New Machine Build- New build 8020 5 axis

[ec300]

Starting to put things together for my first CNC build.

I will be using 8020 for the mst part as I have some laying around. Some plate aluminum were needed as i have access to it.

I am looking at using skate bearings for the most part as I have a good number laying around from other projects.

I am looking for minumum 30inX30inX20in cut area. I will primaraly be using this for foam, wax, and some wood.

I am looking at the B/C rotational axis on the Z for my 5th and 6 axis.

Attached are my current plans, not the best renders and I tossed it together fairly quickly to get an idea. So please ask questions if you have any.

I am at the point now of looking for input from people telling me what i have thats ok, and what is terribly wrong. Hope the embeded picas is ok, only one i have access to at work.

EC300

[ec300]

Just looking quickly at this I think its hard to see what I have planed for the Z. The Z is a long 2X4 bar that is inside the long piller attached to the via the ACME screws and supported by a good number of bearings. My thought on this is to reduce any backlash due to the long Z axis.

[kawazuki]

Maybe being naive but how is this 5 axis?

[ec300]

Sorry I didn't include that in the mock up or explanation.

I intend to add a B/C rotational axis on the Z. Still looking into how I am going to do that as of yet. Am looking at possibly planetary gears or harmonic drives.

EC

[PaulRowntree]

Originally Posted by ec300 Just looking quickly at this I think its hard to see what I have planed for the Z. The Z is a long 2X4 bar that is inside the long piller attached to the via the ACME screws and supported by a good number of bearings. My thought on this is to reduce any backlash due to the long Z axis.

A 5 axis build is an ambitious undertaking for a first build; not many have tried this. There are a few very robust 5 axis designs here on the forum that may be useful to look through. My guess is that you are going to need a much stiffer frame to support an extended B/C stage which then holds the spindle. It is offset relatively far from the primary support, so rigidity and vibrations are going to be a problem, even with light cuts in foam.

Backlash is measured parallel to the motion axis. It reflects how well the lead nuts secure against the screws; if properly designed and adjusted, the bearings will constrain unwanted motion perpendicular to the motion axis (ie the slop). But just adding more bearings will not improve the tracking, any more than adding more legs to a table will ensure that they all touch the floor. Properly designed and adjusted, 3-4 legs per table (and 3-4 bearings per degree of freedom) make more sense, IMO.

[ec300]

Thanks for the input.

I know the 5 axis is adding a good bit of complexity to the machine but am fairly set on going this route.

I have done a good bit of looking through the forums and got some of my ideas from the other 5-axis machines as well as CNC-toolkit.

I understand what you are saying about the extra bearings, that dose make since.

What Key things do you think could improve this design?

I would like to stay with the 8020 due to ease of use and not having the right tools to do a steel frame. I have looked at rails instead of bearings and opted for bearings due to cost but if they will make a huge difference I might reconsider that option.

I can defiantly build a bigger based to allow more separation / support on the z(B/C) axis. Possibly add some 45 degree cross supports to the tower.

[PaulRowntree]

Well, here are my thoughts : use freely until better ones come along!
1) I don't know what size of 8020 you are using, but go as stout as you can afford.
2) Add cross bracing (45 degree diagonals) into every square area of the frame to keep it from racking. Diagonals inside the frame from opposite corners of the cube may be a good plan too.
3) Don't forget to put enough members to support the worktable.
4) I used skate bearings. They work, are easy to fab, but I can see them digging into the Al angle track a bit. Making adjustable tensioners was a bit of a pain as well. My rebuild will use V-groove bearings running on steel angle.
5) My machine also has the rails raised above the table. But on a 30"x30" table, consider how much extra space you will need to accommodate the 5/6 axes spindle stage; it is probably at least 12" in each direction, so the rails move out to ~54" to maintain the 30" cutting width. Your table is getting bigger, and needing thicker 8020, more braces and more support. UNLESS the head can swing out over the side of the table, which then requires the rails to be below the work table.
6) 20" is a huge Z stroke, probably 4x greater than most 3 axis machines. You are going to pay dearly for this in terms of stability and rigidity. If it really must be this big, spend a lot of time thinking about Z and the associated 5/6 axes before buying anything.
Cheers!

