[Sockles]

Hey all, this is going to be my first build straight from scratch including designing structure. I have some knowledge about CNC's due to first owning the ZenToolworks 7x7 kit, then building 2x4' machine from Buildyourcnc.com, and finally I have built a Thing-O-Matic from MakerBot Industries.

I have decided to make this machine wide and low profile if you will. I'm not sure what compelled me to think of this build, but you will notice I have based my design off of the MicroCarve A4.

My main purpose for this machine will be strictly engraving and milling plexiglas. I really dont think I will be milling metal, unless my other CNC's are down. So i'm hoping on very low tolerances, unlike my 2x4' at 2mm tol. due to the bowing(sp).

The machine will be 2 ft. wide by 18in. in length/depth. I will be using 3/4 MDF unless, I can find a place that sells PVC board. It will be held together by those screw barrel connector things. Sorry, I can't think of the official name. And the spindle I will be using is Dremel model 225 flexible shaft. I'm using this for the most wide area cover as I can get. Although my friend brought up the point of not being strong enough to with-hold the power. I said, just remeber its only going to be plexiglas.

I have designed the machine using Solidworks.






**If anyone has any doubts on the designing of this build, please let me know. I'm going out on a limb here**


Tyler

[silyavski]

(wedge)hi,
sorry for my opinion but:
v carving, engraving and cutting plexiglas involves working with micro tooling and even the smallest inaccuracy in the machine will make you break a lot of bits and i am talking about microns here, so:
1. to me your machine looks nice if it was meant to be from Aluminum
2. unsupported rails for me are not an option even to consider whatever the machine is, even if its made from paper
3. whatever the Dremel is , its still a Dremel so even if the rest is good it will screw the project

i imagine you want to go on the cheap, though some times its not entirely possible.

if i were you and wanted to do it cheap but sturdy:

1. frame welded from metal, with moving gantry look at this design and simplify it for your purpose . no legs, just base and gantry. metal is cheap, can be from scrap also. go to the local shop, order the pieces cut to sizes, speak with them for you to do the hard job of aligning and fastening it together and they just to solder it here and there
2. such small table also can be belt driven, which is cheaper, study the above design y apart from the base and gantry make all the rest from plastic, like thick HDPE and put some ribs here and there for sturdiness
3. buy a 0.8kw water cooled spindle cheap from ebay and a hitachi inverter, again: hitachi inverter
4.make the x axis from supported round rails from VXB
invest some money in cheap ebay HKS square supported rails for the Y and the Z, you can find them en ebay 1/5 th from the original pice

Now you can sit down and cut some aluminum if you like

i live in europe so its more expensive and i know what cost me here in Euro and if all is thought out carefully the bill would be like:

frame and gantry material - 30e so: 45usd
plastic 20mm 60x 30mm sheet : 60usd
spindle 150usd
inverter VFD 200usd
all rails 200usd
belt, pulleys and screws 100usd

hey, its getting expensive but you get what you pay for

with electronics and motors it would be like 1000$ and you will have a machine better than what they sell for 3000$

[Sockles]

Thanks for your opinion, I respect that.

I may only be 21, and without a job, but making these machines on the cheap isn't as hard as you or everyone may think. Yeah it may be a couple thousandths of an inch off but its fine for what I'm doing, hobbies. I've been working with my machines for at least 3 years.

I spent just over $500 to build my 2'x4' machine and $400 of that were the 475oz in motors and electronics. I also use a Dremel with it and have't had a material that It would mill. (as long as you use the right parameters for that material)

I also have no problem engraving or milling plexiglass on my Zen Toolworks machine. That also has a Dremel as a spindle.

Now on the other hand you do have a point of the rails maybe being too long and unsupported. I definitely can see bowing of the shafts, but spindle is not that heavy. Heck maybe for the tables shafts i'll put 4. Who knows.

Anyway, I will definitely consider what you have said. I don't want to make you guys think that I'm some stuck up kid that knows everything.


Sometimes you gotta push the limits of what is possible, and enjoy the failures.

[microcarve]

As you probably already know, I've been very hesitant to extend
the machine design by much more than it is. Flex can be a problem
easily once it gets too large.

It's also very often that flex has less to do with the shafts
themselves as it has to do with construction and how the shafts
are attached. Case hardened steel shafts aren't easy to bend.

