DIY Laser/XY Gantry
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Background
RussleH and 'RepRap' Matt (talk) took a look at the work is of the IMP Pick and Place at Ciseco
Locking a magnetic tape linear encoders, simlar to used on the PnP
This can give very high accuracy position feed back and at high speed
http://www.machine-dro.co.uk/digital-readout-systems/magnetic-tape-linear-encoders.html?p=1
Specifications
Size:
- Minimum working area 600mm x 900mm
Speed:
- 1000m/s for scan (X axis)
- 500mm/s for Y axis
Precision:
- 0.01mm
Type of Gantry
Possible driver systems
- Fixed motor and looped belt to carriage
- Carriage mounted motor and fixed belt
- fixed motor driving a leadscrew
- fixed motor driving a ballscrew
Most lower cost laser cutters use belt drives.
Most larger machines use ball screws. Here are notes on the two ideas:
Belt Drive
Advantages
- Low cost
- Standard
- Motors can be smaller (less inertia)
- Most low cost and DIY lasers use this method
Disadvantages
- Precision will get worse (belt wear)
- Not repeatable precision (belts will stretch if moving fast)
Belt Drive costs
- XY gantry for DIY laser is available here for $950 (=£590). The cutting size/ working area is 900mm x 600mm. This comes with 2 x 5A motors.
Ball Screws
More information on ball screws can be found here:
Advantages
- High precision
- Repeatable precision for its whole lifetime
- Used in commercial designs
- Unusual and interesting - not been done for table top lasers before.
Disadvantages
- Need to build this with high precision
- No DIY design available
- Higher cost
- Larger motors required (more inertia)
Ball Screw costs
These prices have come from Zapp Automation (http://www.zappautomation.co.uk/en/). This is not necessarily the lowest cost.
Parts required include:
Ball screw 25mm diameter, 25mm Pitch:
- 2 x 600mm @£6/100mm = £72
- 1 x 900mm @£6/100mm = £54
End mounts:
- 3 x floating 25mm diameter @£30 = £90
- 3 x fixed 25mm diameter @£60 = £180
Ball Nuts:
- 3 x R25-25A2-FSED @£75 = £225
- 3 x Motor couplers @£10 = £30
Ground bar
- 1 x 1m length @£1.20/100mm = £12
- 1 x linear bearings = £4
Total cost = £667
Notes: Supplier of ball screws and parts:
Type of Motor
Motors for each of the above could be one of the following
- DC motor
- stepper motor
- brushless servo motor