[Drools]

After a few years of collecting THK parts and various other parts I think the new machine can be started.
I have laid out the parts for my new machine in the following photos.
Frame: 80/20 3030 and 1530, all precut from supplier.
Gantry: 80/20 3060 and 1545 with .75” thick aluminum uprights, holes drilled by local machine shop.
Rails: HSR25 for X(48”)/Y(38”) and SHS25 for Z(13.5”).
Bearings: HSR25A/B and SHS25C.
Screws: ACME X(1/2-10 2 start), Y(1/2-10 2 start),Z(1/2-10 single start).
Nuts: Dumpster and CNCRP.
Screw Bearing blocks: CNCRP.
Drivers: G540.
Motors: Steppers X/Y 620oz, Z 380oz.
Spindle: Porter Cable and Wolfgang.

I have included pictures of my first machine which I will need to cannibalize for parts to build the new one. After I make a few parts for the new one J
Thanks for looking, comments are welcome.

[roy_okc]

Subscribed.

Are the rails/bearings new?

Roy

[Drools]

Today I cut the legs on the CNC, they are made from Baltic Birch. Dimensions (LxWxH) 10"x2.25”x7”, I will be laminating them together. On the bottom of each leg I will be mounting a hockey puck.
I also made a bearing block for my screws. On my first build I made 2 mistakes, first I did not make the frame strong enough. Second I did not understand the importance of bearing blocks for the screws. All of my screws have the ends machined like the picture below. It shows the free-wheeling end, instead of using the expensive blocks from CNCRP I decided the free-wheeling end just needs to be supported to prevent whipping like crazy. On the driven end I will be using CNCRP bearing blocks and thrust bearings.
Roy:
Yes they are all new. I have some other used blocks but I would rather use the new ones and keep the used ones as spares.

[roy_okc]

... instead of using the expensive blocks from CNCRP I decided the free-wheeling end just needs to be supported to prevent whipping like crazy.

Drools,

I had a problem with my CNCRP sleeve blocks apparently deforming under even mild tightening, making the Acme difficult to impossible to turn by hand. I cut the shoulders down about 1/4" on the one I ended up using and it now works fine. (EDIT: disregard if you're using the bearing blocks that you made.)

Roy

[Drools]

Roy, was that the "low profile" block or the larger block with a bearing?

[Drools]

To attach the rails to the 80/20 I will use "8020 T Slot Roll In T Nuts 15 S 1/4-20 13096 N". ( eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices ) I bought some 1" 1/4-20 socket head bolts and the proper washers from fastenal. The hole diameter in the THK25 series rails are .2756 this leaves me a little bit of wiggle room and the nuts are somewhat self centering in the slot. In testing the fit was very nice. I could not find similar nuts in metric thread and the bolts would have been special order and more expensive.

[roy_okc]

Roy, was that the "low profile" block or the larger block with a bearing?

Drools,

I had the problem with the low profile blocks that I bought for my Z. The larger bearing blocks work fine.

Roy

[Drools]

Today I made the mounts for the Dumpster nuts and a couple more of the orange bearing blocks. I think that just about does it for parts that I need to make before tearing down this machine. Maybe tomorrow I will start the teardown. The legs for the new one are laminated and now need to be painted. I wanted them to set for a day before sanding and painting.

[Drools]

I did a bit more today.
Earlier I asked a question about http://www.cnczone.com/forums/diy-cn...ing_voids.html . The measurable difference between filling them and leaving them open may not be much but at this stage why not, will it hurt anything?
I made some plugs for the ends of the 3030 which also fit the 3060. I don't think the area inside the 1530 would amount to much. I should do the math though just to be sure.
I also made a mount for the X axis DumpsterCNC Nut. I really wanted to make it out of ali but my machine is not stiff enough to cut ali I made it from .5 UHMW Polyethylene and reinforced with 2 corner brackets. The brackets will need to get a hair-cut to clear the undercarriage. I made two mounts just in case more strength is needed. The nut shown is not the one that I will be using.