MDF is easily compressed a little bit at points where steel
shafts attach directly into holes. That can make it appear as though
the steel is more flexible than it really is, and it progressively
gets a little worse over time. So I use all the metal fittings
and plates to prevent the MDF itself from being a problem.

I probably wouldn't try for 24" wide myself....though it does
look like it's easily extended that far....

But...if someone really wanted it 24" wide, and they knew it's not
going to work well for metals...and used it within it's limits....

I'd go to 3/4" shafts on the bridge/gantry.

I'd separate them...probably to 4" - 5" (from 3")

I'd increase the sizes of the cross members that tie the sides
together to at least 5" wide...and maybe 6"....(long narrow strips
of MDF are way too flexible on their own)

And, I'd Definitely use threaded rod tensioning to tie the cross
members together. Much stronger than the cross dowel connectors.

If the extended cross members were too flexible -later -in use of
the machine, some inexpensive aluminum angles will brace them
and make them stronger. And it's easy to add them in if needed.

I think that'd make it good for hobby work, and have it to a point
where any problems were easily adjusted out or modified/fixed.

One potential problem is the Z and accounting for the cutter being
in the center of the moving table. At 18" depth of the machine, the cutter
could end up in a position where you only have 7-8" of actual usable
cutting area of the moving table....(front to back)

I've seen Dremels do Great work. But if need be, these sort of things work
Very well....

WECHEER CORPORATION

I used one for a couple years to make plastic Z axis parts, and it's
cheap and works great. Harbor Freight has a version. If they still carry it...


I think I've learned a lot more from many failures than successes. Most
times, I'm suspicious of something if it works too well and too easily.
That's when I know something will go wrong when I least expect it....


I'm glad to see someone experimenting with the A4 design.


John

[silyavski]

no offense, but i continue to wonder what will make sb have pouring money in 3 inaccurate hobby machines instead of one accurate hobby machine which can make him money and pay it self with 1 or 2 sign lettering jobs for example

[Sockles]

I wouldn't necessarily say my projects/machines are inaccurate (If that's towards me, if it is, your are mocking Zen Toolworks machine, Buildyourcnc.com and Makerbot industries, cause up till now, they were all kits that I have built{great people by the way, every one of them}). I have made plenty of money making signs and circuit boards for people, hence not having the need of a real job.


A couple of my projects by Sockles1, on Flickr
I won't even show you my plexiglass designs because my machines are too inaccurate to show you.


I came here to this site thinking of getting inspiration, Which John has done. Thank you! But I feel like I also have been mocked for even trying to design and build my own machine from nothing but a reference picture and my own requirements.

Thanks John! I really appreciate you taking your own time to help me with my project. I hope its okay for using some of your A4 design in my project? I'll make use of your suggestions and see what I can come up with. :wave:

[silyavski]

hey,
sorry, as i told you no offense meant! you said in the first post that one of your machines has 2mm tolerance, if you believe that is accurate :cheers:

[microcarve]

Thanks John! I really appreciate you taking your own time to help me with my project. I hope its okay for using some of your A4 design in my project? I'll make use of your suggestions and see what I can come up with. :wave:

You're Very Welcome and Yep, I'm Very happy to see someone making
use of the design. Especially so from just looking at it....

Here's some pictures of some of my very first machines.

http://www.microcarve.com/zone14/fireball/


What should ordinarily be interesting about them is that they
were the tools I had to make many more cnc machines....that got shipped
all around the world. And did...and do...Very fine work still.

The small yellow one made plastic Z axis parts that had press fit holes.
So that's pretty accurate.....else the z wouldn't work...


http://www.microcarve.com/zone14/fireball/Bushing.wmv


http://www.microcarve.com/zone14/fireball/ZPlates.wmv


The one that's enclosed made the MDF parts for the machines.

I did have a small mini lathe, but those are what made a few hundred
small cnc machines for a year or two.

Three things I thought were important....

Make them as small...(and tight)...as they needed to be for the
intended job.

Have an intended job. Know what I wanted from the machine to begin
with....

Use them within their obvious limitations.

As close to 100% reliable...and highly accurate...as I could ask for.

Those are some Great examples you've shown!!


John