My DIY CNC machine build mk4

**routercnc** · 01-28-2018, 04:51 PM

OK, time for Episode 11. We dismantle Mk3, and start building the bed frame for Mk4.

**routercnc** · 02-19-2018, 08:49 AM

Episode 12 is ready. Machining the second ballscrew and test run of the mechanism:

**routercnc** · 03-16-2018, 03:42 AM

Episode 13 now ready - machining and installing the ball screws on the bed.
Contains some paid for content.

**routercnc** · 04-07-2018, 02:36 AM

OK, episode 14 is now ready. This time we finished the Z axis ball screws and wire up the new steppers.

**routercnc** · 05-03-2018, 01:44 PM

Episode 15 is now ready for viewing. Setting out the epoxy leveling for the X rails. This was my first time using epoxy like this and I certainly learnt some things along the way - especially those bubbles !

**routercnc** · 05-28-2018, 03:55 PM

Episode 16. Having another go at the epoxy leveling . . .

**Abuckeye** · 05-30-2018, 09:28 PM

I?ve been keeping up with this build on Your channel. Great looking machine! Can?t wait to see what it can do

**pippin88** · 05-31-2018, 05:52 PM

Epoxy levelling can be a bit tricky.

My tips (too late but maybe they'll help someone)
Use a quick setting epoxy to seal the dam / container. Just paint it on all the joints / seams - only need a little bit.
Use a slow setting epoxy for the actual leveling

You need a thick layer of epoxy to level - 5-6mm. If your epoxy is too thin, it will not level due to surface tension (probably).

Avoid introducing bubbles when mixing!
Use a small blow torch passed quickly over the surface to pop bubbles that do get poured.

Pour evenly over the epoxy area, don't just pour in one spot. There is limited time and you want the epoxy to level, not spend time getting from A to B.

You need to have epoxy on a wider area than you actually need flat. E.g. If your linear rails are 20mm wide, I would epoxy at least 40mm wide. There is quite a big meniscus.

**routercnc** · 06-09-2018, 01:15 PM

Sorry, only check in occasionally and missed these.

Hi Abuckeye,
Glad you are enjoying it, thanks !

Hi Pippin88,
I've got one more lay up to do on the gantry a bit later in the build for the Y axis, so all comments are still welcome.
I think I did all the things you mention:
I can't remember if I put it in the last video but yes I did paint on some epoxy over all the joints prior to the lay up.
I used West 209 hardener which is a very slow setting (meant for tropical conditions, so when used in the UK it basically takes much longer to set).
The depth gauge I made in ep15, and you briefly saw it in ep16, was set to 5mm to overcome the surface tension and allow it to flow.
Yes, I learnt the hard way to mix it slowly - ep16 where I mixed it slowly worked out much better then ep15 where I was worried about not getting a proper mix so mixed it quickly.
I did try a hot air heat gun (won't do that again), but have since seen others use a small chefs blow torch so I'll have a look at those next time, thanks.
Yes, I ran around the complete channel - 2 laps I think to give it a chance of being level rather than relying it flowing.
The channels where the 20mm rails sit are 40mm wide, so there should be room for the miniscus.

Something else I'll look at next time is pouring the mixed epoxy into a fresh container with a hole in the side with tape over it. This apparently also helps with bubbles? Then removing the tape to pour from the bottom, leaving more bubbles at the top which stay out of the mix.

Working on the next episode but quite a lot of work to do on the machine before that is ready. Thanks.

**routercnc** · 06-30-2018, 12:42 PM

Episode 17 - time to find out if the epoxy worked and how flat it is . . .

**ianagos** · 06-30-2018, 01:13 PM

Very nice but I think your method for checking the rail flatness is a bit flawed. I don’t think the stone you are using nor the setup is nearly sturdy enough. But still cudos you are doing a very good job with what you have.

**routercnc** · 06-30-2018, 01:54 PM

Originally Posted by ianagos

Very nice but I think your method for checking the rail flatness is a bit flawed. I don’t think the stone you are using nor the setup is nearly sturdy enough. But still cudos you are doing a very good job with what you have.

Hi ianagos
Yes I’m just using the things I have in the workshop and this is along way from a metrology lab. I agree that it can’t be relied on and guaranteed but those are the tools I have.
The stone is a marble slab from an old fireplace. I’ve checked it against other surfaces and ground items and trust it to at least 0.05mm. It was shimmed underneath off the old bed so I could read direct off the DTI and not have to subtract a best fit curve. There was also a heavy block on it (out of shot) to keep it stable plus I lifted the angle plate and pushed down to see if the weight of the angle was moving the DTI but it was less than 0.01mm. I couldn’t do much about any flex in the DTI arm though which can cause an error before it moves the plunger. Good comments thanks