Tired of missing opportunities for jobs due to not having a small, fast VMC available to take in the small parts and crank them out quickly. The machines in the shop are old, slow, but I was able to pay for them so they get work done. Time to expand.
I can't outlay the 30-50K to purchase a good machine to do this with right now, and banks aren't loaning money at favorable terms in my area. I missed a few good ones this past summer, but I have layed in a good supply of parts and equipment over the last 10 years so why not build one now?
I started modeling around the components on hand, digging through the scrap pile, and watching machinery sales and scrapyards for the missing components.
A few weeks ago, I figured I finally had enough modeled to get started, and commenced work with the spindle mount and Z-axis column.
Both are weldments of A36 plate, mostly waterjet scraps and sprues pulled from the scrap bins. I plan to build the whole machine this way, but some material was plasma cut...which was a mistake.
All weldments are heat treated or will be heat treated at 630C for 1hr/25mm thickness, and allowed to cool in still air. It's not hot enough to anneal anything, but it is hot enough to remove the stresses and by removing it from the furnace after the heat and allowing it to cool, it does regain some of it's strength, similar to normalizing but not as much.
Here's the spindle mounting block, which was welded up out of saw-cut bits of waterjet scrap:
The spindle cartridge:
Getting started on the block. The mounting ring was turned and bored from a waterjet cut circle of 1.125" plate, and then a pair of plates were sawn and tack-welded together. The two plates were bored and faced, and a shallow counterbore cut to receive the prepped mounting ring.
The weld prep is just over half the width of the face, making sure that the mounting bolts for the spindle cartridge are going to be through the weld prep.
After the mounting ring was fully welded in place, the plates were set back up in the lathe, dialed in on the mounting ring face and bore, and the rough-bore was completed and a pair of counterbores were cut to receive a spindle tube.
After the main bore components were aligned and the mounting plate for the block to the Z-axis was partially welded in place, all internal welding was completed and the block was set up in the bridgeport to cut in a deep U-groove weld prep. Plenty of room to get a very deep penetrating weld.
Finished up the weld here, just showing off a bit.
After that, side plates were welded in to complete the box, but the front was left open for access to the mounting bolts, and the drawbar operator release button.
Fully welded and loaded into the heat-treat oven:
After heat treating, the scale and carbon was cleaned off and the part was set up in the mill. The stress-relieved weldment machined very nicely, and the machined faces have not moved at all during or in the weeks after machining.
Once the millwork was finished up, I set up the weldment on the boring table on the lathe and took some measurements. I need to make a new line-boring bar, to finish-machine this bore to 90mm+some clearance to match the spindle cartridge. I haven't decided if I want a snug slip fit, or a looser clearance. The tramming is handled in the backing plate, but spindle cooling is a concern. I am considering wrapping cooling lines around the spindle, as it's easy to do that now but not easy later.
I can't outlay the 30-50K to purchase a good machine to do this with right now, and banks aren't loaning money at favorable terms in my area. I missed a few good ones this past summer, but I have layed in a good supply of parts and equipment over the last 10 years so why not build one now?
I started modeling around the components on hand, digging through the scrap pile, and watching machinery sales and scrapyards for the missing components.
A few weeks ago, I figured I finally had enough modeled to get started, and commenced work with the spindle mount and Z-axis column.
Both are weldments of A36 plate, mostly waterjet scraps and sprues pulled from the scrap bins. I plan to build the whole machine this way, but some material was plasma cut...which was a mistake.
All weldments are heat treated or will be heat treated at 630C for 1hr/25mm thickness, and allowed to cool in still air. It's not hot enough to anneal anything, but it is hot enough to remove the stresses and by removing it from the furnace after the heat and allowing it to cool, it does regain some of it's strength, similar to normalizing but not as much.
Here's the spindle mounting block, which was welded up out of saw-cut bits of waterjet scrap:
The spindle cartridge:
Getting started on the block. The mounting ring was turned and bored from a waterjet cut circle of 1.125" plate, and then a pair of plates were sawn and tack-welded together. The two plates were bored and faced, and a shallow counterbore cut to receive the prepped mounting ring.
The weld prep is just over half the width of the face, making sure that the mounting bolts for the spindle cartridge are going to be through the weld prep.
After the mounting ring was fully welded in place, the plates were set back up in the lathe, dialed in on the mounting ring face and bore, and the rough-bore was completed and a pair of counterbores were cut to receive a spindle tube.
After the main bore components were aligned and the mounting plate for the block to the Z-axis was partially welded in place, all internal welding was completed and the block was set up in the bridgeport to cut in a deep U-groove weld prep. Plenty of room to get a very deep penetrating weld.
Finished up the weld here, just showing off a bit.
After that, side plates were welded in to complete the box, but the front was left open for access to the mounting bolts, and the drawbar operator release button.
Fully welded and loaded into the heat-treat oven:
After heat treating, the scale and carbon was cleaned off and the part was set up in the mill. The stress-relieved weldment machined very nicely, and the machined faces have not moved at all during or in the weeks after machining.
Once the millwork was finished up, I set up the weldment on the boring table on the lathe and took some measurements. I need to make a new line-boring bar, to finish-machine this bore to 90mm+some clearance to match the spindle cartridge. I haven't decided if I want a snug slip fit, or a looser clearance. The tramming is handled in the backing plate, but spindle cooling is a concern. I am considering wrapping cooling lines around the spindle, as it's easy to do that now but not easy later.
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