Originally Posted by
Beefy
Hi Everyone,
I've built my 2.4 x 1.5m plasma table using dual chain drive on the X-axis. Did my very first test cut and then had a haunting thought about the accuracy implications of dual chain (or belt) drives which are driven from a single cross shaft as mine are.
I squared the gantry to the table at one end then realised that due to the high likelyhood of the chains not being equal lengths over a 2.4m distance, the gantry could be ran to the opposite end and would be out of square. And there's nothing that can be done about this. Even if the total length of chain was exactly the same length from new (for a given number of links of course) it would be unlikely that wear and stretch in the chain would occur equally and so you could only square the gantry to the table at one end but when at the opposite end would be out of square by the length difference of the chain.
So if anyone is considering a single shaft drive with only one drive motor and accuracy is a concern then maybe it would be better to spend the extra cash and drive each chain individually so the steps per mm / inch could be calibrated for each side.
After the above thoughts I think rack and pinion is the very best way for a plasma table. No stretch, more dirt resistant if they are mounted with the spur gear underneath, no tensioning issues.
Just a thought for anyone who's thinking of doing the same design as me. It's my first table and like a lot of other people I've been doing the money saving thing and have done a lot of living and learning as a result.
Anybody had any such issues with accuracy ?
All the best for the New Year.
Keith. :cheers: