Feeback on cnc design

[ger21]

If you slide the spindle clamp up 2-3", and let the spindle hang out the same amount, the plate that the clamp mounts to gets shorter, and the clamp is directly over the bearings, eliminating any chance of flex in the plate.

[louieatienza]

If you slide the spindle clamp up 2-3", and let the spindle hang out the same amount, the plate that the clamp mounts to gets shorter, and the clamp is directly over the bearings, eliminating any chance of flex in the plate.

Correct, but regardless, as the spindle goes up, so does the lower bearings, increasing the lever arm of the carriage, reducing the distance between bearing blocks (unless a taller gantry is made), and reducing the stiffness of the system overall. But I suppose it's po-tay-tow, po-tah-tow

[ger21]

No, his plate extends below the lower bearings. By keeping the bearings where they are, shortening the plate, and extending the spindle, it gets stiffer.

[R0bbie]

Hey Metiz,
I have been following this tread with interest.

I have a question, what are your X-Y-Z travel dimensions?

Regards,
Rob.

[metiz]

Hey Metiz, I have been following this tread with interest. I have a question, what are your X-Y-Z travel dimensions? Regards, Rob.

535x620x130, respectively, although the Z is still being tweaked

[metiz]

I took Ger21's advice and modified the clamping arangement somewhat. There is still a bit of stickout but the combined plate thickness is 22mm so that should be fine I think.

[R0bbie]

535x620x130, respectively, although the Z is still being tweaked

That is about the same travel as my machine (475X665X100).
I am also from the Netherlands (I don't have a clue how to edit my profile to show my location ...,it must be age).
However, The Netherlands is very large so chances you are close to me are very dim, but still I would like to invite you to my place to have a chat and share knowledge.

Regards,

Rob.

[metiz]

That is about the same travel as my machine (475X665X100). Regards, Rob.

Hi Rob, Can you post a picture of your machine, or share some experience on your machine? Like is there anything you would have done differently, any areas that are problematic, what parts tend to flex or vibrate more than others etc?

[R0bbie]

Wow Metiz, that are a bunch of really great questions that also confront me.

1, "Posting a picture", easy but you could also look at my previous posts, there's a picture or two.
2. "Share some experience", easy, I am as happy as I could be with my machine, however it has been a very steep learning curve.
3 "Would I have done things differently", This is the confronting one, I am not sure, I never thought about this, my machine dimensions and quality of build are dictated by the parts I found on the internet, however my quality standards where set quit high like THK lineair rails and NSK C3 ground ball screws. "I ASK YOU AGAIN, Would I have done things differently!!!" ohh sorry, I got carried away.... O.K. to answer your question, probably dual motors on my Y axis, but that is just by feeling because the machine performs great!
4."any areas that are problematic, what parts tend to flex" ​O.K. finally the time has arrived for me to get arrogant , No, sorry but NO, This is my first build and I did a lot of reading and research, especially on this great forum, I had a lot of trouble (who hasn't) witch I was able to solve.

O.K. back to your question 1 "Posting a picture" I'l make life easy on you,here you go ;-) ;

[metiz]

Thanks for the answers and pictures - great looking machine, realy clean. I like how your gantry risers are connected underneath your bed, over the X. Your risers are realy angled, but there's still no issue with vibration or flex - I'll think I'll angle my risers a bit more too then. How thick are your gantry riser plates? Do you use those dial gages to calibrate your machine?

[R0bbie]

Thanks for the answers and pictures - great looking machine, realy clean. I like how your gantry risers are connected underneath your bed, over the X. Your risers are realy angled, but there's still no issue with vibration or flex - I'll think I'll angle my risers a bit more too then. How thick are your gantry riser plates? Do you use those dial gages to calibrate your machine?

Hi Metiz,
Thanks for the compliments.
The gantry risers are connected underneath because I use a single ball screw to drive the Y axis.
The angle of the risers is because I wanted the tool to be between the lineair blocks to prevent raking, for the same reason I moved the rails and ball screw of the X axes to the other side of the gantry. Another pro of moving the rails and screw to the other side is that they stay much more outside dirt and chips flying around.
Thickness of the gantry plates is 15mm, the ribs I placed on the outside of the risers are 20mm and they make quite a difference.
About the dial indicators see my thread here.

