Just finished my CNC mill design in SolidWorks, construction should begin soon

[tjschweizer]

So I've been designing a CNC mill for the last month and a half. The current design is Version 5, and I have about 60 hours total invested in this whole project. I plan on using Misumi aluminum extrusion to build a basic frame, which will have standoffs bolted to it that I will mount Misumi linear guides on. I will use Automation Technologies ballscrews and close-loop hybrid stepper motors for linear motion. The entire frame, everything besides the motors, ballscrews, and linear guides, will be casted into epoxy granite for rigidity. I am currently working on a mixture that I believe will be strong enough. I will be using a 2.2kW spindle from Automation Technologies. The estimated travels will be 24" in the X (minus the width of the table), 10" in the Y, 8" in the Z with about 6" in spindle adjustment for a total of 14" in the Z (in case I use a drill chuck or something). This will be used for mostly aluminum cutting, as well as wood and plastic. Rough estimated calculations suggest I should be able to handle steel, but currently I don't hardly machine any steel at all so this mill was designed to handle aluminum (with a factor of safety of course).

My future goals include adding a 4th and 5th axis, but I am waiting to finish testing with the epoxy granite to see what my total cost is. I have a $4000 budget planned for this project, and I am estimating roughly $3200 on it so far, not including the 4th and 5th axis. Again, I have to wait and see how much the entire epoxy granite will cost before I even start designing the 4th and 5th axis. I have MasterCam available, and will soon have the full 5 axis license, so it would be nice to have the full 5 axis machine, but time will tell.

My SolidWorks model is about 98% complete, I have to finish up some ballnut mounts and do some more editing of the epoxy granite, but I modeled every single nut, bolt and washer; this is by far the most expensive project I've taken on and I don't want any surprises when building.

Next on my to-do list is obviously to finish the epoxy granite testing, and then I will be making a huge PDF file that has all of the blueprints for the parts I need to machine, as well as rough dimensions for the parts I will buy, a complete price breakdown (hopefully when I actually purchase parts I won't be off of my estimate by more than $50 or so), a machining set up sheet so I have it planned out how I will machine every part that needs machining, and most importantly a planned out step-by-step assembly guide. Again, I don't want any surprises during assembly (besides the mistakes I'm bound to make while assembling...).

I will update this thread as often as possible. I have some pictures of my model to start off. My end-of-the-line pipe dream is to hopefully be able to offer local 5-axis machining to make a little side cash, and I am considering the possibility of selling the PDF file I am making (depending on how well the mill works, of course.)

I am open to constructive criticism, and I am willing to provide any information if someone is curious. Here's to an exciting start to an ambitious project!




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[ftkalcevic]

I'm planning on building something similar. I'm going to make my Y-axis wider than the y-width of the table so I can move the spindle completely off the machine. (I saw this on a Sony Robokid). This will allow me to either put a tool changer on it, and/or a 4th/5th axis, and not use up valuable table space.

[aarggh]

Very nice design there. Do you expect much distortion from the epoxy process?

cheers, Ian

[G59]

I like it. It's different. I think if you can get the proper epoxy to granite mix, distortion should be minimal. It's gonna make for one heavy sucker. Rigid too.

[tjschweizer]

ftkalcevic, my original plan was to do something like that, but the only cheap Chinese ballscrews I could find sold by an american company (always want a p.o. box just in case) came in just 4 lengths. I had to work a lot of my design around that.

aarggh, I actually think the epoxy will be the most stable. Based on a few test pieces I've done, there is actually very little heat generated since the amount of epoxy is so low.

G59, I think I found a perfect solution. Quikrete sells precision non shrink grout. I plan to mix that with epoxy. The grout provides an extremely nice aggregate for the epoxy, and the test pieces I've made are far more rigid and hard than I could have hoped for.

Since I mad this I've been swamped between work and classes, but I got a chance to pencil out the EG costs and realized I needed a serious design change. I think I'm going to put PVC tubes inside the base that are filled with water based grout to reduce cost.

[G59]

Can you take one of those test pieces and put in a freezer? I just want to see if temperature has an effect on it once cured. I ask because sometimes it gets mighty cold in the garage. Just need to know if cracks will develop.

[tjschweizer]

Yea, I've got one curing now it should be done tomorrow night. I'll stick it in the freezer for a day and let you know. If you want to try a simple test, Lowes sells an epoxy grout made by spektralock. The epoxy comes in two parts in a bucket, and the filler comes in a jug that looks like a pint of milk. That's where I got the idea to use grout for the aggregate.

[G59]

Ok thanks, just make sure to allow plenty of time for curing. Maybe even a week if you don't forget by then lol. I don't want any false results, so let the curing happen and then freeze it overnight. when you thaw it out, let it do that slowly. That way, you know you didn't have a hand in any failure should it happen. I think EG machines have a lot of potential, and I subscribed to this thread to see what was possible to do from home.
Thanks for the efforts.

[rowbare]

I like your overall concept however...

I think all of those standoffs are going to cause you grief. I think you would be better off using a larger rectangular extrusion on end or a piece of Durabar or steel with a machined/ground surface. Are you aware that you need a reference edge for mounting linear rails? See this document: https://tech.thk.com/en/products/pdf/en_b01_089.pdf.

You don't really need to tie the ballscrew mounts to the rail mounts however that might help keep things aligned when you are casting. OTOH you end up with a lot of expensive hardware potted into epoxy...

Are you planning to cast the gantry and base in one?

I look forward to seeing the evolution of your design and seeing your project come to life!

bob

[tjschweizer]

Bob,

I agree about the standoffs. I have actually changed my design so I will be casting two metal bars in the epoxy granite surface, so they stick above the surface roughly 0.25". The bars will be secured in the epoxy with elevator bolts, or just a bolt with a washer (I just want some surface area for the EG to hold the bolt). The bars will have tapped holes for the rails to bolt to, and I will mill the top surfaces after the base is cast, ensuring parallelism. I don't think I will be using any aluminum extrusion anymore, instead I will be using PVC tubes filled with inexpensive water-based grout. This will reduce the amount of EG needed.

My new design doesn't have the ballscrew mounts connected to anything, they will just be located using standoffs. I won't necessarily need a reference edge (thanks for that document by the way, good information), as long as the two rails are parallel which I can achieve with a dial indicator. As for the squareness of the axes, I am actually considering moving the X axis down and mounting it on the Y axis, instead of having the X axis on the gantry. Then the squareness will be taken care of by how it bolts on.

I don't plan on casting the gantry and base in one, not anymore. I have some serious redesigning to do, hopefully I'll have some free time after tomorrow to get a new model and post some more pictures.

[tjschweizer]

So I froze that sample piece for a few days. Took it out and it was still solid. Whacked it hard with a hammer and it just scuffed the surface. I ordered a few trial size epoxys from smooth on. But due to time contraints I am actually going to do a g0704 cnc conversion before I do this mill. I will do some testing with the epoxy I got and post results, but this build won't be starting for a while.

[Khalid]

this is drafting not a design.. designing tools are available in Solidworks u never used