Thread: Chris's 2nd Build "Big K4huna"

Square root of the inductance in mH times 32

34H2120-60-4A

sqrt 6.2 = 2.49 x 32 = 79.68 So 80v should do it

Of course you will need drivers capable of 80v and 6 amps too.

Are you sure these are the motors you need?

Greg

Originally Posted by Greolt

Square root of the inductance in mH times 32

34H2120-60-4A

sqrt 6.2 = 2.49 x 32 = 79.68 So 80v should do it

Of course you will need drivers capable of 80v and 6 amps too.

Are you sure these are the motors you need?

Greg

Is there a better one there that you would recomend greg?

That is the one MS-Motor put me on, I just gave them some specs and they told me that one.

Going from what you said I would gather 34H2120-85-4A would be a better option at

40V, 8.5 Amps each.


Best power supply I can find would be this one

KL-320-36 36V/8.8A
110V/220V $59.95USD

Only problem is I need 3 of them and a smaller one for the Nema 24 motor. Is this the best option as I cant find many in the 36-42V range.

A lot of guys I know use meths as a cutting fluid sprayed from a pump action bottle
or you could try a old windscreen washer system...

Originally Posted by blue^ray

Is there a better one there that you would recomend greg?

That is the one MS-Motor put me on, I just gave them some specs and they told me that one.

Chris

I would not pretend to be able to recommend a motor for your application.

I have very little idea of the machine you are building. Size, weight, drive method, frictional losses, speed expected, etc.

Even if I did know all that I would still be guessing.

I do know however that many builders fall for the "bigger must be better" trap regarding motor sizes. There are many cases when smaller is better.

If you have done the research and decided what you need then that is great, go for it.

If not then this would be a starting point,

https://www.geckodrive.com/upload/Step_motor_basics.pdf

Another good read. Not all to do with your question but contains a lot you need to know,

http://www.cnczone.com/forums/showthread.php?t=52090

Greg

Originally Posted by Greolt

I do know however that many builders fall for the "bigger must be better" trap regarding motor sizes. There are many cases when smaller is better.

I know the 1160oz-in motors would be overkill but I might as well grab them as the Nema 24's which I would have prefered cut out at 495 oz-in.

The Gantry I am estimating to be 40-50kg with everything attached.

2x Rails = 5kg ea. (weighed)
1x Gantry Aluminium Profile = 17kg (from spec sheet)
4x slide trucks = ~ 1kg all up (guess)
Spindle = 4.5kg (weighed)
Z axis = ~9kg (guess)
2x Nema 34 and 1x Nema 24 stepper motor = 10KG total atleast.
+ aluminium side plates and all the other stuff.

Lets say 70kg tops

The motors will be on a 3:1 Reduction, in your opinion would 425's be more than adequate? I have been looking at the 4 axis kit from Xyoltex but the price is a bit more if I go for the more powerful motors.

BTW about the amount of volts for the steppers caculation does that mean the stepper motors from Xyoltex can be run on 40-50v as I could not find a Nema 23 or 24 motor which had a ideal voltage of 24, smallest was around 44V.


Ms-Motor can do the PSU's for 33USD, 36V, 8.8Amp

(OK for 34H2120-85-4A and A-320-36 power supply
36V is enough for your speed?)


Got this reply from ms-motor when I asked about the other motors.

My Gecko 201 Drivers are on their way, and also my Rack and Pinion is on its way.

Its about time on the R&P

R&P's and Gecko Drives have arrived.

The Gecko 251 is bigger than I pictured.


Just waiting on some motors from MS-Motors, going to go with some ~900oz-in motors as they are smaller and will not have the problem of clearance like the bigger 1200oz-in.

95mm length compared to 115mm length. Running dual X axis motors on a 70KG max gantry with a 4:1 ratio I dont think it will have a problem, if it does I will just have to add a larger reduction ratio.


With the Pulleys would a XL belt be more than good enough? There would be dual belts on the X axis (Y axis has a 3:1 reduction gear). The Belt is around 8mm wide.

Belts are just for the reduction, it is driven by R&P.

Hello Chris

I think you need to check the loading capacity and breaking strain of your belts, you might be sailing close to the wind with 8mm wide belts, how hard is it if fit wider belts to the machine now if the belt width is to narrow?

Ed

Originally Posted by appiwood

Hello Chris

I think you need to check the loading capacity and breaking strain of your belts, you might be sailing close to the wind with 8mm wide belts, how hard is it if fit wider belts to the machine now if the belt width is to narrow?

Ed

ah well, ill give it a go, they are pretty strong. Ie. I could hang off from a single belt and it will stretch but I dont think it would snap.

If there are problems it would be easy to change the pulleys and belt width.


Steel ETA is thursday so hopefully I can get some work done.

Finally got some pictures.

Looking to see if I can get someone to mill the whole top flat but I doubt anyone can do anything so big. So I will probbaly just put a piece of MDF on there and plane it.

Measured like 50 times before welding anything.

Slowly got better at welding hence the picture.

Hi Chris
Great work.
There are ways to get the top flat without planing the top. Part of the problem of planing the top is that the cutter will probably not reach the outer edges.
You can either shim from undeneath or use a push/pull fixing method.
Do not do this until you have the machine on a base and most thing finished else you will have to repeat it later.

Originally Posted by rodm

Hi Chris
Great work.
There are ways to get the top flat without planing the top. Part of the problem of planing the top is that the cutter will probably not reach the outer edges.
You can either shim from undeneath or use a push/pull fixing method.
Do not do this until you have the machine on a base and most thing finished else you will have to repeat it later.

I made it to cut a full sheet 2400x1200, it is able to cut over 1200mm and just over 2400. So I could plane the whole sheet of MDF so that there are no lips. The machine is 1550x2600 (that frame there) A little bit wide but I just wanted to be able to cut right to the edge. It is allowing the Z axis carriage to be upto 20cm long.


Whats this push pull method you are talking about?

Overall once welded up it should be pretty accurate, I will be getting the aluminium cut by a water jet mob close to my dads work, apparently there are 3 businesses around the area that do waterjet cutting, so im sure I can get it cut by one of them.


Also I will be ordering that 120x80 heavy aluminium on the 5th, failed to find a substitute, and will be using 16mm and 20mm plate instead of 12mm for the gantry sides.

I would be happy with 1000mm/min

Hi Chris,
Impressive specs.
The push/pull is where a grub screw is used to push the table up and then a socket head screw pulls it down. You place one of each about 10mm apart from each other and then adjust it up or down to get the table flat. These are placed on a grid over your table and typically I have them at about 200 grid spacing depending on the thichness of the table top. In an aluminum table top you just tap into the ally for the grub screw then tap into the frame below for the socket head screw. The socket head screw is drilled through the table top and counterbored so the head is below the surface.

In MDF tops you use a "knock down" screw in insert. They have a 6mm thread internal as well as a hex to screw the insert in. See two types of them in the attached photos. Carbatec and Timbecon carry these and you should be able to get them from other suppliers. This would be used for the grub screw and the socket head screw is tapped into the frame underneath.

I have used this method for the last five machines and it works very well. When you adjust the table top you fix a dial gauge from the gantry and just zero each point making sure you do not use gorilla force on the socket head screw else you will get small dips between the contact points.