[praneetn7]

Hey guys,

I have been silently looking over many of the amazing builds on the website and have gathered a wealth of knowledge thanks to you guys!

A bit about myself, I am 16 years old and for my senior project for high school, I plan on building a small CNC router.

The CNC router will be used for; PCB's, wood work, plastics and (hopefully) Aluminium.

The main base frame is made from 40x40 and 40x80 extrusion and the Z axis is made of 12mm aluminium. The side plate are made from 12mm steel plate.

The linear rails that are going to be used are the 16mm supported rail type that you can get from ebay.

The proposed working area is 300x200mm with 110mm z.

Attached is my design so far and was just looking for you guys opinions and improvements!

Thanks

Praneet

[louieatienza]

Nice and clean design, though I think you might be better served with at least 20mm side plate...

[Phife]

Just a bit of advice,

Go for thicker gantry uprights.. go for 20mm rails instead of the 16mm, and use extrusion that is compatible with the rails hole spacing (30mm), it will save you a ton of work.

Also, if possible drive your Z from the center instead of the side, less chance of binding.

Just my 2c.

Looks good though, keep it up!

[DonFrambach]

Looking very good. I agree with 20mm rails, thicker sideplates, and a center driven "z" axis. I would also suggest that you consider adding corner braces where possible to stiffen your frame. Please keep posting!

[Phife]

Oh, one more thing, remove the center support between your Gantry Y Rails, you will want to mount the ballscrew/lead screw in this space most likely, you can replace the center support with a solid plate across the entire back of the gantry to maintain support.

Also, if your budget allows, try to mount the supported rails for your Y gantry on the top and bottom of the gantry instead of the front like it is now. The supported rails work better this way, having them on the front will cause the bearings to push and pull away from the rails when your cutting in the X direction.

[lamesh99]

looks good. man, if i had access to any kind of extrusions, i wouldn't give mdf a second thought. just pay attention to accuracy, and squareness, and you're on to something.
good luck!

[Drools]

I really like this design, it is very similar to what has been keeping me awake at night.
12mm vs 20mm steel plate for the gantry uprights... Will 12mm or (1/2") steel plate really flex that much?
I was thinking about the height of the Y (gantry axis) do you need it to be as high as the illustrations are showing? The distance from the bottom of the Y axis to the table top looks to be large for doing PCB/plastic/Aluminum.

[praneetn7]

Thanks guys for all the recommendations

I have redesigned my y axis to incorporate the rails on the top and bottom of the gantry, instead of the front.

Also will the center drive on the z axis make much difference? If I do decide to incorporate the lead screw in the center i will lose about 50mm of y travel and i would like to avoid this as much as possible.

As for the 16mm rails; this is all my budget can allow as the 20mm rails are much more expensive if i go out of the ebay listing that has 200,300 and 450mm rails.

And as for using 30 series profile instead of the 40 so that I can bolt the rails directly on the profile is a great idea, however the 30 series profile that is available to me is a "light series" and has no where near as much mass as the 40 series.

I plan to run the y axis leadscrew behind the rails so that it will stay out of the way and be less prone to dust.

Another question:

As drools has said will the 12mm (or 1/2in) flex that much?

thanks

Praneet

[crane550]

Keep up the good work! I would agree with the 20mm side plates, I think that is the weak point in your system. I would also concur with using the SBR 20 rails instead of the 16's. It is really not much more money, and I think for your application they would work better.

The last thing I would add, is I would use a single extrusion for your gantry instead of two separated. Mathematically you get so much more strength, plus I think it would be easier to align, assemble, fabricate, etc.

In the end though you need to build it the way YOU want to build it. It will be a fantastic learning experience for you- mine sure was. Then you will unquestionably want to build another better one. Taking everyone's advice without question is just as foolish as taking no ones advice. You'll do fine.

I don't think you will have any problem cutting aluminum in light passes. Keep it up! I will be follow this.

[DonFrambach]

In the end though you need to build it the way YOU want to build it. . . . Taking everyone's advice without question is just as foolish as taking no ones advice.

Totally agree. This will be YOUR project. Good luck! Please post your progess.

[CarveOne]

Another question:

As drools has said will the 12mm (or 1/2in) flex that much?

thanks

Praneet

If you find too much flex under cutting loads you can add triangular side plates or rectangular strips on each side to stiffen it after it is in operation.

CarveOne

[RomanLini]

Half inch thick steel sideplates in that size are not going to flex much at all, the machine will be a lot more rigid than most people's.

One thing I would suggest is to check all the suppliers for the exact lengths that the linear bearing rails (and ballscrews) come in, and adjust the machine dimensions to suit those so you don't have to try to cut the rails or waste inches with rails that are a tiny bit short etc.

