My "to be" diy cnc

[djem]

Hi, I've been looking into this diy CNC stuff now for about a year and I feel ready to start building my first one. I like to think that I have collected enough information and stayed interested long enough that this will be something that I actually finish some day (hopefully in less that a year).

Having some spare time today I decided to sit down and make some quick modeling of what I've got in my head. I want this router to be small enough to transport in a normal size car (since I don't have a permanent home atm). I also want this to be a cheap build as I don't expect my first attempt to be a keeper. For these reasons I decided to go for a working area of about 300x200x70mm and use a dremel and not some fancy brushless system. I decided to go for the slide system shown at makeyourcnc.com (unless you know of something better for the same price). I hope this will be useful for PCB milling and on thin plywood, any comments on that?

I intend to make all the electronics involved myself using microcontrollers and MOSFETs. This will be very good exercise for me as I am an electronics engineering student atm.

I've attached some nice renderings of my sketchup in Autodesk Inventor. This was done directly from my head and I have only had today to work on this, so I took some shurtcuts to get a finished model. This means that the model is no good for making drawings from. I'll make a new model later where every part is separated.

So, what do you think? Do you see anything that could be done better?
Do note that this is a sketch, not work plans.





as a bonus I made a little anaglyph just for the fun of it.

[pminmo]

looks good!

[djem]

thanks pminmo. How does your spindle compare to a dremel? I think I can afford that Paul Jones spindle with ease.

What would be better, plywood or MDF?
I see that most peoples here use MDF, but why?
I would do this in steel if only I had the tools and knowledge...

How do you make the MDF pretty and moisture resistant after you finished building? I'm guessing that painting everything would work, or maybe apply a thin layer of filler and spray paint it so it looks like metal would be nice. This might be a bit in the future, but I like to have all angles covered. If I choose to spray paint I can't glue down the aluminum profiles until after the painting proses or they will be painted as well and that might lead to flakes later as the bearings grind down the paint.

[mcphill]

MDF is much more stable than plywood. The layers of plywood will warp differently for every sheet you buy.

With MDF, seal it with Killz or BIN, then paint it whatever color you want. You do want to seal all the cut edges, at least, as they will absorb moisture and break down quickly if wet.

[djem]

Thanks a lot mcPhill, that explains it then. What is Killz or BIN? I'm in Europe so the brand names from USA don't always apply here. When you say BIN i think of that small garbage bin next to my desk.

[pminmo]

Don't use regular plywood. MDF is stable and inexpensive. Look for sanding sealer to seal wood. It's a clear viscous fluid that is intended to seal wood. It will take serval coats of sanding seal, and even more on the edges of MDF. You can then paint over sanding sealer with compatable paint.

[djem]

I have to buy MDF now then. From what I understand a normal size sheet is 2440x1220 right? I found that I can with 1/3 of that size. I was not able to got it down to a 1/4 sheet so I'm going to get a lot of left overs. If this was for manufacturing I would have to redesign, but I'm only making one so the material waste is acceptable. I've already got the ball bearings and most of the tools I need so I hope to start building by the end of next week. I just have to find where to get that aluminum profile, the closest store I know that has it for sure is about 100km away so..

I've attached a drawing of of the main cuts, hoping the store can do that as I don't have a table saw. I'm not sure how much the blade steals, but I've made the drawing adaptable, so when I know that I can automatically update the drawing. It's been set to 1mm atm, but I haven't included the absolute measures yet anyway. The small peaces I'll cut myself.

[CarveOne]

Originally Posted by djem Thanks a lot mcPhill, that explains it then. What is Killz or BIN? I'm in Europe so the brand names from USA don't always apply here. When you say BIN i think of that small garbage bin next to my desk.

I haven't used BIN, but Kilz is a flat white sealer for wood and ceiling tile that can hide mildew spots and printed text on paneling. It comes in a water based and oil based version. For OSB (oriented strand board) and MDF wood products it is recommended to use oil based Kilz first, then you can paint over the Kilz sealer with water based or oil based paints. If water based Kilz is used on OSB or MDF it will cause the surface to swell unevenly due to absorbing water from the Kilz sealer. The name is from the chemicals that kill or retard mildew spores. The oil based Kilz is very irritating to the eyes and nose if used in a closed space. Use outside or with lots of ventilation and proper paint mask filters.

CarveOne

[djem]

Originally Posted by CarveOne I haven't used BIN, but Kilz is a flat white sealer for wood and ceiling tile that can hide mildew spots and printed text on paneling. It comes in a water based and oil based version. For OSB (oriented strand board) and MDF wood products it is recommended to use oil based Kilz first, then you can paint over the Kilz sealer with water based or oil based paints. If water based Kilz is used on OSB or MDF it will cause the surface to swell unevenly due to absorbing water from the Kilz sealer. The name is from the chemicals that kill or retard mildew spores. The oil based Kilz is very irritating to the eyes and nose if used in a closed space. Use outside or with lots of ventilation and proper paint mask filters. CarveOne

Can't say that I know about that stuff. Sounds like a cross between the normal Jotun filler and knot sealer, would that be about right? Maybe its the stuff we call 'beis' in Norway and translates to stain using the dictionary, thats an oil based mildew killer that smells funny and is opaque.
I used some two component top coat on chipboard once and that made it very water resistant, might be an idea to use on top of a oil based primer. I love two component stuff, It's hard as hell and resists about everything and is very glossy.

[djem]

I took a closer look at the dremel knockoff I had planed to use as a spindle to start with. It turns out that the runout on this thing is a little bigger that I had anticipated and might not work very well for PCB milling. Is there any hope that a real dremel is going to be much better, or should I start looking for a more professional solution? cnconabudget got a interesting one, but its 110V so I would need a converter to use it (I'm on a 220V net). Any tips on what I can use, it has to take 3,2mm (1/8") tools to be suitable.

I don't have equipments to measure the runout, but as I could see it with my naked eye I'm guessing it is close to 0,5mm. Might work for some of the simpler PCB designs with no surface mounts, but I don't want the spindle to be my limiting factor. I'm guessing the roller bearing design might end up as the limiting factor?

[SScnc]

Have you guys seen the waterproof MDF ? My local ACE hdwr carries it and I will be building one out of this stuff soon.

HERE it is.

[pminmo]

Originally Posted by djem I took a closer look at the dremel knockoff I had planed to use as a spindle to start with. It turns out that the runout on this thing is a little bigger that I had anticipated and might not work very well for PCB milling. Is there any hope that a real dremel is going to be much better, or should I start looking for a more professional solution? cnconabudget got a interesting one, but its 110V so I would need a converter to use it (I'm on a 220V net). Any tips on what I can use, it has to take 3,2mm (1/8") tools to be suitable. I don't have equipments to measure the runout, but as I could see it with my naked eye I'm guessing it is close to 0,5mm. Might work for some of the simpler PCB designs with no surface mounts, but I don't want the spindle to be my limiting factor. I'm guessing the roller bearing design might end up as the limiting factor?

the cnconabudget spindle will give you much finer pitch pcb traces over a dremel.