Mostly Printed CNC

[Rovida]

Thanks Innkeeper, I appreciate your comment.

Finally I start using Sanguino with Repetier Host and it works perfectly except for the fact that I can't move the axes in a negative position, but probably is my fault.

If I use positive coordinates it works like a charme!

[innkeeper]

Thanks Innkeeper, I appreciate your comment.

Finally I start using Sanguino with Repetier Host and it works perfectly except for the fact that I can't move the axes in a negative position

seems odd, there's no reason for that...I would guess that the board thinks the end stop is in a triggered state, allowing it to only move away from it.... I am sure you will figure that out. I bet the issue is on the reprap forums, someone's had to had the same issue before.

as for me, I am up and running, but haven't done any actual milling with it....only simulated.
I've decided on swapping out my steppers. going for the 84 oz ones from OMC. not that the ones I had were terrible. they are 66 oz at only 0.56a I was running them at 0.5a microstepped.. so getting about 40 oz/in out of them / 80 total in/oz per x/y axsis

new ones will be here tomorrow and are rated at 84 oz OMC are 2.0A which would be more then your board can drive them considering you would need to drive 2 per channel..... i'll run them at 1.8A, and 1/32 microstepping and get about 53 in/oz out of them in the real world... [you loose ~30% off the spec just for micro-stepping over full step dual phase drive which is how bipolars are alwasy spec'ed] . ... that will translate to about 106 oz/in per x/y axsis... I am estimating that translates into 27 lbs of pressure at the x and y axsis ... as opposed to 20 with the 66 in/oz steppers. ... as opposed about 12 lbs of pressure with your run of the mill 40 oz steppers. ...

Still...no were close to what even low end Nema 23, 24 or 34 can produce, but .. a good starting point for the dollar.

if you want to source the 66oz ones let me know, you can get 5 for 40 bucks. and since you will likely run those in a "star" configuration (in parallel) they would still be drivable with your electronics. Sadly the person I know selling them for that price is mis spec'ed them online.. so you need to disregard their spec's ... since they refuse to change it in their ad, so I am not about to widely post them .. as I think that is just bad business making people think they are buying something they are not... .. if they don't know what they have they should just say it..none the less they are a good deal for what they are. there minebea stepeprs (also known as nmb and mishushita )

those 66 oz steppers appear to be pulls from Xerox equipment. they can run both unipolar and bipolar... in bi polar series mode (the higher torque usage) there a bit high on the inductance, which can be a problem for maintaining torque at high speeds, but running the curves, it would appear its not at speeds anywhere close where you would be using to actually mill at and you might approach on rapids... which should be a non issue .. if I keep them under .5a they seem to not get overly hot.

I managed to source the 5 OMC motors for under 60 bucks. if all goes well I'll have them swapped out and will be milling with them this weekend. I sourced those from steppersonline.com though ebay but you can get them from their website too.

(just to make things more confusing. ... omc was acquired by osm about a year ago.. omc / stepeprsonline seem to have a good rep for cheap steppers, so i am giving them a shot .. What i am understanding having read about them that similar to kysan, they don't actually manufacture their own steppers)

I do need to install the spoil board.. and I want to raise the entire cnc, to give me more Z .. I can have an extra 6" of Z if I raise it...

I'll still need to do a lot of cleanup... making cases for the electronics and the lcd and drag chains for the cabling etc...but that's mostly cosmetics.

(edit to fix torque specs and typos)

[jsc]

Any updates? I'd love to hear how it turned out. I was looking at the X-Carve again, but I can't really justify it.

[innkeeper]

It's actual been sitting...i ahd a few more important things that i needed to concentrate on.
I did some torque tests on my new steppers, just to be sure they were to spec, and they are.. then stopped.
I should have some time cumming up to get back at it.

[willnewton]

Couldn't resist this kit. I have the electronics, just need EMT tubing and the M2 is busy printing parts now. Certainly not expecting to replace the M2 and Shopbot with it, but I do hope to have some fun.

[willnewton]

I am calling mine "The Watermelon".

Well over 100 hours of print time. I used PLA (black and pink) and PETG (green). I used a wedge tip soldering iron and PLA filament to weld the joint where the foot meets pipe holder.

This has a VERY heavily designed/built Z axis carriage compared to what you would see on a 3d printer. Can you say inertia? The chassis moves surprisingly smoothly. The PLA keeps the bearings preloaded. I am interested to see how it all works once firmed up and loaded.

So, I just decided to go for the biggest size I thought I might want and scale down as needed. My bars are 30x36" which gives me an 18x24" work area. I am not sure what my working height will be, as I have to get those parts installed, but it's probably 4-5 inches.

Pic 1 is a plain shot of where I am at.
Pic 2 shows the print area holding four 16oz homebrews in the corners and my 500-sized hexacopter.

[willnewton]

The build is mostly done and working. I can make a passable print but it's not fully calibrated, not does it have the final 18x24" bed yet. This was a pretty cool project. I was really proud of the little 15x15x1mm block that was my first print.

I learned A LOT building my own printer. The first thing I learned is that there is a lot to be said for buying one ready-made. I would not recommend a scratchbuild as a first build. The MPCNC is not really a kit for a finished printer by any means, just a source for some base parts and a set of plans. You will have a lot of assembly, wiring, programming, and testing to do. If you are already successful with 3d printing you will know what it takes to make a decent print via software/machine setup and that will save you a huge part of the learning curve.

As for the actual prints produced, they are passable. This printer shows evidence of Z-banding, and does not the make prettiest surface finish, and does not currently make a print that would be worthy of comparison to something off my M2. Not. Even. Close.

That being said, it does as good a job as I have seen on other lower-end import/homemade printers. I expect improvement as it gets dialed in, but this is just a chassis and motion control system issue. It is a flexy chassis running bearings in PLA mounts on EMT rails and a "meh" extruder. You just aren't going to make this thing print as well as a higher end model, no matter how well-tuned the firmware/software is.

Now that your expectations have been lowered some, keep in mind a cube that looks a bit wonky in white filament at 15 mm will look WAY different at 450mm in a translucent or clear filament. Similarly, a jump from a .40 tip to a .80 and layer heights from .25mm to .60mm will also change things as well. I have not reached that part in my testing, but I have hopes that when this machine is printing items designed for its huge build volume the .1-.2mm errors it currently exhibits will become less apparent.

Time will tell, but for now this is what it boils down to this- M2 vs. MPCNC = Scalpel vs. Shovel

[jsc]

Oh, you put an extruder on it? I figured you were going to run a spindle and get some nice subtractive machining action going.

[Jules]

I thought it was going to be a cutter too!

[willnewton]

Well, I kinda have the CNC router part covered already.

I will say that I am thinking about adding a laser attachment for some engraving at a later date.