[Hezz]

Hi Guys,

I've been designing some DIY CNC machines for the last couple of years but have not really got around to building things much due to working part time and having limited funds and space and also a house remodeling project going. I have been searching DIY CNC designs for quite a while but only recently found this thread on CNC zone. Perhaps because all of my searches have been terms like DIY CNC rather then uncategorized metal working machines.

I thought that it would be nice to start a build thread for a couple of my designs. It will be a long slow jog. Now I am slowly collecting parts, materials and tools that I think I will need to do the job. My approach will be to get the most I can out of limited funds and tool resources. I will not have access to large mills and lathes. I really like the epoxy granite structures but have determined that I will have to use limited amounts of this material due to costs for large castings. My goal is to build a small but rigid benchtop mill that is kind of a hybrid manual/CNC mill. I really prefer to work with all manual or all cnc machines. But I have not been in the machine shop for some time and now I can see the need for a small but stiff hybrid hobby CNC mill. Hopefully with a DRO readout eventually.

The other project is a little more ambitious. Trying to build a fully enclosed CNC mill that has really good accuracy and repeatability in a 40 x 36 inch footprint and weight no more than 700-800 pounds and be movable enough so that it can be rolled out of the way in my small workshop when not needed. I also don't have thousands of dollars to spent on linear ways so I will be moving towards another technology that I'm hoping to implement for much lower cost.

Here is a 3D CAD model of my first vision of my roll around mill. I have since decided to abandon this design in favor of another more accurate machine topology. But I post it here to give an idea of what I am after. The newer design has had a concept model created but I am still in the early concept modeling stages. And since it may be a couple of years until I really can get started on this machine I thought that I would post some of the history of my CAD modeling and design iterations. Over time I have gained a grater understanding of machine design principles but I still consider myself a learner in this regard.

[Hezz]

After designing the above concept portable mill I realized that it would not be stiff enough and accurate enough with the round steel rod rails attached at each end and all three axis stacked on each other. I have gravitated more towards something like this approach. But it is still only a basic concept. Essentially, it will be a heavy space frame with EG filled structural members. The issue of course is how to build a complicated weldment accurately and have it adjustable enough so that the machine can be aligned and dialed in for accuracy. I believe that i have this worked out to some degree.

[Hezz]

Here is the basic concept for the benchtop hybrid CNC/manual mill. The idea was to base it around a Grizzly X & Y table and to make a really stiff Z axis column and base really cheap from scrap steel. I already have most of the steel for this project. I'm still in need of building or procuring some lapping plates and a few steel pieces. Basically the headstock will be a weldment perhaps filled with EG and the Z axis column will be a double square steel column filled with EG. I'm still decided how to mount the rails. Which unfortunately will have to be used for this projects budget. But once that it is built I can always get new rails and blocks. I want something that can machine steel and if I can get .001" tolerances I will be happy.

[pippin88]

Don't bother with manual capabilities. MDI mode replaces manual milling and does a much better job.

[Hezz]

Don't bother with manual capabilities. MDI mode replaces manual milling and does a much better job.

Does cutter compensation automatically work when using this mode so you don't have tedious calculations to make at every non 90 degree angle turn.

It seems like this could be both useful and dangerous. too easy to make a mistake if your machining an expensive or complex part but for something quick and dirty might be quite useful.

[Hezz]

Sorry for being slow to post.

I haven't really done much except think about what I am going to do. From a design perspective this project is turning into two separate CNC mill builds. One is going to be a bed type column mill made from weldments. This will probably be the first on that I get done since I have collected some of the materials already. For the most part the design will be straight forward. The interesting part is that I want to design and build a small tool changer for this mill that can hold at least 8 tools. Eventually, I want to make a small machining center with a roll around steel kart that will allow me to use coolant.

My goal with the space frame cage mill is to enhance the design and build a 4th and/or 5th axis trunnion type of unit to put on the table. I want to be able to machine any type of project with that setup. I am studying up on that topic now.

The ideas that I have come up with to improve the space cage mill are the following.

1) The frame will be made in four weldments:

A) The roll around kart which will hold the electronics and coolant system
B) The main torsion box bed frame.
C) The upper gantry support and coolant containment frame
D) The gantry beam.

