[shaun111]

Hi everyone,
first of all thank you for all your help. (been reading for a couple of weeks now)
I have already built the table, gantry etc. just waiting for 16mm rails for z-axis but had some 1" steel bar off a table saw for the X and Y and was lucky enough to drop onto 8 x 1" linear pillow blocks on the bay for £40
I have ordered ball screws and nuts from motion products although after reading some posts i have also ordered a length of trapezoidal for the Z as I keep reading about the Z crashing onto the top when power is turned off with ball screws? so will try and cancel the z ballscrew and nut tomorrow as they haven't sent it yet.
I have a friends dad who can mill the screws for me so that has saved some cash. It is mainly made from 30mm HDPE but I won't be using it again as it is a pita to join so the design changed a few times so i could bolt it, then i found some hex head screws for brickwork that work a treat, other than that other than that it very easy to cut and plane (I have a woodwork shop which is my main job) it did need reinforcing along the base frame as it bent slightly but some steel angle sorted that out and is not visible. and as rough setup is within .1mm in every direction possible. The work area is smallish at about 60cm x 50cm but should be big enough for me, engraving, milling in wood and light steel.
My main problems are the electrics/electronics side as it is something i have never come across before.
I have just ordered the kress 1050 and these motors which are probably overkill
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=170295845816
2.8A @ 4.76V 4 phase & 3.8nm not sure if i have done right or not but my bidding finger jumped in.
i havent ordered the drivers, breakout board or power supply as yet, but from what i have read these are my options. I would really appreciate some feedback as to what to buy and if the larger drivers are needed or beneficial.
breakout boards:
http://www.motioncontrolproducts.co....99212289636b96
http://www.routoutcnc.com/lptcon.html
Drivers:
http://www.routoutcnc.com/lpkits.html
http://www.routoutcnc.com/10ampkits.html
http://www.motioncontrolproducts.co....99212289636b96
http://www.motioncontrolproducts.co....99212289636b96.
i would like to think i dont need the larger drivers (money thing) but if i do or will get a huge difference in performance then i dont mind shelling out the extra. I am presuming it would only be for the voltage.
I am also wanting to add 3 limit switches, 1 x e stop, and keep trying to figure out how to control the kress through mach3 as well but have no idea how other than i may need a relay board, but this can wait if to expensive.

Anyway sorry for the long post but hopefully someone will be able to help, and i am sure i will have more questions.

[audioandy1762]

Hi Shaun

Both the BOB's don't seem to have any opto isolation, this is not absolutely necessary but very advisable, it will help to protect your PC.
Looking at your motor spec I think you would be better off with the larger of the two and don't forget you will have to build/buy a power supply.
Motion Control sell drivers with the power supply built in might be worth considering if you are not up to speed on your electronics.

Where abouts are you in the UK?

Andy

[shaun111]

Hi Andy,

thanks for the reply, the drivers have opto isolation, didnt realise the bob's needed them aswell. I am certainly leaning towards the bigger drivers.

I have looked at making a power supply but taking all this in is to much so opted to buy one, might have made one if thats all i had to learn, but havent even started with the software yet.
I will probably get the one from motion products but their kits come with the motors aswell and they didnt have any in stock for a few weeks.

only had a mad idea about a cnc about 2 weeks ago after looking at lasers and now my head hurts good job i'm snowed in.

by the way I'm from Chesterfield.

[audioandy1762]

Not too far away Huthwaite!
I have more or less finished my eledtronics (had the steppers running) starting on the build maybe this week.
If you want to meet up sometime just pm me we can arrange it.

All the best

Andy

[shaun111]

Not too far away Huthwaite!
I have more or less finished my eledtronics (had the steppers running) starting on the build maybe this week.
If you want to meet up sometime just pm me we can arrange it.

All the best

Andy

that sounds good mate, i used to live at Pilsley which is not to far from you, if i remember right. i'm hopefully fetching a laser engraver this week so it might be interesting as they basically the same thing (very basically before someone rips into to me) apart from probably rubbish drivers and wiring etc.

i will Pm you later in week

cheers Andy

[Kammo1]

Hey guys what a small world I'm from Long Eaton Nottingham, you 2 live real close. I'm building my own homebrew at the moment but am on a mission to get it done ASAP but you know technical glitches and making it as you go along is frustrating but its a great learning curve. My MDF machine when done will have a cutting area of about 27 inches long X 16 inches wide X 4 3/4 inches on the Z. It is a moving gantry design and I have not worked from a plan but from skethches that I've done and also I built as I went along and its kinda took a slow build but I'm loving it and can't wait to get it cutting. Maybe we can all put our heads together and all learn of each other ?? I have all my electronics which I bought of e-bay about 2 years ago and to be honest I do not know whether they will work or not but I'll cross that bridge when it comes to it. What sort of machine are you guys making??

