First CNC machine

[kev]

Hi everyone,
this is my first post, basically im building a cnc machine for my college project,
so far this is what i have got and made,
http://www.mycncuk.com/forums/photoplog/images/1428/medium/1_24112009303.jpg

http://www.mycncuk.com/forums/photoplog/images/1428/medium/1_24112009304.jpg

http://www.mycncuk.com/forums/photoplog/images/1428/medium/1_24112009306.jpg

Its made from 45x90x1000mm aluminium profile,
i have used igus drylin linear bearings and rails
and thats about it really.

its about 1090mm x 965mm and i should be able to get a cut area of around 800mm2.

im planning on keeping the y axis as close down to the x axis as possible, and then making a long z axis so it will cut below its frame so i can raise it up if needed and cut bigger things.

i will be using 2 steppers on the x axis with the screws running along the top of the rails.

but now im a bit stuck on where to go from here, im trying to design it on autocad but its not going to well.

so suggestions are much welcome

Thanks.

O and how do u keep the pictures big? they look realy small on this post?

[Tom]

Hi Kev,

Looks good so far - should be nice and rigid with those large alu sections.
You have an interesting concept with the Z reaching to cut below the frame, do you have any sketches?

Next you need to decide where to put your y axis gantries, and how to mount your leadscrews and steppers.

When does your college project finish - a deadline is healthy! I wish CNCs were around when I was at college! :) (actually they were, but you fed code to them on punched card, not usb keys!)

Keep it up and keep us posted!

[irving2008]

Welcome Kev...

Rather than insert your pictures inline using the IMG tags, attach them using the 'manage attachments' button below the edit box... this will put thumbnails in the post and will auto-enlarge them on mouseover.

[kev]

Looks good so far - should be nice and rigid with those large alu sections.
You have an interesting concept with the Z reaching to cut below the frame, do you have any sketches?


yea its pretty solid, bit of a pain using the connectors tho.

with the z axis i got the idea from here (http://www.cnc-router-routers.com/S-720_Fraesmaschine_CNC_STEP_1.jpg)

basically its going to be used for sign making but if i want to put something tall inside it then i can raise the machine up on a stand im going to make, thats why im planning on having no obstructions in the cutting area.

i will post up some autocad drawings that i have made so far tomorrow.

with the y axis im thinking of using some more rail, perhaps mounted on the top and bottom of another piece of alu box section. or perhaps top and side.

My deadline is around june time.

[kev]

http://www.mycncuk.com/forums/photoplog/index.php?n=119Hi,
right just made some stuff up on autocad,
im not sure how heavy the z axis will be tho as it uses a lot of 10mm plate.
Any thoughts?
thanks

[irving2008]

http://www.mycncuk.com/forums/photoplog/index.php?n=119Hi,
right just made some stuff up on autocad,
im not sure how heavy the z axis will be tho as it uses a lot of 10mm plate.
Any thoughts?
thanks

thats easy... work out the total surface area of the 10mm plate used in square millimetres (just work it for each piece then add them all together), multiply the result by the plate thickness (10) and multiply by 0.00275 will give the weight in kg. (weight of aluminium is 2750kg per cubic metre)

[Ross77]

Hi Kev.

just 1 observation. Are you only using one rail on the y axis? if so then the 250mm travel + the distance to the rail + the length of the cutting tool will put quite a bit of force on it!

Good luck with the build.

[kev]

Hi Kev.

just 1 observation. Are you only using one rail on the y axis? if so then the 250mm travel + the distance to the rail + the length of the cutting tool will put quite a bit of force on it!

Good luck with the build.

hi, no i was thinking of using one rail on the top and one one of the bottom, tho im going to redesign the z axis so that the motor is not so high up, possibly mount it on the other side of the alu profile, offset the weight a bit. im also thinking of keeping the linear bearings fixed and letting the rails move up and down on the z axis instead, this should keep 250mm of 12mm aluminium sheet fairly rigid.

Its hard designing things :thumbdown:, might just order lots of bits and make it up as i go haha

[Ross77]

Sorry didnt notice the label tag was dog legged through the lower one. :redface:

Good idea to fix the blocks and let the rails move up and down on the z axis. Are they 4 way equal loading? Thats how I'm going to do it on mine. I would allow for a least a 1/3 of the rail to be held in the blocks. So for a 250mm travel you would need 375mm rails.

If its just for sign making then do you need so much travel? Why dont you just use the stand idea but have different size collars to rise it up in increments. Some people have also used multiple mounting heights on the z axis plate to allow for the cutting tool, might be worth looking at.



