DIY Epoxy composite gantry frame milling machine

[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 Pippin

I will be posting the results soon, my workload has piled up so have not had much time for the machine.

I have managed to prepare and undercoat the casting, there were more blemishes than I would have liked, I filled them with body filler and the part is now undercoated. The part is very massive too heavy for me to lift. Tapping it with a hemmer yields a dull click only, even on the metal parts. the damping propertied of mineral cast epoxy is clearly evident

A prelim check with a straight edge indicates that the cast in position rail mounts are accurately located and co-planar . By eye I was unable to see a gap. However I will feel happier when I have tested them properly. Now that the part is clean I will set it up on jacks on surface plate to take some proper measurements.

Regards
John

[John McNamara]

Hi All

I have reviewed the accuracy of the casting and am very pleased. Link below.

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

The maximum error is 0.0018" as cast, that will be reduced by lapping to high accuracy there is not a lot of metal to remove so the process will not take a lot of time.

Regards
John

[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