*First CNC Router.....*

[AcadianCNC]

Let me start by saying that this is a great wesite/community. As well as my first cnc router this is also my first post . Over the past year or two I have read many posts and bought different parts but it is not until you actually start putting one of these cool machines together when you realize/understand the contruction process.

Most everyone that builds there own machine wants two things 1) To build it to their own specs (cutting area, height, tolerences, etc.) and 2) Wants to save money doing it. If money was no factor and you wanted to start in the least amount of time, then we would get a store bought machine instead, right? . So the combination of these two factors "directs" us in many different ways during planning and construction.

My frame is made from 1/2" aluminum that I layed out 2D in AutoCAD and had the parts waterjet cut. Notice I notched out holes in areas to save on weight but designed in such a way to keep its strength.

All axis rails are pillow blocks over hardened stainless steel round bar. This saved money and I could order the different size rod to fit my specs. When you buy on ebay, especially linear bearings (which are better) they are more expensive and the diminsions of your machine is at the mercy of whats available.

The propulsion will be small servo motors and will turn ballscrews. Again, leadscrews may be better but to get an inexpensive leadscrew off of ebay your at the mercy of what size is available. Even then the end may not match up with the diameter of your motor's coupling and may have to be machined anyway. The tolerances on the ballscrew is acceptable in my application of .004" per foot with minimun backlash from a preloaded nut.

Well I will end my first post here for now and welcome comments and feedback. Thanks.

[haciman]

Wowwww great machine.

How much bar size (diameter)?

[AcadianCNC]

x= 1" diameter w/ SPB-16 Pillow blocks
y= 3/4" diameter w/ SPB-12 Pillow blocks
z=5/8" diameter w/ SPB-10 Pillow blocks

[mar999]

nice machine there keep up the good work

[crocky]

Hi,

Nice job so far.

The only comment is the spacing of the pillow blocks on the X axis, wouldn't they be better spaced apart a little more like the Y and Z are? You may have some problems because of the height etc.

My 2cents worth

Bob

[AcadianCNC]

Point taken Bob but the wider you get the more "unused" space there is. In other words, a 10" bottom support will hit the ends of your frame before this 6" will giving me 4 extra inches of useable cutting area. Plus the 1" blocks are very firm with no noticable movement.

My X cutting area will be 48". So I designed the total inside length to be 56" minus 6" for bottom support strut and 1" each side for kill switches.

My Y cutting area will be 36"+ with 6" for gantry block and enough area for kill switches gave me a total of 44" inside gantry supports.

Thanks.

[Oldmanandhistoy]

Not wanting to put a downer on it but to me it screams flexing and racking.

I have to agree with Bob the blokes on the X axis are far to close together. Imho it is better to have 44” of good travel than 48” of problems.

If the machine is designed for light work you might get away with it but I see lots of areas that will cause problems.

Sorry if all this seems negative but I hope you appreciate an honest opinion.

John

[AcadianCNC]

Speculating is one thing, having done it and knowing for a fact is another. I am confident the way the center of gravity is on the gantry with router installed and linear pressure while routing into material against the x axis, this thing will be solid. If you can show me where you have worked with these pillow blocks in a similar application supporting your claim then I be more concerned. I guess the proof will show when it is complete.

[Oldmanandhistoy]

Originally Posted by AcadianCNC Speculating is one thing, having done it and knowing for a fact is another. I am confident the way the center of gravity is on the gantry with router installed and linear pressure while routing into material against the x axis, this thing will be solid. If you can show me where you have worked with these pillow blocks in a similar application supporting your claim then I be more concerned. I guess the proof will show when it is complete.

Then we will say no more and see as you say. I did hesitate with a reply and did half expect a reply as posted. Maybe people should think more carefully about asking for opinions if they aren’t going to like any thing other than praise. Obviously I will keep my opinions to myself if I see you post again you obviously know best. I should of realised that by your reply to Bob. Maybe questioning my reply would have been more constructive.

[mar999]

ok lets say he has for x axis 2 (thomson closed bearings 1") each bearing is (in fact) 2.81" long(take away for housing each is 2.25 and get total bearing size) so we get with two bearings 4.5 inches total ( i dont know) but it looks like he has the right amount of bearing>note!! its just that the lower x rails for a 1 inch rail dont have the right amount of support for the span. again this is just my opinion. (does it sag at all just sitting like that in the pic with y and z in the middle of travel?) even .002 Note: remember theres no spindle attached yet just trying to help all the people in this forum thats all they do is help(they did with me ) and i can make a sure bet they will with you too!! so far i would say very nice work though!! i like how ya reduced the weight(very slick) >reminds me of american chopper on the water jet keep it coming looks great

[mar999]

They Are The Best In The World!!

[the__extreme]

Originally Posted by Oldmanandhistoy Not wanting to put a downer on it but to me it screams flexing and racking. I have to agree with Bob the blokes on the X axis are far to close together. Imho it is better to have 44” of good travel than 48” of problems. If the machine is designed for light work you might get away with it but I see lots of areas that will cause problems. Sorry if all this seems negative but I hope you appreciate an honest opinion. John

I'd have to agree with John. I can't tell what your X span is from the images, but let me guess that its 60". If you're at the middle of the span, 30", with a total load of 100 lb (including the gantry etc.) supported only by the two 1" rails, you would probably see sag between 0.04-0.15" depending on how rigid the end connections are. Just from looking at the gantry, I'm guessing it'll weigh over 100 lb on its own, forget about cutting loads. Rods that long will act like stiff springs. You could expect similar results on the Y axis, with the additional problem of twisting from cutting loads applied from cutting in the X direction.

You can consider that there may be some validity to my comments, of perform some simple calculations to convince yourself.
http://www.clag.org.uk/beam.html
The performance you should expect will be somewhere between a simply supported beam and a double cantilever setup.

I like the work you've done so far, looks very professional, but I would hate to see you disappointed in the end after all your invested work, time and money.

- Shawn