3 Axis CNC router

[JAZZCNC]

Hi Joe,

Sorry not replyed to some of your previous post's where you asked me directly, I've had eye trouble so time on computer has been limited hence me not being around much.!

Others have answered the belt Q's regards width, pitch etc but there are things you need to be made aware about with this size machine.?
One of the things I found when I built my machine was that long belts where not available in 5 x 15mm HTD so depending on the X axis screw centres you may have the same trouble.?
The X screw centre's on my machine are 1300mm using 30T pulleys so needed belt length over 2750mm the longest HTD 5mm pitch 15mm wide I could find was around 2400-2500mm.
The way I got around it was to have them special made costing around £20 each. I bought 2 keeping one for spare, that was over 3yrs ago and I've only recently swapped for the spare and that was because I left a pulley lose after changing ratios from 1:2 to 1:1 for high resolution job and it fell off killing the belt in the process.!!

Regards mounting pulleys you will need the ballscrew ends machining longer than standard so the shaft goes all the way thru the pulley giving better purchase for the grub screws. Also grind a small flat on the shaft for the grub screw to grip and stop the pulley spinning.
Regards idlers and tension then You don't need lots of tension on the belt and infact if you put them under too much tension they wear quicker and it also puts tension on the ballscrew bearings and if Ott can cause binding and possible missed steps.? Just enough tension to stop the belts flapping around and jumping teeth is all thats needed and lightly tensioned idlers is all thats required. (I just use 2 bearings with large penny repair washers for guides)

I'm posting the pics of my well used setup and While my setup looks ugly and is roughly thrown together it's simple, works very very good and accurate with high reliabilty even thou I run it in some of the worst conditions for running belts.!!
I dont have any guards or shields, the machine mostly 98% of time cuts Aluminium with chips flying every where and it has never failed or lost position either thru skipped teeth or missed steps. While It's capable of max rapids around 11mtr/min with 5mm pitch screw 1:2 ratio(effective 10mm pitch) 6Nm Nema 34 motor running 75Vdc I detune it to 7mtr/min which is more than enough for my needs and also why It's NEVER, NOT WOUNCE missed steps or lost position or sync under cutting conditions or rapid movement.

To give you an idea of the resolution and what 1:2(10mm pitch) belts can achive then I've attached the Aztec calender pic with a link to video see the detail better.

Hope this helps and inspires.!

http://www.youtube.com/watch?v=wjDvi...ature=youtu.be

[JoeHarris]

Hi Joe,

Sorry not replyed to some of your previous post's where you asked me directly, I've had eye trouble so time on computer has been limited hence me not being around much.!

Others have answered the belt Q's regards width, pitch etc but there are things you need to be made aware about with this size machine.?
One of the things I found when I built my machine was that long belts where not available in 5 x 15mm HTD so depending on the X axis screw centres you may have the same trouble.?
The X screw centre's on my machine are 1300mm using 30T pulleys so needed belt length over 2750mm the longest HTD 5mm pitch 15mm wide I could find was around 2400-2500mm.
The way I got around it was to have them special made costing around £20 each. I bought 2 keeping one for spare, that was over 3yrs ago and I've only recently swapped for the spare and that was because I left a pulley lose after changing ratios from 1:2 to 1:1 for high resolution job and it fell off killing the belt in the process.!!

Regards mounting pulleys you will need the ballscrew ends machining longer than standard so the shaft goes all the way thru the pulley giving better purchase for the grub screws. Also grind a small flat on the shaft for the grub screw to grip and stop the pulley spinning.
Regards idlers and tension then You don't need lots of tension on the belt and infact if you put them under too much tension they wear quicker and it also puts tension on the ballscrew bearings and if Ott can cause binding and possible missed steps.? Just enough tension to stop the belts flapping around and jumping teeth is all thats needed and lightly tensioned idlers is all thats required. (I just use 2 bearings with large penny repair washers for guides)

I'm posting the pics of my well used setup and While my setup looks ugly and is roughly thrown together it's simple, works very very good and accurate with high reliabilty even thou I run it in some of the worst conditions for running belts.!!
I dont have any guards or shields, the machine mostly 98% of time cuts Aluminium with chips flying every where and it has never failed or lost position either thru skipped teeth or missed steps. While It's capable of max rapids around 11mtr/min with 5mm pitch screw 1:2 ratio(effective 10mm pitch) 6Nm Nema 34 motor running 75Vdc I detune it to 7mtr/min which is more than enough for my needs and also why It's NEVER, NOT WOUNCE missed steps or lost position or sync under cutting conditions or rapid movement.

To give you an idea of the resolution and what 1:2(10mm pitch) belts can achive then I've attached the Aztec calender pic with a link to video see the detail better.

Hope this helps and inspires.!

http://www.youtube.com/watch?v=wjDvi...ature=youtu.be