2) The torsion box will have a 1/2 inch top plate and a 1/4 inch bottom plate with four coolant through pipes to allow drainage. This will make it a true torsion box. The top plate will be lapped flat to direct mount the linear rails.

3) The gantry support frame will be bolted to the 1/2 inch steel lapped plate that will act as both a setup table and a reference surface to build the frame on.

4) The gantry beam will have adjustable bolted connections to the gantry support frame that will allow it to be dialed in square and then EG will be poured in the gap and the structural bolts will be tightened. This should allow good gantry
setup and some vibration decoupling from the lower frame. At least in theory. Since resonances are tricky things we can hope.

5) the roll around kart will be partially decoupled from the main unit so that small out of level conditions can be compenstated for.

6) My idea to save money one this machine and make it highly accurate is to use triple filtered coolant injected hydrostatic large surface bearings. I think that if I am able to get a manual benchtop mill that I can make the rails and blocks myself.

7) The EG milling plate will be reinforced with rebar and a steel torsion box inside.

8) Two ballscrews will be used on the lower Y axis and maybe three rails and blocks for high regidity.

9) The hydrostatic blocks will have a large surface area with about .001 clearance for the fluid to fill the void.

10) If not too heavy the spindle head will be a steel weldment with EG an EG filled cavity.

More before too long.....

[Tkamsker]

hi hezz looking at your 3rd picture it is exactely what we build. it even has an pinole that you have manual drilling capabilities. i personally believe depending on your projects manual capabilities ar sometimes needed even if you need an quick cut an fast flattening whatever. so if you have more fun building it on yourself go ahead otherwise the machine is based on 20 years experience ,..


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[Hezz]

hi hezz looking at your 3rd picture it is exactely what we build. it even has an pinole that you have manual drilling capabilities. i personally believe depending on your projects manual capabilities ar sometimes needed even if you need an quick cut an fast flattening whatever. so if you have more fun building it on yourself go ahead otherwise the machine is based on 20 years experience ,..


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Thanks for the feedback Tkamsker, I agree that there are times it's nice to have a manual machine. I'm still trying to decide what to do if i will make this first machine I am building a manual or a CNC. Do you have a picture of your manual build?

Paul

[Tkamsker]

yes i have but it is not an build they have 20 years experience in manual i just made an cnc version of it so they adjust to my plans in the factory ,..


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[Tkamsker]

Thanks for the feedback Tkamsker, I agree that there are times it's nice to have a manual machine. I'm still trying to decide what to do if i will make this first machine I am building a manual or a CNC. Do you have a picture of your manual build?

Paul

Yes i have today for instance i did 80% cnc and all drill s Manual Attachment 291978
So i cnc all the stuff then i let do call Center drill and Then i use the Manual for drilling because that is much faster
Attachment 291980
And this piece used an 8mm and 4mm miller and then Manual drill Attachment 291982

But i work on an atc Version aß well cu thomas

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[Hezz]

A couple of days ago I ordered a Grizzly Tools dovetail X & Y table. So I think that I am going to follow through with making my first steel column bed mill a manual mill. My goal will be to make it more rigid and accurate that the typical bench top mills. If this manual mill build is successful it will go a long way in helping me to build my CNC cage mill with a 4th and 5th axis and my slant bed lathe.

I have been working on a few preliminary concepts for the slant bed lathe. If I have my way it will have an automatic chuck and twin turrets with live tooling. I am brainstorming how to do this on a small DIY hobby scale and I think that I have most of the turret figured out.

Here is the preliminary concept design. I will post occasional updates. If and when I start building it (a couple of years down the road) I will start a new build thread for the lathe. Or maybe I'll just keep this one thread for all of my projects.

[Tkamsker]

hi what do you mean by rigid and accurate ? in numbers ? how deep you cut in steel and the repeat ?


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[pippin88]

A square tube will be stiffer than round and then you don't need the ribs.

[Hezz]

hi what do you mean by rigid and accurate ? in numbers ? how deep you cut in steel and the repeat ?


