretting this a bit now but I have laid out the cash so I had better make use of it...

Offline Tweakie.CNC

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Re: N00b - DRO innacurate / calibration
« Reply #8 on: April 09, 2020, 01:22:23 AM »
Hi Burf86,

My suggestion is that you get your existing T-D controller running correctly with Mach3 before embarking on buying new stuff. You will, however, need a 32bit PC with parallel port (not laptop) and the LPT port must output the 5 Volt TTL standard not the newer 3.3 Volt TTL standard. WinXP would be a good OS to use.
Unfortunately such computers are now becoming rare and perhaps hard to get.

If you attach your <your profile> .xml file (Typically Mach3Mill.xml) found in your Mach3 folder (you need to rename it to burf.xml as all attachments require a unique name) this file contains all your settings and we can check them and hopefully advise on any settings that may need to be changed.

Tweakie.
KEEP SAFE !
Re: N00b - DRO innacurate / calibration
« Reply #9 on: April 09, 2020, 04:18:10 AM »
Thanks for the info Tweakie and Craig.
The PC tower is pretty old, and this router has been running off of it before it came into my possession. There is wood dust all over the router etc.
So here is the Mach profile you requested, and a couple of extra pics just to show my setup, perhaps it will shed some light...?