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View Full Version : Which controller and motors? Newbie advice please



Nealieboyee
16-10-2012, 03:30 AM
Hi All,
Pleased to meet you. Im Neal and pretty new to CNC stuff. I'm currently building a CNC router for home use. It will measure 1200mm x 600mm. The problem im having is choosing the electronics and im hoping somebody more experienced could give me some insight.
Initially i was going to buy a G540 controller kit complete with power supply, controller and stepper motors (280 oz in) but the taxes and price are really putting me off as i have to get it shipped from the states. Any recommendations for a cheaper yet reliable kit from the uk that wont break on the first day? Ive heard that leadshine drives arent too bad but i dont know where to start. Please forgive my ignorance.
Neal

D.C.
16-10-2012, 04:23 AM
I'm also in the planning stages of my first build, I was looking at some stuff from cnc4you.co.uk

Nema 23 3.1Nm steppers for 25
6.0A 80V Driver - Cw8060 for 62
600W PSU for 56

How do those prices compare? PS I'm also cluless so you might want to check with one of the more experinced members before throwing your wallet at the screen. :)

martin54
16-10-2012, 12:00 PM
Before giving you any advice on what electronics to buy the guys in the know will want some extra details from you. Construction of machine for a start as to much power can rip the machine apart. Type of work you want to do with it, ie what are you hoping to cut.
While your waiting try reading this thread as it may help.

http://www.mycncuk.com/forums/faqs-problems-solutions/1524-what-size-stepper-motor-do-i-need.html

Nealieboyee
16-10-2012, 01:24 PM
Before giving you any advice on what electronics to buy the guys in the know will want some extra details from you. Construction of machine for a start as to much power can rip the machine apart. Type of work you want to do with it, ie what are you hoping to cut.
While your waiting try reading this thread as it may help.

http://www.mycncuk.com/forums/faqs-problems-solutions/1524-what-size-stepper-motor-do-i-need.html

Thank you for your reply Martin. Much appreciated.
The machine is a moving gantry design made from MDF. The rails are 3/4 x 3/4 aluminium angle and the bearings are skate bearings. The design is from Buildyourcnc.com.
I will be cutting mostly 2-8mm acrylic, up to 15mm wood, and hopefully up to 5mm aluminium.
I was planning on using 8mm threaded rod for the lead screw, but your excel calculation sheet gives me bad results with that and 10mm and 12mm, possible because the pitch is so fine (1.25).

The lead screw will be 1300mm long on the x-axis.

Edit. Ok 8mm works fine now. Here are my results.

http://i.imgur.com/oOFv7.png

martin54
16-10-2012, 01:39 PM
That's the same machine that I am building but I have already started looking in to building another machine because of the problems & limitations this sort of machine has.
The book uses 1/2" threaded bar so not sure why you were looking as low as 8mm especially over that sort of length. Pitch on 12mm is generally 1.76 is it not?? Could be wrong about that as it's a while since I looked.

What are you looking to do with the machine?? What materials are you looking to cut with it. New myself so all I know is what I have picked up in a short time here. Tar as stuff like electronics goes I have been told to try & buy stuff that I can migrate to another build when the time comes.

Nealieboyee
16-10-2012, 01:44 PM
I wanted to stick to 8mm to save on buying more bearings lol. I guess I'll go with 12mm then. I think the pitch on 12mm is about 1.5 or so. I've edited my previous post to show what I want to use it for.

Edit: Have you ever thought of using the drawer slide system on a budget?

irving2008
16-10-2012, 01:57 PM
1400mm axis on 8mm x 1mm leadscrew is a bit iffy, both from a whipping perspective and speed, you'll struggle to get better than 600mm/minute which is a very low traverse speed for a 1.4m axis. That's not to say it can't be done, but its hard to get it any better because the efficiency of the screw is so poor and it ideally needs to be geared up to get the motor running closer to its corner speed. and maintain torque My first build was 800mm on 12mm x 2mm trapezoidal but its tediously slow as the motors cant do more than 400rpm i.e. 800mm/minute and a minute feels like eternity, and anyway the acceleration is so low that the real achievable cutting speed is 1/2 that.

irving2008
16-10-2012, 02:01 PM
I wanted to stick to 8mm to save on buying more bearings lol. I guess I'll go with 12mm then. I think the pitch on 12mm is about 1.5 or so. I've edited my previous post to show what I want to use it for.

