I am in the process of building my first CNC router... though I am still in the research phase of a the build process and I was wondering if anyone could point me towards a good thread either within Skibuilders or CNCzone or where-ever.
Here are a couple links that I have found useful so far:
http://www.cnczone.com/forums/diy_cnc_r ... og%5D.html
http://www.skibuilders.com/phpBB2/viewt ... hlight=cnc
What are the pros and cons to a rack and pinion vs a ballscrew setup?
it seems like the threaded rod would sag along the longer travel X axis? Or do you tension the ends of the rod to take the sag out? or maybe the gantry system helps with that?
Do you think i could erect this thing without "outsourcing" any parts to a CNC shop? meaning, could i do this with my garage shop tolerances? seems like the 8020 could help me achieve this. It seems like folks beef up their 8020 with some steel C channels. thoughts on that?
i was considering buying "grunblau's" 40$ plan and use that as a jumping off point to develop my own design, anyone purchased it? (http://www.grunblau.com/MDF3790.htm)
thanks!
Building a CNC router?
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petemorgan(pmoskico)
- Posts: 85
- Joined: Thu Dec 22, 2011 8:41 am
- Location: Tacoma, Washington, USA! USA!
- Contact:
since you put a link to my journal and to the Platform CNC which I took as a reference I have some advise :
- the 45degrees rails are not ideal (especially the longer ones for X), on paper the idea is great, however it's been a PITA to have those rails made (laser cut + bent), I had to have them made twice by 2 different companies... twice the price.
If I was to do it again I would go with Hiwin rails (THK rails) at least for X and Y, which would have ended up costing almost the same... A cheaper alternative would be to use the carriages from cncrouterparts.com and use flat steel as rails.
- the gantry sides on the Platform are great, very rigid yet not that heavy, I would add some adjustment possibilities though for the final "squaring".
- The Platform concept is very neat and sharp looking, I have to admit that's why I've been interested in it at first. Now the CNC is built and functionnal I sometimes feel I could have gone with some proven concept with less pimp factor (read cncrouterparts kits), I would have saved time and money to get a machine at least equal in terms of precision (and probably better)... but everytime I show the machine to some friends I kinda feel OK with the pimp factor :p
Oh and for rack&Pinion VS ACME rod :
- rods suck for longer length (more than 4 ft), if you make them rotate fast they start wobbling. You can put some tension on them but it will not be miraculous... using a rotating nut on longer rods could be a solution, but then you lose one of the benefits (for the X axis) which is not having the steppers (for X) on the gantry..
- rack&pinion : it's not that much more expensive, you can go faster and precision is totally fine if you use appropriate reduction. Downfall is is you have a dual drive for X you'll have the weight of 2 steppers to move with your gantry... Steppers are pretty powerful and I didn't find it to be a real problem though.
- have a look at belt drives, it's pretty interesting too and I have a few ideas to use them with the same benefits and R&P, without having the weight on the gantry... when I looked into it I found all the pulleys and idlers to be quite expensive compared to an "off the shelf" R&P system which already have an optimal gear reduction for my particular steppers.
Again if I was to do it again : X AND Y would have R&P, Z would get a 5-start ACME rod. For now I have R&P on X, 5-start ACME rod on Y and 1-start ACME rod on Z.. it's working OK but it can limit the speed (Y and Z) on "rapid" moves.
- the 45degrees rails are not ideal (especially the longer ones for X), on paper the idea is great, however it's been a PITA to have those rails made (laser cut + bent), I had to have them made twice by 2 different companies... twice the price.
If I was to do it again I would go with Hiwin rails (THK rails) at least for X and Y, which would have ended up costing almost the same... A cheaper alternative would be to use the carriages from cncrouterparts.com and use flat steel as rails.
- the gantry sides on the Platform are great, very rigid yet not that heavy, I would add some adjustment possibilities though for the final "squaring".
- The Platform concept is very neat and sharp looking, I have to admit that's why I've been interested in it at first. Now the CNC is built and functionnal I sometimes feel I could have gone with some proven concept with less pimp factor (read cncrouterparts kits), I would have saved time and money to get a machine at least equal in terms of precision (and probably better)... but everytime I show the machine to some friends I kinda feel OK with the pimp factor :p
Oh and for rack&Pinion VS ACME rod :
- rods suck for longer length (more than 4 ft), if you make them rotate fast they start wobbling. You can put some tension on them but it will not be miraculous... using a rotating nut on longer rods could be a solution, but then you lose one of the benefits (for the X axis) which is not having the steppers (for X) on the gantry..
- rack&pinion : it's not that much more expensive, you can go faster and precision is totally fine if you use appropriate reduction. Downfall is is you have a dual drive for X you'll have the weight of 2 steppers to move with your gantry... Steppers are pretty powerful and I didn't find it to be a real problem though.
