[eurikain]

Hi,

Four years ago, I followed buildyourcnc.com's tutorials and build a router out of MDF. It was a failure, as I didn't own sufficient tools and talent to make a good build. I have decided to build a new machine from metal, but as I am fairly new to the CNC world, I need your advice for a couple of things.

1. I have been looking at different options:

• X-Carve: shipping cost and taxes out of reasonable ranges
• ShapeOko: too small, and seemed too complicated to upgrade for Nema 23s, and I didn't feel comfortable with buying all the pieces, and making mistakes. ShapeOko 3 is way overprice + 400 Euros for shipping to Europe makes it a no-go for me.
• OpenBuilds OX: interesting build, I like the fact that you can get standard parts from their site (except for plates)
• OpenBuilds ROUTY: interesting build, seems quite simple, but the part list does not seem reliable (after reading the discussions on their site)

2. I want a build that is like a "lego". Therefore, there are two options:

• Find a build like the OpenBuilds OX, and order parts online. Problem is: shipping cost will explode, taxes will kill me.
• Find a CNC Router plan online and order the parts from a local store that will laser cut the parts. Wheels, spacers and such could be bought from OpenBuilds. This options is by far the cheapest according to me.

3. I already own a few things:

• 3 x Nema 23 425oz
• 3 x Stepper Drivers CW230
• Power Supply 36V 9.7A
• 6 x limit switches
• 5 Axis Controller with parallel port
• PC with parallel port
• Mach 3
• E-STOP
• Bunch of electrical cable

4. I want to buy the following to complete this electronics kit:

• 1 more Nema 23 425oz: 1 Axis NEMA 23 Stepper Motor 425 oz in Dual Driver DM542A 4 2A 128MICSTEP CNC | eBay
• Spindle: 400W CNC Spindle Motor Kits PWM Speed Controller with Mount Bracket | eBay

In conclusion, here are the questions I have:

• What do you think about the links I provided for my new Nema 23 425oz and spindle ?
• With the new spindle, do I need an additional power supply, or is the one I have sufficient ?
• Openbuilds beams are hard to find in Europe, and expensive to ship to Europe. Wouldn't it be easier to find a CNC Router plan and order the parts needed from a local welder shop that has a laser cutter ?
• Can you guide me to a good plan ?
• From which material will it be cheaper to build a CNC Router: steel or aluminium ? Forget about MDF

Budget: max 1000 Euros.

Thanks a lot for any of you that will be able and take the time to help me out !

Best regards,
Eurikain.

[ger21]

How big of a machine are you looking for? You're budget is very low, and your unlikely to find any good plans to build a metal machine.
Steel is much cheaper than aluminum, but requires welding and the tools and equipment to work with it.

Your best option might be to buy a chinese machine with no electronics. That's the cheapest option, but may still be over your budget.

[eurikain]

Hi,

Thanks for your reply !

Let's say I want something maximum 1m x 1.5m

I understand your concern. However, I am surprised that you can find 1mx1m OpenBuilds OX kits (no electronics) in the UK for less than 800 Euros. How is it that the ShapeOko 2 was only $300 ? Theoretically, building the a machine yourself is cheaper than buying a kit, right ? My logical sense might be fooling me

Are there other options, better than MDF, cheaper than aluminium ?

[ger21]

Welded steel is possibly the least expensive, and strongest.
But you must have the tools and skill to be able to do it.

[eurikain]

I do have access to a welder shop for cheap (long story), I am not able to weld but they can do it for me
Any free plans that have proven good builds ?

[ger21]

I don't know of any plans, but there are a lot of steel builds at the mycncuk forum.

[wizard]

The first thing we honed to do is to clear up what you expect to do with the machine! This is a very serious issue as things like the open builds extrusions might be suitable for a light duty machine but might not work well at all if you have more demanding uses in mind.

The second issue, for a DIY build, is that Aluminum extrusions are expensive. I personally don't like T slotted extrusions for machine structures either. I just don't consider the bolting methods to be reliable.

As has already been mentioned your budget is tight but apparently you already have a start on components. Your tight budget may end up leading to a very light duty machine.

[wizard]

Hi,

Thanks for your reply !

Let's say I want something maximum 1m x 1.5m

I understand your concern. However, I am surprised that you can find 1mx1m OpenBuilds OX kits (no electronics) in the UK for less than 800 Euros. How is it that the ShapeOko 2 was only $300 ? Theoretically, building the a machine yourself is cheaper than buying a kit, right ?

This is a tough one to answer because much depends upon your raw materials availability and your ability to get reasonable prices. Plus you need to be able to handle the materials.

If DIYing it do not underestimate the cost of tools. If you have them or consider tools investments it might not seem so bad. But if you have zero tools and don't have a strong need for the tools post build they can bloat your build costs.

My logical sense might be fooling me

Are there other options, better than MDF, cheaper than aluminium ?

Not knowing what you intend to do with the machine makes suggesting alternatives hard. If all machining is expected to be done dry a Baltic birch plywood build is doable. Some here have used bamboo plywood.

Your best bet, in a small machine, might be steel though. It is cheap for one and it adds mass better than other low cost materials. In a small machine a bit of mass can be a good thing to help keep the machine anchored. Plus the mass (if it is In the right place) can help with vibration thus improving cut quality.

The third alternative is epoxy granites, which aren't cheap nor easy without a well equipped shop. Epoxy granites can also be used for in fills to dampen vibration and add mass.

