This week has seen a bit of work and some milestones achieved. I was going to buy a rotating laser level to get the gantry rails all levelled out and had a brain wave that a mate had a laser level already. And he did, so I got away with being able to spend another $500 on the table instead of a leveller. Happy days!! So the laser level worked brilliantly and the gantry side rails are now level. The left hand was slightly higher than the right so I had to raise it up using slim packing strips. I think one of the gaps is 4mm and lower from there. I've got some steel and I'll pack that in and weld the side into place. I wasn't going to weld them in, but it's the easiest way to go at the moment.
I had 2 6mm plates water jet cut for the uprights of the gantry. It may be a bit heavy but the more I think about it the more I think it would be about the same weight as the aluminium I would have used. Also it is about a tenth of the work and headache. I have used 100 x 100 x 3mm RHS as the gantry cross member. I think this is too heavy but it was the only thing that was 100 x 100 that was cheap and easy to work with. No matter, I will be making some weight saving cuts to the bottom of it to be able to get my hand in there to bolt the linear bearings in place.
On that note, I have changed the design. I was going to use 2 x SBR16 rails with 4 bearings but the bearings have taken 3 weeks and still no luck with getting delivery and because of the delay I have over thought it and then made a better design decision. I am going to use 2 x HGR15 rails with 2 bearings on the top rail and one on the bottom. The rails are pretty small but the load shouldn't be all that much compared to the x axis having to hold up the gantry and the z axis head. The parts have been marked as shipped today so I'll have them all next week.
I had a guy at work machine up the spacer blocks for the uprights. He is actually a fitter and turner by trade as opposed to a mechanic hack like myself. They came out pretty spiffy. We used the marking out table and vernier height gauge to mark out the mounting holes and I took them home to drill. What I got wrong was that I drilled the holes in the first 2 blocks at exactly 6mm and the bolts are 6mm. This caused the rear bearing block on the left to be slightly crooked and caused 4 of the ball bearings to be forced out. I saved them all and got all but one back in. I still have it safe, so I will have to pull that bearing block apart and get it complete again. I then changed to a 7mm drill and did the other blocks. Perfect. I have 1 bolt on the other side that just does not want to go home. I think this machinist hack got a bolt hole slightly wrong.
I think the gantry isn't as smooth as I expected. It still moves pretty good and doesn't need too much force to get it moving. I still haven't filled the bearing blocks with grease yet. So hopefully its a combination of lack of lubrication and the blocks being brand new. It is however square and flat. There is a possibility that there is a little bit of twist when only one side is pushed. I'll have to weld it all together and work out if it needs a stiffening plate on the uprights. It will have a stepped and reduction drive on either side though which will also keep it running true.
It's my first time building this and I'm sure that there are things I have done which are not correct and possibly appear stupid. The fact is this - I'm doing it. If there is any arm chair critics out there who have never attempted to give this a go and desire to tell me I'm wrong i'll listen, but whether i'll take notice is another matter. Just one or two people who I know have never even thought about it have given me advice on things which pisses me off.
On the other hand, I would like to take this opportunity to thank all the guys on the Plasmaspider forum who have helped out with constructive feedback, ideas and information. It has been such a good resource for me, and has helped a great deal in making this build happen.
