Is this Probotix kit ok?

[slashmaster]

I already have an X3 mill and am seriously thinking about either this kit http://www.probotix.com/3_axis_stepp...or_driver_kit/
or this kit with 2 bigger steppers http://www.probotix.com/index.php?vi...&product_id=48 I know it's not the best but is it worth it for what it is? Has anyone here had problems with Probotix?

[hoss2006]

Sure the price looks enticing but but it's not a good match.
They use a smaller motor for the Z which would benefit a cnc router but not a mill.
If you can't spend the money for the 6050's or Geckos, look at the cheap Keling packages.
Versus the Probotix, it's bipolar vs unipolar, it's 36V vs 24V and the motors are bigger for $20 more.
Not as good as what been suggested in the past (gecko) just better than the Probotix.
Hoss

[slashmaster]

Thanks Hoss! I was trying to figure out why they would have kits with with a lower powered Z axis. Yes the Kelling kits do look like better deals when I compare the most similar kits from each company. Looks like what you pointed out is what I want. But I plan on hooking to the 10 thread per inch leadscrews I have now so I was thinking I need more speed than torque right? I thought I read somewhere Unipolar was better for speed and bipolar better for torque. Does an extra 12 volts make up for that? I know you're running 270 oz-in steppers, are you also running these same kl-4030 drivers and that same 6 axis breakout board?

Oh yeah, one more thing. What shall I get to connect the shafts to the leadscrews?

[hoss2006]

You need to look at current and inductance when matching a motor to the driver.
You want to get a power supply that equals the Voltage of the driver, more voltage = more power/speed.
the formula for getting the motor voltage is square root of the inductance (mH) times 32.
The kl-4030 is rated to 40V and 3.0 Amps. A perfect motor would be one that needs as close to 3.0 Amps as possible without going over
and as close to 40 volts as possible without going under.
You can lower the Amps on the driver but you're missing out on potential.
The KL23H2100-35-4B 318 oz-in seem to be a good compromise, only off .5 Amps and 13 Volts from perfect.

Flexible couplings (spiders) can be had at Keling, McMaster Carr and SDP/SI to name a few.

[mcphill]

Sure the price looks enticing but but it's not a good match.
They use a smaller motor for the Z which would benefit a cnc router but not a mill.
If you can't spend the money for the 6050's or Geckos, look at the cheap Keling packages.
Versus the Probotix, it's bipolar vs unipolar, it's 36V vs 24V and the motors are bigger for $20 more.
Not as good as what been suggested in the past (gecko) just better than the Probotix.
Hoss

Not sure where you are getting your information. It looks like you are quoting Probotix's minimum specs. They have 32 V and 40 V power supplies available as upgrades (not just 24V) and they support both Unipolar and Bipolar motors - the customer's choice. They also have 400 in-Oz motors available. Any combination of motors, drives, power supplies is available - send them an e-mail and I am sure they would be happy to put together the combination of parts to make you happy. Not saying they are the best choice or not, but they have options far beyond the "low spec" ones you imply in your post.

[hoss2006]

Not sure where you are getting your information. It looks like you are quoting Probotix's minimum specs. They have 32 V and 40 V power supplies available as upgrades (not just 24V) and they support both Unipolar and Bipolar motors - the customer's choice. They also have 400 in-Oz motors available. Any combination of motors, drives, power supplies is available - send them an e-mail and I am sure they would be happy to put together the combination of parts to make you happy. Not saying they are the best choice or not, but they have options far beyond the "low spec" ones you imply in your post.

I'm getting my information from the links provided by slashmaster for Unipolar driver kits so I'm not implying anything, it's black and white.
The "low spec" is the price for the base kit which is only $30 less than Kelings.
Upgrading the probotix to 40V adds $90.
He can upgrade the motors, drivers and power supply at probotix to almost equal the keling kit specs and it would only cost $489.99 versus kelings $379.
I'm sure probotix would be happy to put together the kit for him but it just isn't the best deal.
Hoss

[Torchhead]

Before you write the check:

Gecko 540 Bipolar 4 axis stepper controller with microstepping and anti-resonance. Integrated BOB (Breakout Board)
HomeShopCNC 620 oz-in 23 frame high torque motors (perfect match to Gecko 540 with 3.5A windings, 48VDC). Same frame as RS23-570 but rated at 3.5A per winding and 620 oz-in. Low inductance.
48V 8.3 A power supply (two 24V 8.3 supplies wired in series) from: http://www.mpja.com/prodinfo.asp?number=16855+PS ($19.95 each)

This combo will run circles around the Probotix unit even the upgraded one

With steppers, voltage gives you RPM, current gives you torque. More volts means you can spin the leadscrews faster.

