[cyclestart]

Here I have all the standard tools (cordless drill, brushless jigsaw, circular saw (with alum cutting blade) grinder, taps etc), but I have a friend with a drill press (or I'll buy one) which I know I'll need!

Using jigs hand operated routers can cut aluminium and even do some pocketing and slotting. Handy thing to have in any workshop.

[cyclestart]

Here I have all the standard tools (cordless drill, brushless jigsaw, circular saw (with alum cutting blade) grinder, taps etc), but I have a friend with a drill press (or I'll buy one) which I know I'll need!

(this may show up as a double post....forum software did something strange)

Using simple jigs a hand operated router can cut aluminium, even slots and pockets. A handy tool to have in any workshop.

[cyclestart]

Of course not - I appreciate your warning and it's a good reminder. I'm expecting this to be a month and a months-long project with many sleepless nights. Here I have all the standard tools (cordless drill, brushless jigsaw, circular saw (with alum cutting blade) grinder, taps etc), but I have a friend with a drill press (or I'll buy one) which I know I'll need!

(forum ate my earlier reply somehow)
A woodworker's router can cut aluminium, even pockets and slots with the help of a jig. Handy thing to have around the shop in any case.
If the decision has been made to go DIY enjoy the journey.

[redding]

Thanks Cyclestart - I have a router, but I'd certainly need to load some of the milling bits into it right?.. I'll looking how to do that before I hurt myself haha.

So I have taken everyone's advice. Keen for some feedback. See the attached images

Key Changes:

1. Will update Z-axis to include the bearings on the fixed side, and rails on the spindle side. This will help keep the bearings more separate and gives me now a z-axis range of 160-170mm. I'm happy with that.

2. Updated X-axis rails from 1 ballscrew underneath, to two on either side of the base. I will put some 110x16mm or 110x12mm flat plate on top of the 80x120 Alum T-Slot to mount everything to. This allows me to move the ballscrew closer to the gantry side so there is better clearance. Later I will also add some kind of protective case over the entire side like what is done in the "ripper" build. This was the best spot which allowed me to the fit the motor without hanging over the edge. Happy for any other ideas!

See pictures for the rough concept.

Notes about the rest of design:

I wanted to keep the Gantry as it is. It seems simple enough to build without over complicating things. I will put some reinforcing bracks between the two 80x80 on the rear side later.
I decided to keep the connecting 40x80 t-slot which runs underneath. Most of these designs have something like this, and will hope it keeps everything more stable. I may change this to either 40x120 T-slot OR 20mm thick plate (also 120mm wide).

What do you think? And yes, took everyones feedback and will certainly finish the design before ordering parts. I have already ordered the NEMA34 motors, DMA860H Controllers and 48V power supplies (4pcs of each) so going to make that work. For ball screws etc I will get new ones to suit the design.

EDIT: I noticed some of my models didn't update correctly - ignore some of the basic errors (like bearing locations, plate not going all way to the end etc).

[peteeng]

Hi Redding - If you are to have the bridge underneath you may as well have one drive underneath. This saves the cost of the "extra" drive and associated electronics. Agreed the lower bridge (or saddle) makes it stiffer laterally but usually the bridge width also restricts possible motion at the ends and it limits the thickness or ability to support the bed underneath the table. eg for heavy objects or heavy plunging loads you need a stiff machine base.

I think you have costed up and made it more complex with no real benefits. Cheers Peter

[Sterob]

Hi Reading,
Where are you going to get your Aluminium Extrusion from?

[redding]

I think you're right Peteeng - I'll remove it - What do you think about the positioning of the ball screws on top of the 80x120 T-Slot Frame? I will cover it with a channel or something similar.

[redding]

Hi Reading,
Where are you going to get your Aluminium Extrusion from?

I'm getting from a supplier in China
This one: https://detail.tmall.com/item.htm?sp...=4220935717296

[cyclestart]

The edit function was working weird last time I posted and ended up as 3 posts. Oh well.

Some options for frame design Link --->Build your own CNC router Step 2: The frame
I like the idea of fully supported frame. Of course it can't be fully supported while sitting on saw horses so there's more structure to consider.

The CAD stage is the time to think about the max Z clearance required. My router has 5.25" between spoil board and the bottom of the gantry and the fixed plate on the Z reduces the clearance to 4". I've never regretted it and could have gotten away with less. If building a new machine today I'd be tempted to build the frame deep enough to do away with the gantry side plates.

Ball screw blocks are made in BK and FK design. The FK types may be a better choice for the Y screw.

[NIC 77]

I took the liberty of drawing up a couple ideas real fast. Nothing polished about it, it's just easier to draw it than to try and explain it. Please use all, some, or none of the concepts here, it's up to you .

I used the same 80x80 and 80x120 extrusions. Those are Rexroth size 25 rails and a 25mm ballscrew....simply because that's what I had some drawings of to modify.

To assemble this there would be many countersunk socket head cap screws throughout.

