My Cnc build

[kingcreaky]

thanks for all the pics!. keep them coming. Shame you live such a mission away, you seem to be of the same cast!.

well done looks like you have been quite busy

surely that rack and pinion drive on the x shoulders will need reducing via some kind of pulley or gearbox as 1:1 resolution on those steppers wont make a very high resolution machine?

im sure my big machine, is 12:1 drive

matt

[Skiprat]

Hello All

I have just cut the new square section to go into the y axis to expand the surface area for the z to travel along and hopefully be putting that in this week and get rid of a few gremlins there.
I have tried it out and it works in virtual mode but doesn't seem to know where it is in real mode...have been doing a lot of research in this department on the net and think it is the relationship between homing and machine co-ordinates but will fiddle with that once the y axis is complete and i have eliminated them few problems there first.
The perske spindle is a monster and it rips through wood like butter but obviously no good if i cant control it.

Kingcreaky, thanks for the reply and you mentioned reducing the x axis....is this a solution only if my steppers and the controls havent got a good enough resolution?

It does go very slow to extremely fast depending on the settings.

This is my first build and i am learning enormous amounts which believe it or not, i am enjoying.

Pictures to follow as i will have to reduce the size.

Cheers for now Tommy

[Skiprat]

[kingcreaky]

Kingcreaky, thanks for the reply and you mentioned reducing the x axis....is this a solution only if my steppers and the controls havent got a good enough resolution?

It does go very slow to extremely fast depending on the settings.
Cheers for now Tommy

Due to a lack of response of any more concise, studious, or literate members I shall do my best to try and explain. However Id urge you to check this explanation before taking it as gospel.

assuming your gantry is being driven by 1 stepper either side, each stepper direct driving a cog running on the rack.. Il assume that one turn of the cog, will move the gantry about 1" or say 25mm. Im unsure of exactly why, and this is the basis of my argument, so Il hold my hand up if im wrong, but although the stepper drivers allow you to go to a crazy resolution (ie say 3200 steps per revolution) its not wise to be running in this setup. Ive always been advised to set them to something like 800 steps per rev. This maybe because all my machines have always ran direct off parallel port and I see you have a smooth stepper.

so, assuming one revolution of your drive cog, moves 25mm along the rack. that means, when your setting up mach and you have to tell it your steps per mm your figure is going to be

800 / 25mm = 32 steps per mm

essentially, the greater you can make the steps per unit, the greater the resolution of the machine... but of course, lower top speed etc


hence my comment, I would expect to see that pinion cog being driven by a belt. and the the belt changing the ratio of the drive from 1:1 to something like 12:1

just bear this in mind, its not necessary a show stopper.

Love the pictures though... keep them coming

matt

[Skiprat]

Been looking in my draws and i have loads of bearings, cogs even belt driven spares. I could build some of my own reducing plates but very amateurish on the cad cam side of things yet. Unless someone has the dxf, swg files for me to use or pay for, it might be good for me to buy some premade.

I have looked all over for rack and pinion drive plates but most seem to be in the USA, does anyone know where to buy any reducing motor cog plate "thingies", in the uk as i am not sure of the right wording for them?

If i can buy some and get my machine working, then i think it gives you more incentive to build other things and probably more accurate as well.

Cheers Tommy.

This is what i am sort of looking for.

[Skiprat]

Thanks for that Matt

I think i get your idea and will do some looking in my shed for the relevant bits and bobs and see what i have.

Cheers Tommy

[D.C.]

For the gears & belt, http://www.beltingonline.com/ comes up a lot on this site as a good supplier.
For the adjustable plate, figure out what you need and post an RFQ, I'm sure someone will be willing to make some for you.

[kingcreaky]

Thanks for that Matt

I think i get your idea and will do some looking in my shed for the relevant bits and bobs and see what i have.

Cheers Tommy

feel like ive pi$$ed on your fire now chap, sorry.

if your anything like me, you wont want to wait around getting plates cut for you...

if it were me, id buy some toothed pulleys from the place suggested above, or bearingstation or something.

get something like this say 10mm

http://www.ebay.co.uk/itm/10-12-15-2...item4d32dc19cd

get some round silver steel for a shaft...

http://www.ebay.co.uk/itm/Silver-Ste...item3f2523697b

put your pinion cog on one side of the shaft

and a big ass belt pulley on the other.
http://www.bearingstation.co.uk/Prod...y_5mm/725M25PB


then drive the big pulley via another smaller pulley oo your stepper?
http://www.bearingstation.co.uk/Prod...y_5mm/125M25PB

get me?

[Skiprat]

No way Kingcreaky far from it....should of asked these questions ages ago.

I am going to put the new bar in on the y axis so its all coming apart anyway....

I have loads of bearings so should hopefully be able to throw something up unless i stumble across some plates.

Once the machine is up and running correct, i intend to make some new bits for it to improve its appearance / accuracy if you know what i mean. I have also been looking at a load of other threads and google pages and have got a load more improvements in mind, whether they are an improvement or not will be seen.

Keep the thoughts coming please.

Cheers Tommy

[kingcreaky]

any update on this skiprat?