Author Topic: Tiny CNC router (Read 66978 times)

j45on · « **on:** April 09, 2011, 04:30:41 PM »

I am building a tiny CNC router based on this http://makeyourbot.org/mantis9-1
But I am beefing it up a little with proper ball bearing slides with a view to remaking the frame from aluminium if I can get it all working correctly

This is what I have "thrown" together so far

I have now got to the point where I need electronics

I was originally going to use some salvaged printer stepper motors but I don't think they will be up to the job.
Does anybody see any problem with one of these ? http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280655297567&ssPageName=STRK:MEWAX:IT#ht_6455wt_1141

I only want to engrave wood and maybe some aluminium with this either using a dremmel or a custom spindle and brushless motor

Rob.Wilson · « **Reply #1 on:** April 09, 2011, 04:48:18 PM »

Hi Jason

sorry i cant answer your question

Looks a cool project

,,,,,,,,,, what size is the work table ?

Rob

j45on · « **Reply #2 on:** April 09, 2011, 04:58:24 PM »

I'm unsure

I will measure it tomorrow I also don't know what the usable table surface area is yet
The whole thing is only 300mm x 300mm square though.

Rob.Wilson · « **Reply #3 on:** April 09, 2011, 05:31:09 PM »

Jason

would this be any use to you on your build ?

280 x 220 x 25 ally ,,,,,,,,,needs a clean

Rob

saw · « **Reply #4 on:** April 09, 2011, 05:46:15 PM »

This looks to be an very intressting project, I will follow this

raynerd · « **Reply #5 on:** April 09, 2011, 05:56:33 PM »

Jason, good luck with this. It is something I am massively interested in, infact I started making one a while back:
http://www.raynerd.co.uk/?p=532

However, it was a little bit too big AND the electronics were just working out far too expensive. I purchased a very cheap driver off ebay for £10 and it blew up with imo, no fault of my own I! I then purchased a cheap second hand motor and couldn`t get it to work. Then I went and purchased a motor and driver from ArcEuro and had no issue with them, they worked perfectly but they were for my milling maching x-axis stepper driver controller so for three more, I just couldn`t afford it!! I sold the lead screw and infact, I sold the table as far as I had got with it!!

I`m hoping I`m going to get some help with a build during summer so I`d be really interested to see if those drivers and motors do the business! I have seen them on ebay before and wondered!

Chris

j45on · « **Reply #6 on:** April 09, 2011, 06:09:48 PM »

Quote from: Rob.Wilson on April 09, 2011, 05:31:09 PM

Jason

would this be any use to you on your build ?
Rob

Might be rob if I get it working

I shall keep it in mind

I went with this one in the end Chris as it also had a power supply http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=260754805346&ssPageName=ADME:B:EOIBSA:GB:1123#ht_6225wt_1141
I will let you know if it is any good.

Imagineering · « **Reply #7 on:** April 09, 2011, 07:04:00 PM »

Hi Jason,

Have a look at http://cnczone.com/
There you will find many answers to the many questions you will have on your quest for CNC.

Murray.

Swarfing · « **Reply #8 on:** April 10, 2011, 03:46:13 AM »

Jason

I use a similar board for my router with the same size motors and it works fines. Setting up the board can be a bit of a pain but with the screw you are using i don't see a problem. My work area is 700 x500. Join this site as is very useful and a dam good bunch of blokes http://www.mycncuk.com.

j45on · « **Reply #9 on:** April 10, 2011, 06:46:55 AM »

Cheers for the links guys

there is so much information to take in

j45on · « **Reply #10 on:** April 10, 2011, 01:05:39 PM »

I had a bit of time this afternoon so I knocked up a new anti-backlash nut from some Delrin I was not happy with my previous effort.( on the right)
The new one (left) is longer and has three thin slots (very hard no see) in the end which are held shut with an o-ring.

This all runs nice and smoothly now with no noticeable backlash in the screw and nut

But I now need to find some thicker angle or another way to mount the nut as the current piece of angle flexes

j45on · « **Reply #11 on:** April 10, 2011, 03:28:14 PM »

Managed a bit more shed time and finished up a clamp thingy

The lead screw is supported by two bearings at the front which are the same thickness as the wood and are a very tight fit with a flanged screw to prevent movement.
at the rear I have just one bearing.

To stop the lead screw from moving I just have a spacer between the oldham coupling at the front which rides on the inner race.

And on the other side a have a pinch clamp thingy I knocked up which rides on the inner race, these are held tight against the bearings and then have their screws tightened preventing the lead screw from moving
Not as good as a thrust washer but seems to be ok time will tell.

j45on · « **Reply #12 on:** April 13, 2011, 03:57:05 AM »

Well my steppers and controller have arrived

And after a while last night I had all three running, as to if it is any good as mentioned in the "lost posts" time will tell.

