Thread: Chris's First CNC Build

Hello Blueray


One other way you could brace the table is to rely on the strength of the MDF, welded steel would most likely be better but if builders can use 6mm masonite to brace timber frames then your router should be a doddle.

Before you go melting sinkers why not try and see how much force your Z system is applying, I think you might be surprised how much force is generated, I have seen one of my machines ( NEMA 23 motors, ACME screw ) cut into a high tensile 10mm bolt and the bolt came off worse than the carbide cutter,

I have attached a sign I did today, engraving tip, 35K RPM, spindle and WD40 ( slightly out of focus ).

If you are still worried about weight some seem to have luck with gas struts, just remember the heavier you make the any part of yout machine the more inertia needs to be overcome.

Ed

I'll give it a go without couterweights and see how it runs.

Worst case I can see is the bearings diging into the aluminium my main concern, or the aluminium box (1.6mm, wanted thicker but its all I could find) bends right out of shape.

I was thinking about taking the mount off the Z axis and using a belt and pulley method to drive the Z axis, K2 cnc didnt give me much to work with in terms of the mounting part of the acme leadscrew. It will remove some of the weight from the edge and counter some of it.

Hopefully I can get some motors attached tommorow and give it a little run with semi auto cnc'in, might just leave the Z axis motor off for now.

Hi Chris
Do not start doubting yourself now. Your Z axis will drive easily with a Nema23 motor - I am going to run the setup in the photo below. That is 12kg sitting there and probably around 9kg in the slide. The Nema23 motor will drive it easy.
There is a big mechanical advantage in the ballscrew (effectively a lever) so unless you way over those weights then try it first before changing anything.
Counterweights on X and Y will be of benefit in one direction only and a counterweoght on Z will just get in the way.

Ed,
Nice engraving on the ally.

Na, I know the Z axis wont have a problem, just the thought of belts and pulleys to shift some of the weight around, the ratio would remain 1:1.

Ive got all the parts here already as ive planned for my next build

The idea is to use this one to build a bigger one.

Your X axis has a large pulley so I assume you have a mechanical advantage on that axis. Y is possibly the axis you are worried about but you haven't got a motor mounted on any of the photos so hard to tell there. I imagine you could match a large and small pulley on an idler shaft and achieve a mechanical advantage if you had to.

An interesting thing about stepper motors are that they have their greatest torque at standstill. So low down revs are high torque and the power band drops off the faster they move. On a Xylotex board about 300 RPM is about all the useful speed/torque you will get.

High gearing should not be a huge problem in getting the machine running. The disadvatage of high gearing is that you loose resolution and your steppers will not reach their potential speed.

I would give it a run without modifying anything at this stage just to see what you have got.

Spot on with the Y axis, no gear down but I was going to see how it performed. I think 17 turns did the whole 70cm, where the X axis is something like 150 turns for the whole 120cm I think, I havnt played with them since I stuffed up one of the computers (now I have 3 to choose from)

Will see tommorow, ill add some pics of the motor mounted also.


If the Y axis is ever a problem I can just weld some more steel and easily give it something like 3:1 ratio. If the X axis is too slow I will just change the pulleys also.

Then your X is equivalent to about an 8mm pitch screw and the Y is 41 mm pitch. I would halve or third the Y axis but see how it runs first. It is going to be very quick on Y axis.

Hooked the router up and just moved it around manually

The 2 Flute end mill Bits I got which I was told to get just make a mess of the MDF, what type am I spose to be using?


am I spose to be using a bit like this?

[media]http://media.toolbarn.com/images/amana/454xx.jpg[/media]

I was told to buy the 2 Flute End Mill bits ages ago, like below.

[media]http://deltatool.net/resources/2flute/2fendmills.jpg[/media]

Did I stuff up and buy the wrong one or is there something I am not doing right.



Still no alu from bunnings as they are still rearranging their ????.

Hi Chris,
I use both types on MDF. Sounds a bit like your router was not on high enough speed or maybe travelling too fast over the MDF.
Show us a picture and tell how you did the cut.

Ozito full speed (number 7 I think it is)

I'll get some pics tommorow.

Pics attached.

Do you know anyone who sells the Nema 23 gear boxes? I have seen them with drives but I dont know anyone who sells them seperately. This would be the best solution in my opinion for the Y axis.

The Big bit was kinda cleaned up with the bit that is on the router, it was a flush bit and I just removed the bearing to have a play around with it.

That bit of MDF that is seperate was cut with the bit that is removed from the router, about 6 passes.

Originally Posted by blue^ray

Pics attached.

Do you know anyone who sells the Nema 23 gear boxes? I have seen them with drives but I dont know anyone who sells them seperately.

You could try MS-Motor. They sell a stepper with gearbox attached but I'm sure they would sell just the gearbox. Although if the price they've quoted me for just motors, you could afford to buy the motor/gearbox and throw the motors away

That is a pretty mean cut!

Originally Posted by snowyskiesau

You could try MS-Motor. They sell a stepper with gearbox attached but I'm sure they would sell just the gearbox. Although if the price they've quoted me for just motors, you could afford to buy the motor/gearbox and throw the motors away

Thanks sent them a email ill see what they say.

I think this is where I saw the gearbox first, I have seen some on ebay but they are like 12:1 15:1 ratios which are too much.

Originally Posted by crocky

That is a pretty mean cut!

I was a bit shocked also, maby it was my manual cutting. I never forced it much.