View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000168 | 3D machine tool | build | public | 2015-10-29 20:44 | 2015-11-05 18:36 |
| Reporter | DigitalMy | ||||
| Priority | none | Severity | major | Reproducibility | always |
| Status | confirmed | Resolution | open | ||
| Summary | 0000168: Heated bed power usage and temperature | ||||
| Description | Based on RepRap hardware MK3 and MK2B boards are tested to heat up to 81°C max, instead of ABS target 110°C, power supply is 30A 12V used | ||||
| Tags | No tags attached. | ||||
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Tested MK3 black heatbed. Resistance at 25°C 1 - (2+3) =1.8? 1 - 2 =3.2? 1 - 3 =3.2? 2 - 3 =6.0? Visual examination discovered 4 areas of heating tracks: terminal 1 has 4 exits terminal 2 has 2 exits (far from terminals half) terminal 3 has 2 exits (near terminals half board) So, there are 4 areas with R=5.6Ohm each and 0.4Ohm wire. When use 12V scheme, I=12/1.8=6.7A , but the target is 10A 1.2? . Which means 0.8Ohm tracks total , N=5.6/0.8=7 tracks need remake from 4, each will be 5.6*4/7=3.2 ?. This remake may be tricky. Better try to split 2 edge tracks only, to total 6 tracks. So, Resulting resistance will be near 1.0-1.1 Ohm |
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Maximim temperature is 83°C when connected using 20A relay, and the same result with direct connection to 30A power supply. Decided to test on more powerful PS. |
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On the market there are LED PS up to 60A in those standard sizes 100*50*200mm and 115*50*215mm. Optimal price is for SANPU SMPS PS600-H1V12 12V 50A 600W. |
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For test got IBM 24R2730 Artesyn 12V 69A 7001138-Y000 REV E On PS out it has 12.18V , and on table it has 11.86V , loosing potential in wire. Result is the same 83°C Decided to change wire to cuprum 2.5mm |
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So, power supply is not a problem here. Need to remove heat sink, isolate bed from frame. used PP carpet 2mm as heat isolation under the table and covered that now MK3 can reach 111°C but drops temp if uncovered to 100°C (surface) and 107°C (inside) this test was using copper 2.5mm wire direct connection to PS |
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Found on bed sides electric tracks -> so, no drilling allowed. |
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Tested red MK2B heatbed (geeetech) Resistance at 25°C 1 - (2+3) =1.6? 1 - 2 =2.6? 1 - 3 =2.6? 2 - 3 =5.0? So, there are 4 quaters with R=5.0 Ohm and 0.2Ohm wire. When use 12V scheme, I=12/1.6=7.5A Tested black MK2B terminal 1 to 2-3 gives 1.2? Tested white MK2B terminal 1 to 2-3 gives 1.3? Tested red MK2Y round terminal 1 to 2 gives 1.6? |
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So, conclusion is: need to change resistance of red PCB to near 1.2 Ohm , black and white MK2B give acceptable result |