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Of course I want it as accurate as possible and it remains to be seen how accurate I can make this machine. I want to be able to cut all but the hardest alloys at least .030 inches deep at a pass. Nothing like the big machines can do. My budget will limit the horsepower that I can afford to a few HP so no heavy cuts will be made on this machine.

[Hezz]

A square tube will be stiffer than round and then you don't need the ribs.

The engineering papers that I have read conclude that a round pipe is stiffer for the same mass as a square tube. At least torsionally. And the way I see it most of the forces on the main bed will be ones that have a tendency to twist it. This will make the round tube all the more effective. Also, cost is an object and scrape steel tube is easier to find and cheap. Large cross section square steel tubes are not.

[hanermo]

Round is stiffer per mass, yes.
BUT..
Round is not accurate enough, so you cannot use it directly.

Flat surfaces are much easier to mill/file/sand flat.
Bolt assys onto.
And so on..

The more I have built (about 15.000 hours so far) the more important I see saving work, and the less important I see saving money.
Currently, everything is made from "F1 calibrado" a local basic tool steel, usually 2-3 cm thick in stuff I make.

My machines have gotten better, and my building times /unit lower.
Currently at 0.3 micron theoretical step sizes, and industrial stiffnes levels (20-30N/um).

Gonna go make the saddle clamps now, to mount the new x axis servo behind the lathe.
0.750 rolled ballscrew from roton (not too good),
750W - 220V ac brushless servo, 10.000 count encoder (excellent),
HTD 8/30 belts 24:48 for 1:2 (excellent)

Clamps are 40x80x700 mm tool steel, bolted onto the saddle.
Servo is behind lathe, out of the way, fully enclosed, and full manual look & feel is maintained.

The saddle gets an MPG dedicated to X axis.

[toneV8]

hanermo: what brand and model of 750W - 220V ac brushless servo drive and servo motor you have

[Hezz]

Round is stiffer per mass, yes.
BUT..
Round is not accurate enough, so you cannot use it directly.

Flat surfaces are much easier to mill/file/sand flat.
Bolt assys onto.
And so on..

The more I have built (about 15.000 hours so far) the more important I see saving work, and the less important I see saving money.
Currently, everything is made from "F1 calibrado" a local basic tool steel, usually 2-3 cm thick in stuff I make.

My machines have gotten better, and my building times /unit lower.
Currently at 0.3 micron theoretical step sizes, and industrial stiffnes levels (20-30N/um).

Gonna go make the saddle clamps now, to mount the new x axis servo behind the lathe.
0.750 rolled ballscrew from roton (not too good),
750W - 220V ac brushless servo, 10.000 count encoder (excellent),
HTD 8/30 belts 24:48 for 1:2 (excellent)

Clamps are 40x80x700 mm tool steel, bolted onto the saddle.
Servo is behind lathe, out of the way, fully enclosed, and full manual look & feel is maintained.

The saddle gets an MPG dedicated to X axis.

I agree fastening is easier to flat surfaces but with a weldment it shouldn't be too hard to work with the round tube. I think the cost of stress relieving will be a bigger issue. It will cost more than the materials for me.

Do you have any pictures of your CNC builds?

[Hezz]

Hey Guys,

I have got a new idea for my small portable CNC machining center. I was looking at CNC mill pictures and noticed this kind of hybrid gantry/column mill layout. I started thinking about it and then after mocking up a simple 3D model for visualization purposes I decided that I could expand on the idea to make a mill with an easy to design tool changer. Essentially it is a fixed gantry mill with dual Y axis. One aixs is used for a for milling table and the other will have a router type tool changer and space for a small trunnion 4th and 5th axis. The entire footprint is 48 x 32 inches. Here is an early mockup of the basic frame. Consisting of steel reinforced EG and a EG filled steel weldment. The basic machine structure is in three parts as shown.

[Hezz]

Update,

I Just did some minor modeling to this dual Y Axis mill design. Reduced the thickness of the gantry beam as it was too big for the bed and added some reinforcing steel wings on the sides that also act as a containment for coolant spray. I think that I can build a front and side enclosure system for this design pretty easy out of tubular and aluminum sheet and plexi-glass.

It will have a sturdy torsion box kart to sit on too.