The gantry is now almost complete...It is built from 45x90mm heavy weight aluminium extrusion with end plates cut from 20mm cast aluminium tooling plate
The gantry end plates and bearing mounts are made out of 20mm ground aluminium tooling plate. The smallest size available is 100 x 100mm so some parts had to be cut down further on the band saw. Where possible I have ordered the parts at the correct size (although they come -0/+2mm and almost always +2mm in my experience – I have tried to design the machine to allow for this). I machined the gantry end plates using a ½” router fitted with a 10mm solid carbide endmill. I built an MDF template to run the router along which was bolted to the endplate and clamped to my bench. Taking 0.5mm passes was a bit slow! But I am surprised and how well they turned out. A lot of effort when the shape is purely for aesthetics, but I want the machine to look elegant and considered as well as perform – this is a principle which was once important in machine building. If I want to use it to make beautiful things and I’m building it, it ought to be “beautiful” itself right?
The basic design of the machine has not changed massively in terms of its size and basic principles since the early drawings at the bottom of the page. However, the design has developed and improved as I gain more information on the various parts and better understand various constraints and parameters. A key element that has cause the redesign of several elements is the requirement for adjustment. This adjustment need only be very slight for the most part, but given the overall tolerances are very tight allowing for adjustment in the design is very important. This is particularly the case given I am building this with relatively basic tools (pillar drill, band saw, router etc.). Another important change to the design has been the replacement of cheap Chinese SBR bearings and supported circular section shaft to Hiwin linear bearings. This will improve the stiffness and accuracy of the machine but introduces the requirement for much higher levels of precision in the building of the machine as these bearings are built to extremely tight tolerances and will bind if not set perfectly straight, level and parallel with one another. In order to avoid mistakes, which are costly and frustratingly time consuming I have modeled the machine down to every bolt. Each part has then be transferred to a 2D cad drawing before making.
The images below show the building the frame from 80x80x3 SHS steel. The steel was marked up and sawn down with a large cutoff saw to within >1mm tolerance. Each piece was given a reference code to match the drawings. There are more bits than you might think and it can get confusing! The frame is MMA welded into several large sections which were then bolted together using 6mm thick plated connections. The bed is height adjustable and is built from 50x50x3 SHS steel. It is mounted to the legs of the frame with 6mm rolled steel angles and M8 bolts. So as to give the wall of the box section legs of the frame some thickness steel plates were mounted inside with holes tapped to receive the bolts. To allow overall leveling of the frame I have mounted it on height adjustable feet which are taped into 12mm steel plates welded to the bottom of the four corner legs.