Hi!
I switched to update everything on CNC Zone instead of Industry Arena. I like it better here lol
Copypasta:
G'Day fellas!
I'm from Brisbane, Australia and new here in this forum.
After reading some impressive build threads, I will take some inspiration from Jaynes build for my own attempt. I hope this is OK
My plan is to build a machine capable of milling all sorts of wood and also aluminium while try to use only plywood for the design.
The machine will be located in my workshop and is exposed to temperature and humidity. I will need to find a suitable wood stain treatment to prevent warping/shrinkage/expansion etc. Any tips?
With the exception of a table saw and bench press, I only have very basic wood working tools like cordless drills and saws. No access to another CNC. So this will be a challenge!
Some facts:
Budget $2000AUD ($1400USD)
Plywood thicknesses used are 32mm and 15mm.
Panel connections will mainly be angle brackets, bolts, wood glue and some other joining hardware used in furniture.
Overall size is L1400mm x W1000mm and will be sitting on a sturdy table.
2010 ball screws on X and Y and 1605 ball screws on Z. All in combination with HGR20 linear rails.
Stepper motors Nema23 ~3NM powered by DM542T drivers and Mach3 USB breakout board.
Not sure about the spindle yet but will start with a 500W brushless ER11 spindle - likely from AliExpress.
Have a 3D printer on hand.
The design will take place in SolidWorks 2021 and I'm already halfway finished - I think at least
Future plans are adding a 4th axis, and depending on how sturdy the machine is in the end, a 5th axis aka trunnion table.
In the past I worked on 5 axis machining centers which I hope will come in useful while building my own machine.
How does this sound?
Cheers
Dan
- - - Updated - - -
Hello everyone!
I thought I'd share a first look at my model
Obviously it isn't quite finished yet. Missing all holes, fasteners and finishing touches. Also, I think I want to modify the machine bed to be a torsion box instead of single ribs only (orange).
Material is all plywood (32mm and 15mm) and a couple of 5mm spacers are PLA 3D printed.
The spindle looks (and is) a bit small compared to all other dimensions, but I'm not too worried for now. Will likely add another spindle holder as it looks quite wobbly with just one.
According to Solid Works Evaluation, overall weight is around 70kg with a plywood density of 575kg/m3.
With all the fasteners added I think I'll hit the 100kg.
Hi Dan - I have built a couple of machines like this so here goes:
1) I'd make the blue baseboard go out to the edges, it will be stiffer
2) I'd use a bigger spindle. Your structure will take a bigger spindle and a 500W DC spindle is a bit small and its shaft will break in say 400hrs due to fatigue. You will stall it easily. I'd go 800W AC spindle, big shaft big bearings
3) Sealing the timber is a good plan. I'd use vinyl ester resin designed for infusion., its very thin soaks in really well and 2 coats is waterproof, 3 coats is even better. I can vouch for that as my workshop has just been through a flood and the floor and various bits where submerged for 2 days and have come through unscathed. VE is also cheaper then epoxy and cheaper then varnish. Or use formply as its already sealed just need to seal edges. Plus formply is stiff.
4) I doubt you'll do it for $2000AUD but have a go. International freight will be just under $1000AUD for a set of parts that you are talking about... freight has leapt up recently.
5) The thick bottom base is unnecessary as the blue base and bottom base act as a huge beam if you carry the "base" through. I would flip the cross braces inside the bed to fwd and back makes it easier to clean from the front...
6) I'd make the gantry face 2 pieces thick
7) Your Z is going to need to be stiffer to match the rest of the structure, put some time into the Z, it will be the first thing you notice is not stiff enough if its not stiff enough and then its hard to fix it.
8) otherwise its design trajectory is good... Peter
Hi Peter!
Yay a reply! Thanks for the suggestions!
I already updated the machine a bit, will post pictures tomorrow.
1. You mean make the blue machine bed and he red panel where the ribs sit on one piece?
2. I know. What do you think of brushed spindles? There's a bit more choice.
3. I think I'll go with sealing the parts as I don't think I find affordable form ply in 32mm thickness. I read something about hot linseed oil or similar for sealing works too?
4. We'll find out
5. I "changed" the thick green base and the blue machine bed into a torsion box. Can I swap the 32mm green base plate for a 15mm thickness?
6. 2 pieces of 15mm thick or could I use one 32mm thick plate? Then the whole gantry is made out of 32mm panels.