John Swift · « **Reply #13 on:** April 13, 2011, 05:32:40 AM »

Hi jason ,

I'm following your progress with great interest

it looks like a good machine to try out our diy cnc skills ,

I hope your board has the problems fix that existed in the early versions of the board described in the cnczone posts

missing link from lost post :- How I fixed my Chinese TB6560 controller (updated)

http://www.cnczone.com/forums/general_electronics_discussion/110986-how_i_fixed_my_chinese.html

good luck

John

j45on · « **Reply #14 on:** April 13, 2011, 07:26:48 AM »

Thanks John I had not bookmarked the link,I have now

I also thought this would be great to learn about cnc.
There would be no point converting my mill for example if I could never figure out how to use the software.
I was watching some Mach3 videos last night I would have been stuffed without them,very helpfull.
http://www.machsupport.com/videos/

John Stevenson · « **Reply #15 on:** April 13, 2011, 08:21:26 AM »

Jason,
Shout up if you get stuck on programming or Mach, I have used it the odd time or so.

John S.

j45on · « **Reply #16 on:** April 13, 2011, 05:02:41 PM »

Quote from: John Stevenson on April 13, 2011, 08:21:26 AM

Jason,
Shout up if you get stuck on programming or Mach, I have used it the odd time or so.

John S.

Many thanks John

hopefully I wont have to but with so much cnc info on the net it can all get a bit confusing

For the life of me I cant find out how to work out my steps per mm when using micro-stepping

My motors are 200 step per revolution
My lead screws are 2mm per revolution
I have the stepper driver set to 1/8 micro steps (the motors seem a lot quieter set like that)

John Stevenson · « **Reply #17 on:** April 13, 2011, 05:09:06 PM »

Steps per revolution x microsteps / pitch

so 200 x 8 =1600 / 2 = 800

j45on · « **Reply #18 on:** April 13, 2011, 05:15:23 PM »

Quote from: John Stevenson on April 13, 2011, 05:09:06 PM

Steps per revolution x microsteps / pitch

so 200 x 8 =1600 / 2 = 800

Thank you John

j45on · « **Reply #19 on:** April 16, 2011, 05:23:27 PM »

Just a quick video of one axis working I'm still playing and tuning so it will probably go a bit quicker

hhmmmm video not imbedding

John Swift · « **Reply #20 on:** April 16, 2011, 07:40:43 PM »

Hi Jason,

it will be a while before i'm ready but

i've had a look at the Mach3 videos , lots of information to keep in mind thanks

your video looks like a good start

can't wait for the next one when its all running

one thing missing from your board is a charge pump circuit

just incase the computer stops working

http://www.machsupport.com/docs/ChargePumpSafety.pdf

while the madmodders move has been taking place

I had another look at the cnczone thread and decided for problem boards

most of the mods could be made as a plug in adaptor / new breakout board

that plugs in the opto isolator and IC sockets

John

j45on · « **Reply #21 on:** April 17, 2011, 02:50:45 PM »

Cheers John
Knowing next to nothing about CNC or mach3 I dont know if my driver board is faulty or not yet

All I know so far is that all three motors move when I press some keys and the DRO'S match the distance traveled.
Until I get it finished I guess I wont know.

I did some googling on charge pumps and I'm still confused

John Swift · « **Reply #22 on:** April 17, 2011, 04:09:43 PM »

Hi Jason ,

the charge pump circuit is a simple voltage doubler circuit thats used as a "missing pulse" detector

this is used to generate a E-stop signal if the computer stops working

mach 3 can be configured to send 12500 pulses a second to pin 1 ,say

this is ac coupled to the junction of the two bat85 diodes to ensure the circuit doesn't respond to a static logic level

the hidden gate capacitance is charged as long as the pulses arrive on time

the fet is now on and via the relay and E-stop circuit power enabled for the machine

if / when the pc stops working the pulses to the circuit is lost and the E-stop activated

the second circuit achives the same thing with a timer circuit as long as it is reset in time

hope this makes sence

John

j45on · « **Reply #23 on:** April 17, 2011, 05:53:41 PM »

That make sense

I have noticed that the motors make a "misfire like noise" every so often is this missed steps ?
And the motors make a hell of a noise when stopped would this be the motors or the driver ?

I think rather than trying to mod this driver I would go for separate drivers and a break out board
For my tiny machine these would probably do http://www.skpang.co.uk/catalog/product_info.php?products_id=576 worth trying one at that price
and use one of these http://www.diycnc.co.uk/html/pcpps.html it has a built in charge pump

John Swift · « **Reply #24 on:** April 17, 2011, 07:27:27 PM »

Hi Jason ,

at the moment I don't have a system to play with so you are a few steps on from me

but if you can move your table up and down several times under load and the real position

is the same as mach thinks it is , your probably not missing steps

the noise you hear from the motor is mainly because the supply to the motor winding is chopped (PWM) to limit the current

this in conjunction with motor resonances and the interaction of a switch mode power supply you will hear various noises

if you don't need all signals in and out isolating the breakout board looks ok

the stepper drivers are a bit small for you motors I expect you will need to run them at the limit of 2A per phase

and still under run your motors

John

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Author Topic: Tiny CNC router (Read 66978 times)

Rob.Wilson

Rob.Wilson