Attachment 446306
Attachment 446308
Attachment 446310

Yellow: Countersunk socket head cap screws bolt this into the T-Slot, leaving the rest of the plate to be drilled and tapped as desired.

Blue: The 80x80 and 80x120 extrusions

Orange: Chip guard....the idea is that any flying chips that can get over this will most likely have enough energy to miss the linear rails and ballscrew....I would be more concerned about getting chips in the ballscrew as the wipers on the linear rails are usually pretty good.

Red: Rest for your Cat Track / Drag Chain....

Hope this helps with your concept design....I really like the concept from LinuxFan of bolting aluminum plate together and filling with epoxy concrete...but I tried to go with the same extrusions you want to use.

Like I said, not trying to steal your thunder, I won't be offended in the least if you go a different direction. Just some ideas.

How long are your ballscrews in your design?

[redding]

This is fantastic NIC77 - Thanks so much for your efforts. I think I will use most of this design. Going to work on it this weekend and will show how it's looking! One question: On the Gantry y-axis, why do you bolt the rails into flat bar before the T-slot, and not into the t-slot directly?

X-Axis = 700mm Ball Screw SFU2010 (to buy) x 2
Y-Axis = 600mm Ball screw SFU2005 (brought)
Z-Axis = 250mm Ball Screw SFU1605 (to buy)

[NIC 77]

redding,

I should have read your post more carefully before I made mine.

So you already bought your motors? The reason I asked what the lengths of your ballscrews are is because I was thinking of doing some math to show you some theoretical differences that gantry weight would have on your design using a few different motors.

So what motors did you buy? I would need a torque vs speed graph for them (preferably a table of RPM vs Torque in Nm with 14 points) and the rotor inertia in kg*m^2 as well as the ballscrew lengths if you want me to do this.

[NIC 77]

On the Gantry y-axis, why do you bolt the rails into flat bar before the T-slot, and not into the t-slot directly?

I didn't know how much of a lip you have on either side of the rail compared to the T-Slot Gap. Using the wider aluminum acts as a bit of a washer.

[peteeng]

Hi All - Now your getting serious with the design I think this element needs sorting a bit. The drive nut needs to be integrated with the column or the bearing plate so it is a more direct connection. It will wobble a bit as drawn. Perhaps the column plate can be extended so the nut bolts direct to it. More thought bubbles needed. Peter

[NIC 77]

Hi All - Now your getting serious with the design I think this element needs sorting a bit. The drive nut needs to be integrated with the column or the bearing plate so it is a more direct connection. It will wobble a bit as drawn. Perhaps the column plate can be extended so the nut bolts direct to it. More thought bubbles needed. Peter

Good point. It is simply a conceptual mock up. But it can be improved. The flatbar it bolts into is 1" thick as drawn. But yes, it can be improved .

[peteeng]

Hi Redding - for your X axis you have 2x20mm ball screws. !6mm will be fine saves you some $$$.. and less inertia now your getting down to numbers...Peter

[redding]

So you already bought your motors? The reason I asked what the lengths of your ballscrews are is because I was thinking of doing some math to show you some theoretical differences that gantry weight would have on your design using a few different motors.

So what motors did you buy? I would need a torque vs speed graph for them (preferably a table of RPM vs Torque in Nm with 14 points) and the rotor inertia in kg*m^2 as well as the ballscrew lengths if you want me to do this.

This would be very very useful - I'd love to learn how todo do this also. Yes I have got these NEMA34 Motors "86HS11860A4" driven by DMA860 controllers (same as MA860).

Ball Screw Length (between Floating/Fixed ends - inner distance):
Y: 628mm (700mm total length)
X: 528mm (600mm total length)
Z: 185mm (250mm total length)
Rotor Inertia: 1800g/cm^2 which I converted to 0.00000018 kg/m^2
RPM v Torque: Attached - Similar motor (in RPM vs Nm @ 48V), but also attached this motor PPS with 60VAC. I think just refer to the similar motor graph will be fine.

[redding]

Hi Redding - for your X axis you have 2x20mm ball screws. !6mm will be fine saves you some $$$.. and less inertia now your getting down to numbers...Peter

This is a good idea, but if the difference between 16 and 20mm is $5 USD for a 700mm length, which is why I was just going to upside if I was going to do it anyway.

[redding]

NIC - One disadvantage of this design is I'll likely lose maybe 50-100mm in x-direction. I guess that's just one disadvantage of this solid design?

[routalot]

Maybe while you are playing with the suggested design improvements over the weekend,you can find advantageous locations for some of the components within the overall footprint of the machine.It certainly costs a lot less to adjust things within a parametric design program than to toss actual metal into the scrap bin.I would suggest you model a cutting tool in the collet of the machine and then check to see which projections on the Z axis mounting plate will limit your access into corners and recesses when you are machining.there may be gains to be had.We will be eagerly anticipating a look at the revised design.