[shaun111]

Hi kammo,
I have been down Long Eaton a few times. Snow is bad down there at the mo isnt it. Im waiting for some oak that they cant get out of the yard.

My build sounds very similar to yours even in size sketches and on the fly.
I seem to be the other way around to you guys and have it almost built but no electrics. I will post some pics tonight if my 1" bearings arrive today.

I'm still hoping for some advice on the size of drivers and confirmation on the bob needing opto isolation as well as the drivers. Thinking about it and with Andys reply i am presuming the bob does need it as well especially if i am hoping to add control to the kress and extras at a later date as well. i have tried searching but there is so much info on here you get snowed under (pun intended)

Thanks.

[audioandy1762]

Hi Shaun/kammo

The meet up would be great.

Right Shaun back on topic. I have read through the spec's on the MSD542 stepper drive from Motion Control it states "suitable for driving 2 phase stepper motors" as your motors are 4 phase just make sure before ordering they will fit the job. Regarding the breakout board the one I have is from cnc4pc I think from memory the C10(I will check when I get home).
When looking to choose your driver yes the voltage is important but I would say more important is the current rating. I have a load of info on my PC at home that I gathered in the early part of my design, some of it from this site and from elsewhere on the net
I will dig it out and forward it on to you it might be of help.

Regards

Andy

[audioandy1762]

Shaun have a read of this
http://www.geckodrive.com/upload/Step_motor_basics.pdf
I know you are not using Gecko drives but the principle is the same.

Andy

[shaun111]

Thanks again Andy.

I am going to go with the larger drivers they do support 4 phase motors and are opto-isolated I will get a 48v un-regulated power supply and the amps can be taken down to 2.5

As for the bob I am going to order one from the states with opto isolation and charge pump, but will make do with the one stated for now at £12.
Think i should have gone for a kit after all this.

I also found a this which looks interesting but not sure if needed
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA:IT&ih=005

Thanks again
Shaun

[audioandy1762]

BUMP

Come on all you CNC aficionado's give Shaun a helping hand please

[shaun111]

Hi,
couple of more questions for those in though.

The motors have arrived and it states rated current 2.8A (which i have been working off) but parallel connection and phase current 4A, therefore i am presuming it is the 4A that i am using to calculate the power supply and driver board.

Luckily on Andy's advice and from what i have read i went for the bigger drivers anyway at 4.2A and 50V

So can someone confirm that my powers supply needs to 48V @ 8A+

Also i am struggling to find a non regulated PSU of that rating, so if anyone knows of a supplier under £100 then that would be great (why are regulated psu's so much cheaper.

I have also read that regulated can be used if a 2000uf or above capacitor is used but can someone explain how to do that in very simple terms.

I keep reading how easy it is to build one but cannot find any simple how to's other than schematics that make no sense to me at all.
is there a how to for dummies anywhere


I am not stupid by any means but have never had any experience with cnc or electronics and power supplies until 2 weeks ago and it is extremely hard to understand everything when you have never actually seen any of the parts in person, when it all arrives and is infront of me it will probably be much easier to understand.

So all help and advice is welcome???

by the way Motion control kept messing me about with my order so i have canceled the lot and ordered it all from http://www.rhonmac-cnc.co.uk who i cannot praise enough, he has been very helpful. Highly recommended.

[shaun111]

Anyone ??

[audioandy1762]

Hi Shaun

If you want to build your own supply I can give you a hand I have built my own for my machine and have built a number of supplys for various projects in the past.

Andy

ps which driver have you gone for now that you are using a different supplier?

[audioandy1762]

Shaun
I have done a few calculations based on your motors and drive

Unipolar Current = 2.8amp
Bipolar Serial = 2.8 x 0.707 = 1.979amp (2amp)
Bipolar Parallel = 2.8 x 1.414 = 3.959 (4 amp)

If you wire your motors:-

unipolar 2.8 x 3 = 8.4 amp 67% = 5.62 amp

Bipolar Serial 2 x 3 = 6amp 67%= 4.02 amp

Bipolar Parallel 4 x 3 = 12amp 67%= 8.04 amp

Your driver is the limiting factor for the voltage being 50vdc max
So to allow for variation (safety) if you use a transformer with a secondary voltage of 30volts ac once rectified it will give you a DC voltage of:-

30 x 1.4 = 42 volts dc

Transformer Va rating

42 x 5.62 = 236 VA

42 x 4 = 168 VA

42 x 8 = 336 VA

So based on the above which ever way you decide to wire your motors I would go for a 500VA transformer then if you decide to add a 4th axis at a later date you have plenty to spare without doing a complete overall of your system.

For the smoothing cap value use the following formula

C= (80,000 x amps) / volts answer in mF

Bipolar Parallel (80,000x 8)= 640000/ 42= 15238 mF (20,000)

Hope this helps a little

Andy