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cncJim
19-06-2013, 10:18 PM
Ok here is my first go at something since my shocking egg shape circle test cuts and I have to say I am proper chuffed with it!

I have seen the aztec sun stones many of you guys have which look great but thought it may be a bit ambitious for my first go so i decided on a maya calendar design which looks far simpler!

I don't have any nice wood but I had an old piece of timber in the garage (pine I think) so I cut into 3 bits, surfaced the sides on the cnc, glued them together and then cut the calendar design.

A little bit of tweaking after the cut to tidy up and happy days!

9087

I know there is lots of room to improve so if you guys spot anything and have advice I would be happy to hear it.

Very happy! :thumsup:

Jim

Lee Roberts
19-06-2013, 10:43 PM
Nice one Jim, pleased you got the machine sorted!

What was the total run time for the job, cutter used and the size of the part?

.Me

cncJim
19-06-2013, 11:20 PM
Thanks Lee!
Finished size is 260mm diameter and 35mm thick.
90deg 9.5mm v bit - 40 mins (it was quicker but I had to slow the feeds right down as I have a bit of flex in my machine and slowing it down seemed to compensate well enough)
3 mm end mill to tack the flats down 2 mm - about 10 mins
6mm end mill for the profile cut out - 4 mins

Jim :smile:

WandrinAndy
20-06-2013, 04:55 PM
I think that looks great Jim!
Are you sure about the Mayan origin though? That dude in the centre........ I could swear I've seen that dude walking down Hemsworth high street.:friendly_wink:

GEOFFREY
20-06-2013, 05:04 PM
Jim, that looks great. No more scrambled eggs for you then!! G.

kingcreaky
20-06-2013, 09:59 PM
Now.. that is a peace of fine work sir!. One you should be very proud of :D. Dont leave it above radiator though....

hey the trick is... make the inverse of that... fill it with cement... and you can make paving slabs!!

How much sanding was involved? did it frey on the detail? Ive looked through your previous posts no photos of your machine? lets have a look....

kepp us posted with your progress and lessons learnt etc... we are all very interested.. even though some people dont tell you how much they love looking at some pictures!

cncJim
20-06-2013, 10:13 PM
I think that looks great Jim!
Are you sure about the Mayan origin though? That dude in the centre........ I could swear I've seen that dude walking down Hemsworth high street.:friendly_wink:

Lol - thanks andy - The geezer looks a bit dodgy to me, Looks like he has a pc monitor in his swag bag!


Jim, that looks great. No more scrambled eggs for you then!! G.

Thanks G, hopefully every shape I cut out from now on will be as intended!


Now.. that is a peace of fine work sir!. One you should be very proud of :D. Dont leave it above radiator though....

hey the trick is... make the inverse of that... fill it with cement... and you can make paving slabs!!

How much sanding was involved? did it frey on the detail? Ive looked through your previous posts no photos of your machine? lets have a look....

kepp us posted with your progress and lessons learnt etc... we are all very interested.. even though some people dont tell you how much they love looking at some pictures!

Really kind words, thank you!

Don't worry about the radiator, only stuck it there for the pic as it was the only window with enough light!

I like the inverse idea, very clever indeed, that's given me quite a few ideas.....:thumsup:

I used a brand new v bit and there was hardly any clean up on the detail to do after. Just a couple of sections needed a scrape with a blade. Unfortunately the flat areas was a different matter..... Very bad fraying around every edge! I do wonder if it would have been better to do the flat spots first followed by the v carving? I imagine the v bit would have cleaned it up quite a bit?

Also the flat areas really showed up the alignment issues I have the z axis. It left lots of lines on every flat area, which needed a bit of sanding. I have been looking into getting a dial test indicator to measure and sort the alignment but I also think I have an issue with flex on the gantry....the z is fixed to the gantry by two (thin) unsupported rails....yeah I know, the unsupported rails are not great and I think one of my next posts will be to ask advice on how I might approach changing them. I will strike some pics of the machine up then for everyone to have a laugh at! :courage:

Jim

Jonathan
21-06-2013, 01:40 PM
That looks good. There's a more ambitious one here (http://www.mycncuk.com/forums/open-source-discussion/5520-how-about-mycncuk-cnc-router-project-2.html#post40025) if you want to try it. This is the one I cut, aluminium naturally:

9101



90deg 9.5mm v bit - 40 mins (it was quicker but I had to slow the feeds right down as I have a bit of flex in my machine and slowing it down to compensate well enough)

When the machine isn't sufficiently rigid it's better to lower the depth of cut and keep the feedrate at the correct value. The reason for this is clearly you need to lower the force on the cutter, which lowering the depth of cut will of course do, but you don't want to lower the feedrate as that lowers the chipload (assuming constant spindle speed), as that will cause more wear on the cutter and more heat.

cncJim
21-06-2013, 02:02 PM
Hi Jonathan, That is the one I thought about having a go at, but the total time to cut put me off! Also I don't have a dedicated dust removal set up of dust shoe yet (should have been my first project but I got carried away!) and standing around for 3-4 hours with the vacuum didn't sound fun! Your cut in aluminium looks ace! I will definitely give this a try in wood one day.

Thanks for the advice, that makes sense. Would it also be possible to lower the spindle speed and feed rate to keep the same depth of cut (and keep the correct chipload)?

Jim

martin54
22-06-2013, 08:37 PM
looks good Jim, hopefully I will be doing stuff like that once I get the machine sorted properly.

Jonathan
23-06-2013, 03:32 PM
Thanks for the advice, that makes sense. Would it also be possible to lower the spindle speed and feed rate to keep the same depth of cut (and keep the correct chipload)?

Yes to an extent, but bear in mind the available spindle power drops with speed so if you go too low the spindle may stall, hence it's safer to advise keeping the spindle speed near the calculated value.

cncJim
24-06-2013, 02:24 PM
Yes to an extent, but bear in mind the available spindle power drops with speed so if you go too low the spindle may stall, hence it's safer to advise keeping the spindle speed near the calculated value.

I see - Thanks for that.

Another question if I may - I noticed that after the circle profile cut it was uneven in a couple of places. It seems to be on the Y axis and from what I have read I think it may be backlash in that axis, does that sound right? one side of the circle it was very obvious, a slight jut out from the circle, the opposite side not so much - I wish I measured it now but I gave it to my Dad for fathers day!

Jonathan
24-06-2013, 06:44 PM
I noticed that after the circle profile cut it was uneven in a couple of places. It seems to be on the Y axis and from what I have read I think it may be backlash in that axis, does that sound right? one side of the circle it was very obvious, a slight jut out from the circle, the opposite side not so much

Backlash can cause the effect you describe. It could be something else, like a slightly loose pulley/coupling, but that seems less likely since the rest of the part isn't all over the place. If you're machine is driven by ballscrews then you're unlikely to notice their backlash on wood, since it's very small (<0.05mm). That's not the case if you've used ACME or threaded rod...

cncJim
24-06-2013, 07:08 PM
Backlash can cause the effect you describe. It could be something else, like a slightly loose pulley/coupling, but that seems less likely since the rest of the part isn't all over the place. If you're machine is driven by ballscrews then you're unlikely to notice their backlash on wood, since it's very small (<0.05mm). That's not the case if you've used ACME or threaded rod...

That's a worry then as I do have ballscrews! Just got a dial gauge so i will check later and report back :)

Jim