[zool]

With a 5-axis machine the complexity does not increase linearly from 3 to 5, but exponentially from 3 to 5. You have been forewarned!!

Take a look though this site as Colin has 5-axis figured out: DoughtyDrive

Also: remember that the mechanical portion of your dream is the easy part. Before starting to spend money, start looking at software, and start using it as well. This is one choice: The CNC Toolkit - Creative Toolpath Control

Also take a look at this for a manual of how to use CNC ToolKit: cnc4free.org homepage

I too started out wanted to start out with a 5-axis machine [which is my second CNC machine build], and spent several months with CNC ToolKit and the manual at cnc4free, all the while building the second machine. Though I have not given up, I have lengthened the time frame for achieving my goals.

I'd suggest having all your computer and all related software set up and running before you start building the mechanical portions.

Have the entire software work process up and running before buying the first piece of the frame for the machine; by this I mean: The CAD portion; the CAM portion; the post processor [MACH or EMC2]. Its not the individual pieces of software, its the way they interact .. they will be like 5 two-year olds in a room with only 4 toys!!!

The above also includes wiring up the stepper motor controllers and stepper motors, and all the limit and homing switches.

Have you thought of where you are going to locate the home and limits switches? Better know before hand .. thinking about it, and actually doing it after the machine is built is REALLY time consuming .. and frustrating. Have you given thought to all the wiring for the stepper motors, the home and limit switches, the power to the spindle and the hose for the dust collection are going to be routed? Where is it all going to run and how it is going to be controlled and protected. Think about how they are going to get in the way of each other, as they will. Think about the financial side of this as well.

The software and electronic portion is going to take the most time and effort, by far, way more than the mechanical portion. I wish I knew this before I started with my second build ... but then that is why I have a three-volume encyclopedia of errors.

I wish you every success as it will be a great accomplishment. We are all here to help.

[ec300]

thanks for the info Zool.

I had not gotten as far as were to place limit switches and cable runs as of yet. I was going to just attach during the wiring but I can see especially with the 4/5 axis that this will be important to figure out prior to getting started on the build.

I have the PC built that I will be using, so i will get things setup on it during the design phase. Being a computer engineer I know how software can be. I am looking at cnc_toolkit and EC2 as they are open source. I have a copy of 3D studio Max so I figure I will use that.

Do you happen to have any pics of your 5-axis setup you would be willing to share? If its in the forums its possible I have already run across it.

Thanks
EC

[yohudi]

Hi There,

good to see someone else willing to take the bull by the horns on the first build...

There are a few ways to ge re 5 axis plans.. really it depends on your final use for the machine. i.e. if you plan on machining hardwoods with a Z envelope of about 400m.. the Doughty Drive 5-axis machine plan and B/C head kit is your best proven option by far. Checkout the Chatham carving video on youtube... enough said.

If you plan on some thing a little smaller then the DD50 mini-drives really are something... for wax and softwoods on a smaller machine these are ideal.. also they allow the rotary axes to be configured as trunnions and so forth.. this might be a way to go that helps you with rigidity..

Your initial design is similar to a free design available in 3DSmax format at the cnc_toolkit yahoo group. It's Rab Gordon's design.. the chap who wrote CNC_Toolkit... it works well.. and there are some videos of the machine in action available via the CNC_Toolkit web page and development links.

Best of luck... do stick at it... keep in mind that this has been done before and is being done everyday.. with much success... if others can and have done this... there's nothing stopping you also acheiving this goal..

Hope this helps

Danny

[ec300]

yohudi,

Thanks for the info and encouragement.

Ya, I actually got a quote for the Doughty Drive B/C head and it was a little out of my price range. I do however think I am going to try and see what I can come up with that is close to that.

I will defiantly check out Rab Gordon's design always good to use something that is already proven.

Thanks again,
EC

[Bartuss1]

some kind of flaccid