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Help needed to design open source laser x-axis.
Looking to make a gantry similer to a Trotec speedy 300 laser engraver. This is very similer to a belt driven linear actuator/stage from compaines like bosch and Thomson. It a nice project as its isolating the rest of the laser design and just concetrating on producing a high speed linear stage. Speeds will hopefully be in the 200 Meters per Minute range :courage:
Any help and advice would be appreciated.
Gav
I guess a starting point would be to find out some specs on the individual components of the current "best laser cutters on the market"
Trotec, Epilog, Laser Pro, ULS.
We could find out the specs by looking at service manuals and sites that sell replacement parts, websites and brochures are unlikely to quote specific details of the belts, linear bearings and motors
Manufacturer--------------Belt-------------Gear Reduction (Yes/No & Ratio)------------Motor--------------Linear Bearing---------------Max speed-------------Max Accereration
Epilog
Trotec
ULS
Laser Pro
Personally i think if you want speed and accuracy then a servo and belt configuration is the only way to go. ive been planning to make a laser cutter for some time now. i have got all the optics and control system including a 120w Reki laser tube but not had time to get around to making it.. i will this summer :-)
But i would say Servos and belt for motion along with a small Hi-Win block and rail. like an HGH15 or HGW15 block and some HGR15 Rail. would not cost a lot for the quality kit it is.
You might want to take a look at openservo.com it is an opensource project that upgrades the electronics in bog standard servos to get much better performance.
It is interesting that £20-£30 worth of electronics will get you a 12bit resolution mag non contact mag sensor, a cortex brain and a high power mosfet...
Hardware_Feature_Requests - OpenServo Wiki
I also think block and rail, belt and servo is the way to go, with the possibility of moving to a stepper to reduce costs.
On my current setup I am using a hiwin HGR15 Rail. I have learned from this setup that a smaller rail with a much lower overall height would be better than the HG15. The lower the height of the rail the smaller the pulley you need to make a loop of belt around the rail, connecting the belt ends at the front ethier side of the carriage.
Hiwin MG Linear Guideway is available in sizes (Rail Width) 5, 7, 9, 12, 15 (mm) and the height of the rails start at 3.6mm and go up to 10mm. In comparison the RG rail 15mm pitch has a height of 16.5mm so even at the 15mm pitch size the MG rail is significatly lower in profile.
I also found that only the lowest preload option gave a free moving carriage.
Another main issue I had was securing the pulley to the shaft of the motor. I have tried grub screws but the high acceleration rates and sudden change of direction when rastering work them loose in no time at all. A few possible solutions would be using an anerobic glue like locite bearing fit or a roll pin through the pulley and shaft. I like the look of these keyless bushing for small pulleys from CMT though, but they look expensive.
http://www.youtube.com/watch?v=ocuMN-aOKZA
That clamping system looks brilliant. G.
You could try Fenner Drives trantorque keyless bushes or Lenze ETP Mini locking bushes. I have used both types and both are very good.
Thanks Web Goblin both look like good options, what was the smallest diameter of shaft you have used these on?
Searching for mini linear rails I can across this video. check out the 3mm rail in the bottom right corner.
https://www.youtube.com/watch?v=S4xDCvr7Ca0
I think the smallest I used was on a 10mm shaft. What I really liked about them apart from ease of fitting is that they are easily adjustable along the shaft to line up a pair of pulleys.
I have to be honest it all seems a rather expensive solution to move something that is relatively light?w why not go for something like the IGUS linear type rails and slides? very rigid and light and designed for this type of application?
Have a look at this
igus® CNC-controlled laser cutting machine
Igus is also a good choice, I have seen a few different laser cutters so far using Igus successfully. Comparing price and spec in terms of max speed and accerelation would be a route forward.
The way i see it if i had laser beams bouncing of mirrors that are moving, i would want not only rigidity but as smooth running as possible. Linear bearings may be great but there is still a lot of movement especially in small component form. In my opinion plastic or bronze bushe bearings would be my choice. I have used home made acetol bearings for my 3d printer build and work very well. Igus bearings would be better than because it allows for thermal expansion. With no real cutting forces going on you can get away with quite a lot...Drill some wood and give it a go, you will see what i mean.