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11-09-2017 #21
These depend on the mass of the moving item and your acceleration/deceleration curves.
Don't forget - acceleration/deceleration is king of the hill, its more important than travelling velocity, far more, as it will directly affect the path following ability of the software controller - with these figures too low you will see bad corner rounding etc where the trajectory planner cannot perform the moves in time, the only solution then, if you cant increase accel/decel is to lower the speed, this then gives you issues with cutter burning etc - its a vicious circle but all determined by your acceleration/deceleration curves.
My plasma machine only has a very light gantry - no motor, no cut forces, and it can shake quite badly at times, that has a steel frame too.
Always build as stiff as possible :)
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11-09-2017 #22
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07-10-2017 #23
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07-10-2017 #25
Hi Clive S.
Hahah no, no movement yet.
Progress is slow.
Work related issues use up near all of my time. Well it pays for the bills.
I am still working on the gantry.
I need to get some bracing in, in the gantry uprights. Also i need to finish beefing up the mounting surfaces, some welds need finishing.
When all that is done the big pour is next.
After that a lot of big decisions are to be made.
I am near ready to order the linear parts.
I need advice on ballascrew end machining for pulley's.
Also .. will quality angle bearing bf bk type blocks fixed / float setup do?
Does one gain lots of rigidity by going fixed fixed? is it much more complicated to setup ?
I am now designing based on fixed/float setup.
So maximum speeds vs screw rpm vs pitch vs screw length and diameter are based on fixed float.
Grtz. Bert
Verstuurd vanaf mijn SM-A320FL met Tapatalk
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08-10-2017 #26
Looking good but I would have added another member to the top of the black frame work to support the underside of the white cross members. Not too late to bolt something in and shim or epoxy any gaps.
Fixed float is fine for the screws but I'm thinking of fixed fixed on my long axis (as per Boyans machine) to reduce a slight buzz / vibration when the machine is towards one end. In theory you might worry about heat and expansion but for the amount I use my machine and the speeds etc I think it is a low risk. Not sure yet but might make it with a spring preload . . . Or keep it simple and lock it in place.
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08-10-2017 #27
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11-10-2017 #28
At the moment my 3m long ball screws in Fixed/Fixed config are without a glitch. Though as i said somewhere, when i start machining very fast like more than 12m/min then the rotating nuts start to heat and heat the screws. I think the fact that the gantry is ~200kg and moves with such high acceleration plus the speed , helps that. Which is cured by additional greasing prior to that. Otherwise no problems till now.
I think one of the biggest problems when DIYcnc is not locking the bolts with a thread locker. Now i lock any bolt on a machine. Not only the obvious that need that. That is also valid for the shafts and the pulleys. A must do , i would say.
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The Following User Says Thank You to Boyan Silyavski For This Useful Post:
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13-10-2017 #29
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17-10-2017 #30
Hi guys,
I am about ready for the big pour.
Planning to do it this week or next.
I plan to put the frame under a tarp with a thermostat controlled heater during curing.
And set it to 25 C.
Now i need some looking over my shoulder before ordering linearcomponents.
I have a quote from Fred.
The shopping list:
Rail.
2pcs HIWIN HGR20-L1830mm Linear rail
2pcs HIWIN HGR20-L1000mm Linear rail
2pcs HIWIN HGR20-L500mm Linear rail
12pcs HIWIN HGH20CA Linear carriage
Ballscrews rolled C7.
End machining fixed float for a pulley
Z-axis
1set C7 RM1610-L350mm Ball screw with ballnut
Change Length F to 30mm*
Y-axis
1set C7 RM1610-L1150mm Ball screw with ballnut
Change Length F to 30mm*
X-axis
2 sets C7 RM2010-L1700mm Ball screw with ballnut
Change Length F to 30mm*
2pcs 1610 Ballnut Housing
2pcs 2010 Ballnut Housing
2 sets bk bf12 1610
2sets bk bf15 2010
Upgrade all of the 4set BK/BF* to Superior bearing type.
Any thoughts?
Grtz Bert
Verstuurd vanaf mijn SM-A320FL met Tapatalk
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