And it also looks as though you could extend the length of the machine a bit without increasing the cost much. This again depends on the standard lengths for rails and ballscrews, but it does look like you could make the machine slightly longer (10%? 25%?) with very little added cost (as the gantry remains the same) so it's worth looking into.

[praneetn7]

Half inch thick steel sideplates in that size are not going to flex much at all, the machine will be a lot more rigid than most people's.

One thing I would suggest is to check all the suppliers for the exact lengths that the linear bearing rails (and ballscrews) come in, and adjust the machine dimensions to suit those so you don't have to try to cut the rails or waste inches with rails that are a tiny bit short etc.

And it also looks as though you could extend the length of the machine a bit without increasing the cost much. This again depends on the standard lengths for rails and ballscrews, but it does look like you could make the machine slightly longer (10%? 25%?) with very little added cost (as the gantry remains the same) so it's worth looking into.

I was going for more of a "desktop" machine so extending the actual frame will not be feasible, however if I do need a larger working area I could use the same gantry and use new 40x80 pieces and rails.

But I did design it with this ebay listing in mind:

linear bearing slide SBR16 (6 supported rails+12blocks) | eBay

As C1 has said I will probably add the triangular side pieces if there is an excessive amount of flex.

As for the lead screws I'm going to be using 12mm, 2 start trapezoidal screws with dumpster AB nuts.

Will 2 start screws make a huge difference over the 1 start for this size of machine?

Thanks

Praneet

[CarveOne]

Will 2 start screws make a huge difference over the 1 start for this size of machine?

Thanks

Praneet

It should theoretically double whatever you get with a one start screw. 4 start will be even better. Any loss of resolution will be less than you will notice when cutting wood and plastics. You can always calibrate the small error out if you intend to cut aluminum to 0.001" accuracies. Do that with the steps per inch (or mm) number.

CarveOne

[Drools]

I'm not sure if Don kept his single start ACME screws on his build of almost the same size. He has a very nice build here http://www.cnczone.com/forums/diy-cn...ry_router.html

[DonFrambach]

I'm not sure if Don kept his single start ACME screws on his build of almost the same size.

I used 1/2" 10 tpi single start screws on my small router until I replaced the x axis and z axis with linear actuators. The lead on one of the actuators is .2" and the other is 5mm. (Not sure if the linear actuators was such a good idea because the acme lead screws and CNCRouterParts linear slides were working fine.)

Hope this helps you.

Don

[praneetn7]

Thanks Don,

Did u find that the ballscrews in the acuators make a huge difference in accuracy over the acme?

I probably will stick to the 2 start Trapezoidal as it is only going to be about $20 extra and will theoretically double my speed.

TBH I did get my inspiration from your machine.

Thanks

Praneet

[DonFrambach]

Did u find that the ballscrews in the acuators make a huge difference in accuracy over the acme?

I can detect no difference in accuracy or quality of cut between my old system with acme leadscews and the linear actuators with ground ballscrews. I'm making fairly detailed wooden carvings using mostly 1/8" ball nosed bits (sometimes 1/16"). There is very little cutting force when making these fine cuts. When I set up my acme leadscrew system, I could detect no backlash with a cheap Grizzley indicator and no cutting load.

I typically cut at 20-30 ipm with my acme leadscrews. I'm hoping that I'll be able to cut substantially faster with the ballscrews. I hope to reduce 20 hour jobs down to 5 hours. (That's the only way I can "justify" the expense and hassle of the actuators.)

[praneetn7]

Most of the things that i will cut will be shorter runs (like 1-2hr jobs or less).

Well from what I have heard the trapezoidal will do just fine

I am going to have the thrust bearings between the radial bearing and a collar to secure the screw and on the stepper side i will have a thrust bearing between the radial bearing and the shaft coupler will secure it down.

Does this make sense? I couldn't rephrase it any other way..

Praneet

[DonFrambach]

Most of the things that i will cut will be shorter runs (like 1-2hr jobs or less).

Well from what I have heard the trapezoidal will do just fine

I am going to have the thrust bearings between the radial bearing and a collar to secure the screw and on the stepper side i will have a thrust bearing between the radial bearing and the shaft coupler will secure it down.

Does this make sense? I couldn't rephrase it any other way..

Praneet

I think you will be pleased with your choice of lead screws.

I think I understand what you're saying about the thrust bearings. To be clear, you need to have two thrust bearings, one on each side of something fixed to your frame. You don't want to use the bearings in the motors as thrust bearings. Not recommending that you do what I did but I just uploaded a photo of the bearings I'm using. Here's a link: http://www.cnczone.com/forums/1078437-post228.html (The photo on the left shows some tapered roller bearings I'm going to install. The second photo shows much simplier and much less expensive thrust bearings that I purchased from CNCRouterParts.)