Regards,

Rob.

[metiz]

15mm is huge! My plates are 10mm, but they are from steel so maybe that will offset things. I made a modification to the riser plates and shortend them yet again by 10mm

[R0bbie]

Hi Metiz,

looking at your design I think that 40 X 40 mm T slot profile supporting your lineair rails for your Y axis is a little bit flimsy.
These parts are actually carrying your X,Y and the Z axis.
I thought that this same profile was sufficient to "only" use as legs for my machine (look at my first picture which is in a early building stage), after building the structure it looked and felt O.K. , until the machine started moving rapidly, this material flexes a lot! I had to put in diagonal cross members to prevent the machine from walking through my workshop.
And I am talking only about the legs of my machine.

Regards,

Rob.

[metiz]

Hi Metiz, looking at your design I think that 40 X 40 mm T slot profile supporting your lineair rails for your Y axis is a little bit flimsy. These parts are actually carrying your X,Y and the Z axis. I thought that this same profile was sufficient to "only" use as legs for my machine (look at my first picture which is in a early building stage), after building the structure it looked and felt O.K. , until the machine started moving rapidly, this material flexes a lot! I had to put in diagonal cross members to prevent the machine from walking through my workshop. And I am talking only about the legs of my machine. Regards, Rob.

I have two types of profiles: "normal" and realy beefy. I can barely even find a picture on the internet for the good profiles. I will use those for the Y axis. The Y axis will also be stiffend up by the steel rail on either side and 5 crossmembers, each stiffend up by angle plates and THOSE crossmembers are stiffend up yet again by thick plates over the Y direction and each of THOSE are affixed by 10 angle plates themselfs. There's a lot of things that can go wrong with this cnc, but if the Y axis flexes in any significant way, I will buy a hat and eat it.

[metiz]

I'm looking for stepper motors online (nema 24) and there are several options available: 4, 6, and 8 wire motors. What's the difference between them? Also, each motor needs a controller, but how many drivers do I need? I've seen ebay listings with 4 motors and 2 drivers and 3 motors with one driver etc. What is it dependant on?

[sparkness]

Nema 23 motor, and each motor needs its own motor driver .some controllers combine 3 or 4 drivers to simplify and make a smaller footprint like the gecko 540 or the leadshine MX4660, 6, 8 wire motors the windings have different taps to allow many different series or parallel configurations.Decide on what motor torque and speed you need then select motor, then the appropriate drive. do not settle on the cheap chineese drives go for a trusted brand and seller

[louieatienza]

I'm looking for stepper motors online (nema 24) and there are several options available: 4, 6, and 8 wire motors. What's the difference between them? Also, each motor needs a controller, but how many drivers do I need? I've seen ebay listings with 4 motors and 2 drivers and 3 motors with one driver etc. What is it dependant on?

8 gives you the most options, though for most applications here 4 wire would suffice. You need a drive for each motor; you'll see some units that have three or 4 drives, breakout board, all integrated, which makes wiring easier.

[wizard]

As others have said you need a drive for each stepper. The gotcha these days is that you can have a number of drives in one box or chassis. Each of those drives ganged together in a chassis though needs to be easily adjusted for current and needs to be able to handle the required voltage.

Personally i prefer one driver unit per axis as it makes service and debug easier. If a drive goes bad it is generally easier to replace one such drive. It should be noted though that modern protected drives are hard to kill.

As far as the number of wires offered up, they offer implemtation options to the user. In most cases you are fine with four wires IF you can match the right driver and power supply. Remember inductance is a signficant issue and is something you should have on your check list.

One other thing to keep in mind, drives with built in power supplies are now reasonably priced and might make sense. It isnt always easy to source the proper power supply so such drives can be an advantage in that regard.

[metiz]

Thanks for your replies, I'll do some digging.

[metiz]

I found this at the scrapyard, good condition. Paid like 3 euro's for it! So that's the Z axis taken care of. Those rails are just a bit too short for the X, but beggars can't be choosers right