Finally an option exist to use aluminum to cast the structural members of your machine. I guy named Gingery wrote a whole series of books about building machine tools from cast aluminum. This approach doesn't often come up in these forums but given a decent founder capability and probably a little help you can do very nice components this way. You might see this as the hot approach that mirrors epoxy granite casting.

[hub]

Just some thoughts.. Welding will stress/distort the framing a bit. Depending on your needs you might have to relieve the stress and/or grind it straight. At least surfaces which will be attached to linear rails.

[eurikain]

@ger21:
Thanks for the hint, I will research their forums

@wizard:
You're right, they're expensive, I definitely agree on the bolting method. It just looks convenient to build when you don't have a lot of tools around.

As for the uses, well, they will be various: wood, plastic, aluminium, acrylic. I would say aluminium is the key factor right ? I do want a decent cutting area (80mm x 100mm at least).

My budget is low but bear in mind that I have access to a welder shop, and they can weld for very cheap, if not for free (I'll pay just the cost of material).

@wizard:
Thanks a lot for your reply, the different options you talk about are very interesting. I think I have a preferance for steel, as I have access to a welder shop. The machine will be heavier, but it will save me quite some bolting and frustration with shipping cost and import taxes with those expensive T-slotted extrusions !

@hub:
Thanks for the info ! Actually, the welder shop I go to can braze, would that be a better approch ?

General questions:
As for linear rails, I have seen a few options, and it's possible to find quite a variety of them on ebay, ranging in many different prices. Which type of rails should I use, though I know that it will depend on the design ?

Also, I was thinking about using drive chain for the X and Y axis, and a standard threaded rod for the Z axis. Is rubber drive chain an option or should I just go with metal chain ?

[hub]

I think brazing would be better. Also, structural steel isn't perfectly straight from factory. You still might want to grind (have them ground at a shop) the surfaces that couples linear slides.
Depending on what linears you use etc. Some allow a bit of misalignment. Some don't, or they will jam/lock.

[eurikain]

@hub:
Thanks for the great info, it's nice to see read your experience.
I am going to use SBR20 linear blocks off of eBay. Rods will be sourced and welded locally, as I am not a huge fan of eBay prices for complete sets (rail + block).
As for the spindle, I haven't chosen yet, and honestly don't really know where to go.. I know that there are air and water cooled spindles, I read a few threads that talked about it, and as I understood they advised to go with air cooled spindles (probably cheaper in the end, as you don't need a whole water set for pumping, tubing etc.). As for power, I see that a lot of people go with 400W spindles, but find that a bit small. I was thinking about a 1.5kw or 2.2kw, but air cooled becomes hard to find with that power.. 1.5kW keeps the ER11 spindle, but 2.2kW goes to ER20, is that an issue ?
So what do you think ? Air, water, 1.5kW, 2.2kW ? I am truly lost

[hub]

The spindle power depends on what you cut with the machine. If it's rigid and uses lots of cutting force you need a powerful spindle.
My machine is "semi-rigid" AL frame and I have a 1.1kW spindle. It lost torque once when drilling fast in hard wood with a 32mm drill. Smaller drills & endmills work just fine even drilling steel.
Not sure what you intend to cut? But try with the 400W spindle first I guess.

[eurikain]

I definitely want to cut aluminium at some point, so I'm guessing going with 1.5kW is a good idea. That will be a good start if I decide to go water cooled I'll see what I can cut with that But in the end, fine tuned speed and feed rate are the key to success, as it's turned out in my readings
I am going to start modeling the design of my machine. I got inspired from a mycncuk thread. However, I think I'll go with drive chain for X and Y, and standard threaded rod for Z.

[ger21]

Just some thoughts.. Welding will stress/distort the framing a bit. Depending on your needs you might have to relieve the stress and/or grind it straight. At least surfaces which will be attached to linear rails.

All the welded steel builds at the mycncuk forum use self leveling epoxy to achieve flat and level rail mounting surfaces.

However, I think I'll go with drive chain for X and Y

Not a good choice, imo.
Timing belt is a little better than chain, but will flex a lot. Ballscrews are your best choice here.

[Azalin]

I definitely want to cut aluminium at some point, so I'm guessing going with 1.5kW is a good idea. That will be a good start if I decide to go water cooled I'll see what I can cut with that But in the end, fine tuned speed and feed rate are the key to success, as it's turned out in my readings
I am going to start modeling the design of my machine. I got inspired from a mycncuk thread. However, I think I'll go with drive chain for X and Y, and standard threaded rod for Z.

I'd get a 2.2kw spindle for aluminum. 1.5 will also cut alu but it will slow down at some conditions.

[eurikain]

@ger21

Not a good choice, imo.
Timing belt is a little better than chain, but will flex a lot. Ballscrews are your best choice here.

Sounds good, I'll go with lead screws then, as it seems a better choice. But by curiosity, why isn't chain / timing belt a bad choice ? Chain won't flex :/
@Azalin
Sounds like the stronger the better ! Bits quality will also impact cut quality and speed / feed rate tolerance, right ?

[ger21]

The only machines you'll see with chain drive are from BuildyourCNC. Those machines are not very good.
Chain stretches, and needs to be constantly adjusted. To minimize backlash, it needs to be extremely tight, which leads to more stretching. And as chain travels around a sprocket, it speeds up and slows down, causing a cogging effect.

[eurikain]

Interesting Is rack and pinion viable an option according to you ?

[Azalin]

+1 for what ger said. Ballscrew is the way to go.