Materials questions

[Jencen]

Hi all.
Have ordered a new rockcliffe driver today so hopefully will get back on track with my machine soon.

during testing with the broken board i managed to break my Z axis (heavyhandedness. not mechanical or programming)
Due to this i'm considering rebuilding in a plastic. I've found a supplier at http://theplasticshop.co.uk/
And i'm wondering if anyone else has tried in plastics. i'm possibly looking into either PVC, nylon or acetal/delrin.

am also considering rebuilding as it may be taken out as an engraver to shows. and MDF may look a little... odd. especially the way i've treated mine.

Also if i'm going to rebuild i'm tempted to go for the model D anyone got any advice with that one?

Many thanks

[Boort]

Jencen,

What part of your Z axis was broken? (or more specifically what part(s) are you planning to recreate in plastic?)

I made my router from 3/4" 12 ply Baltic Birch plywood and have been happy with it so far. If you are talking about making the main Z slide (Parts 25,26,27 from the Assembly.pdf diagram) from plastic. I have heard good things about Alumilite (http://www.alumilite.com/) This is a machinable resin that allows you to cast parts or sheets. I know that others in the DIY CNC community are using this to make parts for their CNC machine designs, but I do not know how well it would work for the size of the Rockcliff Design.

I have worked with a (brand name) CNC Router that used either 1/2 or 3/4" HDPE for it's construction and was not impressed by it's rigidity. Aluminum angle needed to be added to the edges in order to reduce flex in longer pieces.

Regards,
BoorT

[Jencen]

Hi there.
The part i used for the leadscrew had slipped out of where i'd placed it. mainly because i was rough and just glued it in. also used the wrong type of glue.

Because i didn't have access to a router at the time of building i'd made up a little block assembly that would hold the nut securely (so i'd thought)

unfortunatly to repair it i've had to remove the X-axis and in doing so have damaged beyond repair. there's only so many times you can drill wood. plus i think it's gotten damp at some point

I've godden some samples of the plastics and they seem fairly rigid at 19mm. the delrin especially so.
The thing i like about the nylon is it's machineability. it's rigid, easy to cut and easy to machine. delrin even more so but much more expensive.
Have not looked into HDPE because of it's flex


One other thing we have over here is something called polymorph. it's beads of a nylon based material that can be moulded by hand at quite low temperatures 30-50 decrees celcius i think. quite handy for prototyping and once hard can be cut and machined just like nylon

[rockcliff]

Hi
a couple of years back a builder used plastic for his cross slide x-z and he claimed to have some trouble with warping,
I think it looked like lexan / polycarbonate, which can easily distort from machining large amounts of material.

If I were to atempt plastic, I would lean towards PVC, it's fairly cheap, very machineable like delrin, but the good thing about it is you can glue it,
my only real concern with any plastic, is when you cut it, keep it as cool as possible to minimize warping.

Originally Posted by Jencen

Hi there.
The part i used for the leadscrew had slipped out of where i'd placed it. mainly because i was rough and just glued it in. also used the wrong type of glue.

Because i didn't have access to a router at the time of building i'd made up a little block assembly that would hold the nut securely (so i'd thought)

unfortunatly to repair it i've had to remove the X-axis and in doing so have damaged beyond repair. there's only so many times you can drill wood. plus i think it's gotten damp at some point

I've godden some samples of the plastics and they seem fairly rigid at 19mm. the delrin especially so.
The thing i like about the nylon is it's machineability. it's rigid, easy to cut and easy to machine. delrin even more so but much more expensive.
Have not looked into HDPE because of it's flex


One other thing we have over here is something called polymorph. it's beads of a nylon based material that can be moulded by hand at quite low temperatures 30-50 decrees celcius i think. quite handy for prototyping and once hard can be cut and machined just like nylon

[Jencen]

Pvc can also be welded which is making it attractive to me as well as the cheapness.

are there any other types of wood that are fairly resistant to damp or that are easily treatable for such?

Another concern i have with plastics is fumes given off when overheating. i know that perspex can give off nasty gasses when heated.
And i would so love to have a completely clear machine

I'm also considering grabbing some ACME screws. is there a need for them to be supported at the opposite end of the motor or can they be left?

[Alien_X]

I have built my machine from moisture resistant mdf.
We have trapezoidal screws over here, and I would recommend supporting them at both ends.

[Magster]

Originally Posted by Boort

Jencen,

What part of your Z axis was broken? (or more specifically what part(s) are you planning to recreate in plastic?)

I made my router from 3/4" 12 ply Baltic Birch plywood and have been happy with it so far. If you are talking about making the main Z slide (Parts 25,26,27 from the Assembly.pdf diagram) from plastic. I have heard good things about Alumilite (http://www.alumilite.com/) This is a machinable resin that allows you to cast parts or sheets. I know that others in the DIY CNC community are using this to make parts for their CNC machine designs, but I do not know how well it would work for the size of the Rockcliff Design.

I have worked with a (brand name) CNC Router that used either 1/2 or 3/4" HDPE for it's construction and was not impressed by it's rigidity. Aluminum angle needed to be added to the edges in order to reduce flex in longer pieces.

Regards,
BoorT

Hi,

I have used Alumilite quite a bit for making moulds and also a similar material called Metapor (which is kind of porous and lets air escape). Both these are quite similar materials which machine very well, only I would not recommend using these for any large spans or thin parts as I have found them quite brittle and can shatter or break quite easily.
The other down side is that they are quite expensive, if I can remember correctly the last time we bought any it was around £70 for a 500x500x15mm sheet, although I can't remember whether that was metapor or alumalite.

Hope this helps,

Magnus.

[jhelmstetter]

From what I have read, plastic is more sensitive to temperature changes and expands and contracts more than MDF. I have seen people use cast acrylic o machines. It looks super but unfortunately I don't how it reacts to temperature changes.