[Drools]

I recieved my new motors and other assorted parts from Ahren today, thanks very much Ahren! That was fast!
I have a question on my Z axis, as I want to use parts I have on hand and I will be using a single start ACME 1/2-10 screw but looking over a comment Gerry made about single start screws he thinks it may not have the speed needed. Should I use a timing belt system on the Z?

[DonFrambach]

Should I use a timing belt system on the Z?

How fast do you want to plunge? I have a 1/2 x 10 single start ACME lead screw on the Z axis of my small router and can achieve 75 ipm movement. That's much faster than I want to move so I'm very happy with a direct drive system w/o the complexity and possible problems associated with a timing belt system. Of course, YMMV.

[Drools]

That is a good question Don!
My current machine uses a 1/2-10 single and has been working ok, however I have not routed anything faster than 50ipm and only 2D. If I want to do 3D reliefs at 50+ ipm I’m wondering if a single start screw will be ok. That is assuming this new machine will cut at speeds of 50+ipm!

[ger21]

My Z has a max of 50ipm. When I do 3D cutting at 170ipm, the Z is the slowest part.
Also, I do a lot of peck drilling, and the slow Z rapids really take a toll on run times.


But, in the end, it's just a question of how fast do YOU want it to be. If you're happy with 50ipm, it doesn't really matter what I prefer.

[Drools]

I watched a friends Bridgeport cutting at full speed (240ipm) and wow that is fast. I can't imagine my machine cutting over 100ipm. I will just have to wait and see, I have a ways to go yet to find out.

[Drools]

what is that saying, "in for a penny, in for a pound".
I made plugs for the 1530 as well. I have some very dry normal sand the type you may find on a beach here in northern Ontario. Grain size anywhere from very small to grain of rice sized. I also have some black sand blasting stuff, looks like gun powder.
Which one should I use and should it be packed in or should I leave a little space in the viod?
Thanks for the help.

[PaulRowntree]

When I filled a frame I used white quartz used for sand blasting, and it worked well. I don't think you can easily pack this stuff in, and I can't see it helping. Damping requires some flow with resistance, so there has to be somewhere to flow (to and from).

[Drools]

I'm sure you are right Paul, but it sure does add weight! Later i will get the scales out and get some weights of the filled extrusions.

[Drools]

I was cleaning up my ali plates and I noticed they are not flat! ouch I guess ali flat bar is not always flat. I took them to the machine shop to be surface milled flat, I don't think any more than .05 will have to be taken off the insides of the gantry uprights but the Z mount plates will need both sides done. Good thing I started with .75 thick material? Is this common with wider ali? The piece I purchased was 5.5' long at 8" wide. I was thinking maybe the way the shop stored the stuff might have caused the warping...?
Anyway not a huge problem but I was a little disappointed that I would not end up with .75" thick uprights.
One other question, I'm thinking the lighter a gantry is the better correct? or am I way off on that thinking.
Thanks for the help.

[ger21]

The only aluminum that's truly flat is cast aluminum tooling plate.

One other question, I'm thinking the lighter a gantry is the better correct? or am I way off on that thinking.

Way off. The more mass you have, the better. As more mass tends to dampen vibrations more. The downside is that the more weight you have, the bigger your motors need to be to move the extra weight. There are tradeoffs involved in most of the choices you make.

My advice is to try to make it as rigid as possible, with rigidity more important than weight. The main goal should be for as little flex as possible. Everything flexes, but if you can see it flex, it's too much.

[Drools]

According to the 8020 tool kit 3060 weighs in at 7.5lbs per foot and 1545 weighs in at 3.5lbs per foot. I have to weigh the rest of the Ali to get a total weight but the 3060 and 1545 weighs combined ~33lbs. I have to haul my old bathroom scale to the garage and weigh the 3060 now that the voids have been filled but I can say off the top that the weight has doubled for the 3060. I'm thinking if I leave the voids filled the weight will likely be 100lbs or maybe more. Will my 620oz nema23 stepper move that much weight?
The stepper is built for comfort not speed but
I'm thinking a 100lb gantry might be too much for a single stepper with a 1/2-10 2 start screw.