- have a look at belt drives, it's pretty interesting too and I have a few ideas to use them with the same benefits and R&P, without having the weight on the gantry... when I looked into it I found all the pulleys and idlers to be quite expensive compared to an "off the shelf" R&P system which already have an optimal gear reduction for my particular steppers.
Again if I was to do it again : X AND Y would have R&P, Z would get a 5-start ACME rod. For now I have R&P on X, 5-start ACME rod on Y and 1-start ACME rod on Z.. it's working OK but it can limit the speed (Y and Z) on "rapid" moves.
A bad day skiing is always better than a good one at work...
I thought this machine was quite interesting ... the website is a little jumbled, but then the guy is obviously busy with his next machine!
http://onel.se/all_files/images.html
http://onel.se/all_files/images.html
Friend of mine's company, but his belt drive systems are lovely.
http://bell-everman.com/products/linear ... linear-sbl
http://bell-everman.com/products/linear ... linear-sbl
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twizzstyle
- Posts: 2204
- Joined: Tue Mar 07, 2006 8:25 pm
- Location: Kenmore, Wa USA
Here is my thread about my CNC router, with lots of pictures (including some showing how I did the single motor with outputs to either side of the gantry, for my x-axis, that you requested)
edit: forgot to put the link
http://www.skibuilders.com/phpBB2/viewtopic.php?t=3761
That's good info about not doing long lengths of ballscrews, since I have been long considering switching my x-axis to ballscrew. I guess I will throw that idea in the bin!
My rack and pinion works fine, but how I did the shaft/gear isn't great, and adjusting for slop isn't trivial. At some point I need to do a bit of re-design there, but for now it works great.
As for garage shop tolerances, it's hard to say. How sloppy are you?
Some of my router is built using CNC laser cut 1/4" steel. Very precise... only to be MIG welded together by a yahoo (myself). I did use a lot of levels and lasers when putting everything together, so it turned out very square, and I like to think that I am generally fairly thorough and careful with all of the work I do. Just remember, the results you get from the completed router will only be as good as the accuracy/precision/rigidity that goes into it. My machine, being all steel, is VERY rigid. If I could slow the router way down, I bet I could machine aluminum on it with decent surface finishes.
One other piece of advice - have a realistic budget. I thought I could do it "on the cheap", and in the end I spent nearly double what I originally planned. Still cheaper than buying a completed machine, but still a ton of money.
Also, if you're an engineer and you can design/build skis, I think spending any amount of money on plans is a waste of money - personal opinion. You can probably design a machine yourself.
edit: forgot to put the link
http://www.skibuilders.com/phpBB2/viewtopic.php?t=3761
That's good info about not doing long lengths of ballscrews, since I have been long considering switching my x-axis to ballscrew. I guess I will throw that idea in the bin!
My rack and pinion works fine, but how I did the shaft/gear isn't great, and adjusting for slop isn't trivial. At some point I need to do a bit of re-design there, but for now it works great.
As for garage shop tolerances, it's hard to say. How sloppy are you?
Some of my router is built using CNC laser cut 1/4" steel. Very precise... only to be MIG welded together by a yahoo (myself). I did use a lot of levels and lasers when putting everything together, so it turned out very square, and I like to think that I am generally fairly thorough and careful with all of the work I do. Just remember, the results you get from the completed router will only be as good as the accuracy/precision/rigidity that goes into it. My machine, being all steel, is VERY rigid. If I could slow the router way down, I bet I could machine aluminum on it with decent surface finishes.
One other piece of advice - have a realistic budget. I thought I could do it "on the cheap", and in the end I spent nearly double what I originally planned. Still cheaper than buying a completed machine, but still a ton of money.
Also, if you're an engineer and you can design/build skis, I think spending any amount of money on plans is a waste of money - personal opinion. You can probably design a machine yourself.
Last edited by twizzstyle on Mon Jul 01, 2013 7:29 pm, edited 1 time in total.
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knightsofnii
- Posts: 1148
- Joined: Tue Jan 08, 2008 6:02 am
- Location: NJ USA
- Contact:
mine's 2 motors for x, with belt drive reductions, 1motor for y with belt reduction (both x/y r&p style), and a ballscrew z axis.
so far its just great, and seems to move fast enough to suit my needs,
still putting finishing touches on it like cable tracks and dust collection etc but I've cut stuff with it, and it works fine.
ps i got a full kit from cncrouterparts.com. I'd highly recommend them if youd rather shell out a pinch more $ and get it done right the first time.
or you can buy partial kits from them, or whatever parts you need
so far its just great, and seems to move fast enough to suit my needs,
still putting finishing touches on it like cable tracks and dust collection etc but I've cut stuff with it, and it works fine
. ps i got a full kit from cncrouterparts.com. I'd highly recommend them if youd rather shell out a pinch more $ and get it done right the first time
. or you can buy partial kits from them, or whatever parts you need
Doug