[evengravy]

Hi,
I have been working away on the Momus v2.0 for some time now. I have extended the Y axis by 8 inches and made some substitutions here and there where necessary. For instance the Y plates are thicker as I could not source the specified plate, not a huge change. I also used thicker angle stock for the X rail angles... this did cause some issue with bolt clearance on the right side of the gantry (bearing affixed to lower portion of part 06) as a result I had to grind the heads of the bolts for clearance, again not a huge issue but one that took some time to resolve.

This is my first attempt at any form of metalwork so I've been taking it slow and steady, but the purchase of a cross slide vice for my cheapo drill stand made aligning the drill holes easier when making the aluminium parts. These are normally intended for light milling applications but are really handy as very small alignment adjustments can be made under the drill.

Metal was sourced from Forward Metals Ltd. | Small Quantity Metals in Aluminium | Tube | Round Bar | Sheet | Treadplate
Fasteners were sourced from Stainless Nuts and Bolts, Screws, Fasteners, and Hose Clips - Westfield Fasteners Limited

Find attached some BOM's and substitution charts I made for converting from imperial to metric. *note i'm not complete yet so there may be small omissions/errors

I'll upload a pic shortly, its on my other comp

By the way I'm currently at moving gantry (by hand) stage and have most of the metalwork complete, however, I intend to use the Kress 1050 router so I will have to rethink the Z plate mounting

[evengravy]

here are the conversion charts/boms

[evengravy]

Here are some pics of the work in progress, as I said the Y axis has been extended by 8 inches.

The main issues I've had are due to substitutions I've had, or chosen, to make. If you stick to the plan 100% you should be fine

I have to figure out the Kress router mounting, I'll likely draw it up in sketchup first.

Those with a keen eye will notice the the right outer skin in the first picture has three doors rather than the normal two. Since I extended the axis by 8 inches I felt in necessary to add two supports rather than 1 to ensure a solid footing for my plates above. The centre section is smaller with the left and right openings being kept to the original dimensions more or less.

[evengravy]

So, rather than wait I went ahead and drew up a solution for mounting the Kress router to the Z axis.

The main mount at the bottom is an off the shelf clamp from daemoncnc, under which I have arranged three 6.35mm cold rolled (bright rolled) steel that was left over from the rails. The main mounting block will be tapped and studded so it can be bolted to the Z plate through the 6.35mm steel spacers.

The issue with the Kress, compared to the recommended routers is that it is very tall. This causes a clearance issue with the mounting point for the leadscrew, resulting in one of two solutions:

1. make the plate longer essentially losing 3" of travel from the Z axis or
2. move the router out from the plate to allow sufficient clearance. I have chosen option 2

The Z plate is still 2" longer than the original spec, however I believe I may be able to recover this by moving the Z motor assembly upwards by two inches... we'll see when we get to that point, for now the quick render.

If anyone wants a sketchup file of the Kress 1050 let me know, it took some effort!

[momus_cnc]

Thanks so much for posting that link to the UK supplier of Imperial sized metal. I'm sure that will be very helpful to many builders. I was looking around their site and it looks like they carry all of the aluminum sizes that are needed, including the gantry tube.

The machine is looking great. So does the clamp design. Having the two clamps that are spaced wide apart should make it very solid.

Looking forward to seeing more progress photos.

-Bob

[evengravy]

Sure thing,

I found forward metals to be great to deal with, rapid as well. Nice to hear the z design should be strong enough, I have actually have gotten some of it built but am awaiting some longer aluminium parts to attach to the extended plate and the length which carries the z motor mount, so I will wait until it is complete until posting any updates. Until then thanks!

[evengravy]

Thinking ahead to the base, what would your thoughts be on using casting resin instead of the low viscosity epoxy. In particular I've been looking at EasyFlo 95 By Polytek. It's generally used for casting plastic models and should be relatively low vis but loads easier to source locally. It's recommended for casting of, amongst other things, tools (according to their blurb) and is classed as tough polyurethane plastic...? Not sure on hardness rating however.

Edit. Hardness is shore D 65.. Also available in ultra low vis Easyflow 60

[evengravy]

Hey,

So I've been flat out with the hacksaw and file making the Kress mount for my extended V.2 Momus. Here are some images of the final result. With my rudimentary measuring tools it seems to be straight and parallel and i'm hoping my "hillbilly engineering" will be strong enough for my intention for the machine; which is to mill primarily aluminium front panels for audio gear of my own design. I'd appreciate comments good or bad on it so fire away.

