[WolfmansBrother]

I would like to continue this conversation at the frequency of 2007-2008, anyone interested?

[scipione205]

I was hired by a newborn ONG here in South Italy to build an affordable CNC milling machine able to cut tactile maps. The budget is extremely tight. I am considering building the frame in polymer concrete (to avoid casting iron and welding/annealing steel) and use DWH resin (from Diamant) for squaring (to avoid milling, surface grinding and/or shimming).

Looking around on youtube videos, forum threads (including this one), thesis and scientific pubblications (most of all were already cited here), blog posts (ike CNC cookbok - which remainds here)... I'm just getting more and more confused.

[RCaffin]

an affordable CNC milling machine able to cut tactile maps. The budget is extremely tight.

Step 1: realise that you did not make that budget decision, so you do not carry the responsibility for any problems coming from that budget decision. If the company wants to play real cheap, they get real cheap. You do the best you can and don't lose any sleep.

Cheers
Roger

[rocketflier]

I was hired by a newborn ONG here in South Italy to build an affordable CNC milling machine able to cut tactile maps. The budget is extremely tight. I am considering building the frame in polymer concrete (to avoid casting iron and welding/annealing steel) and use DWH resin (from Diamant) for squaring (to avoid milling, surface grinding and/or shimming).

Looking around on youtube videos, forum threads (including this one), thesis and scientific pubblications (most of all were already cited here), blog posts (ike CNC cookbok - which remainds here)... I'm just getting more and more confused.

Part size, material, needed precision are all factors in recommendations. On the cheap(er) I'd point you to kit or plan wood cnc routers. You don't have to design and rework design when something doesn't fit.

I'd also suggest getting with local metal working clubs, maybe someone would be interested in a team project. Maybe they weld, you pick up scrap steel and 2 units get build.

One epoxy/granite project was started but the guy found he could get a granite slab fairly cheap and drilled and epoxied in inserts.

Which your location made me think of. Maybe hunt for stone drops, sink cutouts, defective tombstones.

[RCaffin]

defective tombstones.
The Mafia hit failed. The guy is not yet dead.

Cheers
Roger

[scipione205]

Part size, material, needed precision are all factors in recommendations. On the cheap(er) I'd point you to kit or plan wood cnc routers. You don't have to design and rework design when something doesn't fit.

I'd also suggest getting with local metal working clubs, maybe someone would be interested in a team project. Maybe they weld, you pick up scrap steel and 2 units get build.

One epoxy/granite project was started but the guy found he could get a granite slab fairly cheap and drilled and epoxied in inserts.

Which your location made me think of. Maybe hunt for stone drops, sink cutouts, defective tombstones.

Every kit and/or built machine I looked for just sucks... I know that I'm used on HAAS, Hermle and Matsuura machines... but paying 10,000$ for a machine which vibrates like hell doing a dry routine (with even the motor disabled)...

"Metal working clubs" ? Nothing. Only an old man who can to do the face milling for cheap on his large, old cast-iron milling machine in his huge all-manual shop.

I also considered using granite slabs, like this guy did: https://www.youtube.com/watch?v=sFrVdoOhu1Q

But the costs went in the sky (we need a minimum working area of 600x400) trying to use scraped granite plates.

[WolfmansBrother]

Has anyone tried using those hand held pneumatic or electric concrete vibrators?

[castinite]

es, I have tried about anything you can think of with polymer concrete. It is important that the vibration compacts the material and does not induce air. You can manually compact the material using a tamper (a 2X4 and hammer).

[NeoTech]

Tried the concrete vibrators like the "rod style".. dont work, EG is to sticky. Best sucess has been with one of those grain bin vibrators that is bolted to the outside.

[rocketflier]

Very simply 2 bearings, shaft, pulley, adjustable offset weight

https://www.youtube.com/watch?v=gwaUm_egCPw

[NeoTech]

That could work, my experience is that you wanna shake the aggregate to a point where it is basicly fluid tho. While shaking you should be able to press your hand or a roundbar or something down into the bottom of the container with no effort.. And i mixed in the epoxy during this state of shaking, make it dispearse and really cover all the aggregate properly.

[RCaffin]

Looks like a job for a mallet and a wide tamping bar to me. It's solid stuff.

Cheers
Roger

[RotarySMP]

I bolted one of those grain silo vibrators to the mould, and used a VFD to tune the frequency till I find one to help it sag. I would not expect anything less to be effective.
Mark

[rocketflier]

The inside of those silo vibrators is a motor and 2 offset weights. That's what gave me the idea for using a grinder with 2 pulley's to which you could bolt panels. But I didn't think the grinder's bearings would be sufficient. Started me thinking about the axle and offset weights when I found some uTubes of concrete block forming and a couple showed the same setup.

Attachment 379496
Attachment 379498

https://www.youtube.com/watch?v=yY0nEoH0v04

https://www.youtube.com/watch?v=R2hO--TIjjA

[RotarySMP]

Yep. I used one of them, with a VFD to look for resonant frequencies.

[scipione205]

Yep. I used one of them, with a VFD to look for resonant frequencies.

What do you mean for VFD ?

However, we are about to start building the machine and I still don't know where/how to find the needed materials... We are in South Italy, does somebody knows where we could source the pebbels and sand?

[RotarySMP]

Variable frequency drive otherwise known as an inverter. The one I used was 1 phade 240v in and three phase 240V out.

[vib]

You need pretty violent vibration. I used a 3 phase concrete vibrator which weighed about 15kg to compact the M/G I used on the head support for my mill and it still took a fairly long time to compact. Also I still had some air bubbles. To do the vibrating accoustically, you would need to borrow the The Who's PA system.

If you have a nearly ideal packing density, this stuff is really still. An orbital sander won't impress it at all.
Mark

Hi Mark
Do you still have the excel sheet from Thomas?
I can't find it unfortunately

Thank you

@all: thank you for all your efforts. I'm going to poor the first batch of test in May I hope. let's see what happen
I really struggle to find zeeosphere, I think I will use crushed sand of abarasive glass balls instead...

[scipione205]

Hi Mark
Do you still have the excel sheet from Thomas?
I can't find it unfortunately

Thank you

@all: thank you for all your efforts. I'm going to poor the first batch of test in May I hope. let's see what happen
I really struggle to find zeeosphere, I think I will use crushed sand of abarasive glass balls instead...

I do. Send me a PM

[kevincnc]

Hi all,
I obtained a good headstock from a dropped 12X36 lathe and decided to build a CNC from stuff that I already had, which pretty much drove the design. I know it could be better, but it should do what I want it to. The bed will be an 80mm tall AL extrusion frame sandwiched by 1" thick AL tooling plate. Hopefully the pictures show what I'm doing adequately. The space to fill is about 1/2 ft^3.

I haven't read this thread in detail but I think I got the idea. I don't want to turn this into rocket science, just get maybe 80-90% there. So here's what I'm thinking will be cheap & easy. Get a 5 gallon bucket and fill it with a 50lb bag of play sand. I think that's about 1/2 cubic foot. Then I can mix up some 635 thin epoxy from US Composites and mix it in with a paint mixer on a drill until it's wet but not runny. Tip the bed up on end with one end extrusion removed, dump it in, and pack with a 2X4.

Is this a good or at least good enough plan? Should I do something different? Will a 1/2 gallon kit be enough? Will I need to do it in 2 or more batches? I suppose I could also fill the 80X80 side extrusions also if that would do much good. There will be triangular plates bolted in on each side to help with rigidity.

Any advice would be appreciated.

Kevin