[cavemancarver]

Hello All:

I am a fairly experienced "hobby" CNC router user running a 2' x 4' machine with Nema 23 570 oz/in motors and a Porter Cable 3.75 HP router. I upgraded the motors and router from much smaller components and yes, I do realize that I went "overboard" when I did it. I thought I needed the extra torque and power but in hindsight I was wrong...which is why I am writing this now.

I use Vectric Aspire and Mach 3 for all of my work and love this combination of software. I have been cutting mostly wooden and acrylic signs and boxes and some aluminum at times and have been able to produce some fairly nice products with the setup I have. Recently I have been cutting a lot of 1/8" Baltic Birch plywood from the local "Woodworkers Source" and have fallen in love with this product. It cuts quickly and beautifully and it is also fairly inexpensive. So...here it is.

My younger sister has recently been hanging around with me in my shop, along with her daughter, and they have seen me produce some pretty cool stuff using the 1/8" Baltic Birch plywood and now they would like to try their hand at running a CNC router. I have been teaching them in my home shop and I think they are ready to get their own machine. Of course, I have volunteered to build one for them.

I would like to build them a "moving table" router around X = 16" Y = 24" Z = 5" with the table moving in the 16" direction but I only want to build it sturdy enough to cut 1/8" to maybe 1/4" Baltic Birch plywood and maybe some acrylic also. I definitely do not want to go "overboard" again. I am thinking of building it from HDPE or maybe PVC combined with 8020 extrusions. I would like to use Acme screws or maybe ballscrews for this project. I do not want to build a belt driven machine.

I want to use a Makita 1.25 HP "trim" router as the spindle and I need your help in deciding which stepper motors I should use as well as recommendations for ballscrew size and maybe info on motor drivers and/or controllers. I chose the Makita 1.25 hp router because it is capable of spinning at 30,000 rpm and I think the higher speed will be good for cutting the thin plywood. I have been cutting this plywood on my larger router using a .05" bit spinning at 21,000 rpm with a cutting speed of around 70 inches per minute and cutting the full depth of the material at 1/8" with very good results (no broken bits) and I want to be able to do at least the same on this new machine. Maybe even get a little faster cutting speed out of it since the "spindle" will be spinning an additional 10,000 rpm faster than my larger machine?

Any and all recommendations will be greatly appreciated and I will be posting drawings and photos here as I go along for anyone interested.

Thanks, in advance for all of your input.

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[wizard]

This will be quick, posting from my truck.

The first thought is will they be happy with the smaller router?

The second thought is build a stiff machine is not over doing anything. You don't want to oversize the router and steppers of course but a stiff machine frame is a wonderful thing. The good thing is that on a smallish machine with a moving table arraignment achieving a stiff frame isn't that difficult. As for the use of aluminum extrusions in the frame that is up to you, I don't like the stuff simply due to the cost and the les than optimal arraignments that T-slots often produce.

Now as far as plastics in a machine frame I'd say forget it unless you have experience using the stuff. Honestly if prefer wood to PVC, This isn't form the lack of experience we use such materials at work for parts of machinery (medical industry) and while it may be clean PVC isn't very rugged.

So I don't think you want to skimp on the frame of a machine, it is never a good idea. However this amounts to a table top machine so producing a suitably stiff machine isn't that hard nor demanding of materials.

If she is of the mind for it involving the daughter in the build might be very educational for her. It is certainly a good way to,learn about the trade offs made in all designs. Plus if you turn her into a technician you will have far fewer support calls!!

[goalie098]

This sounds like a fun project for a good reason. I am looking forward to following it.

[109jb]

Just a thought. Depending on the age of the child it may be prudent to enclose the machine and wire the router up through a safety door switch so that she cannot start the router with the door open.

[cavemancarver]

This will be quick, posting from my truck.

The first thought is will they be happy with the smaller router?

The second thought is build a stiff machine is not over doing anything. You don't want to oversize the router and steppers of course but a stiff machine frame is a wonderful thing. The good thing is that on a smallish machine with a moving table arraignment achieving a stiff frame isn't that difficult. As for the use of aluminum extrusions in the frame that is up to you, I don't like the stuff simply due to the cost and the les than optimal arraignments that T-slots often produce.

Now as far as plastics in a machine frame I'd say forget it unless you have experience using the stuff. Honestly if prefer wood to PVC, This isn't form the lack of experience we use such materials at work for parts of machinery (medical industry) and while it may be clean PVC isn't very rugged.

So I don't think you want to skimp on the frame of a machine, it is never a good idea. However this amounts to a table top machine so producing a suitably stiff machine isn't that hard nor demanding of materials.

If she is of the mind for it involving the daughter in the build might be very educational for her. It is certainly a good way to,learn about the trade offs made in all designs. Plus if you turn her into a technician you will have far fewer support calls!!

Thank you for your input everyone...

Yes, I agree that the frame of this machine should be pretty stiff and to tell the truth I really am not happy about using either HDPE or PVC for some of the frame elements but if I opt to exclude them then my only choice would be either 8020 extrusion, MDF or maybe welding a steel frame which I don't think I could do very well. I have welded stuff in the past with marginal results and I am not sure I would be able to weld up something that would qualify as "square" and "plumb". As far as MDF goes...I do have access to 1" thick MDF but I am not sure a machine built with that material would stay "square" and "plumb" over an extended period of time. It seems you might have to constantly re-surface the top in order to keep everything level and true. Correct me if I am wrong as I have never tried using MDF for something like this.

So...the first item is how to get a pretty stiff frame built that a novice won't have to "monkey" around with in order to get some quality cuts made? Any and all suggestions would be appreciated. I did neglect to mention aluminum in the above paragraph. 8020 extrusions combined with 1/2" aluminum might be the best way to go...that is how my machine is made and I have never had any problems although I do machine the top fairly regularly but I am not sure if it is because of the extrusions or if my 3.25hp router is too heavy for it.

As far as size goes. My sister and her daughter would be thrilled with the smaller machine. They pretty much would like something that they can cut small boxes and lampshades with and a few signs now and then but it is important they have a "quality" machine they can depend on that they won't have to "mess" around with to be able to make some good cuts. I think 16" x 24" would be a pretty good size for them but I have been thinking about moving up the size a bit to 18" x 26" because there are a few projects I have designed that would fit the larger size.

I am a retired guy working at home and my sister is just a few years behind me. Her daughter is 33 and I do think they are capable of handling this type of machine without worrying that they might hurt themselves. The "spindle" will be a small 1.25hp trim router and they have been working with me on my larger machine fairly regularly so I have been able to watch how they act around the machine and I truly think they would be able to run a smaller version on their own without many problems.

Here are a few photos of what I am running. I might try to "re-design" this one to fit the bill. What do you guys think? Keep in mind I am pretty much set on building a fixed gantry machine. Thanks again for your input.

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