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16th August 2012, 12:44 PM #31
Sample X Axis End Plate
Last night, I made a sample end plate for the X-Axis.
I drew it up in DraftSight, then loaded the dxf file into Sheetcam and created the G-Code.
The end-plate is cut out of 12mm Corian. I used Corian, as it is easy to cut, yet stable enough to be used to check the alignment etc. I'm even considering that I may be able to use the Corian endplates on the mill to allow me to cut the final plates out off 12mm aluminium, rather than cutting them on my Taig mill.
The holes for the 6mm cap screws that fasten the end-plate to the table were drilled to 6mm, so it is a tight fit. I did this to see how accurately the holes in the table were drilled. The bolts fitted up very well, so they may have been machine/jig aligned and drilled. This is in contrast to the locating pins which were obviously hand drilled as the holes are not even perpendicular.
Later on it may be necessary to increase the clearance on these holes so that some slight adjustment is available. That is also the reason that the countersink diameter on these holes is quite large.
If you notice the fit, the top of the side plate is slightly below the table sides. I'm not sure what this means in terms of fit. When I measured up the original plate. The lead screw centre appeared to be 50mm from the top of the plate, and the mounting holes appeared to be 25mm below the top of the plate. The mounting holes were 160mm apart. These were the dimensions I used as I figured that the mill was built of a blueprint somewhere and it was logical to use these dimensions.
The FK12 bearing block is held in with four M4 bolts.
I also put in four holes tapped for M6 bolts. These will be used to mount the plate that will hold the stepper or servo motors. The plate will have elongated holes that will allow me to tension the timing belts. There are holes either side of the centre as I haven't decided yet which side of the table I'll be mounting the motors.
The next step is to make the plate for the FF12 bearing block. It requires a slightly smaller hole.Homann Designs - http://www.homanndesigns.com
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16th August 2012, 12:49 PM #32
One thing I'm thinking of changing is to change the mounting of the FK12 bearing block from the other side. That way the inside of the flange will line up with the end of the table and the ballscrew length needed will not be dependant on the thickness of the end-plate.
That way, it would not matter if the endplate material was 12mm or 1/2" plate.Homann Designs - http://www.homanndesigns.com
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17th August 2012, 11:18 AM #33
I tried putting the bearing block on the inside but there is not enough clearance to the underside of the table. It's probably less than 1mm but I think I'll just leave them on the out side.
I also made up the other end-plate for the floating bearing block.
It's almost time to order some ballscrews .
I'm not sure on what diameter to have on the end for the timing pulleys. I am tossing up between 10mm, 3/8" or 8mm.
At this stage I'm thinking of getting 3/8" as there seems to be a better range of XL pulleys and also the stepper shafts are 3/8"
Cheers,
Peter.Homann Designs - http://www.homanndesigns.com
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17th August 2012, 11:45 AM #34GOLD MEMBER
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Hi Peter,
Think about protection for the bearings and motor as you will proably use coolant if only CRC or WD40.
A cover would also prevent pinching if fingers got in the belt/pulley area.
If you start thinking about it now you could incorporate mounting it on your end plates.Cheers,
Rod
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17th August 2012, 03:01 PM #35
Hi Rod,
Thanks for the input. I have some end covers for the motors and the pulley end will be covered by the housing that holds the belts, etc.
I haven't decided yet as to which way the motors will be mounted. I want to fold them back so as to reduce the extension and overhang, but without taking away from the travel.
Cheers,
Peter.Homann Designs - http://www.homanndesigns.com
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29th August 2012, 12:02 PM #36
Progress is slow due to all of life's other pressures and demands.
I've been working on ways to mount the Y-axis belt drive set-up and motor. Attached is an image of my planned layout.
I was a bit worried about the belt (XL) length as I'm concerned that it may too long. The length is needed so I can tuck the motor out of the way, rather than it sticking out the front. From a reply on the CncZone I think I'll be ok
The idler bearing is set quite low so that I can use a smaller pulley on the motor and get a 2:1 ratio.
Cheers,
PeterHomann Designs - http://www.homanndesigns.com
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29th August 2012, 12:05 PM #37
Ballscrew Drawings
Attached are images for the ballscrew dimensions. I plan to send these to Chai from linearmotionbearings2008.
Before I send them off, can anyone see any errors or deficiencies with the drawings?
Cheers,
PeterHomann Designs - http://www.homanndesigns.com
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29th August 2012, 12:43 PM #38GOLD MEMBER
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Drawings look fine. It took a little while to realise you want a flat milled on the end of the shaft (pulley end) so might be an idea to describe that on the drawings.
Cheers,
Rod
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29th August 2012, 01:42 PM #39
Hi Rod,
Thanks for the comment. I'll add a note about the flat.
Do you think it's OK to have two negative tolerances on the 12mm shaft for the bearing? Or would it be better to specify the diameter to 11.992 with a single -.009 tolerance?
same for the 3/8" and 10mm shaft ends
Cheers,
PeterHomann Designs - http://www.homanndesigns.com
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29th August 2012, 02:45 PM #40GOLD MEMBER
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Hi Peter,
OK as is. To be honest I doubt you will get them returned at the tolerance of your drawing. Even a standard screw with BK/BF blocks requires a bit of tweaking on the lathe for a good fit.Cheers,
Rod
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29th August 2012, 04:19 PM #41
Hi Rod,
Yeah I reckon your right. I put the comments "end machined for FK12 bearing support" so that they may machine them to fit.
It will be interesting to see what turns up.
Cheers,
Peter.Homann Designs - http://www.homanndesigns.com
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30th August 2012, 04:43 PM #42
Hey Peter,
Just with the idler you had in the first picture, i would also look to keep this deflection in the belt to a minimum as it will take power away from the drive system. (Stepper)
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30th August 2012, 06:30 PM #43
Hi Mike,
Good point, thanks. The idler is there to clear the saddle as it moves out over the pulleys.
For the idler, I'm planning to use 2 of these bearing stacked on top of each other.
10 Bearing 696-2RS 6x15 Sealed 6x15x5 Miniature Ball Bearings
10 Bearing 6x12x4 Sealed Miniature Ball Bearings
Unless thare are better solutions?
Cheers,
PeterHomann Designs - http://www.homanndesigns.com
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31st August 2012, 12:15 AM #44
Nothing to contribute, but I'm enjoying your build Peter.
Brad.
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31st August 2012, 08:57 AM #45
Thanks Brad. I wish I was enjoying it a bit more.
All of the nut holders are going to be problematic. I has expecting the mill to be similar to the BF20 mills.
I guess I should enjoy the challenge.
Cheers,
Peter.Homann Designs - http://www.homanndesigns.com
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