Its hard designing things :thumbdown:, might just order lots of bits and make it up as i go haha

Yes but isnt that the fun part. :smile:

[kev]

Sorry didnt notice the label tag was dog legged through the lower one. :redface:

Good idea to fix the blocks and let the rails move up and down on the z axis. Are they 4 way equal loading? Thats how I'm going to do it on mine. I would allow for a least a 1/3 of the rail to be held in the blocks. So for a 250mm travel you would need 375mm rails.

If its just for sign making then do you need so much travel? Why dont you just use the stand idea but have different size collars to rise it up in increments. Some people have also used multiple mounting heights on the z axis plate to allow for the cutting tool, might be worth looking at.


Yes but isnt that the fun part. :smile:

Yes i think the bearings are 4 way equal loading, they are adjustable as well, theres a close up picture of one in my gallery.

It is supposed to be for sign making and would actually only require about 10mm of z travel but i want to cut big things inside of it lol, i might not go for 250mm of z travel i think i will test it first, see how much flex there is.

I have ordered some 45x45mm box section and some more rails so i think i might try the make it up approach until i come up with some good ideas.

[Ross77]

I know what you mean about just making it up, its so much easier when its there in front of you, than sitting at a computer with CAD. Have you seen the design guide for the blocks? looks like you will have to be careful with the spacing as any racking will cause them to bind.

Since they are 4 way loading have you considered putting the x axis rails on their side, that way you just need a flat plate to bolt the carrages to the y axis rail.

Where do you get the ali sections from?

[kev]

Yea i have seen there website, i think you are suppossed to use one block without the side bearings, hopefully it should work ok though.

I have thought about putting the rails on the side but then there will only be one contact patch per block instead of 2, but putting them on the side would give me a bigger y axis. il see how it goes.

the alu profile is from RS

[kev]

quick update,

i have put the rails on the side, and its made everything alot easier,
i have made a design on autocad and started to roughly make it out of steel, as you can see not many holes line up lol.

im currently waiting for some 45x45 alu profile and the plan is to have two vertical sections bolted onto the alu side plates then, two long pieces across forming the y axis. im also planning on mounting the y axis motor on the inside and using a pulley to attach to the screw that will go down the middle of the y axis.

[Ross77]

Looking good. with regard to the rails being on their side with only one contact then in dosnt matter as in reallity you are only supporting the weight of the y and z axis. The plunge of the z axis will counter some this and you will then have max strength (4 contacts) in the sideways movement of the x axis where you need it to counter the cutting forces.

Not sure it I would have moved the y axis rails as well tho. For that long travel on the z you need them as far appart as poss to reduce the moment, the other side effect is that the y rail has moved the spindle futher way! You might want to shift the y axis rail back a bit further to compensate, dosnt mater if the motor overhangs a bit. mind it would be easy the remake the side plates later if it dose cause any problems. (Chatter, binding etc.)

Did you find RS the cheapest for the aluminium sections?

[kev]

Not sure it I would have moved the y axis rails as well tho. For that long travel on the z you need them as far appart as poss to reduce the moment, the other side effect is that the y rail has moved the spindle futher way! You might want to shift the y axis rail back a bit further to compensate, dosnt mater if the motor overhangs a bit. mind it would be easy the remake the side plates later if it dose cause any problems. (Chatter, binding etc.)

Did you find RS the cheapest for the aluminium sections?


i put the y axis rails on the front as it keeps them a meter long and is alot easier to mount a plate straight on, instead of building a box around.

plus i may be using some low height rails instead, about 9mm instead of 30mm.

but ye i might have to move the y axis further over the rear bearing.

as regards to RS being cheapest? probably not but my work always gets stuff from there so its easy, i think it was about 20 quid per section,
the rails and bearings are cheaper than igus tho,

[kev]

Hi,

i got the 45x45 alu profile today, so i made the y axis, its rock solid with no flex, but i think the igus bearings may have to go as it barely moves on the x axis, so i may have to get some proper ball bearing carriages for the x axis and use the igus bearings on the y axis.

does anyone know where to get cheap rails and carriages?

[Tom]

Hi Kev, it' looking good - loads of progress...

I cant help you with the rails & carriages (I made my own), but I like your whiteboard sketches! I do alot of thinking out loud on a whiteboard in my workshop... Can't beat it...!

[Ross77]

Thats a shame, I didnt think you would have a problem this soon.:eek:
Is it binding because of the long distance of the y compared to the truck spacing or is it just the weight causing excesive friction? If its the former then it should disapear if you drive it with a screw on each side. (eliminate the racking) might be worth pursuing before for you make major changes.

For the rails I beleive Gary at Zapp sells the 15mm rails and 4 way loading trucks for the same as the Igus stuff you bought. £50-60 for 1m rail and £35 ish a truck. These also have way more capacity as well.