Edit: Have you ever thought of using the drawer slide system on a budget?

standard metric coarse thread on 12mm is 1.75mm. You can get 1, 1.25 and 1.5 metric fine threads but threaded rod is likely to be coarse. Consider 12 x 3 or 12 x 4 trapezoidal rather than threaded rod if cost prevents you going to ballscrews.

Oh and you'll struggle to cut aluminium unless its a very very light cut. The spreadsheet shows 5Nm cutting force which is light wood, ali could be 25+ Nm, acrylic could be an issue too as that needs fast cutting speeds and a fast spindle speed to actual cut rather than melt the material!

Nealieboyee
16-10-2012, 02:06 PM
Thanks irving. I'll have a look for those. With that info are you able to recommend which electronics I can have a look at?

martin54
16-10-2012, 02:08 PM
Like I said in the post above I am new to the world of cnc myself but from reading the build logs & general help from members on the forum I don't think you will be able to do much of what you want to with the machine as it stands.
If I were you I would spend a bit of time reading some of the build threads & asking questions before you go buying any electronics. Like I say I am not an expert but I doubt if it will cut ally very well at all, acrylic you will need some kind of spindle speed control because DIY router speeds are to fast to cut acrylic & it just melts back together. I would think your motors are a bit on the week side for what you want to cut.

One thing I have learnt is that there is a lot more to this than buying the book & building the machine, especially if you want to use it for business use.

irving2008
16-10-2012, 02:12 PM
Depends on your budget.

Ideally you want to go for the highest voltage drivers you can if you plan to upgrade the machine and reuse the electroincs but without blowing the budget. With 3Nm motors you could probably get away with 50v drives and there are some good cheap deals with a 48v PSU and 3 drivers on ebay, the MD542 type drives. Avoid the all-in-one TB type 30v drivers unless you really have a budget issue. They'll work but you'll not get the best out of the motors.


I wanted to stick to 8mm to save on buying more bearings lol. I guess I'll go with 12mm then. I think the pitch on 12mm is about 1.5 or so. I've edited my previous post to show what I want to use it for.

Edit: Have you ever thought of using the drawer slide system on a budget?


Thanks irving. I'll have a look for those. With that info are you able to recommend which electronics I can have a look at?

Nealieboyee
16-10-2012, 02:51 PM
I see Zapp Automation have a kit using the PM542 drives and Nema 23 motors for about 350. I couldn't find MD542 drives anywhere. Are they the same thing?

Jonathan
16-10-2012, 03:19 PM
I see Zapp Automation have a kit using the PM542 drives and Nema 23 motors for about 350. I couldn't find MD542 drives anywhere. Are they the same thing?

Yes if you see M542 in the part number it's the same thing.

D.C. mentioned the motors from CNC4You (http://www.cnc4you.co.uk/index.php?route=product/product&path=83_84&product_id=67), which are good however their drivers and PSUs are not the cheapest. There are plenty of eBay sellers with good prices for the drivers. For 350 you should be able to get four 3Nm motors, four 80V (e.g. DQ860MA) drivers and a suitable PSU. With a 600mm Y-axis you would be better off with two motors and leadscrews/ballscrews to prevent racking, or one motor and a long belt to link them.

Nealieboyee
16-10-2012, 03:42 PM
Yes if you see M542 in the part number it's the same thing.

D.C. mentioned the motors from CNC4You (http://www.cnc4you.co.uk/index.php?route=product/product&path=83_84&product_id=67), which are good however their drivers and PSUs are not the cheapest. There are plenty of eBay sellers with good prices for the drivers. For 350 you should be able to get four 3Nm motors, four 80V (e.g. DQ860MA) drivers and a suitable PSU. With a 600mm Y-axis you would be better off with two motors and leadscrews/ballscrews to prevent racking, or one motor and a long belt to link them.

Thank you John. Some good stuff there. Don't I need a breakout board too?

Jonathan
16-10-2012, 03:56 PM
Don't I need a breakout board too?

Strictly speaking no, since the drivers are already opto-isolated the breakout board isn't required. However I would always advise getting one anyway as it just makes it generally easier to connect up everything safely, in particular the inputs.