I know the goal is to save money but if you get something that won't work whatever you pay is too much!

TOM Caudle
www.CandCNC.com
Totally Modular CNC Electronics.

[ger21]

Before you write the check:

HomeShopCNC 620 oz-in 23 frame high torque motors (perfect match to Gecko 540 with 3.5A windings, 48VDC). Same frame as RS23-570 but rated at 3.5A per winding and 620 oz-in. Low inductance.

Is this a new item they're offering? I don't see it on their website??

[Torchhead]

I noticed it was not on their website. I have been buying them from HSCNC for several months. I worked with the owner to have the motors optimized for the G250 series drives. We use the G251 in our table top controllers and the 620 oz-in gives some impressive performance with the new small Gecko's.

Maybe I better keep my mouth shut. I don't want there to be a run on their motors and leave me with no immediate source. We have packaged the 620's with our BladeRunner Dragon-Cut and there have been a lot of 4 X 4 and 4 X 8 plasma and router tables built. Sometimes I forget that a few short years ago a 300 oz-in motor was a 34 frame and expensive and now I can buy a 300 oz-in that is no bigger than the 80 oz-in we used to get!

If you want some of the 620's call Ric at HSCNC and tell him "Tom Said to call" He has specs on the motors. Interesting side note: They are 8 wire motors and designed to run at 3.5A in series or 7A in parallel so they work with either sizes of Gecko drives. They do run pretty hot in parallel mode if they are not bolted to a plate.

TOM Caudle
www.CandCNC.com

[HackMax]

Before you write the check:

Gecko 540 Bipolar 4 axis stepper controller with microstepping and anti-resonance. Integrated BOB (Breakout Board)
HomeShopCNC 620 oz-in 23 frame high torque motors (perfect match to Gecko 540 with 3.5A windings, 48VDC). Same frame as RS23-570 but rated at 3.5A per winding and 620 oz-in. Low inductance.
48V 8.3 A power supply (two 24V 8.3 supplies wired in series) from: http://www.mpja.com/prodinfo.asp?number=16855+PS ($19.95 each)

This combo will run circles around the Probotix unit even the upgraded one

With steppers, voltage gives you RPM, current gives you torque. More volts means you can spin the leadscrews faster.

I know the goal is to save money but if you get something that won't work whatever you pay is too much!

TOM Caudle
www.CandCNC.com
Totally Modular CNC Electronics.

I've been looking to increase my voltage on the z axis as cheap as I can and those power supplies look interesting but I have a question about them. How do you wire these in series? I'm familiar with wiring transformers in series but whole power supplies I'm not.

Thanks,

Rick

[escott76]

I've been looking to increase my voltage on the z axis as cheap as I can and those power supplies look interesting but I have a question about them. How do you wire these in series? I'm familiar with wiring transformers in series but whole power supplies I'm not.

Thanks,

Rick

Some power supplies can be wired in series, some cannot. Generally check the manufacturers specs to see if they can be. Of course this becomes harder with surplus supplies that may have custom or non-existent part numbers.

[Torchhead]

Consider a power supply to be a two teminal battery. It has a + and - Output. It can be wired in series to ANY other DC power supply (even different voltage, different max current) AS long as the - output is NOT connected to the chassis ground. You wire them like batteries in series + to - and the outputs from the ends. [( - + - +) A lot of cheap computer supplies have their ground tied to chassis and AC safety ground via the AC Cord so they won't work without modification but commercial switching supplies (like the ones I listed) do not assume you want - to be earth ground.

The AC side gets tied in parallel and the + and - output terminals tied in series. Each supply regulates it's part of the voltage so in theory you can hang different voltages in series and each supply regulates the voltage across it's terminals.

Since the same current (total circuit current) flows across all series components each supply has to supply the same amount of current. If you mix supplies as to current capability the max current is the smallest number in the string.

It's just not that difficult. Even if you hook them up wrong ( - + + - ) all that happens is you get the difference rather than the sum (essentially zero volts if they are the same). Nothing blows up. Just no current flow.

Now, running two regulated supplies in PARALLEL to get double the CURRENT is NOT easy and requires that the power supplies have special Master and Slave current sharing circuitry. They have to be very close to each other as to output voltage. Otherwise one will always take all the load. You can diode isolate each one and or use series "balance" resistors but it eats up power and is less than truely balanced.

There is a lot of FUD about power supplies and how to size them and what kind is best and what you can and cannot do. Thing is, that magnetics and power conversion is the heavy lifting part of electronics and runs under it's own set of physics and rules. Someone posts something as fact, it gets quoted (sometimes incompletely) and turns into "rules".

TOM Caudle
www.CandCNC.com