DIY Epoxy composite gantry frame milling machine

[John McNamara]

John, looks like a great build.

If you don't mind sharing, where in Aus are you? I'm in Melbourne.

I'm in the early design stages of a DIY mill. Manual conversions are troublesome, and true CNC machines are either tiny or very large and not feasible in the home shop / garage.

I'm planning a steel weldment, stress relieved and machined +/- ground. This is partly because I've struggled to find clear recipes for epoxy granite and don't really want to spend months experimenting. I may use epoxy granite to fill voids and add mass.
I'm looking at doing a planer style mill - double columns, with the gantry moving up and down on the columns. This avoids the long lever arm Z axis, but is a bit more complex to align.

I have a couple of comments and questions about your build:

I really like the rail alignment cams - did you make these or buy them? They are going to be great for both alignment and increasing mounting strength of the rails.

The Z axis travel seems a bit short compared to your other travels. What sort of spindle / tool holder are you going to use?

What was the cost of the laser cut steel? Do they cost it per cm cutting length or similar? I'm interesting in getting a milling head and gantry beam laser cut. I'll probably use square hollow section for the base however.

Hi
I am in Melbourne 3122

John1147 at big pond .net.au

You will have to edit the address above I guess you know how.
If you email your phone number I will give you a call :)

[John McNamara]

Hi
Most laser cutters provide the mild steel and cutting at a quoted price. Many will also have Stainless and Aluminium Etc.
It is not possible to work out the cost on the basis of so much a millimeter.

The main thing is to provide properly drawn 2D files, usually DXF files. The part outline must not have any breaks or overlapping lines, All holes must also be closed. (And nothing else in the file) Each part should have its own file. Don't try to nest the parts yourself in a big file.

Laser cutters are pretty busy businesses, If you provide good files you will be charged as a professional. If you cant provide files some will draw the parts for you, be prepared for a shock when they quote to do this.

Just email your requirements and the file set in a Zip file and most will reply with a quote in a day or two. (A separate zip file should be used for each material type and thickness. this avoids confusion) It is OK to have a short discussion when starting with them asking if they have any special requirements.

I really like the rail alignment cams - did you make these or buy them? They are going to be great for both alignment and increasing mounting strength of the rails.
[
I had them laser cut from 4mm steel they cost about 50c each the laser cutter provided the material

The Z axis travel seems a bit short compared to your other travels. What sort of spindle / tool holder are you going to use?

I drew in an Asian high speed spindle fine for Aluminium Brass and plastics and fairly low cost. I also plan to build a 30 or 40 taper spindle, Possibly using the high speed 2000 rpm spindle with a 4 to one reduction belt drive. I also have a large Manual V Mill, It is easy to make the Z axis taller I decided not to as this machine will be used for smaller parts. Shorter = less deflection

What was the cost of the laser cut steel? Do they cost it per cm cutting length or similar? I'm interesting in getting a milling head and gantry beam laser cut. I'll probably use square hollow section for the base however.
Laser cutting cost of the machine parts was about $500 including material plus the molds that cost more I am sharing the cost of the molds. 160+ part files is a lot quite a few of the parts were in multiples. looking at it that way the cost per part is modest. FWIW the cost per kg of parts was AUD $3.85 All up inc GST/VAT. I would not try to use that figure it will depend on the mix of parts, OK I guess as a ballpark.

[pippin88]

John,

Thanks for the info.

I've sent you an email.

[Nick]

Nice build, following with interest, I am also doing an epoxy build. The laser cut moulds look very neat.

Have you decided on your epoxy % and aggregate mix? Will you be vibrating the molds?

Nick

[John McNamara]

Nice build, following with interest, I am also doing an epoxy build. The laser cut moulds look very neat.

Have you decided on your epoxy % and aggregate mix? Will you be vibrating the molds?

Nick

Hi Nick
I will not be vibrating the molds, some sit on a surface plate that is used to provide a flat plane. I will be tamping the mix down in 25-50mm layers.

The Mix will be nominally 12% epoxy by volume. When I do the pour I will do a test just before to make sure the stone and sand batch has not changed.

Page down this post of a previous pour.

https://www.model-engineer.co.uk/for...p?th=51617&p=3

The objective is to use the least amount of epoxy.

I plan to pour over the weekend if all goes well.

Regards
J

[John McNamara]

Hi All

At last the first casting has been poured
Link below.

I will be very interested to see how accurate the cast in position rail supports are.

I will strip the mold later this week.

Regards
John

https://www.model-engineer.co.uk/for...?th=139042&p=2

[pippin88]

John,

Can you give us an update on the results of the first pour?

In particular - how is the alignment / flatness of the bearing mounting plates?

I've been doing a lot of reading, and am pretty sold on epoxy granite due to the excellent damping characteristics.

If I can cast in a linear bearing mounts with acceptable accuracy at home, and avoiding the need for post-machining, I'll be out the door for 20-40kg of epoxy.

Also, can you share how much the Megapo

[John McNamara]

Hi All

The Base casting is poured!

This is the largest and heaviest casting over 200KG. I cant wait to remove it from the mold, finish and undercoat it than assemble the columns and gantry castings so that I can take some measurements.

Regards
John

https://www.model-engineer.co.uk/for...?th=139042&p=3

[John McNamara]

Hi All

At last the base, columns and cross-member are one and I don't believe I could achieve the level of accuracy obtained without a laser cut mold.

https://www.model-engineer.co.uk/for...?th=139042&p=3

Regards
John

[John McNamara]

Hi All

Assembly of some of the laser cut parts, also some machining done.

Write up here:
https://www.model-engineer.co.uk/for...?th=139042&p=3



Regards
John