Beginner MYCNCDIY Mill Build questions

[suraj1793]

Did some more searching and found this (http://www.mycncuk.com/threads/5790-...tor-and-drives), in this post JAZZCNC also highlighted the fact that 3.8mH is slightly high for motor inductance therefore, my first question has already been answered (unless the inductance rating depends on the application?).

Therefore, I started searching again for available kits/equipment for the electronics part of this build and heres what I found:
Stepper Motors: As per recommendations in Ivars211's thread (http://www.cnc4you.co.uk/index.php?r...product_id=362)

PSU: This was a bit confusing. In JAZCNC's post it was highlighted that for best performance you should run the motors at around 60-70VDC however, the kit on ebay shows 2pcs PSU 350W (36VDC/9.7A) and the 3 axis kits for running 3.1nm steppers on CNC4YOU.com showed 1pc 400W (36Volts) PSU. Are the kit PSU's just making use of large safety margins for the supply? If so, should I be looking for a PSU rated at 60-70V and 8-9A? Does anyone have any recommended suppliers? (Will be looking into building toroidal PSU if necessary)

Drivers: As per the ebay kit (http://www.ebay.co.uk/itm/3Axis-Step...item2eca734c31) However, I just noticed that these are rated at 50V and as per recommendations in the post they should be rated higher than the maximum applied voltage (which is recommended at 60-70V) therefore, are these the wrong drivers? If so, are there any suitable alternatives which are in the same price range? The AM882 were a bit out of my price range for this first build however, seem like a very good upgrade for the future.

[Boyan Silyavski]

All depends on the size of the machine and the weight of the gantry. Then come the motors and so.

What working area??? What is the hardest material you will machine? How much money are you ready to spend on the build?

[suraj1793]

After much guidance and a lot of build log reading I think an achievable goal for my first build is to be able to machine wood (typically at around 40mm depth) and be able to do a lot of carving work (although if I can get more depth it would be preferred). If this could also engrave aluminium this would be a major benefit (although not my primary purpose for this machine).

Cutting area for this would be around 500mm x 500mm. Material and equipment for the frame (steel or aluminium box section, mig welder, drill press and hand tools) are all available for free from work. For the rails I was going to use roller carriages with a cold rolled steel plate as a guide rail and for the linear motion of the axis I was going to be using ACME threaded rod (but setup for later replacement with ball screw).

For the spindle I was thinking of initially going with a simple router like a bosch colt or maybe something smaller which I have already in the workshop such as a pnematic dremel but after some time upgrading to something like a 2.2kW spindle dedicated to the machine.

Budget for the electronics (motors, drivers, PSU) is around £200.

This build seemed to suit all my requirements therefore, I planned on using this setup as a guide: http://www.mycncuk.com/threads/1541-...-framed-router

This was another build I was looking at as an alternative but I am not sure if it would be powerful enough for what I need: http://www.neo7cnc.com/

Also, it may be worth mentioning that I also have an arduino uno available so was thinking of running this from GRBL as this would allow me to use my laptop USB for to communicate with the machine.

[Boyan Silyavski]

I am not a fan of "ultra cheap" builds as at the end you will have "ultra nothing" as a result and money spend for nothing.

500mm wide working area suggests 2 motors at the long axis that moves the gantry hence 4 axis board. 100-300 euro, i would say 200 euro here only for the BOB. Now if you could avoid somehow this using arduino or whatever cheap. / Saying cheap i don't mean crap Chinese boards without support

Next thing are drivers and motors. if the gantry is No more than say 300mm wide, low voltage drivers and motors are possible/<55VDC/ , for 500mm gantry if you want to achieve normal speeds you will need drivers capable of 70-80VDC and motors 4.2A / 3Nm/ . 4 motors here are 100euro and 4 drives 180-250euro

So you see you have to invest if you want something capable.



But lets start backwards.

What you will 100% need is ball screws and square rails, given the current prices you will save next to nothing using round rails.

So start from the frame, the rails and the ball screws. Cause that you can not change later. When you have money just continue the build.

Take care at the steps below or you will spend unnecessary amount of money due to mistakes

1.Make the drawing
2.Show it here
3.Receive critique
4. Finalize the drawing
5. Buy ball screws and rails.
6. Make frame
7. Buy motors,
8. BOB. drives.....etc.

Hope that helps you to organize your thoughts

[suraj1793]

Thanks for explaining silyavski, I keep on underestimating the scale of these builds...I just see some real good builds and instantly want to try and make them! but I have to start understanding that quality costs money!!!

After re-evaluating my requirements and realizing that wanting a router that can machine both ali and wood is a "typical beginner question" I decided upon a simpler first build. The requirements are, a small 300x300 router that is dedicated to wood work (mainly carving and some involving 40mm deep wood cutting on softer woods). As it would be for carving work I am not trying to hold very tight tolerances, just enough for the carved features to look "right" which I am guessing gives a tolerance of around 0.2mm or maybe even more.

A perfect example of what I am talking about is something like this: http://www.youtube.com/watch?v=OX_Pw8XPYMs
Some of the basic specs are shown here (http://www.busybeetools.com/products...LIVER-CSA.html) this shows that the router uses 240 oz-in motors and just a 150W spindle all of which seems to be closer to my budget than other machines I have seen.

Do you think this is a bit more doable for me with my budget? Like I said, all I am looking for is a decent wood carving router that can be ran continuously.

[Boyan Silyavski]

Ok. I understand.

The example you gave is "perfect" example of crappy machine with good marketing. In fact i have something quite similar and i bought it because there was no body to help then and explain me that:
All cheap systems of linear movement are crap and only the square supported rail is the real thing. So as i said, whatever you do, don't go that way/ v wheels, round rails, etc./ Whatever they say!

So go to ebay or BST Automation and search for supported square rails, Hiwin, chinese or whatever. Just saw that Zapp automation has some great deal on ISEl http://www.zappautomation.co.uk/surplus-stock.html you will need size 20 rails and blocks.


Next you will need to know the ballscrew price more or less, BST Automation

So you decide if its doable or not, just follow the steps from my previous post. Dont start the build until you have the screws, rails and nut housings in your hands.

[JAZZCNC]

Do you think this is a bit more doable for me with my budget? Like I said, all I am looking for is a decent wood carving router that can be ran continuously.

What is your total budget for a fully working machine.?

[EddyCurrent]

From what I've read here, I think you would be better off buying a Chinese 3040 off ebay.

[JAZZCNC]

From what I've read here, I think you would be better off buying a Chinese 3040 off ebay.

Nah I wouldn't.!! . . . I'd encourage him to save up a little more and not waste is money on Rubbish.!!

[EddyCurrent]

Nah I wouldn't.!! . . . I'd encourage him to save up a little more and not waste is money on Rubbish.!!

But that's exactly what he's proposing to do anyway, at least the ebay job is ready built and more importantly saleable again.