MDF CNC Router plans / parts for home build beginners

[irving2008]

Are you proposing fixed gantry/moving table or a moving gantry? If the expected workpiece is relatively lightweight (small amount of MDF, balsa wood, PCBs, etc.) I'd suggest a moving table design gives more bang for the buck so to speak. A moving gantry is going to be quite a lot heavier, harder to make rigid and will limit the performance with a small motor.

I concur on the 12x3 trapezoidal. Its not so expensive and even without an antibacklash nut will give a better result than M12 rod.

What about the spindle? Dremmel or something meatier?

Oh and on the stepper drivers, came across these... no idea how good or what chip, was thinking about getting one to find out but at £8.99/channel.... They also do a cheap (£30) 27v/13A PSU

[HiltonSteve]

I was thinking of going for a moving table as like you say it will give more bang for buck and the design should end up simpler which is what we are aiming for.

Spindle - will probably go with a dremel to start with as I happen to have a couple kicking around and they should suit what we will be cutting, there are plenty of dremel's on ebay and also copies for not a lot of money so it makes sense to go down that road. I will design it with the option to put something meatier on there but I really don't think it will be suitable for an entry level type machine but then again you never know!

Just checked out those stepper drivers and they don't look too bad, especially for £8.99. Has anyone ever had a go with one of these before?

[HiltonSteve]

Thinking about the trapezoidal again, just changed my mind and now going for M10 x 2mm. A little bit cheaper and no micro-stepping drivers needed.

1 stepper motor rev = 200 steps @ 2mm pitch means 1 step = 0.01mm - I know you can state whatever steps per unit you want to in mach3 but this way it will keep it simpler for the beginners...

Starting to talk in numbers and equations like Irving now!

[John S]

Had a quick look, can't see how to adjust motor amperage, resistors ? and they are probably unipolar for that money.
Worth sending for a couple of handfuls though just to play with.

[HiltonSteve]

Had a quick look, can't see how to adjust motor amperage, resistors ? and they are probably unipolar for that money.
Worth sending for a couple of handfuls though just to play with.

Bi-polar John, just found some on ebay - http://cgi.ebay.co.uk/Stepper-Motor-...item3f0012d4b4

[John S]

Virtual village UK - rho
From Hong Kong

He's me thinking it was the village down the road ?
.

[HiltonSteve]

Virtual village UK - rho
From Hong Kong

He's me thinking it was the village down the road ?
.

Not on your own.....

[HiltonSteve]

Been playing with a few idea's and I have attached a quick render and also a 3D PDF file to help you understand what I am thinking.

To open the PDF you may need the latest Adobe reader V9 (free to download), you will be able to spin it round, zoom in and out and take it apart. Easier than doing loads of drawings from various angles.

I have used the IGUS N profile 27mm for all the slides, not 100% sure that this is the way to go though.

This is just a concept drawing, 18mm MDF all round and I have tried to make everything as close to actual size as possible so that I can get an idea of how it will fit together.

Anyway take a look and let me know your thoughts, I have a few things that I am not happy with but it would be interesting to get some more opinions.

[Lee Roberts]

Hi Steve,

It’s looking good, I’ve not replied but I’m following :).

I think one thing that sticks out as a possible concern to me is that, when I built my rockcliff machine the 13x13” Y Table (the bit you put your work on):



Started to bend and go banana shaped in a very short amount of time. I did have an unnecessary pocket along the length and I think this helped it on its journey to becoming banana like. My concern is that yours may do the same, an option to stiffen it all up maybe to add some ribs under the table the same shape as the Y Axis ball screw floating end plate in your model.

I would prefer if the machine was a flying gantry type as well, if you think about it the design at the moment needs a bigger foot print then if it was done as a flying gantry type.

So I’m thinking, take off the support footer for each of the gantry side plates, mount them at each end of the Y Table (possibly even double them up), use two lengths of MDF that run underneath/in-between the rails and Y Axis plate, this would then hopefully give you the clearance for the ribs.

Just my observations mate, what do I know :confused:

O nice Z Axis design as well, i like it

[Zephyr]

I have a suggestion about sealing MDF.

As most of us know from experience (there are a lot of MDF 'bananas' around), MDF is hygroscopic and will absorb moisture from the air. If it absorbs water from the air unevenly and/or the MDF sheet is not a uniform thickness it will warp. Sealing it all over against moisture absorption could be the answer to preventing it warping.

One sealant could be plain old boiled linseed oil which, if put on correctly will polymerize like plastic and it’s also a little flexible as well. It's also cheap.

Clean the dust of the MDF. Round off any sharp corners if possible.

The first coat can be boiled linseed oil diluted 50:50 with turpentine or white spirit put on fairly quickly (to prevent warping). Wipe it on with a cloth and leave to dry (supported on blocks) in moving air away from heat or direct sun.

2nd coat can be 75% boiled linseed oil 25% turps. wiped on quickly with a cloth. Don’t leave pools or surplus on the surface - they won’t dry properly and won’t polymerize.

These 2 diluted oil coats will go into the MDF and provide a better key for the next coats.

Next use neat linseed oil wiped on with a cloth and again taking care to remove any surplus. The MDF should then be fairly well sealed but the more coats you put on the more effective and long lasting the seal will be. 3 or 4 more coats at least of neat linseed oil wouldn’t go amiss.

I know it’s time-consuming but people without much money to spare would rather spend their time and it’s low tech.

Don't seal moisture inside damp MDF. Make sure it's as dry as possible and the ambient air isn't humid either.

A very light sanding with fine glass paper between coats will help to key the coats but vacuum-clean the dust off.

Remember safety. Wear rubber gloves, don’t breathe in the fumes or dust, dispose of oily cloths safely - either in a bucket of water or wash them out thoroughly and dry them outside. Oil-soaked cloths are a potential fire hazard.

I'm not suggesting you try this on an important or complex part. Try it on a test piece first.

I hope this helps and that I'm not 'teaching people how to suck eggs'. Let me know if I am and I'll shut up. If anyone tries it I'd be interested in how well it worked for them.

Regards.