I have also extended the section of the z carriage that holds the Z motor above the router, it now measures roughly 260mm. I will post updates as and when the next stage comes together, now time to rest my hand after all the filing

even

[OCNC]

Looks good!

Chris

[evengravy]

Thanks a lot, im pretty happy with it but the only concern is how parallel it is to the back plate, I can't get the callipers in to measure either, know of any tricks?

[OCNC]

Thanks a lot, im pretty happy with it but the only concern is how parallel it is to the back plate, I can't get the callipers in to measure either, know of any tricks?

Put a piece of drill rod in the collet and lay the whole unit down on a flat surface and measure the height of the drill rod off of the surface near the collet and at it's end. This should give you some indication of what's going on. If you don't have precision measuring tools use a block that just clears under the horizontal drill rod and then slide feeler guages between the block and the rod until you get contact.

Chris

[evengravy]

Ah, so simple...thanks Chris il try that

[evengravy]

OK, so here is an update of last weekends work. Still some work to do to create some needed clearance between the middle kress mount that I made by hand and the acme (trapezoidal) lead screw to drive the Z. This, hopefully, I will have done by tomorrow evening and can start to paint the base.

The only concern I have is the weight of the Z axis, I haven't weighed it as such but I could estimate it at 3 - 4kg or more. My chosen motors are from kelling inc, 380 oz inch and will be driven by 2m542 stepper drivers. Hopefully it should be ok. I presume these drivers should be pretty good for my setup.

Im still unsure what solution to use for the epoxy base, the low vis epoxy listed in the plans is rather hard to source here, looking for substitutions in the UK/Ireland.

Cheers, John

[louieatienza]

Now sure how it affects drying, but you can thin epoxy with MEK if you can find it (methyl ethyl ketone)

[evengravy]

Ok, thanks for that il keep it in mind.

I've been looking at maybe using casting resin, polyurethane. Apparently it is low vis and hardness rating is high, not sure how it would compare to epoxy though, maybe someone here knows more than I?

[harryn]

You can get a first order estimate of hardness by comparing the durometers.

If it is really easy to get the casting resin, then perhaps just buy some and do a small test pour on a scrap board roughly the size of your machine base. That will give you both experience before you do this to your own machine and the answer.

Viscosity is one factor in making a polymer self level, but equally important are flow agents, surfactants, fillers, cure time / temperature, pour thickness, bubble management, etc.

None of these polymers are going to be extremely hard. The actual work surface is usually a scrap board so that your router can through your part and you just toss the scrap board as needed.

[evengravy]

Thanks for the info on hardness. I suppose my take is that as long as it provides a flat area to measure from I'm not to concerned with durability. As you say there will be a spoil board on top of it anyway.

I think it will be fairly bubble resistant, if there is such a thing. Casting of models with fine detail would be ruined by bubbles and de gassing isn't required to my knowledge. The only thing is the working time is very short, only a few minutes maximum. I may just try to source some epoxy.

[harryn]

If you go the epoxy route, consider using precision epoxy. That material is specifically formulated for flowing out flat.

Precision Epoxy Products

[evengravy]

Ah nice, thanks for that

[evengravy]

Right so a bit of an update:

I have the machine painted and it's looking well, pics to follow, I have also sourced some low viscocity epoxy for the base which is yet to be applied as the outside temps are -2 degrees at the moment, curing could be an issue.

Today however I decided to tackle the electronics on the bench and ran into a few issues. I went ahead and purchased 380 oz inch motors from kelling inc: KL23H2100-35-4B, three 2M542 drivers and a 48V 10A psu (tamed down to 45.5V via an onboard pot).

Following the PCB Breakout board documentation I could not get the motors to move. According to their pdf the PLS+, ENA+ and DIR+ should be connected to XN on the pcb, which I presume is GND. See attached image 1.

Much head scratching later I tried to connect PLS-, ENA- and DIR- to XN (GND?) and I got the motors to move ok. I'd appreciate it if someone with more experience than I can confirm that this is a correct arrangement.

I have drawn up a diagram of the wiring that I have, see image 2. I had to skip using the Y channel on the pcb as I believe my pins (16 and 3) are not working on my parallel port, hence I used Z on the PCB to drive Y and A on the PCB to drive Z.

I am right in thinking that these PLS-, ENA-, and DIR- pins are ok to be tied to ground and active high? Do I need to make any alterations in Mach3 to account for my change from the original manufacturers documentation or is it likely to be a typo on their end? Chinese manufacturers aren't known for their thorough and correct documentation.

Cheers, John