Stepper motor kits for me requirements?

[Mindcore]

Hi, I'm a newb. My first post here.

I've built a CNC mill, a combo of MDF and extruded aluminum. Running on v-groove bearings. Table is 3' wide X 6' long, with a 6" Z axis.

It's home built, so it won't be perfect, but seems very smooth so far.

I'll be cutting hardwood and some aluminum.

I was looking at the hobbyCNC kits, and after emailing them got the response that their systems are not appropriate for my machine. Now I'm lost because that means I need to do a whoooollleee lot more learning, or come to you guys that know this stuff and ask if you have any recommendations for an all in one kit.

I've been reading the forums for a while now, and I know you guys are passionate about it, but frankly I just want to use it. Knowing which model # gives me that extra 1% is more then I need or want to know.

So, with that any ideas? have I given enough information?

Thanks

[pfred2]

I checked out that hobycnc site and while their kit may not have been optimal for you I cannot imagine it would not have worked at all.

Here are some plug it in and go setups they most likely won't turn you away from buying:
http://www.super-tech.com/root/itm.a...m-emc-geckopwr

Now if you want to make a more informed decision reading this may help:

http://www.cnczone.com/forums/attach...4&d=1107010394

TANFL you get out what you put in.

[Mindcore]

Thanks for the reply. The super-tech link is sum $2000.00 more then the hobbyCNC, there in lies the problem I guess?

[judleroy]

How about something like this? http://www.kelinginc.net/CNCNEMA23Package.html

[pfred2]

I tried to do a little research about just who, or what Keling is and never really came up with any satisfactory answers. For me the real question isn't so much how but what?

This left me a bit sour:
http://www.cnczone.com/forums/showthread.php?t=31438

We all have to decide for ourselves what the threshold of our personal comfort levels are. After seeing what I have I am still not feeling too warm or fuzzy about Keling.

I will keep them in mind the next time I need a hot water heater.
http://www.importgenius.com/shipment...nology-co.html

TANSTAAFL

[James Newton]

I'm not sure how anyone can recommend a driver without knowing what stepper motors you plan to use...

And I don't think you can pick the stepper motors until you know how much torque you need to supply and how fast you want to traverse...

Or did I miss something there?

[Mindcore]

I think you did. I'm looking for an all in one kit. Drivers and steppers that would be suitable for a machine my size that is capable of cutting hardwood and aluminum.

I'd like a decent rate, but I'm not a shop. It's a hobby I'm not charging anyone by the hour. So it doesn't need to be the fastest thing out there, but I'd like it to be faster then by hand

[MrWild]

What kind of lead screws? How many start? Thread pitch per inch? With a machine that large, you want faster rapids than a Hobby CNC kit will give. Their drives don't have enough volts. Keiling sells kits with geckos, motors and matched power supplies. Buy the G540, 381/387 steppers, and 48v power supply for the most pain free bang fr the buck kit. The parts can be bought from many suppliers besides Keiling, but the package is sound.

With the BOB an integral part of the driver set up, including a charge pump circuit, PWM motor control, 2 x outputs, 4 x inputs, and Estop, the wiring is much easier using a G540. About the best bang for the buck.

If you want faster rapids, three G203s, a 70v power supply and 600+ozin motors with five start lead screws would be a nicer but also a more involved and expensive choice. Spending the huge bucks for one of the kits shown with over $2,000 price tags is silliness. IMO

Just because one person is a little sour over an unrelated product from years ago isn't a reason to pass by a supplier. Keiling has stood by it's products and refunded/replaced with no hassle when needed. I've had nothing but good results so far with my purchases from Keiling.

[Mindcore]

Thanks for the reply. I'm using standard threaded rod at the moment, but may change after to lead screws. I don't recall the TPI at the moment, I'm thinking 14 or so?

Not sure what how many starts means.. like I said, I am really new.

I'm going to take a look at your suggestions now. thanks

[MrWild]

Lead screws come in single start, double start and five start. This means there can be a single thread (single start) that will move the nut one thread per full turn. double start or two start has two screw threads that overlap. This will move the nut two threads per full turn of the lead screw. Five start has five screw threads that overlap.

If you have single start 1/2" -10. (ten threads per inch) it will take ten turns of the lead screw to move an inch. With a two start 1/2"-10, it will move an inch in just FIVE turns. A five start moves a whole inch in just one turn.

This is important to know because stepper motors lose power the faster they spin. People have had huge speed improvements by going with multi start lead screws using the same motors because the motor has the power at low rpms to turn the screw EVEN WITH MORE TRAVEL PER REVOLUTION.

Large and/or more powerful steppers can actually have less power at higher rpm than smaller weaker ones. This is due to the size of the windings and how fast electrical current can fill the coils. So you want something that matches the entire system.

With 1/2-13 or 3/8-16, you want a motor that has more power at higher rpms and that means a smaller stepper than those monster kits for over $2k. My suggestion for a set up would be 1/2-10 two start lead screws, DumpsterCNC anti-backlash lead nuts, Gecko G540, Keiling 381/387ozin steppers (they match the G540 very well) and a 48v 7.2A power supply. This will give fair rapids for your large machine without breaking the bank. Trust me on this, I am Mr Cheap and tried to go the as inexpensive as I could route. This winds up costing much more in the end due to buying things twice or three times. If your router were 1/2 the size, you'd be okay with a cheaper set of motors, weaker power supply, and junk Chinese drives from ebay. With a good sized router like yours, weak will work, but the speed will be teeth pulling slow.

The great thing about a Gecko drive is that it holds a much better resale value if you decide you want even more power/speed and move up from a G540 to three G203s and a BOB with higher voltage power supply. Just like racing speed costs money and you don't put a lawn mower engine in a street car expecting to move faster than a snails pace. Cheap drives/motors and a large router is painful.

If you need to save bucks, look into EMC2 (free versus Mach3 ($150) for your control program. The more I play with EMC2, the more I like it.

[James Newton]

Yeah, all in one kit, I understood that. What I don't get is how you can know what size motors you need if you haven't measured the torque required to turn the lead screws on your machine...

[jschmitt]

you will not like the rapids of a 14tpi screw on a 3' x 6' machine. Also you need to consider screw whip on the 6' axis. You would be wise to consider either a belt setup or rack and pinion. I had screw whip limiting my rapids on a 48" axis with 10 tpi.