[mchlmacdonald]

new to the forum, and to benchtop CNC'ing.

i work in an aerospace machine shop, just got into the industry 6 months ago. i'm currently an operator on a Mazak Vortex 1400/160-II, i'm pretty much just doing setups and pressing the GO button and letting the machine do all the work.

i would like to run some parts for my airsoft guns, rail systems and metal body's and whatnot. the stock stuff is cheap potmetal and i want to make better ones out of 6061 aluminum. which means i am in the market for a good benchtop cnc machine, with a fairly large work area (20" x 10" x ?" is what i'd prefer to have), and able to keep tight tolerances. should i be looking for a built machine or be looking to build my own?

any info and/or opinions on the matter is greatly appreciated.

Mike

[hoss2006]

20 inches in the x isn't hard to find but 10 in the y is a little harder to find in a "benchtop".
SX4's have about 10 y and the IH clones about 12 inches.
RF45's and clones go about 21-22 x and 8-9 y.
bf30's also are about 8-9 inches y travel.
the bf46 is also 10 inches y.
Hoss

[wizard]

new to the forum, and to benchtop CNC'ing.

i work in an aerospace machine shop, just got into the industry 6 months ago. i'm currently an operator on a Mazak Vortex 1400/160-II, i'm pretty much just doing setups and pressing the GO button and letting the machine do all the work.

Nice hardware to start out on.

i would like to run some parts for my airsoft guns, rail systems and metal body's and whatnot. the stock stuff is cheap potmetal and i want to make better ones out of 6061 aluminum. which means i am in the market for a good benchtop cnc machine, with a fairly large work area (20" x 10" x ?" is what i'd prefer to have),

That is tough to get in a bench top machine. Frankly such a machine deserves a dedicated stand at the minimal and an enclosure of some sort to manage swarf and lube/coolant.

and able to keep tight tolerances. should i be looking for a built machine or be looking to build my own?

Tight tolerances mean nothing, I work in the optics industry, what is considered tight here or good surface finish is dramatically different than what is seen in mainstream machining. You really need to define what you need to achieve before you go searching for hardware.

Once you define what you need to achieve then you need to determine if buying makes sense for you. A machine guaranteed to run with good repeatability and accuracy will not be cheap to purchase. Going home built you may get there but to be honest it might not be on your first go around as rebuilding a machine to achieve a certain level of precision has a learning curve. However if you are less concerned about accuracy, CNC conversions can be fairly straight forward if you have modest mechanical and electrical skills.

For some there is the chicken and the egg problem, that is it really helps to have a certain amount of shop equipment before doing a conversion. Hopefully you have access to a lathe and mill at your place of employment.

any info and/or opinions on the matter is greatly appreciated.

Mike

You could always build a whole mill from the ground up. You won't save all that much though and your need for access to machine shop equipment will be even greater. Here I'm thinking the approach that uses square steel tubing and linear bearings. You really have to be into this approach to see it through. On the other hand you can size the mill almost exactly to your needs.

For most people the most rational and cost effective solution is to DIY a Chinese mill conversion. Depending upon the donor machine choosen this can be done from a kit of parts in many cases. If not a kit the general process is detailed in these forums. Realize there are levels of accuracy in things like ball screws and that the better components come at a significant cost. Further realize that the base hardware of the imports might not be up to the task of supporting things like high precision ball screws.

In the end don't expect the precision of even a Tormach in a home built machine without a lot of work. If there is a business angle to this endeavor I would seriously consider a larger commercial mill probably a used one. Note too that you will be DIYing a rather heavy mill to get the dimensions you are looking for that means you will need either human or mechanical helpers for fit up. That is most people will not be able to walk up to one of these machines and properly handle the castings. This class of machine can weigh in at anywhere from 600 to 1200 pounds.

[mchlmacdonald]

Thank you hoss and wizard for the replies. I was expecting the need for a heavier duty machine, though I would still like to keep the machine fairly compact. As for tolerances and repeatability, I'd like to keep it within .005, if that's an attainable goal with a conversion or self built machine. I'm willing to spend the dough on good ballscrews and servo motors if that's what I need to get the accuracy I require. And if self built is the way to go, then heavy duty steel and a full enclosure will be used. So, which way would be better to go, a conversion or self built?

[wizard]

Generally you need some shop equipment to do a ground up mill build. With a bit of effort a conversion of a mill can be done with that mill and a lathe. Hopefully you have access to a lathe.

The biggest problem with a ground up build, beyond access to equipment to build the machine, is the time to actually take on the task. If your primary goal is to knock out parts on the mill then do a conversion or find a used mill.

As to the mass of the machine that is what happens when you want certain parameters that don't fit in well on the benchtop machines. To get what you want axis travel wise is going to lead you to a big machine. Consider this Tormachs 1100 machine comes in slightly under the dimensions you are looking for and it weighs in at around 1400 pounds. Search long enough and you might find a machine with the travels you want that fits on a bench, but it is very likely to be "light duty".

It's kinda funny but I have to ask if you are sure you need a machine this big. It's funny because I'm usually accused of guiding people to larger machines. In your case the idea of a benchtop is a bit at odds with the physical size you are after.

[mchlmacdonald]

No, I don't think I'll need 20 inches on x. The max length rail I will be machining is 12 inches,
so i need a workable area around that. And they don't get much wider than 3-4 inches, but i
would like to keep y travel flexible in case i would like to setup multiple parts. Z travel also needs
to be pretty flexible.

There will more than likely be some complex cutting involved, might even do some 4th axis work
as well, so I need to have a sturdy and accurate machine. I'm also limited in space so a small machine
is what i need, and that's why i posted this in the benchtop forums, because the majority of posters
here are familiar and knowledgeable with small machines.

I'm leaning more towards building my own, with a stationary gantry and moving table. ill make it out of
quality steel for rigidity, and whatever components i'll need to get repeatability within .005". I have a
Bridgeport at home with a Newall DRO as well as a lathe, so making parts for the machine won't be an
issue. My dad and i are in this together, with his 30+ years experience in the machining industry and
both of our mechanical abilities building our own shouldn't be too far out of our reach.

[wizard]

No, I don't think I'll need 20 inches on x. The max length rail I will be machining is 12 inches. And they don't get much wider than 3-4 inches so y can be cut down as well.

Just don't go too small vv

But there will be some complex cutting involved, might even do some 4th axis work as well, so I need to have a sturdy and accurate machine. I'm leaning more towards building my own, with a stationary gantry and moving table.

That would be interesting and frankly would allow you to hit your axis travels easier. Just build it stiff enough to handle milling aluminum.

I have a Bridgeport at home with a Newall DRO as well as a lathe, so making parts for the machine won't be an issue.

Well that is one little detail that makes a huge difference. I was thinking
that this was a bootstrap project. Now it is more of a mechanical engineering project that anything else. Before you do any of that engineering you should determine what we you will be using for the fourth axis. That to determine how much clearance you will need in the Z.

As a side note some of your message above got truncated in the quote. Having a partner in this build will go a long way to keeping the project on track. That is an important element in these DIY machines. Best of luck.

[TiagoSantos]

I had a lot of ideas for building my own machine from scratch, but lack of tools, help and, frankly, skill.. Meant a conversion was a better option for me. Please keep us updated on this, I love seeing what people come up with.