7. Have it already updated to be stiffer. I think at least it looks stiffer. Will post pics soon.
8. Thank you!
1- yes
2 - brushed spindles - I've used a 600W one and it quite good. But the shaft is small and will break eventually. Spend the money up front on a good spindle vs spending it twice
3 - you do not need 32mm thick ply. By the time you buy paint or resin the formply looks good value. Bunnings have a coated ply 17mm about $70 per sheet good value... called film face ply (specrite brand)
4 - I see your a strong optimist
5 - yes
6 - use 2 pieces glued together then you dont buy the expensive 32mm ply
7 - good oh Peter
Hi Dan - The cheapest sealing is to use acrylic paint. Go to your local hardware and ask for a deal on old paint. Dilute 1:1 with water so it penetrates well... But film face from bunnings or a timber wholesaler is better and I think cheaper in the end. Do the math before you decide..
In regard to machine design. I would make the walls a separate part. So the base is a part and the walls are parts. The issue is when you build the walls they will not be the same height or level. Your CAD makes it look easy but reality sucks. By making the walls separate they can be brought together on your level base and made to be the same height and level easily. Then they can be moved out to the sides and bolted down then checked for level and height deltas. I use epoxy putty to screed and then lap the tops with a long solid extrusion. Some time needs to be put into the top of the walls (rail foundations) otherwise your gantry to base relationship will never be right... Peter
The machine bed is extended in width, making it a closed torsion box now. All X Axis gantry parts are 32mm and I also increased the spacing between the Y Axis linear rail carriages so the COG of the gantry is in bewteen the carriages.
Any more suggestions in how to make Z Axis more rigid? I maximised the spacing between the linear rails on X and Z without compromising too much travel reach.
Reason for me using 32mm ply is because I already have a sheet flying around. It is just non structural ply I think. I also checked form ply and film faced ply but all they come is in 17mm thickness, at least at Bunnings. Guess I'll be going with diluted paint?! I have a leftover can of nice baby blue paint
For the spindle, I found 500W spindles where the motor shaft is the same diameter up to the collet. That will at least sort out shaft breakage.
I'm not too sure about making the walls a separate part. The most level "item" I have is probably our granite kitchen bench. I will try and get the Y Axis mounting plates as straight and parallel as possible with a table saw, Maybe sending the side walls and mounting plates mounted together through the saw will work. Don't know yet.
Hi Dan - There is a good argument for the Z to be metal. Its tough to get to the required stiffness in plywood without getting really thick. Since your going plywood I suggest you look at Al/ply/al laminate. I'd go 2mm al / 32mm ply (since you have it) / and 2mm al. 3mm al is good too. I usually aim at about 32mm solid aluminium thickness equivalent especially if the Z is high. My current builds have a 3mm steel bent Z that is equivalent to over 40mm thick steel plate... Can't be too stiff... What is your target z movement? Peter Oh your saddle will need to be a bit thicker as well... again use the laminate
steel/ply/steel works as well... steel is 3x stiffer then al so 1.6mm steel is light and very stiff when laminated... use galvanised sheet so you don't have to paint, use epoxy to laminate.
Thanks for the PDF! Very useful. Does sound like a good plan laminating plywood with alu sheets. I will keep that in mind if we can't find other possible solutions.
My alternative plan is to use 32mm plywood for the Z Axis base and use as bracing (purple in above photo) some 40x30x4 Alu RHS. I found about 6m of it laying around at work. Maybe I can use these for underneath the Y Axis linear rails too?
Also, I've seen 100x50 steel RHS laying around. Maybe for the gantry?
Hi Dan - You said your using solidworks. It comes with basic FEA I think? If so you have the tool to make decisions. I suggest you stay in one medium universe. Its fine to augment plywood with sheet but if you start using RHS etc you can come unstuck with different expansion coefficents, different processing etc... KISS Peter maybe the sink is useful too?
early on you mention a rotary axis. If you really want this I suggest you put some time into planning it. If you think it can be plonked on the machine bed you will have no room for vertical motion or tools. Usually they live in a pit at the front of the bed or they bolt onto an apron at the front of the bed. Best to plan that now if 4th is on the list.... especially if it has a big throw....
Fair enough, I got your point. I was just overwhelmed with all the possible solutions which came into my head with these RHS I found...
For the Z Axis I will try and stick to the basics. But I don't see an issue with using Alu RHS for underneath the Y Axis rails. It likely is more flat than a strip of ply.
For the Rotary Axis, if needed for a job, I thought of bolting them on to the wall and bed with dowel pins etc. Not sure yet as I think it is more of a gimmick for now.
Hi Dan - I doubt you will have room to do anything if you bolt to the wall. Since you have your torsion box make the front top of it removable and the webs removal to create a pit. Or at least make it possible then hurdle that when you get a rotary. Overwhelmed? some say drowning! just keep chewing at it and progress will be made. Peter
I reworked the Z Axis a bit, replaced the 15mm for a 32mm with 2mm alu sheets each side. Also, after doing some simple FEA, I'm using the 40x25x4 alu RHS which I found for Z Axis bracing now instead of laminated 15mm ply as it's a tiny bit more rigid and less work involved. Only issue I currently have is that I can't find any 2 or 3mm aluminium sheet cut offs near me Bunnings only has 0.5mm or checker plate and others are just selling whole sheets. Will be looking for a 1.6mm steel sheet alternatively.
The forward stack height has already increased by 20mm and I haven't changed the saddle yet as I'm not sure what exactly to change other than make it thicker. Will have a think about this.
I changed the 3D printed 5mm spacers (red) to 6mm aluminium bars. I can get them easily on eBay, they will ad significantly more overall strength to the saddle, only add about 2mm to the forward stack height and are not too heavy with ~260g/bar.
I know that the machine won't win a beauty contest haha
Hello everyone!
I had a thought or two about what else I could make with this machine other than my initial thoughts and I think I'm going to expand its footprint a little. Currently the maximum cutting size is like Y1100 x X600 something - an odd number.
Ideally it should take at least a half sheet of wood (1200x1200 or 4'x4'). I will see how I go with the design and budgeting. Maybe the gantry needs some beefing up as it will be half a meter longer.
Will keep you posted
Just remodeled the cutting area to 1200x1200mm and made sure the cutter can reach the edges of the half sheet. Obviously it got a significantly larger footprint from 1400 x 1000 to 1600 x 1600. Current budget increased about $150AUD which is not too bad considering how much more flexibility it offers.
One new issue is that I have to somehow split up the top (purple machine bed) and bottom sheet (green) of the torsion box as the dimensions don't fit on a standard sheet anymore. Any ideas how to best split it?
EDIT: I slightly increased the height of the X Axis plate where the rails are mounted (green) to give more rigidity across the length and moved the X Axis rails further apart.
Hi Dan - Don't split : either get 16mm mdf boards 2400x1800 or ply 2440x6100mm or 1800x3600mm and have it cut up. I get large boards from DMK Forest, give them a cutting list. If you do join it use dowels or a butt strap or biscuit joiners. My last "timber" machine I made out of all16mm white MDF and its flat and very strong (some machine malfunctions really tested it hard) . So consider white MDF for the large bits and ply for the rest. Peter
Hi Dan - Topic Gantry geometry. I think you have an open back gantry supporting the front face with many webs. Although this is partially good in local shear its not good in torsion. I suggest you make the gantry triangular and hollow. This will be excellent in shear and in torsional stiffness. Triangular gantries have always done very well when I model them in FE. In metal they are a bit more inconvenient to make but in timber its easy. I have seen they do exist in some high-tech laser machines so they are not unique. Your webbed design provides good stiffness when the bearings align with the webs but less stiffness when they are not in line with the webs. The triangular design has the same torsional and local shear stiffness the entire gantry length, this gives a much more uniform response to tool loads... Peter
I've attached an image of Scoot. It's made from white 16mm MDF. Half the price of ply and I think could be a little more stable. Material wise not as stiff but when built as a torsion box very stiff and strong. When I was setting this machine up it had an electronic issue and occasionally one wall motor would swap directions and twist the table hugely! Once I thought it would break in half as it groaned horribly before I got to the kill switch. But it survived and has been flat and very stiff. So MDF is worthwhile to think about. The issue was with a low 5V supply to the BOB which decided to change the dirn of the motors randomly. Took quite an effort to find that little bug...
Hi Dan - spitting is not a bad idea just think about alternatives before you do it. If you do split, split at the back in the direction of the gantry (across the machine), this area never gets used, maybe for hold downs but its in the dead space of the machine. Then use a good adhesive and biscuits etc to keep that joint level... Peter
Raised Y Axis Plywood CNC Router Vol.2
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Re: Raised Y Axis Plywood CNC Router Vol.2
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Bunnings only has 0.5mm or checker plate and others are just selling whole sheets. Will be looking for a 1.6mm steel sheet alternatively. 