[kev]

Hi Kev, it' looking good - loads of progress...

I cant help you with the rails & carriages (I made my own), but I like your whiteboard sketches! I do alot of thinking out loud on a whiteboard in my workshop... Can't beat it...!


Ha ha yea its sometimes easier to just sketch ideas down.

[kev]

Thats a shame, I didnt think you would have a problem this soon.:eek:
Is it binding because of the long distance of the y compared to the truck spacing or is it just the weight causing excesive friction? If its the former then it should disapear if you drive it with a screw on each side. (eliminate the racking) might be worth pursuing before for you make major changes.

For the rails I beleive Gary at Zapp sells the 15mm rails and 4 way loading trucks for the same as the Igus stuff you bought. £50-60 for 1m rail and £35 ish a truck. These also have way more capacity as well.

I have been playing with it today, i had one screw in each bearing block tightened up, one side of the frame loosened off so it would move but it is still binding and hard to move, i even tried adjusting the bearings but no joy.

I took the y axis frame off leaving the 2 plates on, and if u put any slight sidways pressure on the plate it locks the bearings up.

It could be due to the y axis being so big compared to the bearing spacing.

Hopefully work should be ordering the 20mm rails and carriages from zapp, they should be alot better due to having bearings, and they only work out to be about 40 quid more than the igus set.

Im going to try the igus rails on the y axis where everything should be more square and closer together.

[Ross77]

I have been playing with it today, i had one screw in each bearing block tightened up, one side of the frame loosened off so it would move but it is still binding and hard to move, i even tried adjusting the bearings but no joy.

Sorry I meant the ballscrew/leadscrew



I took the y axis frame off leaving the 2 plates on, and if u put any slight sidways pressure on the plate it locks the bearings up.


With a leadscrew on each side and linked with a belt, (which you will need anyway with the ball bearing rails) then both sides would be moved evenly and should'nt bind.

but then again if you can get the bearing type then that will solve everything. I've got 20mm THK's and they are solid..

If you are still going to use the igus on the y axis then try to follow the design guide on the width to truck spacing ratio, also make sure the leadscrew is perfectly in the middle otherwise you will have the same problem with binding....especially with the 250mm z axis.

I would try again with the igus on the x axis with twin lead screws and use the bearing type on the y axis. just my 2 penneth :smile:

out of interest what are you using for the spindle?

[kev]

Sorry I meant the ballscrew/leadscrew

With a leadscrew on each side and linked with a belt, (which you will need anyway with the ball bearing rails) then both sides would be moved evenly and should'nt bind.

but then again if you can get the bearing type then that will solve everything. I've got 20mm THK's and they are solid..

If you are still going to use the igus on the y axis then try to follow the design guide on the width to truck spacing ratio, also make sure the leadscrew is perfectly in the middle otherwise you will have the same problem with binding....especially with the 250mm z axis.

I would try again with the igus on the x axis with twin lead screws and use the bearing type on the y axis. just my 2 penneth :smile:

out of interest what are you using for the spindle?

I have not got any leadscrews yet, im just trying to get the frame made up and running smooth, at the moment the X axis is very stiff and would give the stepper motors a good workout.

i think i am going to run a motor each side on the X axis.

I have sort of fallen out with the igus bearings haha, the difference between them being sort of moving and locking up was half a screw turn on one of the carriages.

for the spindle i was looking at using a kress, are these any good for cutting aluminum?

[irving2008]

for the spindle i was looking at using a kress, are these any good for cutting aluminum?

Up to a point... as long as you keep the depth of cut small and get a reasonable feed rate and stick with 1 or 2 flute cutters...

[kev]

Up to a point... as long as you keep the depth of cut small and get a reasonable feed rate and stick with 1 or 2 flute cutters...

Ok what would be a better choice?

[Ross77]

Now theres a question, theres a lot of "what ifs" and whats it "gunna do" The two main considerations are power and shaft run out. Which leads to bigger size and cost......

I would have thought you'd be ok with a good quality router above 1200W



I have sort of fallen out with the igus bearings haha, the difference between them being sort of moving and locking up was half a screw turn on one of the carriages.


I had the same problem setting the ways on my lathe and x-y table, after a bit of practice it got easier. The biggest killer was the fiction caused to remove the backlash in the leadscrew. So from now on I will only use bearing rails and ballscrews. :smile:

Hows the rest of the machine going?

[kev]

Tbh iv not done anything lately, im just waiting for the rails and bearing carriages,
then im gonna try and get the X axis moving freely, probably redesign the side plates by moving the y axis frame further back over the rear bearings, then i can concentrate on the y axis and z axis, or maybe get some screws on the x axis first.
im just hoping the igus bearings will work ok on the y axis, but probably not haha.